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<li><a class="reference internal" href="#"><code class="docutils literal notranslate"><span class="pre">pplib</span></code> 2.x</a></li>
<li><a class="reference internal" href="#c-api">C-API</a><ul>
<li><a class="reference internal" href="#types">Types</a></li>
<li><a class="reference internal" href="#object">Object</a></li>
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<li><a class="reference internal" href="#string">String</a></li>
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<li><a class="reference internal" href="#encryption">Encryption</a></li>
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<div class="section" id="pplib-2-x">
<h1><code class="docutils literal notranslate"><span class="pre">pplib</span></code> 2.x<a class="headerlink" href="#pplib-2-x" title="Permalink to this headline">¶</a></h1>
<p><code class="docutils literal notranslate"><span class="pre">pplib</span></code> is a library for raw PDF access. It parses PDF documents and provides an interface to access document structures in C.</p>
</div>
<div class="section" id="c-api">
<h1>C-API<a class="headerlink" href="#c-api" title="Permalink to this headline">¶</a></h1>
<div class="section" id="types">
<h2>Types<a class="headerlink" href="#types" title="Permalink to this headline">¶</a></h2>
<p><code class="docutils literal notranslate"><span class="pre">pplib</span></code> defines several C-types to represent PDF types:</p>
<ul class="simple">
<li><code class="docutils literal notranslate"><span class="pre">ppbyte</span></code> - char</li>
<li><code class="docutils literal notranslate"><span class="pre">ppint</span></code> - signed integer (<code class="docutils literal notranslate"><span class="pre">int64_t</span></code>)</li>
<li><code class="docutils literal notranslate"><span class="pre">ppnum</span></code> - real number (double)</li>
<li><code class="docutils literal notranslate"><span class="pre">ppname</span></code> - PDF name</li>
<li><code class="docutils literal notranslate"><span class="pre">ppstring</span></code> - PDF string</li>
<li><code class="docutils literal notranslate"><span class="pre">pparray</span></code> - PDF array</li>
<li><code class="docutils literal notranslate"><span class="pre">ppdict</span></code> - PDF dict</li>
<li><code class="docutils literal notranslate"><span class="pre">ppstream</span></code> - PDF stream</li>
<li><code class="docutils literal notranslate"><span class="pre">ppref</span></code> - PDF indirect reference</li>
<li><code class="docutils literal notranslate"><span class="pre">ppobj</span></code> - a container of all above</li>
</ul>
<p>Among <code class="docutils literal notranslate"><span class="pre">ppint</span></code> and <code class="docutils literal notranslate"><span class="pre">ppnum</span></code>, we also use <code class="docutils literal notranslate"><span class="pre">ppuint</span></code> - unsigned integer (machine word, alias to <code class="docutils literal notranslate"><span class="pre">size_t</span></code>).</p>
<p>Other API types:</p>
<ul class="simple">
<li><code class="docutils literal notranslate"><span class="pre">ppdoc</span></code> - PDF document</li>
<li><code class="docutils literal notranslate"><span class="pre">ppxref</span></code> - cross-references table</li>
<li><code class="docutils literal notranslate"><span class="pre">ppcontext</span></code> - … later</li>
<li><code class="docutils literal notranslate"><span class="pre">pprect</span></code> - rectangle</li>
<li><code class="docutils literal notranslate"><span class="pre">ppmatrix</span></code> - matrix</li>
</ul>
<p>Integer and number are as simple types. Names and strings used to be aliases to <code class="docutils literal notranslate"><span class="pre">char</span> <span class="pre">*</span></code>
in <code class="docutils literal notranslate"><span class="pre">pplib</span> <span class="pre">1.x</span></code>, now they are structures; all related API functions operate on pointers.
Other types (array, dict, stream, reference, object container, xref, doc) are C-structures,
and you operate it their pointers. So when you declare a simple type variable you say:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppuint</span> <span class="n">u</span><span class="p">;</span>
<span class="n">ppnum</span> <span class="n">n</span><span class="p">;</span>
<span class="o">...</span>
</pre></div>
</div>
<p>And when you declare a compound type you operate on pointers:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppobj</span> <span class="o">*</span><span class="n">obj</span><span class="p">;</span>
<span class="n">ppname</span> <span class="o">*</span><span class="n">name</span><span class="p">;</span>
<span class="n">ppstring</span> <span class="o">*</span><span class="n">string</span><span class="p">;</span>
<span class="n">pparray</span> <span class="o">*</span><span class="n">array</span><span class="p">;</span>
<span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">;</span>
<span class="n">ppstream</span> <span class="o">*</span><span class="n">stream</span><span class="p">;</span>
<span class="n">ppref</span> <span class="o">*</span><span class="n">ref</span><span class="p">;</span>
<span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">;</span>
</pre></div>
</div>
<p>Most of those C-types are defined in library header <code class="docutils literal notranslate"><span class="pre">ppapi.h</span></code> (complete types). Some others are incomplete
(eg. you can’t say <code class="docutils literal notranslate"><span class="pre">sizeof(ppdoc)</span></code> or <code class="docutils literal notranslate"><span class="pre">sizeof(ppxref)</span></code>). This is to avoid unnecesary dependencies in
the header. The library itself uses <code class="docutils literal notranslate"><span class="pre">pplib.h</span></code> header but for auxilary applications including a standalone
<code class="docutils literal notranslate"><span class="pre">ppapi.h</span></code> header should be enough.</p>
<p><code class="docutils literal notranslate"><span class="pre">pplib</span></code> was designed having <strong>read-only</strong> PDF access in mind. Even if some structure is completelly exposed,
so that you can directly access its members, you should treat them as read-only. I don’t make them <code class="docutils literal notranslate"><span class="pre">const</span></code> because
then all variable declarations would need to be <code class="docutils literal notranslate"><span class="pre">const</span></code>, which is annoying, and I’d need some trickery in the library
internals to unconst. Besides, nothing is really const for C type casts.</p>
</div>
<div class="section" id="object">
<h2>Object<a class="headerlink" href="#object" title="Permalink to this headline">¶</a></h2>
<p>A common container for all elementary PDF object types is <code class="docutils literal notranslate"><span class="pre">ppobj</span></code> structure. <code class="docutils literal notranslate"><span class="pre">ppobj</span></code> has a type identifier
(integer) and union of values:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">struct</span> <span class="n">ppobj</span> <span class="p">{</span>
<span class="n">ppobjtp</span> <span class="nb">type</span><span class="p">;</span>
<span class="n">union</span> <span class="p">{</span>
<span class="n">ppint</span> <span class="n">integer</span><span class="p">;</span>
<span class="n">ppnum</span> <span class="n">number</span><span class="p">;</span>
<span class="n">ppname</span> <span class="o">*</span><span class="n">name</span><span class="p">;</span>
<span class="n">ppstring</span> <span class="o">*</span><span class="n">string</span><span class="p">;</span>
<span class="n">pparray</span> <span class="o">*</span><span class="n">array</span><span class="p">;</span>
<span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">;</span>
<span class="n">ppstream</span> <span class="o">*</span><span class="n">stream</span><span class="p">;</span>
<span class="n">ppref</span> <span class="o">*</span><span class="n">ref</span><span class="p">;</span>
<span class="n">void</span> <span class="o">*</span><span class="nb">any</span><span class="p">;</span>
<span class="p">};</span>
<span class="p">};</span>
</pre></div>
</div>
<p>Object type is one of constants (enum):</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">PPNONE</span>
<span class="n">PPNULL</span>
<span class="n">PPBOOL</span>
<span class="n">PPINT</span>
<span class="n">PPNUM</span>
<span class="n">PPNAME</span>
<span class="n">PPSTRING</span>
<span class="n">PPARRAY</span>
<span class="n">PPDICT</span>
<span class="n">PPSTREAM</span>
<span class="n">PPREF</span>
</pre></div>
</div>
<p>The type determines the structure member you’re allowed to access:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppobj</span> <span class="o">*</span><span class="n">obj</span><span class="p">;</span>
<span class="o">...</span>
<span class="n">switch</span> <span class="p">(</span><span class="n">obj</span><span class="o">-></span><span class="nb">type</span><span class="p">)</span>
<span class="p">{</span>
<span class="n">case</span> <span class="n">PPNONE</span><span class="p">:</span> <span class="o">//</span> <span class="n">shouldn</span><span class="s1">'t actually happen, indicates some failure</span>
<span class="k">break</span><span class="p">;</span>
<span class="n">case</span> <span class="n">PPNULL</span><span class="p">:</span> <span class="o">//</span> <span class="n">valid</span> <span class="n">PDF</span> <span class="n">null</span> <span class="nb">object</span><span class="p">,</span> <span class="n">no</span> <span class="n">value</span>
<span class="k">break</span><span class="p">;</span>
<span class="n">case</span> <span class="n">PPBOOL</span><span class="p">:</span> <span class="o">//</span> <span class="n">do</span> <span class="n">something</span> <span class="k">with</span> <span class="n">obj</span><span class="o">-></span><span class="n">integer</span> <span class="p">(</span><span class="n">ppint</span><span class="p">),</span> <span class="n">value</span> <span class="mi">0</span> <span class="ow">or</span> <span class="mi">1</span>
<span class="k">break</span><span class="p">;</span>
<span class="n">case</span> <span class="n">PPINT</span><span class="p">:</span> <span class="o">//</span> <span class="n">do</span> <span class="n">something</span> <span class="k">with</span> <span class="n">obj</span><span class="o">-></span><span class="n">integer</span> <span class="p">(</span><span class="n">ppint</span><span class="p">)</span>
<span class="k">break</span><span class="p">;</span>
<span class="n">case</span> <span class="n">PPNUM</span><span class="p">:</span> <span class="o">//</span> <span class="n">do</span> <span class="n">something</span> <span class="k">with</span> <span class="n">obj</span><span class="o">-></span><span class="n">number</span> <span class="p">(</span><span class="n">ppnum</span><span class="p">)</span>
<span class="k">break</span><span class="p">;</span>
<span class="n">case</span> <span class="n">PPNAME</span><span class="p">:</span> <span class="o">//</span> <span class="n">do</span> <span class="n">something</span> <span class="k">with</span> <span class="n">obj</span><span class="o">-></span><span class="n">name</span> <span class="p">(</span><span class="n">ppname</span> <span class="o">*</span><span class="p">)</span>
<span class="k">break</span><span class="p">;</span>
<span class="n">case</span> <span class="n">PPSTRING</span><span class="p">:</span> <span class="o">//</span> <span class="n">do</span> <span class="n">something</span> <span class="k">with</span> <span class="n">obj</span><span class="o">-></span><span class="n">string</span> <span class="p">(</span><span class="n">ppstring</span> <span class="o">*</span><span class="p">)</span>
<span class="k">break</span><span class="p">;</span>
<span class="n">case</span> <span class="n">PPARRAY</span><span class="p">:</span> <span class="o">//</span> <span class="n">do</span> <span class="n">something</span> <span class="k">with</span> <span class="n">obj</span><span class="o">-></span><span class="n">array</span> <span class="p">(</span><span class="n">pparray</span> <span class="o">*</span><span class="p">)</span>
<span class="k">break</span><span class="p">;</span>
<span class="n">case</span> <span class="n">PPDICT</span><span class="p">:</span> <span class="o">//</span> <span class="n">do</span> <span class="n">something</span> <span class="k">with</span> <span class="n">obj</span><span class="o">-></span><span class="nb">dict</span> <span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="p">)</span>
<span class="k">break</span><span class="p">;</span>
<span class="n">case</span> <span class="n">PPSTREAM</span><span class="p">:</span> <span class="o">//</span> <span class="n">do</span> <span class="n">something</span> <span class="k">with</span> <span class="n">obj</span><span class="o">-></span><span class="n">stream</span> <span class="p">(</span><span class="n">ppstream</span> <span class="o">*</span><span class="p">)</span>
<span class="k">break</span><span class="p">;</span>
<span class="n">case</span> <span class="n">PPREF</span><span class="p">:</span> <span class="o">//</span> <span class="n">do</span> <span class="n">something</span> <span class="k">with</span> <span class="n">obj</span><span class="o">-></span><span class="n">ref</span> <span class="p">(</span><span class="n">ppref</span> <span class="o">*</span><span class="p">)</span>
<span class="k">break</span><span class="p">;</span>
<span class="p">}</span>
</pre></div>
</div>
<p>More often then not you know exactly what type of object value is expected, in which case
you may use one of the following macros:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="o">//</span> <span class="n">returns</span> <span class="mi">1</span> <span class="k">if</span> <span class="n">o</span><span class="o">-></span><span class="nb">type</span> <span class="ow">is</span> <span class="n">PPNULL</span>
<span class="nb">int</span> <span class="n">ppobj_get_null</span><span class="p">(</span><span class="n">o</span><span class="p">)</span> \
<span class="o">//</span> <span class="k">if</span> <span class="n">o</span><span class="o">-></span><span class="nb">type</span> <span class="ow">is</span> <span class="n">PPBOOL</span><span class="p">,</span> <span class="n">sets</span> <span class="nb">int</span> <span class="n">v</span> <span class="n">to</span> <span class="mi">0</span> <span class="ow">or</span> <span class="mi">1</span> <span class="ow">and</span> <span class="n">returns</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">0</span> <span class="n">otherwise</span>
