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<?xml version="1.0" encoding="utf-8" ?>
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<meta name="author" content="Arvid Norberg, arvid@libtorrent.org" />
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<div class="document">
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<a href="index.html"><table id="header">
<tr><td id="orange"></td>
<td id="logo">libtorrent</td></tr>
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<div id="main">
<table class="docinfo" frame="void" rules="none">
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<tbody valign="top">
<tr><th class="docinfo-name">Author:</th>
<td>Arvid Norberg, <a class="last reference external" href="mailto:arvid@libtorrent.org">arvid@libtorrent.org</a></td></tr>
<tr><th class="docinfo-name">Version:</th>
<td>1.1.11</td></tr>
</tbody>
</table>
<p><a class="reference external" href="reference.html">home</a></p>
<div class="section" id="utility">
<h1>Utility</h1>
<div class="contents topic" id="table-of-contents">
<p class="topic-title first">Table of contents</p>
<ul class="simple">
<li><a class="reference internal" href="#utility" id="id46">Utility</a><ul>
<li><a class="reference internal" href="#bitfield" id="id47">bitfield</a></li>
<li><a class="reference internal" href="#hasher" id="id48">hasher</a></li>
<li><a class="reference internal" href="#sha1-hash" id="id49">sha1_hash</a></li>
<li><a class="reference internal" href="#hash-value" id="id50">hash_value()</a></li>
<li><a class="reference internal" href="#id40" id="id51">operator<<()</a></li>
<li><a class="reference internal" href="#id43" id="id52">operator>>()</a></li>
</ul>
</li>
</ul>
</div>
<a name="bitfield"></a><div class="section" id="bitfield">
<h2>bitfield</h2>
<p>Declared in "<a class="reference external" href="../include/libtorrent/bitfield.hpp">libtorrent/bitfield.hpp</a>"</p>
<p>The <a class="reference external" href="reference-Utility.html#bitfield">bitfield</a> type stores any number of bits as a <a class="reference external" href="reference-Utility.html#bitfield">bitfield</a>
in a heap allocated array.</p>
<pre class="literal-block">
struct bitfield
{
<strong>bitfield</strong> (int bits);
<strong>bitfield</strong> (bitfield const& rhs);
<strong>bitfield</strong> (bitfield&& rhs);
<strong>bitfield</strong> (int bits, bool val);
<strong>bitfield</strong> ();
<strong>