<span class="nb">int</span> <span class="n">ppobj_get_bool</span><span class="p">(</span><span class="n">o</span><span class="p">,</span> <span class="n">v</span><span class="p">)</span>
<span class="o">//</span> <span class="k">if</span> <span class="n">o</span><span class="o">-></span><span class="nb">type</span> <span class="ow">is</span> <span class="n">PPINT</span><span class="p">,</span> <span class="n">sets</span> <span class="n">ppint</span> <span class="n">v</span> <span class="ow">and</span> <span class="n">returns</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">0</span> <span class="n">otherwise</span>
<span class="nb">int</span> <span class="n">ppobj_get_int</span><span class="p">(</span><span class="n">o</span><span class="p">,</span> <span class="n">v</span><span class="p">)</span>
<span class="o">//</span> <span class="k">if</span> <span class="n">o</span><span class="o">-></span><span class="nb">type</span> <span class="ow">is</span> <span class="n">PPINT</span> <span class="ow">and</span> <span class="o">>=</span> <span class="mi">0</span><span class="p">,</span> <span class="n">sets</span> <span class="n">ppuint</span> <span class="n">v</span> <span class="ow">and</span> <span class="n">returns</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">0</span> <span class="n">otherwise</span>
<span class="nb">int</span> <span class="n">ppobj_get_uint</span><span class="p">(</span><span class="n">o</span><span class="p">,</span> <span class="n">v</span><span class="p">)</span>
<span class="o">//</span> <span class="k">if</span> <span class="n">o</span><span class="o">-></span><span class="nb">type</span> <span class="ow">is</span> <span class="n">PPNUM</span> <span class="ow">or</span> <span class="n">PPINT</span><span class="p">,</span> <span class="n">sets</span> <span class="n">ppnum</span> <span class="n">v</span> <span class="ow">and</span> <span class="n">returns</span> <span class="mi">1</span><span class="p">,</span> <span class="mi">0</span> <span class="n">otherwise</span>
<span class="nb">int</span> <span class="n">ppobj_get_num</span><span class="p">(</span><span class="n">o</span><span class="p">,</span> <span class="n">v</span><span class="p">)</span>
<span class="o">//</span> <span class="k">if</span> <span class="n">o</span><span class="o">-></span><span class="nb">type</span> <span class="ow">is</span> <span class="n">PPNAME</span> <span class="n">returns</span> <span class="n">the</span> <span class="n">name</span><span class="p">,</span> <span class="n">NULL</span> <span class="n">otherwise</span>
<span class="n">ppname</span> <span class="o">*</span> <span class="n">ppobj_get_name</span><span class="p">(</span><span class="n">o</span><span class="p">)</span>
<span class="o">//</span> <span class="k">if</span> <span class="n">o</span><span class="o">-></span><span class="nb">type</span> <span class="ow">is</span> <span class="n">PPSTRING</span> <span class="n">returns</span> <span class="n">the</span> <span class="n">string</span><span class="p">,</span> <span class="n">NULL</span> <span class="n">otherwise</span>
<span class="n">ppstring</span> <span class="o">*</span> <span class="n">ppobj_get_string</span><span class="p">(</span><span class="n">o</span><span class="p">)</span>
<span class="o">//</span> <span class="k">if</span> <span class="n">o</span><span class="o">-></span><span class="nb">type</span> <span class="ow">is</span> <span class="n">PPARRAY</span> <span class="n">returns</span> <span class="n">the</span> <span class="n">array</span><span class="p">,</span> <span class="n">NULL</span> <span class="n">otherwise</span>
<span class="n">pparray</span> <span class="o">*</span> <span class="n">ppobj_get_array</span><span class="p">(</span><span class="n">o</span><span class="p">)</span>
<span class="o">//</span> <span class="k">if</span> <span class="n">o</span><span class="o">-></span><span class="nb">type</span> <span class="ow">is</span> <span class="n">PPDICT</span> <span class="n">returns</span> <span class="n">the</span> <span class="nb">dict</span><span class="p">,</span> <span class="n">NULL</span> <span class="n">otherwise</span>
<span class="n">ppdict</span> <span class="o">*</span> <span class="n">ppobj_get_dict</span><span class="p">(</span><span class="n">o</span><span class="p">)</span>
<span class="o">//</span> <span class="k">if</span> <span class="n">o</span><span class="o">-></span><span class="nb">type</span> <span class="ow">is</span> <span class="n">PPSTREAM</span> <span class="n">returns</span> <span class="n">the</span> <span class="n">stream</span><span class="p">,</span> <span class="n">NULL</span> <span class="n">otherwise</span>
<span class="n">ppstream</span> <span class="o">*</span> <span class="n">ppobj_get_stream</span><span class="p">(</span><span class="n">o</span><span class="p">)</span>
<span class="o">//</span> <span class="k">if</span> <span class="n">o</span><span class="o">-></span><span class="nb">type</span> <span class="ow">is</span> <span class="n">PPREF</span> <span class="n">returns</span> <span class="n">the</span> <span class="n">reference</span><span class="p">,</span> <span class="n">NULL</span> <span class="n">otherwise</span>
<span class="n">ppref</span> <span class="o">*</span> <span class="n">ppobj_get_ref</span><span class="p">(</span><span class="n">o</span><span class="p">)</span>
</pre></div>
</div>
<p>Note the coercion from integer to real number, but not reverse. In practise, whenever you expect a real number,
you should also handle integer (eg. ‘1’ used instead of ‘1.0’ is pretty common in PDF).</p>
<p>It is a common case that the object is given as an indirect reference, but what you actually
want is not the reference, but the object referred by it. Here is a helper for it:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="o">//</span> <span class="k">if</span> <span class="n">o</span><span class="o">-></span><span class="nb">type</span> <span class="ow">is</span> <span class="n">PPREF</span><span class="p">,</span> <span class="n">returns</span> <span class="n">what</span> <span class="n">the</span> <span class="n">reference</span> <span class="n">points</span><span class="p">,</span> <span class="n">otherwise</span> <span class="n">returns</span> <span class="n">o</span>
<span class="n">ppobj</span> <span class="o">*</span> <span class="n">ppobj_rget_obj</span><span class="p">(</span><span class="n">o</span><span class="p">)</span>
</pre></div>
</div>
<p>Also every <code class="docutils literal notranslate"><span class="pre">ppobj_get_*</span></code> macro has <code class="docutils literal notranslate"><span class="pre">ppobj_rget_*</span></code> counterpart that makes a check
for the expected type, but if the object is PPREF, it jumps to the target object.
So for example <code class="docutils literal notranslate"><span class="pre">ppobj_rget_dict(obj)</span></code> will return dict if <code class="docutils literal notranslate"><span class="pre">obj</span></code> is of type PPDICT
or if it is of type PPREF and <code class="docutils literal notranslate"><span class="pre">obj->ref</span></code> hosts an object of type PPDICT.</p>
</div>
<div class="section" id="names">
<h2>Names<a class="headerlink" href="#names" title="Permalink to this headline">¶</a></h2>
<p>PDF names are represented as <code class="docutils literal notranslate"><span class="pre">ppname</span></code> pointer (<code class="docutils literal notranslate"><span class="pre">ppname</span></code> used to be an alias to <code class="docutils literal notranslate"><span class="pre">char</span> <span class="pre">*</span></code>, now it is a structure).
To access the name data:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppbyte</span> <span class="o">*</span> <span class="n">ppname_data</span><span class="p">(</span><span class="n">name</span><span class="p">)</span> <span class="o">//</span> <span class="n">name</span><span class="o">-></span><span class="n">data</span><span class="p">,</span> <span class="nb">bytes</span> <span class="n">array</span>
</pre></div>
</div>
<p>For convenient use in C, names are <code class="docutils literal notranslate"><span class="pre">'\0'</span></code> terminated. But to get the length of name better always use
<code class="docutils literal notranslate"><span class="pre">ppname_size()</span></code> macro. <code class="docutils literal notranslate"><span class="pre">ppname</span></code> object knows its size, don’t use <code class="docutils literal notranslate"><span class="pre">strlen()</span></code>:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">size_t</span> <span class="n">ppname_size</span><span class="p">(</span><span class="n">ppname</span> <span class="n">name</span><span class="p">);</span> <span class="o">//</span> <span class="n">name</span><span class="o">-></span><span class="n">size</span><span class="p">,</span> <span class="n">the</span> <span class="n">length</span> <span class="n">of</span> <span class="n">name</span> <span class="ow">in</span> <span class="nb">bytes</span>
</pre></div>
</div>
<p>In current implementation names are not hashed anyhow, so name-to-name comparison is not smarter than <code class="docutils literal notranslate"><span class="pre">memcmp()</span></code>.
Use macros:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="nb">int</span> <span class="n">ppname_is</span><span class="p">(</span><span class="n">ppname</span> <span class="n">name</span><span class="p">,</span> <span class="s2">"literal"</span><span class="p">);</span> <span class="o">//</span> <span class="n">to</span> <span class="n">compare</span> <span class="n">ppname</span> <span class="k">with</span> <span class="n">C</span><span class="o">-</span><span class="n">literal</span> <span class="n">string</span>
<span class="nb">int</span> <span class="n">ppname_eq</span><span class="p">(</span><span class="n">ppname</span> <span class="n">name</span><span class="p">,</span> <span class="n">ppname</span> <span class="n">other</span><span class="p">);</span> <span class="o">//</span> <span class="n">to</span> <span class="n">compare</span> <span class="n">ppname</span> <span class="k">with</span> <span class="n">a</span> <span class="n">different</span> <span class="n">name</span>
</pre></div>
</div>
<p>If you use <code class="docutils literal notranslate"><span class="pre">pplib</span></code> to parse contents streams, you may need to distinguish names from operators
(more precisely executable names). Names in PDF are preceeded by ‘/’, executable names aren’t. In both
cases PDF parser will produce <code class="docutils literal notranslate"><span class="pre">ppname</span></code> but the result can be distingushed with:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="nb">int</span> <span class="n">ppname_exec</span><span class="p">(</span><span class="n">ppname</span> <span class="n">name</span><span class="p">);</span> <span class="o">//</span> <span class="n">macro</span><span class="p">,</span> <span class="n">returns</span> <span class="n">non</span><span class="o">-</span><span class="n">zero</span> <span class="k">if</span> <span class="n">the</span> <span class="n">name</span> <span class="ow">is</span> <span class="n">executable</span>
</pre></div>
</div>
<p>Names are kept in their raw form, with possible PDF specific escapes (in text below we call it <strong>encoded</strong> form).
Leading ‘/’ is omitted. One may need a decoded name, with no PDF escapes.
A pair of functions provides a simple interface to switch between those two forms:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="o">//</span> <span class="n">these</span> <span class="n">helpers</span> <span class="n">rely</span> <span class="n">on</span> <span class="n">name</span><span class="o">-></span><span class="n">alterego</span> <span class="n">member</span>
<span class="n">ppname</span> <span class="o">*</span> <span class="n">ppname_decoded</span> <span class="p">(</span><span class="n">ppname</span> <span class="o">*</span><span class="n">name</span><span class="p">);</span> <span class="o">//</span> <span class="n">returns</span> <span class="n">decoded</span> <span class="p">(</span><span class="n">unescaped</span><span class="p">)</span> <span class="n">form</span> <span class="n">of</span> <span class="n">the</span> <span class="n">name</span>
<span class="n">ppname</span> <span class="o">*</span> <span class="n">ppname_encoded</span> <span class="p">(</span><span class="n">ppname</span> <span class="o">*</span><span class="n">name</span><span class="p">);</span> <span class="o">//</span> <span class="n">returns</span> <span class="n">encoded</span> <span class="p">(</span><span class="n">escaped</span><span class="p">)</span> <span class="n">form</span> <span class="n">of</span> <span class="n">the</span> <span class="n">name</span>
<span class="n">ppbyte</span> <span class="o">*</span> <span class="n">ppname_decoded_data</span> <span class="p">(</span><span class="n">ppname</span> <span class="o">*</span><span class="n">name</span><span class="p">);</span>
<span class="n">ppbyte</span> <span class="o">*</span> <span class="n">ppname_encoded_data</span> <span class="p">(</span><span class="n">ppname</span> <span class="o">*</span><span class="n">name</span><span class="p">);</span>
</pre></div>
</div>
<p>In pretty most cases a PDF name contains only letters (no special characters, no escapes), so decoded and encoded forms are identical.
In that case both functions simply return the argument. It is ok to call <code class="docutils literal notranslate"><span class="pre">ppname_decoded()</span></code> on already decoded form
and <code class="docutils literal notranslate"><span class="pre">ppname_encoded()</span></code> on already encoded form. Both forms are produced by PDF objects parser, so accessing <code class="docutils literal notranslate"><span class="pre">ppname</span></code> alter ego
in whatever direction needs no extra decoding or allocation costs (the cost is paid by parser).</p>
</div>
<div class="section" id="string">
<h2>String<a class="headerlink" href="#string" title="Permalink to this headline">¶</a></h2>
<p>PDF strings have the same internal construction as names, so most of names description above applies to strings as well.
<code class="docutils literal notranslate"><span class="pre">ppstring</span></code> is a structure (used to be an alias to <code class="docutils literal notranslate"><span class="pre">char</span> <span class="pre">*</span></code>). <code class="docutils literal notranslate"><span class="pre">string->data</span></code> is <code class="docutils literal notranslate"><span class="pre">\0</span></code>-terminated c-array of <code class="docutils literal notranslate"><span class="pre">ppbytes</span></code>.
To get the data:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppbyte</span> <span class="o">*</span> <span class="n">ppstring_data</span><span class="p">(</span><span class="n">ppstring</span> <span class="o">*</span><span class="n">string</span><span class="p">);</span> <span class="o">//</span> <span class="n">string</span><span class="o">-></span><span class="n">data</span><span class="p">,</span> <span class="n">macro</span>
</pre></div>
</div>
<p>To get the size of the string:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">size_t</span> <span class="n">ppstring_size</span><span class="p">(</span><span class="n">ppstring</span> <span class="o">*</span><span class="n">string</span><span class="p">);</span> <span class="o">//</span> <span class="n">macro</span><span class="p">,</span> <span class="n">returns</span> <span class="n">the</span> <span class="n">length</span> <span class="n">of</span> <span class="n">the</span> <span class="n">string</span> <span class="ow">in</span> <span class="nb">bytes</span>
</pre></div>
</div>
<p>Strings are provided in their raw form, preserving PDF specific escapes, but with no
<code class="docutils literal notranslate"><span class="pre">()</span></code> or <code class="docutils literal notranslate"><span class="pre"><></span></code> delims. To distinguish plain strings from hex strings:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="nb">int</span> <span class="n">ppstring_hex</span><span class="p">(</span><span class="n">ppstring</span> <span class="n">string</span><span class="p">);</span> <span class="o">//</span> <span class="n">macro</span><span class="p">,</span> <span class="n">returns</span> <span class="n">non</span> <span class="n">zero</span> <span class="k">if</span> <span class="nb">hex</span> <span class="n">string</span>
</pre></div>
</div>
<p>Or if you prefer:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span>switch (ppstring_type(string))
{
case PPSTRING_PLAIN: // literal string, surrounded by ``(`` and ``)`` in PDF
break;
case PPSTRING_BASE16: // hex string, surrounded by ``<`` and ``>`` in PDF
break;
case PPSTRING_BASE85: // base85 string surrounded by ``<~`` and ``~>`` in PDF
break;
}
</pre></div>
</div>
<p>The last is actually Postscript specific, not used in PDF, but I think it might appear in contents streams…
No matter how the string is given in PDF (plain or hex), here are two functions to
switch between encoded and decoded strings forms:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppstring</span> <span class="o">*</span> <span class="n">ppstring_decoded</span> <span class="p">(</span><span class="n">ppstring</span> <span class="o">*</span><span class="n">string</span><span class="p">);</span> <span class="o">//</span> <span class="n">returns</span> <span class="n">decoded</span> <span class="n">string</span> <span class="n">possibly</span> <span class="k">with</span> <span class="n">PDF</span> <span class="n">escapes</span>
<span class="n">ppstring</span> <span class="o">*</span> <span class="n">ppstring_encoded</span> <span class="p">(</span><span class="n">ppstring</span> <span class="o">*</span><span class="n">string</span><span class="p">);</span> <span class="o">//</span> <span class="n">returns</span> <span class="n">encoded</span> <span class="n">string</span> <span class="k">with</span> <span class="n">no</span> <span class="n">PDF</span> <span class="n">escapes</span>
<span class="n">ppbyte</span> <span class="o">*</span> <span class="n">ppstring_decoded_data</span> <span class="p">(</span><span class="n">ppstring</span> <span class="o">*</span><span class="n">string</span><span class="p">);</span>
<span class="n">ppbyte</span> <span class="o">*</span> <span class="n">ppstring_encoded_data</span> <span class="p">(</span><span class="n">ppstring</span> <span class="o">*</span><span class="n">string</span><span class="p">);</span>
</pre></div>
</div>
<p>For hex strings, encoded form contains hex digits, while decoded form contains arbitrary bytes (the result of hex decoding).
Plain strings usually contains printable ASCII characters, but they might contain any binary data.
As with names, objects parser produces both forms. The raw form with PDF escapes (or raw hex form) the main one.
Eg. when you access <code class="docutils literal notranslate"><span class="pre">obj->string</span></code> you always get the encoded form. At any moment you can switch to its alter ego.</p>
<p>No matter if the string is plain or hex, if its first two bytes (decoded) are UTF16 BOM, the string is unicode.
<code class="docutils literal notranslate"><span class="pre">ppstring</span></code> object <em>knows</em> it is unicode or not:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">switch</span> <span class="p">(</span><span class="n">ppstring_utf</span><span class="p">(</span><span class="n">string</span><span class="p">))</span>
<span class="p">{</span>
<span class="n">case</span> <span class="n">PPSTRING_UTF16LE</span><span class="p">:</span> <span class="o">//</span> <span class="n">unicode</span> <span class="n">string</span><span class="p">,</span> <span class="n">utf16le</span>
<span class="k">break</span><span class="p">;</span>
<span class="n">case</span> <span class="n">PPSTRING_UTF16BE</span><span class="p">:</span> <span class="o">//</span> <span class="n">unicode</span> <span class="n">string</span><span class="p">,</span> <span class="n">utf16be</span>
<span class="k">break</span><span class="p">;</span>
<span class="n">default</span><span class="p">:</span> <span class="o">//</span> <span class="n">no</span> <span class="n">unicode</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Or simply:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="k">if</span> <span class="p">(</span><span class="n">ppstring_utf</span><span class="p">(</span><span class="n">string</span><span class="p">)</span> <span class="o">!=</span> <span class="mi">0</span><span class="p">)</span> <span class="p">{</span>
<span class="o">//</span> <span class="n">handle</span> <span class="n">unicode</span> <span class="n">string</span>
<span class="p">}</span>
</pre></div>
</div>
<p>If the string is unicode, BOM remains the part of the string – <code class="docutils literal notranslate"><span class="pre">pplib</span></code> parser does not strip it.
Unicode or not, encoded or decoded, strings are always C-arrays of bytes and <code class="docutils literal notranslate"><span class="pre">ppstring_size()</span></code>
always returns the size in bytes.</p>
</div>
<div class="section" id="array">
<h2>Array<a class="headerlink" href="#array" title="Permalink to this headline">¶</a></h2>
<p>PDF arrays are represented as <code class="docutils literal notranslate"><span class="pre">pparray</span></code> type, which is C-array of <code class="docutils literal notranslate"><span class="pre">ppobj</span></code> structures.
To get the size:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">size_t</span> <span class="n">pparray_size</span><span class="p">(</span><span class="n">pparray</span> <span class="o">*</span><span class="n">array</span><span class="p">)</span> <span class="o">//</span> <span class="n">macro</span><span class="p">,</span> <span class="n">returns</span> <span class="n">the</span> <span class="n">number</span> <span class="n">of</span> <span class="n">array</span> <span class="n">items</span>
</pre></div>
</div>
<p>To get <code class="docutils literal notranslate"><span class="pre">ppobj</span> <span class="pre">*</span></code> at a given index:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppobj</span> <span class="o">*</span> <span class="n">pparray_at</span><span class="p">(</span><span class="n">array</span><span class="p">,</span> <span class="n">index</span><span class="p">)</span> <span class="o">//</span> <span class="n">macro</span><span class="p">,</span> <span class="n">returns</span> <span class="n">ppobj</span> <span class="o">*</span> <span class="p">(</span><span class="n">no</span> <span class="n">index</span> <span class="n">check</span><span class="p">)</span>
<span class="n">ppobj</span> <span class="o">*</span> <span class="n">pparray_get</span><span class="p">(</span><span class="n">array</span><span class="p">,</span> <span class="n">index</span><span class="p">)</span> <span class="o">//</span> <span class="n">macro</span><span class="p">,</span> <span class="n">returns</span> <span class="n">ppobj</span> <span class="o">*</span> <span class="ow">or</span> <span class="n">NULL</span> <span class="p">(</span><span class="k">with</span> <span class="n">index</span> <span class="n">check</span><span class="p">)</span>
<span class="n">ppobj</span> <span class="o">*</span> <span class="n">pparray_get_obj</span> <span class="p">(</span><span class="n">pparray</span> <span class="o">*</span><span class="n">array</span><span class="p">,</span> <span class="n">size_t</span> <span class="n">index</span><span class="p">);</span> <span class="o">//</span> <span class="n">function</span> <span class="n">equiv</span> <span class="n">to</span> <span class="n">pparray_get</span><span class="p">()</span>
</pre></div>
</div>
<p>Iterating over array elements:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">pparray</span> <span class="o">*</span><span class="n">array</span><span class="p">;</span>
<span class="n">size_t</span> <span class="n">index</span><span class="p">,</span> <span class="n">size</span><span class="p">;</span>
<span class="n">ppobj</span> <span class="o">*</span><span class="n">obj</span><span class="p">;</span>
<span class="k">for</span> <span class="p">(</span><span class="n">size</span> <span class="o">=</span> <span class="n">pparray_size</span><span class="p">(</span><span class="n">array</span><span class="p">),</span> <span class="n">pparray_first</span><span class="p">(</span><span class="n">array</span><span class="p">,</span> <span class="n">index</span><span class="p">,</span> <span class="n">obj</span><span class="p">);</span> <span class="n">index</span> <span class="o"><</span> <span class="n">size</span><span class="p">;</span> <span class="n">pparray_next</span><span class="p">(</span><span class="n">index</span><span class="p">,</span> <span class="n">obj</span><span class="p">))</span>
<span class="p">{</span>
<span class="o">//</span> <span class="n">do</span> <span class="n">something</span> <span class="k">with</span> <span class="n">index</span> <span class="ow">and</span> <span class="n">obj</span>
<span class="p">}</span>
</pre></div>
</div>
<p>There is no magic first/next macros, just iteration over pointers. One could also use something like:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="k">for</span> <span class="p">(</span><span class="n">index</span> <span class="o">=</span> <span class="mi">0</span><span class="p">,</span> <span class="n">size</span> <span class="o">=</span> <span class="n">array</span><span class="o">-></span><span class="n">size</span><span class="p">;</span> <span class="n">index</span> <span class="o"><</span> <span class="n">size</span><span class="p">;</span> <span class="o">++</span><span class="n">index</span><span class="p">)</span>
<span class="p">{</span>
<span class="n">obj</span> <span class="o">=</span> <span class="n">pparray_at</span><span class="p">(</span><span class="n">array</span><span class="p">,</span> <span class="n">index</span><span class="p">);</span>
<span class="o">//</span> <span class="n">do</span> <span class="n">something</span> <span class="k">with</span> <span class="n">index</span> <span class="ow">and</span> <span class="n">obj</span>
<span class="p">}</span>
</pre></div>
</div>
<p>When getting values from array and expecting a result of known type, use one of the following:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="nb">int</span> <span class="n">pparray_get_bool</span> <span class="p">(</span><span class="n">pparray</span> <span class="o">*</span><span class="n">array</span><span class="p">,</span> <span class="n">size_t</span> <span class="n">index</span><span class="p">,</span> <span class="nb">int</span> <span class="o">*</span><span class="n">v</span><span class="p">);</span> <span class="o">//</span> <span class="n">get</span> <span class="n">boolean</span> <span class="n">value</span>
<span class="nb">int</span> <span class="n">pparray_get_int</span> <span class="p">(</span><span class="n">pparray</span> <span class="o">*</span><span class="n">array</span><span class="p">,</span> <span class="n">size_t</span> <span class="n">index</span><span class="p">,</span> <span class="n">ppint</span> <span class="o">*</span><span class="n">v</span><span class="p">);</span> <span class="o">//</span> <span class="n">get</span> <span class="n">ppint</span> <span class="n">value</span>
<span class="nb">int</span> <span class="n">pparray_get_uint</span> <span class="p">(</span><span class="n">pparray</span> <span class="o">*</span><span class="n">array</span><span class="p">,</span> <span class="n">size_t</span> <span class="n">index</span><span class="p">,</span> <span class="n">ppuint</span> <span class="o">*</span><span class="n">v</span><span class="p">);</span> <span class="o">//</span> <span class="n">get</span> <span class="n">ppuint</span> <span class="n">value</span>
<span class="nb">int</span> <span class="n">pparray_get_num</span> <span class="p">(</span><span class="n">pparray</span> <span class="o">*</span><span class="n">array</span><span class="p">,</span> <span class="n">size_t</span> <span class="n">index</span><span class="p">,</span> <span class="n">ppnum</span> <span class="o">*</span><span class="n">v</span><span class="p">);</span> <span class="o">//</span> <span class="n">get</span> <span class="n">ppnum</span> <span class="n">value</span>
<span class="n">ppname</span> <span class="o">*</span> <span class="n">pparray_get_name</span> <span class="p">(</span><span class="n">pparray</span> <span class="o">*</span><span class="n">array</span><span class="p">,</span> <span class="n">size_t</span> <span class="n">index</span><span class="p">);</span> <span class="o">//</span> <span class="n">get</span> <span class="n">ppname</span> <span class="o">*</span> <span class="n">value</span>
<span class="n">ppstring</span> <span class="o">*</span> <span class="n">pparray_get_string</span> <span class="p">(</span><span class="n">pparray</span> <span class="o">*</span><span class="n">array</span><span class="p">,</span> <span class="n">size_t</span> <span class="n">index</span><span class="p">);</span> <span class="o">//</span> <span class="n">get</span> <span class="n">ppstring</span> <span class="o">*</span> <span class="n">value</span>
<span class="n">pparray</span> <span class="o">*</span> <span class="n">pparray_get_array</span> <span class="p">(</span><span class="n">pparray</span> <span class="o">*</span><span class="n">array</span><span class="p">,</span> <span class="n">size_t</span> <span class="n">index</span><span class="p">);</span> <span class="o">//</span> <span class="n">get</span> <span class="n">pparray</span> <span class="o">*</span> <span class="n">value</span>
<span class="n">ppdict</span> <span class="o">*</span> <span class="n">pparray_get_dict</span> <span class="p">(</span><span class="n">pparray</span> <span class="o">*</span><span class="n">array</span><span class="p">,</span> <span class="n">size_t</span> <span class="n">index</span><span class="p">);</span> <span class="o">//</span> <span class="n">get</span> <span class="n">ppdict</span> <span class="o">*</span> <span class="n">value</span>
<span class="n">ppref</span> <span class="o">*</span> <span class="n">pparray_get_ref</span> <span class="p">(</span><span class="n">pparray</span> <span class="o">*</span><span class="n">array</span><span class="p">,</span> <span class="n">size_t</span> <span class="n">index</span><span class="p">);</span> <span class="o">//</span> <span class="n">get</span> <span class="n">ppref</span> <span class="o">*</span> <span class="n">value</span>
</pre></div>
</div>
<p>As with <code class="docutils literal notranslate"><span class="pre">ppobj_get_*</span></code> suite, numeric types getters set the value of a given type and returns 1, if the type matches.
Otherwise sets nothing and returns 0. Other getters return the value if the type matches, or NULL.</p>
<p>Every function from <code class="docutils literal notranslate"><span class="pre">pparray_get_*</span></code> suite have its <code class="docutils literal notranslate"><span class="pre">pparray_rget_*</span></code> counterpart
that dereferences indirect objects (as explained for <code class="docutils literal notranslate"><span class="pre">ppobj_rget_*</span></code> getters). Note that
there is no <code class="docutils literal notranslate"><span class="pre">pparray_get_stream()</span></code> function, as streams in PDF are always indirect
(may only reside in <code class="docutils literal notranslate"><span class="pre">ref->object.stream</span></code>). To get the stream from array use:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppstream</span> <span class="o">*</span> <span class="n">pparray_rget_stream</span> <span class="p">(</span><span class="n">pparray</span> <span class="o">*</span><span class="n">array</span><span class="p">,</span> <span class="n">size_t</span> <span class="n">index</span><span class="p">);</span>
</pre></div>
</div>
</div>
<div class="section" id="dict">
<h2>Dict<a class="headerlink" href="#dict" title="Permalink to this headline">¶</a></h2>
<p>PDF dicts are represented as <code class="docutils literal notranslate"><span class="pre">ppdict</span></code> structure, which is C-array of <code class="docutils literal notranslate"><span class="pre">ppobj</span></code> with parallel
C-array of <code class="docutils literal notranslate"><span class="pre">ppname</span></code> pointers. To get the size of a dict:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">size_t</span> <span class="n">ppdict_size</span><span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">)</span> <span class="o">//</span> <span class="n">macro</span><span class="p">,</span> <span class="n">returns</span> <span class="n">the</span> <span class="n">number</span> <span class="n">of</span> <span class="n">key</span><span class="o">-</span><span class="n">val</span> <span class="n">pairs</span>
</pre></div>
</div>
<p>To get the value at a given index (integer):</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppobj</span> <span class="o">*</span> <span class="n">ppdict_at</span><span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">,</span> <span class="n">index</span><span class="p">)</span> <span class="o">//</span> <span class="n">macro</span><span class="p">,</span> <span class="n">no</span> <span class="n">index</span> <span class="n">bounds</span> <span class="n">check</span>
</pre></div>
</div>
<p>To get the name (key) at a given index:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppname</span> <span class="o">*</span> <span class="n">ppdict_key</span><span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">,</span> <span class="n">index</span><span class="p">)</span> <span class="o">//</span> <span class="n">macro</span><span class="p">,</span> <span class="n">no</span> <span class="n">index</span> <span class="n">bounds</span> <span class="n">check</span>
</pre></div>
</div>
<p>To iterate over dict key-val pairs:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">;</span>
<span class="n">ppname</span> <span class="o">**</span><span class="n">pkey</span><span class="p">;</span>
<span class="n">ppobj</span> <span class="o">*</span><span class="n">obj</span><span class="p">;</span>
<span class="k">for</span> <span class="p">(</span><span class="n">ppdict_first</span><span class="p">(</span><span class="nb">dict</span><span class="p">,</span> <span class="n">pkey</span><span class="p">,</span> <span class="n">obj</span><span class="p">);</span> <span class="o">*</span><span class="n">pkey</span> <span class="o">!=</span> <span class="n">NULL</span><span class="p">;</span> <span class="n">ppdict_next</span><span class="p">(</span><span class="n">pkey</span><span class="p">,</span> <span class="n">obj</span><span class="p">))</span>
<span class="p">{</span>
<span class="o">//</span> <span class="n">do</span> <span class="n">something</span> <span class="k">with</span> <span class="o">*</span><span class="n">pkey</span> <span class="ow">and</span> <span class="n">obj</span>
<span class="p">}</span>
</pre></div>
</div>
<p>There is no magic in first/next macros, just iteration through keys and values lists pointers.
For convenient iteration, a list of keys is terminated with NULL, so in the code above <code class="docutils literal notranslate"><span class="pre">*pkey</span> <span class="pre">!=</span> <span class="pre">NULL</span></code>
is used as the loop condition. One may also iterate via indices:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">;</span>
<span class="n">size_t</span> <span class="n">index</span><span class="p">,</span> <span class="n">size</span><span class="p">;</span>
<span class="n">ppname</span> <span class="o">*</span><span class="n">key</span><span class="p">;</span>
<span class="n">ppobj</span> <span class="o">*</span><span class="n">obj</span><span class="p">;</span>
<span class="k">for</span> <span class="p">(</span><span class="n">index</span> <span class="o">=</span> <span class="mi">0</span><span class="p">,</span> <span class="n">size</span> <span class="o">=</span> <span class="n">ppdict_size</span><span class="p">(</span><span class="nb">dict</span><span class="p">);</span> <span class="n">index</span> <span class="o"><</span> <span class="n">size</span><span class="p">;</span> <span class="o">++</span><span class="n">index</span><span class="p">)</span>
<span class="p">{</span>
<span class="n">key</span> <span class="o">=</span> <span class="n">ppdict_key</span><span class="p">(</span><span class="nb">dict</span><span class="p">,</span> <span class="n">index</span><span class="p">);</span>
<span class="n">obj</span> <span class="o">=</span> <span class="n">ppdict_at</span><span class="p">(</span><span class="nb">dict</span><span class="p">,</span> <span class="n">index</span><span class="p">);</span>
<span class="o">//</span> <span class="n">do</span> <span class="n">something</span> <span class="k">with</span> <span class="n">key</span> <span class="ow">and</span> <span class="n">obj</span>
<span class="p">}</span>
</pre></div>
</div>
<p>To get the object associated with a given name, use one of the following:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppobj</span> <span class="o">*</span> <span class="n">ppdict_get_obj</span> <span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">,</span> <span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">name</span><span class="p">);</span>
<span class="nb">int</span> <span class="n">ppdict_get_bool</span> <span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">,</span> <span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">name</span><span class="p">,</span> <span class="nb">int</span> <span class="o">*</span><span class="n">v</span><span class="p">);</span>
<span class="nb">int</span> <span class="n">ppdict_get_int</span> <span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">,</span> <span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">name</span><span class="p">,</span> <span class="n">ppint</span> <span class="o">*</span><span class="n">v</span><span class="p">);</span>
<span class="nb">int</span> <span class="n">ppdict_get_uint</span> <span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">,</span> <span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">name</span><span class="p">,</span> <span class="n">ppuint</span> <span class="o">*</span><span class="n">v</span><span class="p">);</span>
<span class="nb">int</span> <span class="n">ppdict_get_num</span> <span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">,</span> <span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">name</span><span class="p">,</span> <span class="n">ppnum</span> <span class="o">*</span><span class="n">v</span><span class="p">);</span>
<span class="n">ppname</span> <span class="n">ppdict_get_name</span> <span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">,</span> <span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">name</span><span class="p">);</span>
<span class="n">ppstring</span> <span class="n">ppdict_get_string</span> <span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">,</span> <span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">name</span><span class="p">);</span>
<span class="n">pparray</span> <span class="o">*</span> <span class="n">ppdict_get_array</span> <span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">,</span> <span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">name</span><span class="p">);</span>
<span class="n">ppdict</span> <span class="o">*</span> <span class="n">ppdict_get_dict</span> <span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">,</span> <span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">name</span><span class="p">);</span>
<span class="n">ppref</span> <span class="o">*</span> <span class="n">ppdict_get_ref</span> <span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">,</span> <span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">name</span><span class="p">);</span>
</pre></div>
</div>
<p>Note that all getters accepts <code class="docutils literal notranslate"><span class="pre">const</span> <span class="pre">char</span> <span class="pre">*</span></code> as key, so it is ok to say:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppdict_rget_dict</span><span class="p">(</span><span class="nb">dict</span><span class="p">,</span> <span class="s2">"Resources"</span><span class="p">);</span>
</pre></div>
</div>
<p>(the most common use I guess). But to use <code class="docutils literal notranslate"><span class="pre">ppname</span></code> object as a key, one have to
use data member:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppdic_rget_dict</span><span class="p">(</span><span class="nb">dict</span><span class="p">,</span> <span class="n">name</span><span class="o">-></span><span class="n">data</span><span class="p">);</span> <span class="o">//</span> <span class="n">ppname</span> <span class="o">*</span><span class="n">name</span>
</pre></div>
</div>
<p>Every <code class="docutils literal notranslate"><span class="pre">ppdict_get_*</span></code> getter has <code class="docutils literal notranslate"><span class="pre">ppdict_rget_*</span></code> counterpart that dereferences
indirect objects if necessary. Note that there is no <code class="docutils literal notranslate"><span class="pre">ppdict_get_stream()</span></code> function,
but there is:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppstream</span> <span class="o">*</span> <span class="n">ppdict_rget_stream</span> <span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">,</span> <span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">name</span><span class="p">);</span>
</pre></div>
</div>
<p>So far dicts comes with no names mapping, so by-name dict accessors perform a linear search
through the keys list. PDF dicts are usually small.</p>
</div>
<div class="section" id="stream">
<h2>Stream<a class="headerlink" href="#stream" title="Permalink to this headline">¶</a></h2>
<p>PDF streams are represented as <code class="docutils literal notranslate"><span class="pre">ppstream</span></code> objects. To get the stream dict:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppdict</span> <span class="o">*</span> <span class="n">ppstream_dict</span><span class="p">(</span><span class="n">ppstream</span> <span class="o">*</span><span class="n">stream</span><span class="p">)</span> <span class="o">//</span> <span class="n">macro</span>
</pre></div>
</div>
<p>To read the stream data:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">uint8_t</span> <span class="o">*</span> <span class="n">ppstream_first</span> <span class="p">(</span><span class="n">ppstream</span> <span class="o">*</span><span class="n">stream</span><span class="p">,</span> <span class="n">size_t</span> <span class="o">*</span><span class="n">size</span><span class="p">,</span> <span class="nb">int</span> <span class="n">decode</span><span class="p">);</span>
<span class="n">uint8_t</span> <span class="o">*</span> <span class="n">ppstream_next</span> <span class="p">(</span><span class="n">ppstream</span> <span class="o">*</span><span class="n">stream</span><span class="p">,</span> <span class="n">size_t</span> <span class="o">*</span><span class="n">size</span><span class="p">);</span>
<span class="n">void</span> <span class="n">ppstream_done</span> <span class="p">(</span><span class="n">ppstream</span> <span class="o">*</span><span class="n">stream</span><span class="p">);</span>
</pre></div>
</div>
<p>Both <code class="docutils literal notranslate"><span class="pre">first`</span> <span class="pre">and</span> <span class="pre">``next</span></code> functions return a chunk of stream data and sets the <code class="docutils literal notranslate"><span class="pre">size</span></code> of the chunk.
<code class="docutils literal notranslate"><span class="pre">decode</span></code> parameter tell the reader to decompress the stream (1) or return raw (0). A call to <code class="docutils literal notranslate"><span class="pre">ppstream_next()</span></code>
must be preceeded by <code class="docutils literal notranslate"><span class="pre">ppstream_first()</span></code>. Once you’re done with the stream, you have to call <code class="docutils literal notranslate"><span class="pre">ppstream_done()</span></code>,
no matter if the stream has been read to the end or not. The stream data iterator in use:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">uint8_t</span> <span class="o">*</span><span class="n">data</span><span class="p">;</span>
<span class="n">size_t</span> <span class="n">size</span><span class="p">;</span>
<span class="n">ppstream</span> <span class="o">*</span><span class="n">stream</span><span class="p">;</span>
<span class="nb">int</span> <span class="n">decode</span> <span class="o">=</span> <span class="mi">1</span><span class="p">;</span> <span class="o">//</span> <span class="mi">1</span> <span class="o">-</span> <span class="n">get</span> <span class="n">decompressed</span><span class="p">,</span> <span class="mi">0</span> <span class="o">-</span> <span class="n">get</span> <span class="n">raw</span>
<span class="k">for</span> <span class="p">(</span><span class="n">data</span> <span class="o">=</span> <span class="n">ppstream_first</span><span class="p">(</span><span class="n">stream</span><span class="p">,</span> <span class="o">&</span><span class="n">size</span><span class="p">,</span> <span class="n">decode</span><span class="p">);</span> <span class="n">data</span> <span class="o">!=</span> <span class="n">NULL</span><span class="p">;</span> <span class="n">data</span> <span class="o">=</span> <span class="n">ppstream_next</span><span class="p">(</span><span class="n">stream</span><span class="p">,</span> <span class="o">&</span><span class="n">size</span><span class="p">))</span>
<span class="p">{</span>
<span class="o">//</span> <span class="n">do</span> <span class="n">something</span> <span class="k">with</span> <span class="n">data</span> <span class="ow">and</span> <span class="n">its</span> <span class="n">size</span>
<span class="p">}</span>
<span class="n">ppstream_done</span><span class="p">(</span><span class="n">stream</span><span class="p">);</span>
</pre></div>
</div>
<p>Every subsequent iterator call invalidates the previous reader output, so you have to utilize the returned chunk
of data just after you ot that. So the following is wrong:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">data1</span> <span class="o">=</span> <span class="n">ppstream_first</span><span class="p">(</span><span class="n">stream</span><span class="p">,</span> <span class="o">&</span><span class="n">size</span><span class="p">,</span> <span class="mi">1</span><span class="p">);</span>
<span class="n">data2</span> <span class="o">=</span> <span class="n">ppstream_next</span><span class="p">(</span><span class="n">stream</span><span class="p">,</span> <span class="o">&</span><span class="n">size</span><span class="p">);</span>
<span class="n">data3</span> <span class="o">=</span> <span class="n">ppstream_next</span><span class="p">(</span><span class="n">stream</span><span class="p">,</span> <span class="o">&</span><span class="n">size</span><span class="p">);</span>
<span class="n">some_output</span><span class="p">(</span><span class="n">data1</span><span class="p">,</span> <span class="n">size</span><span class="p">);</span>
<span class="n">some_output</span><span class="p">(</span><span class="n">data2</span><span class="p">,</span> <span class="n">size</span><span class="p">);</span>
</pre></div>
</div>
<p>The reader calls usually return the same pointer to internal buffer, just filled with a different data.
<code class="docutils literal notranslate"><span class="pre">pplib</span></code> allocates reasonably large buffer and fills that buffer on subsequent calls to the reader.</p>
<p>If the source stream has no compression, using both <code class="docutils literal notranslate"><span class="pre">decode</span> <span class="pre">==</span> <span class="pre">1</span></code> and <code class="docutils literal notranslate"><span class="pre">decode</span> <span class="pre">==</span> <span class="pre">0</span></code> should give the same result.
You can check if the stream is actually compressed with:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppstream_compressed</span><span class="p">(</span><span class="n">stream</span><span class="p">)</span> <span class="o">//</span> <span class="n">macro</span><span class="p">,</span> <span class="n">returns</span> <span class="n">non</span> <span class="n">zero</span> <span class="k">if</span> <span class="o">/</span><span class="n">Filter</span> <span class="ow">is</span> <span class="n">present</span>
</pre></div>
</div>
<p>It might be necessary to load the entire stream data at once:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">uint8_t</span> <span class="o">*</span> <span class="n">ppstream_all</span> <span class="p">(</span><span class="n">ppstream</span> <span class="o">*</span><span class="n">stream</span><span class="p">,</span> <span class="n">size_t</span> <span class="o">*</span><span class="n">size</span><span class="p">,</span> <span class="nb">int</span> <span class="n">decode</span><span class="p">);</span>
</pre></div>
</div>
<p>If the initial buffer size is insufficient, it grows until the entire stream data is loaded. You must call
<code class="docutils literal notranslate"><span class="pre">ppstream_done(stream)</span></code> after using returned data.</p>
<p><code class="docutils literal notranslate"><span class="pre">ppstream_done()</span></code> doesn’t invalidate the stream object, it just closes its internal reader.
The stream itself remains a valid object (eg. one can read it again if necessary),
but the reader buffer is released. It is actually not freed but kept for future the reuse with that on some other stream,
but you still need to mark it ready for reuse to avoid allocating a separate buffer for every stream you’re going to read.</p>
<p>Stream data readers will return <code class="docutils literal notranslate"><span class="pre">NULL</span></code> if you haven’t close the previous reader process with <code class="docutils literal notranslate"><span class="pre">ppstream_done()</span></code>. All below is wrong:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">data1</span> <span class="o">=</span> <span class="n">ppstream_all</span><span class="p">(</span><span class="n">stream</span><span class="p">,</span> <span class="o">&</span><span class="n">size</span><span class="p">,</span> <span class="mi">1</span><span class="p">);</span>
<span class="n">data2</span> <span class="o">=</span> <span class="n">ppstream_all</span><span class="p">(</span><span class="n">stream</span><span class="p">,</span> <span class="o">&</span><span class="n">size</span><span class="p">,</span> <span class="mi">1</span><span class="p">);</span> <span class="o">//</span> <span class="n">data2</span> <span class="o">==</span> <span class="n">NULL</span>
<span class="o">//</span> <span class="ow">or</span>
<span class="n">data1</span> <span class="o">=</span> <span class="n">ppstream_first</span><span class="p">(</span><span class="n">stream</span><span class="p">,</span> <span class="o">&</span><span class="n">size</span><span class="p">,</span> <span class="mi">1</span><span class="p">);</span>
<span class="n">data2</span> <span class="o">=</span> <span class="n">ppstream_first</span><span class="p">(</span><span class="n">stream</span><span class="p">,</span> <span class="o">&</span><span class="n">size</span><span class="p">,</span> <span class="mi">1</span><span class="p">);</span> <span class="o">//</span> <span class="n">data2</span> <span class="o">==</span> <span class="n">NULL</span>
<span class="o">//</span> <span class="ow">or</span>
<span class="n">data1</span> <span class="o">=</span> <span class="n">ppstream_first</span><span class="p">(</span><span class="n">stream</span><span class="p">,</span> <span class="o">&</span><span class="n">size</span><span class="p">,</span> <span class="mi">1</span><span class="p">);</span>
<span class="n">data2</span> <span class="o">=</span> <span class="n">ppstream_all</span><span class="p">(</span><span class="n">stream</span><span class="p">,</span> <span class="o">&</span><span class="n">size</span><span class="p">,</span> <span class="mi">1</span><span class="p">);</span> <span class="o">//</span> <span class="n">data2</span> <span class="o">==</span> <span class="n">NULL</span>
</pre></div>
</div>
<p>To avoid unnecessary dependencies, <code class="docutils literal notranslate"><span class="pre">pplib</span></code> does not support image filters (<code class="docutils literal notranslate"><span class="pre">/DCT</span></code>, <code class="docutils literal notranslate"><span class="pre">/JPX</span></code>, <code class="docutils literal notranslate"><span class="pre">/JBIG</span></code>, <code class="docutils literal notranslate"><span class="pre">/CCITT</span></code>).
But it is ok to read the stream with <code class="docutils literal notranslate"><span class="pre">decode</span></code> set to 1 on such streams. <code class="docutils literal notranslate"><span class="pre">pplib</span></code> assumes that the image is the
final/target stream form and just returns it as-is. Eg. in the case of JPEG (<code class="docutils literal notranslate"><span class="pre">/DCT</span></code> filtered) image both calls should
give the same results:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppstream_all</span><span class="p">(</span><span class="n">jpegstream</span><span class="p">,</span> <span class="o">&</span><span class="n">jpegsize</span><span class="p">,</span> <span class="mi">0</span><span class="p">);</span> <span class="o">//</span> <span class="n">don</span><span class="s1">'t decode, return what'</span><span class="n">s</span> <span class="n">there</span>
<span class="n">ppstream_all</span><span class="p">(</span><span class="n">jpegstream</span><span class="p">,</span> <span class="o">&</span><span class="n">jpegsize</span><span class="p">,</span> <span class="mi">1</span><span class="p">);</span> <span class="o">//</span> <span class="n">decode</span> <span class="n">but</span> <span class="n">found</span> <span class="n">image</span> <span class="nb">filter</span><span class="p">,</span> <span class="n">effectively</span> <span class="n">the</span> <span class="n">same</span>
</pre></div>
</div>
<p>A bit more about streams memory. As mentioned, <code class="docutils literal notranslate"><span class="pre">pplib</span></code> allocates buffers for stream readers. After <code class="docutils literal notranslate"><span class="pre">ppstream_done()</span></code>,
the stream no longer <em>owns</em> the buffer space. But the buffer may remain allocated, to be reused with future readers.
<code class="docutils literal notranslate"><span class="pre">pplib</span></code> keeps a pool of several buffers. This means, that when you use stream readers, <code class="docutils literal notranslate"><span class="pre">pplib</span></code> eats
some memory (1MB or so) that is not freed, even if no streams are used. And even if you free all objects.
If you suffer from this, you can optionally use a pair of functions:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">void</span> <span class="n">ppstream_init_buffers</span> <span class="p">(</span><span class="n">void</span><span class="p">);</span>
<span class="n">void</span> <span class="n">ppstream_free_buffers</span> <span class="p">(</span><span class="n">void</span><span class="p">);</span>
</pre></div>
</div>
<p>The first initializes buffers pool, unless done so far. Currently <code class="docutils literal notranslate"><span class="pre">pplib</span></code> cares of it before opening every stream reader,
so it is not obligatory. The second frees a pool of buffers. The intended use is to call <code class="docutils literal notranslate"><span class="pre">ppstream_init_buffers()</span></code> once
as kind of library initializer and to call <code class="docutils literal notranslate"><span class="pre">ppstream_free_buffers()</span></code> once, as the library finalizer.</p>
</div>
<div class="section" id="filters">
<h2>Filters<a class="headerlink" href="#filters" title="Permalink to this headline">¶</a></h2>
<p><code class="docutils literal notranslate"><span class="pre">ppstream</span></code> knows its filter(s) and keps it as <code class="docutils literal notranslate"><span class="pre">stream->filter</span></code>:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="o">//</span> <span class="n">ppstream</span> <span class="o">*</span><span class="n">stream</span><span class="p">;</span>
<span class="n">ppstream_filter</span> <span class="o">*</span><span class="n">info</span> <span class="o">=</span> <span class="o">&</span><span class="n">stream</span><span class="o">-></span><span class="nb">filter</span><span class="p">;</span>
</pre></div>
</div>
<p><code class="docutils literal notranslate"><span class="pre">ppstream_filter</span></code> is the following structure:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">typedef</span> <span class="n">struct</span> <span class="p">{</span>
<span class="n">ppstreamtp</span> <span class="o">*</span><span class="n">filters</span><span class="p">;</span> <span class="o">//</span> <span class="n">c</span><span class="o">-</span><span class="n">array</span> <span class="n">of</span> <span class="nb">filter</span> <span class="n">identifiers</span> <span class="p">(</span><span class="n">enum</span> <span class="n">integers</span><span class="p">)</span>
<span class="n">ppdict</span> <span class="o">**</span><span class="n">params</span><span class="p">;</span> <span class="o">//</span> <span class="n">c</span><span class="o">-</span><span class="n">array</span> <span class="n">of</span> <span class="n">ppdict</span> <span class="n">pointers</span>
<span class="n">size_t</span> <span class="n">count</span><span class="p">;</span> <span class="o">//</span> <span class="n">number</span> <span class="n">of</span> <span class="n">filters</span><span class="p">,</span> <span class="n">length</span> <span class="n">of</span> <span class="n">the</span> <span class="n">arrays</span> <span class="p">(</span><span class="n">typically</span> <span class="mi">1</span><span class="p">)</span>
<span class="p">}</span> <span class="n">ppstream_filter</span><span class="p">;</span>
</pre></div>
</div>
<p>If <code class="docutils literal notranslate"><span class="pre">count</span> <span class="pre">></span> <span class="pre">0</span></code> then <code class="docutils literal notranslate"><span class="pre">filters</span></code> member is not NULL. Filters array keeps integer constants:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">PPSTREAM_BASE16</span> <span class="o">/*</span> <span class="o">/</span><span class="n">ASCIIHexDecode</span> <span class="o">*/</span>
<span class="n">PPSTREAM_BASE85</span> <span class="o">/*</span> <span class="o">/</span><span class="n">ASCII85Decode</span> <span class="o">*/</span>
<span class="n">PPSTREAM_RUNLENGTH</span> <span class="o">/*</span> <span class="o">/</span><span class="n">RunLengthDecode</span> <span class="o">*/</span>
<span class="n">PPSTREAM_FLATE</span> <span class="o">/*</span> <span class="o">/</span><span class="n">FlateDecode</span> <span class="o">*/</span>
<span class="n">PPSTREAM_LZW</span> <span class="o">/*</span> <span class="o">/</span><span class="n">LZWDecode</span> <span class="o">*/</span>
<span class="n">PPSTREAM_CCITT</span> <span class="o">/*</span> <span class="o">/</span><span class="n">CCITTFaxDecode</span> <span class="o">*/</span>
<span class="n">PPSTREAM_DCT</span> <span class="o">/*</span> <span class="o">/</span><span class="n">DCTDecode</span> <span class="o">*/</span>
<span class="n">PPSTREAM_JBIG2</span> <span class="o">/*</span> <span class="o">/</span><span class="n">JBIG2Decode</span> <span class="o">*/</span>
<span class="n">PPSTREAM_JPX</span> <span class="o">/*</span> <span class="o">/</span><span class="n">JPXDecode</span> <span class="o">*/</span>
<span class="n">PPSTREAM_CRYPT</span> <span class="o">/*</span> <span class="o">/</span><span class="n">Crypt</span> <span class="o">*/</span>
</pre></div>
</div>
<p>Params array keeps corresponding filter parameters (<code class="docutils literal notranslate"><span class="pre">/DecodeParms</span></code>) if present. <code class="docutils literal notranslate"><span class="pre">params</span></code> member is not NULL
if <code class="docutils literal notranslate"><span class="pre">count</span> <span class="pre">></span> <span class="pre">0</span></code> and the stream dict has <code class="docutils literal notranslate"><span class="pre">/DecodeParms</span></code> entry. Even if <code class="docutils literal notranslate"><span class="pre">params</span></code> is there,
for every N-th filter, <code class="docutils literal notranslate"><span class="pre">params[N]</span></code> may be NULL (corresponding to PDF <code class="docutils literal notranslate"><span class="pre">null</span></code>).</p>
<p><code class="docutils literal notranslate"><span class="pre">stream->filter</span></code> keeps the source stream filter information, which may not correspond to the result of stream readers
(<code class="docutils literal notranslate"><span class="pre">ppstream_first()</span></code>, <code class="docutils literal notranslate"><span class="pre">ppstream_next()</span></code>, <code class="docutils literal notranslate"><span class="pre">ppstream_all()</span></code>). The get the filters info relevant to the result from readers:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">void</span> <span class="n">ppstream_filter_info</span> <span class="p">(</span><span class="n">ppstream</span> <span class="o">*</span><span class="n">stream</span><span class="p">,</span> <span class="n">ppstream_filter</span> <span class="o">*</span><span class="n">info</span><span class="p">,</span> <span class="nb">int</span> <span class="n">decode</span><span class="p">);</span>
</pre></div>
</div>
<p>The function fills <code class="docutils literal notranslate"><span class="pre">ppstream_filter</span></code> structure according to the expected result from stream readers (example 3 shows
how to use it to reconstruct <code class="docutils literal notranslate"><span class="pre">/Filter</span></code> and <code class="docutils literal notranslate"><span class="pre">/DecodeParms</span></code> when copying the stream to some other PDF).</p>
<p>To convert filter identifier (<code class="docutils literal notranslate"><span class="pre">ppstreamtp</span></code>) to a corresponding PDF filter name:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">const</span> <span class="n">char</span> <span class="o">*</span> <span class="n">ppstream_filter_name</span><span class="p">[];</span>
</pre></div>
</div>
<p>To covert <code class="docutils literal notranslate"><span class="pre">ppname</span></code> to filter identifier:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="nb">int</span> <span class="n">ppstream_filter_type</span> <span class="p">(</span><span class="n">ppname</span> <span class="n">filtername</span><span class="p">,</span> <span class="n">ppstreamtp</span> <span class="o">*</span><span class="n">filtertype</span><span class="p">);</span>
<span class="o">//</span> <span class="n">returns</span> <span class="mi">1</span> <span class="ow">and</span> <span class="n">sets</span> <span class="n">filtertype</span> <span class="k">if</span> <span class="n">filtername</span> <span class="ow">is</span> <span class="n">the</span> <span class="n">proper</span> <span class="nb">filter</span> <span class="n">name</span>
</pre></div>
</div>
<p>Additional information about the stream can be fetched from macros:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppstream_compressed</span><span class="p">(</span><span class="n">stream</span><span class="p">)</span> <span class="o">/*</span> <span class="n">stream</span><span class="o">-></span><span class="n">flags</span> <span class="o">&</span> <span class="p">(</span><span class="n">PPSTREAM_FILTER</span><span class="o">|</span><span class="n">PPSTREAM_IMAGE</span><span class="p">)</span> <span class="o">*/</span>
<span class="n">ppstream_filtered</span><span class="p">(</span><span class="n">stream</span><span class="p">)</span> <span class="o">/*</span> <span class="n">stream</span><span class="o">-></span><span class="n">flags</span> <span class="o">&</span> <span class="n">PPSTREAM_FILTER</span> <span class="o">*/</span>
<span class="n">ppstream_image</span><span class="p">(</span><span class="n">stream</span><span class="p">)</span> <span class="o">/*</span> <span class="n">stream</span><span class="o">-></span><span class="n">flags</span> <span class="o">*</span> <span class="n">PPSTREAM_IMAGE</span> <span class="o">*/</span>
</pre></div>
</div>
<p><code class="docutils literal notranslate"><span class="pre">stream->flags</span></code> is a binary sum of the following:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">PPSTREAM_FILTER</span> <span class="o">/*</span> <span class="nb">set</span> <span class="n">iff</span> <span class="n">the</span> <span class="n">stream</span> <span class="n">filters</span> <span class="nb">list</span> <span class="n">has</span> <span class="n">one</span> <span class="n">of</span><span class="p">:</span> <span class="n">BASE16</span><span class="p">,</span> <span class="n">BASE85</span><span class="p">,</span> <span class="n">RUNLENGTH</span><span class="p">,</span> <span class="n">FLATE</span><span class="p">,</span> <span class="n">LZW</span> <span class="o">*/</span>
<span class="n">PPSTREAM_IMAGE</span> <span class="o">/*</span> <span class="nb">set</span> <span class="n">iff</span> <span class="n">the</span> <span class="n">stream</span> <span class="n">filters</span> <span class="nb">list</span> <span class="n">has</span> <span class="n">one</span> <span class="n">of</span><span class="p">:</span> <span class="n">CCITT</span><span class="p">,</span> <span class="n">DCT</span><span class="p">,</span> <span class="n">JBIG2</span><span class="p">,</span> <span class="n">JPX</span> <span class="o">*/</span>
<span class="n">PPSTREAM_ENCRYPTED</span> <span class="o">/*</span> <span class="nb">set</span> <span class="n">iff</span> <span class="n">the</span> <span class="n">stream</span> <span class="ow">is</span> <span class="n">encrypted</span> <span class="o">*/</span>
<span class="n">PPSTREAM_ENCRYPTED_OWN</span> <span class="o">/*</span> <span class="nb">set</span> <span class="n">iff</span> <span class="n">the</span> <span class="n">stream</span> <span class="n">has</span> <span class="n">own</span> <span class="n">CRYPT</span> <span class="nb">filter</span> <span class="o">*/</span>
</pre></div>
</div>
<p>Note that <code class="docutils literal notranslate"><span class="pre">PPSTREAM_COMPRESSED</span></code> is not there any longer, use <code class="docutils literal notranslate"><span class="pre">ppstream_compressed()</span></code> instead.
And there is some more, see <code class="docutils literal notranslate"><span class="pre">ppapi.h</span></code>.</p>
</div>
<div class="section" id="ref">
<h2>Ref<a class="headerlink" href="#ref" title="Permalink to this headline">¶</a></h2>
<p>Indirect objects are represented as <code class="docutils literal notranslate"><span class="pre">ppref</span></code> structure. To get the object that the
reference refers to:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppobj</span> <span class="o">*</span> <span class="n">ppref_obj</span><span class="p">(</span><span class="n">ppref</span> <span class="o">*</span><span class="n">ref</span><span class="p">)</span> <span class="o">//</span> <span class="n">macro</span>
</pre></div>
</div>
<p><code class="docutils literal notranslate"><span class="pre">ppref</span></code> structure also keeps the reference number and version, a pointer to cross reference table it belongs
to and others, but I guess you won’t need anything but the referenced object. <code class="docutils literal notranslate"><span class="pre">pplib</span></code> parser resolves references
on-fly. So if there is a dict with indirect objects:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="o"><<</span>
<span class="o">/</span><span class="n">Type</span> <span class="o">/</span><span class="n">Page</span>
<span class="o">/</span><span class="n">Resources</span> <span class="mi">123</span> <span class="mi">0</span> <span class="n">R</span>
<span class="o">...</span>
<span class="o">>></span>
</pre></div>
</div>
<p>the parser will produce <code class="docutils literal notranslate"><span class="pre">ppdict</span></code> with <code class="docutils literal notranslate"><span class="pre">Resources</span></code> key pointing the proper <code class="docutils literal notranslate"><span class="pre">ppref</span> <span class="pre">*</span></code> value.
If you need more, access <code class="docutils literal notranslate"><span class="pre">ppref</span></code> members:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">struct</span> <span class="n">ppref</span> <span class="p">{</span>
<span class="n">ppobj</span> <span class="nb">object</span><span class="p">;</span> <span class="o">//</span> <span class="n">target</span> <span class="nb">object</span>
<span class="n">ppuint</span> <span class="n">number</span><span class="p">,</span> <span class="n">version</span><span class="p">;</span> <span class="o">//</span> <span class="n">identifiers</span>
<span class="n">size_t</span> <span class="n">offset</span><span class="p">;</span> <span class="o">//</span> <span class="n">file</span> <span class="n">offset</span> <span class="p">(</span><span class="n">useless</span> <span class="k">for</span> <span class="n">you</span><span class="p">,</span> <span class="n">may</span> <span class="n">be</span> <span class="n">zero</span> <span class="k">for</span> <span class="n">compressed</span> <span class="n">objects</span><span class="p">)</span>
<span class="n">ppuint</span> <span class="n">length</span><span class="p">;</span> <span class="o">//</span> <span class="n">the</span> <span class="n">length</span> <span class="n">of</span> <span class="n">the</span> <span class="n">original</span> <span class="nb">object</span> <span class="n">data</span>
<span class="n">ppxref</span> <span class="o">*</span><span class="n">xref</span><span class="p">;</span> <span class="o">//</span> <span class="n">cross</span> <span class="n">reference</span> <span class="n">table</span> <span class="n">it</span> <span class="n">belongs</span> <span class="n">to</span>
<span class="p">};</span>
</pre></div>
</div>
</div>
<div class="section" id="xref">
<h2>XRef<a class="headerlink" href="#xref" title="Permalink to this headline">¶</a></h2>
<p>Cross reference table is exposed as <code class="docutils literal notranslate"><span class="pre">ppxref</span></code> (incomplete type, you can only oprate on its pointer).
To get top document xref:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppxref</span> <span class="o">*</span> <span class="n">ppdoc_xref</span> <span class="p">(</span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">);</span>
</pre></div>
</div>
<p>To get previous (older) xref:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppxref</span> <span class="o">*</span> <span class="n">ppxref_prev</span> <span class="p">(</span><span class="n">ppxref</span> <span class="o">*</span><span class="n">xref</span><span class="p">);</span>
</pre></div>
</div>
<p>To find an object of a given refnumber:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppref</span> <span class="o">*</span> <span class="n">ppxref_find</span> <span class="p">(</span><span class="n">ppxref</span> <span class="o">*</span><span class="n">xref</span><span class="p">,</span> <span class="n">ppuint</span> <span class="n">refnumber</span><span class="p">);</span>
</pre></div>
</div>
<p>[Note: since pplib v0.98 in case of documents with incremental update, <code class="docutils literal notranslate"><span class="pre">ppxref_find()</span></code> returns
the newest available version of a given object rather than the object in a given body.]</p>
</div>
<div class="section" id="pdf">
<h2>PDF<a class="headerlink" href="#pdf" title="Permalink to this headline">¶</a></h2>
<p>PDF document is represented as <code class="docutils literal notranslate"><span class="pre">ppdoc</span></code> structure (incomplete type, you can only operate on its pointer).
To load a document from file:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppdoc</span> <span class="o">*</span> <span class="n">ppdoc_load</span> <span class="p">(</span><span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">filename</span><span class="p">);</span>
</pre></div>
</div>
<p>To load a document from file handle:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppdoc</span> <span class="o">*</span> <span class="n">ppdoc_filehandle</span> <span class="p">(</span><span class="n">FILE</span> <span class="o">*</span><span class="n">file</span><span class="p">,</span> <span class="nb">int</span> <span class="n">closefile</span><span class="p">);</span> <span class="o">//</span> <span class="n">closefile</span> <span class="mi">1</span> <span class="n">to</span> <span class="n">fclose</span><span class="p">()</span> <span class="n">on</span> <span class="n">end</span>
</pre></div>
</div>
<p>To load a document from memory data:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppdoc</span> <span class="o">*</span> <span class="n">ppdoc_mem</span> <span class="p">(</span><span class="n">const</span> <span class="n">void</span> <span class="o">*</span><span class="n">data</span><span class="p">,</span> <span class="n">size_t</span> <span class="n">size</span><span class="p">);</span>
</pre></div>
</div>
<p>The data is assumed to be a buffer allocated with <code class="docutils literal notranslate"><span class="pre">malloc</span></code> - it is freed when destroying <code class="docutils literal notranslate"><span class="pre">ppdoc</span></code>.</p>
<p>Both loaders returns <code class="docutils literal notranslate"><span class="pre">NULL</span></code> on failure.</p>
<p>To free <code class="docutils literal notranslate"><span class="pre">ppdoc</span></code> and all objects it refers to:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">void</span> <span class="n">ppdoc_free</span> <span class="p">(</span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">);</span>
</pre></div>
</div>
<p>So far we haven’t mention about any explicit object reclaimers. There are no dedicated <code class="docutils literal notranslate"><span class="pre">free</span></code> functions
for other objects. You don’t allocate or free objects yourself. <code class="docutils literal notranslate"><span class="pre">ppdoc</span></code> object is an owner of all
beings it refers to. It also means that every object described so far is alive as long as the containing
<code class="docutils literal notranslate"><span class="pre">ppdoc</span></code> is alive.</p>
<p>To access main PDF dicts:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppdict</span> <span class="o">*</span> <span class="n">ppdoc_trailer</span><span class="p">(</span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">);</span> <span class="o">//</span> <span class="n">returns</span> <span class="n">top</span> <span class="n">xref</span> <span class="n">trailer</span> <span class="nb">dict</span>
<span class="n">ppdict</span> <span class="o">*</span> <span class="n">ppdoc_catalog</span><span class="p">(</span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">);</span> <span class="o">//</span> <span class="n">returns</span> <span class="n">catalog</span> <span class="n">referred</span> <span class="kn">from</span> <span class="nn">the</span> <span class="n">trailer</span>
<span class="n">ppdict</span> <span class="o">*</span> <span class="n">ppdoc_info</span><span class="p">(</span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">);</span> <span class="o">//</span> <span class="n">returns</span> <span class="n">info</span> <span class="nb">dict</span> <span class="n">referred</span> <span class="kn">from</span> <span class="nn">the</span> <span class="n">trailer</span>
</pre></div>
</div>
<p>To get the PDF version:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">const</span> <span class="n">char</span> <span class="o">*</span> <span class="n">ppdoc_version_string</span> <span class="p">(</span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">);</span> <span class="o">//</span> <span class="n">version</span> <span class="n">string</span>
<span class="nb">int</span> <span class="n">ppdoc_version_number</span> <span class="p">(</span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">,</span> <span class="nb">int</span> <span class="o">*</span><span class="n">minor</span><span class="p">);</span> <span class="o">//</span> <span class="n">minor</span> <span class="ow">and</span> <span class="n">major</span> <span class="n">numbers</span>
</pre></div>
</div>
<p>To get the file size of the source PDF document:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">size_t</span> <span class="n">ppdoc_file_size</span> <span class="p">(</span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">);</span>
</pre></div>
</div>
<p>To get the number of objects in all xrefs:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppuint</span> <span class="n">ppdoc_objects</span> <span class="p">(</span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">);</span>
</pre></div>
</div>
<p>To get the approx usage of memory:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">size_t</span> <span class="n">ppdoc_memory</span> <span class="p">(</span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">,</span> <span class="n">size_t</span> <span class="o">*</span><span class="n">waste</span><span class="p">);</span>
</pre></div>
</div>
</div>
<div class="section" id="encryption">
<h2>Encryption<a class="headerlink" href="#encryption" title="Permalink to this headline">¶</a></h2>
<p><code class="docutils literal notranslate"><span class="pre">pplib</span></code> handles encrypted (password protected) documents. If a document is encrypted, most of strings and streams are ciphered.
In that form they are unreadable and rather useless, you can’t even rewrite such strings/streams as-is to a different PDF output.
It is a common practise to <em>protect</em> documents with an empty password. Such documents remain readable in Acrobat (just opens them without prompting
for a password), but some features (eg. printing) may restricted by the application.</p>
<p>When <code class="docutils literal notranslate"><span class="pre">pplib</span></code> detects encryption, it follows Acrobat approach and first tries an empty password. If it succeeds, <code class="docutils literal notranslate"><span class="pre">pplib</span></code> proceeeds normally, providing
an access to decrypted strings and streams, as if they weren’t ciphered. If the document is protected with non-empty password, you have to call
<code class="docutils literal notranslate"><span class="pre">ppdoc_crypt_pass()</span></code>. Until you provide a password, <code class="docutils literal notranslate"><span class="pre">ppdoc</span></code> object returned by <code class="docutils literal notranslate"><span class="pre">ppdoc_load()</span></code> function has all object entries set to <code class="docutils literal notranslate"><span class="pre">null</span></code>.</p>
<p>Once the document is loaded, encryption status can be checked with:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppcrypt_status</span> <span class="n">ppdoc_crypt_status</span> <span class="p">(</span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">);</span>
</pre></div>
</div>
<p><code class="docutils literal notranslate"><span class="pre">ppcrypt_status</span></code> (enum) may have the following values:</p>
<blockquote>
<div><code class="docutils literal notranslate"><span class="pre">PPCRYPT_NONE</span></code> - no encryption, go ahead
<code class="docutils literal notranslate"><span class="pre">PPCRYPT_DONE</span></code> - encryption present but password succeeded, go ahead
<code class="docutils literal notranslate"><span class="pre">PPCRYPT_PASS</span></code> - encryption present, need non-empty password
<code class="docutils literal notranslate"><span class="pre">PPCRYPT_FAIL</span></code> - invalid or unsupported encryption (eg. undocumented in pdf spec)</div></blockquote>
<p>If a password is needed, you can provide one with:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppcrypt_status</span> <span class="n">ppdoc_crypt_pass</span> <span class="p">(</span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">,</span> <span class="n">const</span> <span class="n">void</span> <span class="o">*</span><span class="n">userpass</span><span class="p">,</span> <span class="n">size_t</span> <span class="n">userpasslength</span><span class="p">,</span>
<span class="n">const</span> <span class="n">void</span> <span class="o">*</span><span class="n">ownerpass</span><span class="p">,</span> <span class="n">size_t</span> <span class="n">ownerpasslength</span><span class="p">);</span>
</pre></div>
</div>
<p>Providing one of two is enough to decrypt the document.
It is ok to use the same password for owner and user – <code class="docutils literal notranslate"><span class="pre">pplib</span></code> will try both.</p>
<p>The function returns <code class="docutils literal notranslate"><span class="pre">PPCRYPT_DONE</span></code> if the password succeeds and the previous crypt status otherwise.</p>
<p>Your custom loader function may look like that:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">;</span>
<span class="n">pdf</span> <span class="o">=</span> <span class="n">ppdoc_load</span><span class="p">(</span><span class="s2">"file.pdf"</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="n">pdf</span> <span class="o">==</span> <span class="n">NULL</span><span class="p">)</span>
<span class="k">return</span> <span class="n">NULL</span><span class="p">;</span>
<span class="n">switch</span> <span class="p">(</span><span class="n">ppdoc_crypt_status</span><span class="p">(</span><span class="n">pdf</span><span class="p">))</span>
<span class="p">{</span>
<span class="n">case</span> <span class="n">PPCRYPT_NONE</span><span class="p">:</span>
<span class="n">case</span> <span class="n">PPCRYPT_DONE</span><span class="p">:</span>
<span class="k">return</span> <span class="n">pdf</span><span class="p">;</span>
<span class="n">case</span> <span class="n">PPCRYPT_PASS</span><span class="p">:</span>
<span class="k">if</span> <span class="p">(</span><span class="n">ppdoc_crypt_pass</span><span class="p">(</span><span class="n">pdf</span><span class="p">,</span> <span class="s2">"dummy"</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="s2">"dummy"</span><span class="p">,</span> <span class="mi">5</span><span class="p">)</span> <span class="o">==</span> <span class="n">PPCRYPT_DONE</span><span class="p">)</span>
<span class="k">return</span> <span class="n">pdf</span><span class="p">;</span>
<span class="n">printf</span><span class="p">(</span><span class="s2">"sorry, password needed</span><span class="se">\n</span><span class="s2">"</span><span class="p">);</span>
<span class="n">ppdoc_free</span><span class="p">(</span><span class="n">pdf</span><span class="p">);</span>
<span class="k">return</span> <span class="n">NULL</span><span class="p">;</span>
<span class="n">case</span> <span class="n">PPCRYPT_FAIL</span><span class="p">:</span>
<span class="n">printf</span><span class="p">(</span><span class="s2">"sorry, encryption failed</span><span class="se">\n</span><span class="s2">"</span><span class="p">);</span>
<span class="n">ppdoc_free</span><span class="p">(</span><span class="n">pdf</span><span class="p">);</span>
<span class="k">return</span> <span class="n">NULL</span><span class="p">;</span>
<span class="p">}</span>
</pre></div>
</div>
<p>See <code class="docutils literal notranslate"><span class="pre">pplib</span></code> tests suite for a complete code.</p>
<p>If you’d like to know what permissions are given/restricted to encrypted document:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppint</span> <span class="n">ppdoc_permissions</span> <span class="p">(</span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">);</span>
</pre></div>
</div>
<p>Returned value can be queried with the following binary flags (you can verify with Acrobat <em>File -> Properties -> Security</em> tab):</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">PPDOC_ALLOW_PRINT</span> <span class="o">//</span> <span class="n">printing</span>
<span class="n">PPDOC_ALLOW_MODIFY</span> <span class="o">//</span> <span class="n">filling</span> <span class="n">form</span> <span class="n">fields</span><span class="p">,</span> <span class="n">signing</span><span class="p">,</span> <span class="n">creating</span> <span class="n">template</span> <span class="n">pages</span>
<span class="n">PPDOC_ALLOW_COPY</span> <span class="o">//</span> <span class="n">copying</span><span class="p">,</span> <span class="n">copying</span> <span class="k">for</span> <span class="n">accessibility</span>
<span class="n">PPDOC_ALLOW_ANNOTS</span> <span class="o">//</span> <span class="n">filling</span> <span class="n">form</span> <span class="n">fields</span><span class="p">,</span> <span class="n">copying</span><span class="p">,</span> <span class="n">signing</span>
<span class="n">PPDOC_ALLOW_EXTRACT</span> <span class="o">//</span> <span class="n">contents</span> <span class="n">copying</span> <span class="k">for</span> <span class="n">accessibility</span>
<span class="n">PPDOC_ALLOW_ASSEMBLY</span> <span class="o">//</span> <span class="p">(</span><span class="n">no</span> <span class="n">effect</span><span class="p">)</span>
<span class="n">PPDOC_ALLOW_PRINT_HIRES</span> <span class="o">//</span> <span class="p">(</span><span class="n">no</span> <span class="n">effect</span><span class="p">)</span>
</pre></div>
</div>
<p><code class="docutils literal notranslate"><span class="pre">pplib</span></code> does absolutelly nothing with permissions, it cares only to decrypt the document. As mentioned, encryption applies to strings
and streams. <code class="docutils literal notranslate"><span class="pre">pplib</span></code> decrypt strings when parsing document objects, so the result you get is <em>normal</em> (not ciphered).
Streams are decrypted whenever you access them. Even if you ask for a raw stream data, you’ll get a raw (compressed) stream, but decrypted.
So except the check to <code class="docutils literal notranslate"><span class="pre">ppdoc_crypt_status()</span></code>, you shouldn’t bother about encryption.</p>
<p>In encrypted documents most of streams are encrypted. To check if a given stream is encrypted:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppstream_encrypted</span><span class="p">(</span><span class="n">stream</span><span class="p">)</span> <span class="o">//</span> <span class="n">macro</span><span class="p">,</span> <span class="n">returns</span> <span class="n">non</span><span class="o">-</span><span class="n">zero</span> <span class="k">if</span> <span class="n">encrypted</span>
</pre></div>
</div>
<p>Encryption is independent from compression, don’t confuse with <code class="docutils literal notranslate"><span class="pre">ppstream_compressed()</span></code></p>
<div class="admonition caution">
<p class="first admonition-title">Caution</p>
<p class="last">Starting from <code class="docutils literal notranslate"><span class="pre">pplib</span> <span class="pre">v2.10</span></code> all passwords should be passed as <code class="docutils literal notranslate"><span class="pre">UTF-8</span></code>.
Earlier PDF encryption algorithms (/V 1..4, PDF 1.7) were based on <code class="docutils literal notranslate"><span class="pre">PdfDocEncoding</span></code>.
Newer algorithms (/V 5, PDF 1.8-2.0) expect Unicode encoded as <code class="docutils literal notranslate"><span class="pre">UTF-8</span></code>.
<code class="docutils literal notranslate"><span class="pre">pplib</span></code> API now expects <code class="docutils literal notranslate"><span class="pre">UTF-8</span></code> and if opening documents with older encryption methods,
it tries to make a conversion to 8-bit encoding. In earlier versions <code class="docutils literal notranslate"><span class="pre">pplib</span></code> didn’t
make any password preprocessing, treating them as raw byte arrays.
So in case of passwords with fancy characters, it may behave differently.</p>
</div>
</div>
<div class="section" id="pages">
<h2>Pages<a class="headerlink" href="#pages" title="Permalink to this headline">¶</a></h2>
<p>Several helpers to deal with pages. To get the number of pages:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppuint</span> <span class="n">ppdoc_page_count</span> <span class="p">(</span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">);</span>
</pre></div>
</div>
<p>To access the root pages tree node:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppref</span> <span class="o">*</span> <span class="n">ppdoc_pages</span><span class="p">(</span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">);</span>
</pre></div>
</div>
<p>To get the page reference at a given index:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppref</span> <span class="o">*</span> <span class="n">ppdoc_page</span> <span class="p">(</span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">,</span> <span class="n">ppuint</span> <span class="n">index</span><span class="p">);</span>
</pre></div>
</div>
<p><code class="docutils literal notranslate"><span class="pre">index</span></code> is a page number. First page has number 1. For index out of bounds <code class="docutils literal notranslate"><span class="pre">ppdoc_page()</span></code> returns NULL.
Iterating over pages using index from 1 to <code class="docutils literal notranslate"><span class="pre">ppdoc_page_count()</span></code> and calling <code class="docutils literal notranslate"><span class="pre">ppdoc_page()</span></code> on each iteration
would be suboptimal. Here is a dedicted iterator for this:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppref</span> <span class="o">*</span> <span class="n">ppdoc_first_page</span> <span class="p">(</span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">);</span>
<span class="n">ppref</span> <span class="o">*</span> <span class="n">ppdoc_next_page</span> <span class="p">(</span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">);</span>
</pre></div>
</div>
<p>The iterator in use:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppdoc</span> <span class="o">*</span><span class="n">pdf</span><span class="p">;</span>
<span class="n">ppref</span> <span class="o">*</span><span class="n">ref</span><span class="p">;</span>
<span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">;</span>
<span class="nb">int</span> <span class="n">pageno</span><span class="p">;</span>
<span class="n">pdf</span> <span class="o">=</span> <span class="n">ppdoc_load</span><span class="p">(</span><span class="s2">"file.pdf"</span><span class="p">);</span>
<span class="k">for</span> <span class="p">(</span><span class="n">ref</span> <span class="o">=</span> <span class="n">ppdoc_first_page</span><span class="p">(</span><span class="n">pdf</span><span class="p">),</span> <span class="n">pageno</span> <span class="o">=</span> <span class="mi">1</span><span class="p">;</span> <span class="n">ref</span> <span class="o">!=</span> <span class="n">NULL</span><span class="p">;</span> <span class="n">ref</span> <span class="o">=</span> <span class="n">ppdoc_next_page</span><span class="p">(</span><span class="n">pdf</span><span class="p">),</span> <span class="o">++</span><span class="n">pageno</span><span class="p">)</span>
<span class="p">{</span>
<span class="nb">dict</span> <span class="o">=</span> <span class="n">ppref_obj</span><span class="p">(</span><span class="n">obj</span><span class="p">)</span><span class="o">-></span><span class="nb">dict</span><span class="p">;</span> <span class="o">//</span> <span class="n">take</span> <span class="k">for</span> <span class="n">granted</span> <span class="n">it</span> <span class="ow">is</span> <span class="n">a</span> <span class="nb">dict</span>
<span class="o">//</span> <span class="n">do</span> <span class="n">something</span> <span class="k">with</span> <span class="n">the</span> <span class="n">page</span> <span class="nb">dict</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Functions related to pages return <code class="docutils literal notranslate"><span class="pre">ppref</span> <span class="pre">*</span></code> ensured to contain dict object, so you don’t need sanity
type checks here.</p>
</div>
<div class="section" id="contents">
<h2>Contents<a class="headerlink" href="#contents" title="Permalink to this headline">¶</a></h2>
<p>PDF page contents can be given as a stream or array of streams. Here is a convenience iterator over page
contents streams:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppstream</span> <span class="o">*</span> <span class="n">ppcontents_first</span> <span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">);</span>
<span class="n">ppstream</span> <span class="o">*</span> <span class="n">ppcontents_next</span> <span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">,</span> <span class="n">ppstream</span> <span class="o">*</span><span class="n">stream</span><span class="p">);</span>
</pre></div>
</div>
<p>A complete example of contents stream parser use is given below (example 2).
But before we get there, we need to introduce <code class="docutils literal notranslate"><span class="pre">ppcontext</span></code> object. Conceptually,
<code class="docutils literal notranslate"><span class="pre">ppcontext</span></code> is an owner (memory handler) of objects created on demand (beyond the <code class="docutils literal notranslate"><span class="pre">ppdoc</span></code>).
So far used only with contents stream parser, which might produce quite some data that we want
to release just after used. To create a new context:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">pcontext</span> <span class="o">*</span> <span class="n">ppcontext_new</span> <span class="p">(</span><span class="n">void</span><span class="p">);</span>
</pre></div>
</div>
<p>It initializes a new context and its internal memory heap, taking about 64kB on start. After that,
the context is ready to produce objects (contents parsing functions below). Once objects produced
from a given context are no longer needed:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">void</span> <span class="n">ppcontext_done</span> <span class="p">(</span><span class="n">ppcontext</span> <span class="o">*</span><span class="n">context</span><span class="p">);</span>
</pre></div>
</div>
<p>It restores the context to its initial state, as after <code class="docutils literal notranslate"><span class="pre">ppcontext_new()</span></code>. It means that the context
is ready to produce another bunch of beings (in the example below, all objects from the next page contents).
Once the context is not needed anymore:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">void</span> <span class="n">ppcontext_free</span> <span class="p">(</span><span class="n">ppcontext</span> <span class="o">*</span><span class="n">context</span><span class="p">);</span>
</pre></div>
</div>
<p>Now, contents stream parser functions take the context as an argument. Iterator form of contents stream parser
that allows to process the contents operator by operator:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppobj</span> <span class="o">*</span> <span class="n">ppcontents_first_op</span> <span class="p">(</span><span class="n">ppcontext</span> <span class="o">*</span><span class="n">context</span><span class="p">,</span> <span class="n">ppstream</span> <span class="o">*</span><span class="n">stream</span><span class="p">,</span> <span class="n">size_t</span> <span class="o">*</span><span class="n">psize</span><span class="p">,</span> <span class="n">ppname</span> <span class="o">*</span><span class="n">pname</span><span class="p">);</span>
<span class="n">ppobj</span> <span class="o">*</span> <span class="n">ppcontents_next_op</span> <span class="p">(</span><span class="n">ppcontext</span> <span class="o">*</span><span class="n">context</span><span class="p">,</span> <span class="n">ppstream</span> <span class="o">*</span><span class="n">stream</span><span class="p">,</span> <span class="n">size_t</span> <span class="o">*</span><span class="n">psize</span><span class="p">,</span> <span class="n">ppname</span> <span class="o">*</span><span class="n">pname</span><span class="p">);</span>
</pre></div>
</div>
<p>Returned <code class="docutils literal notranslate"><span class="pre">ppobj</span> <span class="pre">*</span></code> is a pointer to operands list. <code class="docutils literal notranslate"><span class="pre">*psize</span></code> is the number of operands on stack.
The operator itself is stored as <code class="docutils literal notranslate"><span class="pre">*pname</span></code>.</p>
<p>To parse the entire contents stream at once with no stop at every operator:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppobj</span> <span class="o">*</span> <span class="n">ppcontents_parse</span> <span class="p">(</span><span class="n">ppcontext</span> <span class="o">*</span><span class="n">context</span><span class="p">,</span> <span class="n">ppstream</span> <span class="o">*</span><span class="n">stream</span><span class="p">,</span> <span class="n">size_t</span> <span class="o">*</span><span class="n">psize</span><span class="p">);</span>
</pre></div>
</div>
<p>Returns probably quite long list of all parsed objects (operands and operatos) in one piece.
The number of objects is stored to <code class="docutils literal notranslate"><span class="pre">*psize</span></code>.</p>
<p>[Contents may contain so called inline images, that breaks a simple scheme of operands / operator syntax:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">BI</span> <span class="o"><</span><span class="n">keyval</span> <span class="n">pairs</span><span class="o">></span> <span class="n">ID</span> <span class="o"><</span><span class="n">binary</span> <span class="n">image</span> <span class="n">data</span><span class="o">></span> <span class="n">EI</span>
</pre></div>
</div>
<p>Contents parser treats this genuine triplet as a single piece, producing two operands (dict and string)
followed by <code class="docutils literal notranslate"><span class="pre">EI</span></code> operator name.]</p>
</div>
<div class="section" id="boxes">
<h2>Boxes<a class="headerlink" href="#boxes" title="Permalink to this headline">¶</a></h2>
<p>Boxes (rectangles) in PDF are roughly 4-number arrays, but with a special intent.
<code class="docutils literal notranslate"><span class="pre">pplib</span></code> provides a basic interface for these special arrays:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">typedef</span> <span class="n">struct</span> <span class="p">{</span>
<span class="n">ppnum</span> <span class="n">lx</span><span class="p">,</span> <span class="n">ly</span><span class="p">,</span> <span class="n">rx</span><span class="p">,</span> <span class="n">ry</span><span class="p">;</span>
<span class="p">}</span> <span class="n">pprect</span><span class="p">;</span>
</pre></div>
</div>
<p>This type is used only by helper functions - PDF parser is not aware of the rectangle type.
To convert <code class="docutils literal notranslate"><span class="pre">pparray</span></code> to <code class="docutils literal notranslate"><span class="pre">pprect</span></code>:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">pprect</span> <span class="o">*</span> <span class="n">pparray_to_rect</span> <span class="p">(</span><span class="n">pparray</span> <span class="o">*</span><span class="n">array</span><span class="p">,</span> <span class="n">pprect</span> <span class="o">*</span><span class="n">rect</span><span class="p">);</span> <span class="o">//</span> <span class="n">returns</span> <span class="n">rect</span> <span class="ow">or</span> <span class="n">NULL</span>
</pre></div>
</div>
<p>In example:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">pprect</span> <span class="n">rect</span><span class="p">;</span>
<span class="k">if</span> <span class="p">(</span><span class="n">pparray_to_rect</span><span class="p">(</span><span class="n">array</span><span class="p">,</span> <span class="o">&</span><span class="n">rect</span><span class="p">)</span> <span class="o">!=</span> <span class="n">NULL</span><span class="p">)</span>
<span class="p">;</span> <span class="o">//</span> <span class="n">do</span> <span class="n">something</span> <span class="k">with</span> <span class="n">rect</span>
</pre></div>
</div>
<p>To get some image bounding box:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">pprect</span> <span class="o">*</span> <span class="n">ppdict_get_rect</span> <span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">,</span> <span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">name</span><span class="p">,</span> <span class="n">pprect</span> <span class="o">*</span><span class="n">rect</span><span class="p">);</span>
<span class="o">//</span> <span class="n">eg</span><span class="o">.</span> <span class="n">ppdict_get_rect</span><span class="p">(</span><span class="n">imagedict</span><span class="p">,</span> <span class="s2">"BBox"</span><span class="p">,</span> <span class="o">&</span><span class="n">rect</span><span class="p">)</span>
</pre></div>
</div>
<p>To get some page box:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">pprect</span> <span class="o">*</span> <span class="n">ppdict_get_box</span> <span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">,</span> <span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">name</span><span class="p">,</span> <span class="n">pprect</span> <span class="o">*</span><span class="n">rect</span><span class="p">);</span>
<span class="o">//</span> <span class="n">eg</span><span class="o">.</span> <span class="n">ppdict_get_box</span><span class="p">(</span><span class="n">pagedict</span><span class="p">,</span> <span class="s2">"MediaBox"</span><span class="p">,</span> <span class="o">&</span><span class="n">rect</span><span class="p">)</span>
</pre></div>
</div>
<p>The later not only checks the pagedict, but also goes through parent page nodes.</p>
</div>
<div class="section" id="transforms">
<h2>Transforms<a class="headerlink" href="#transforms" title="Permalink to this headline">¶</a></h2>
<p>Transformations are given as 6-number arrays, but with a special intent.
<code class="docutils literal notranslate"><span class="pre">pplib</span></code> provides a basic interface for these special arrays:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">typedef</span> <span class="n">struct</span> <span class="p">{</span>
<span class="n">ppnum</span> <span class="n">xx</span><span class="p">,</span> <span class="n">xy</span><span class="p">,</span> <span class="n">yx</span><span class="p">,</span> <span class="n">yy</span><span class="p">,</span> <span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">;</span>
<span class="p">}</span> <span class="n">ppmatrix</span><span class="p">;</span>
</pre></div>
</div>
<p>This type is used only by helper functions - PDF parser is not aware of the matrix type.
To convert <code class="docutils literal notranslate"><span class="pre">pparray</span></code> to <code class="docutils literal notranslate"><span class="pre">ppmatrix</span></code>:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppmatrix</span> <span class="o">*</span> <span class="n">pparray_to_matrix</span> <span class="p">(</span><span class="n">pparray</span> <span class="o">*</span><span class="n">array</span><span class="p">,</span> <span class="n">ppmatrix</span> <span class="o">*</span><span class="n">matrix</span><span class="p">);</span>
</pre></div>
</div>
<p>In example:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppmatrix</span> <span class="n">matrix</span><span class="p">;</span>
<span class="k">if</span> <span class="p">(</span><span class="n">pparray_to_matrix</span><span class="p">(</span><span class="n">array</span><span class="p">,</span> <span class="o">&</span><span class="n">matrix</span><span class="p">)</span> <span class="o">!=</span> <span class="n">NULL</span><span class="p">)</span>
<span class="p">;</span> <span class="o">//</span> <span class="n">do</span> <span class="n">something</span> <span class="k">with</span> <span class="n">matrix</span>
</pre></div>
</div>
<p>To get the matrix from dict:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">ppmatrix</span> <span class="o">*</span> <span class="n">ppdict_get_matrix</span> <span class="p">(</span><span class="n">ppdict</span> <span class="o">*</span><span class="nb">dict</span><span class="p">,</span> <span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">name</span><span class="p">,</span> <span class="n">ppmatrix</span> <span class="o">*</span><span class="n">matrix</span><span class="p">);</span>
<span class="o">//</span> <span class="n">eg</span><span class="o">.</span> <span class="n">ppdict_get_matrix</span><span class="p">(</span><span class="n">imagedict</span><span class="p">,</span> <span class="s2">"Matrix"</span><span class="p">,</span> <span class="o">&</span><span class="n">matrix</span><span class="p">)</span>
</pre></div>
</div>
</div>
<div class="section" id="errors-handling">
<h2>Errors handling<a class="headerlink" href="#errors-handling" title="Permalink to this headline">¶</a></h2>
<p><code class="docutils literal notranslate"><span class="pre">pplib</span></code> is not verbose, but might happen that it needs to log some error message, eg. when parsing
of some PDF boject fails due to invalid offsets. By default, <code class="docutils literal notranslate"><span class="pre">pplib</span></code> prints the message to stdout, eg.:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">invalid</span> <span class="mi">123</span> <span class="mi">0</span> <span class="n">R</span> <span class="nb">object</span> <span class="n">at</span> <span class="n">offset</span> <span class="mi">123123</span>
</pre></div>
</div>
<p>To replace the default logger, you can provide your own:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">void</span> <span class="n">pplog_callback</span> <span class="p">(</span><span class="n">pplogger_callback</span> <span class="n">logger</span><span class="p">,</span> <span class="n">void</span> <span class="o">*</span><span class="n">alien</span><span class="p">);</span>
</pre></div>
</div>
<p><code class="docutils literal notranslate"><span class="pre">pplogger_callback</span></code> is a function:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">void</span> <span class="n">your_callback</span> <span class="p">(</span><span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">message</span><span class="p">,</span> <span class="n">void</span> <span class="o">*</span><span class="n">alien</span><span class="p">);</span>
</pre></div>
</div>
<p>In example, to redirect messages to stderr you may define a function:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">void</span> <span class="n">your_callback</span> <span class="p">(</span><span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">message</span><span class="p">,</span> <span class="n">void</span> <span class="o">*</span><span class="n">alien</span><span class="p">)</span>
<span class="p">{</span>
<span class="n">fprintf</span><span class="p">((</span><span class="n">FILE</span> <span class="o">*</span><span class="p">)</span><span class="n">alien</span><span class="p">,</span> <span class="s2">"</span><span class="se">\n</span><span class="s2">ooops: </span><span class="si">%s</span><span class="se">\n</span><span class="s2">"</span><span class="p">,</span> <span class="n">message</span><span class="p">);</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Then set the callback somewhere before loading documents:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">pplog_callback</span><span class="p">(</span><span class="n">your_callback</span><span class="p">,</span> <span class="n">stderr</span><span class="p">);</span>
</pre></div>
</div>
<p>(example 2 uses that).</p>
<p>To set the default log messages prefix, eg. <code class="docutils literal notranslate"><span class="pre">pplib:</span></code>, use:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="nb">int</span> <span class="n">pplog_prefix</span> <span class="p">(</span><span class="n">const</span> <span class="n">char</span> <span class="o">*</span><span class="n">prefix</span><span class="p">)</span>
</pre></div>
</div>
<p>Default is empty. The function succeeds if provided prefix is reasonably short (less then 32 bytes).</p>
</div>
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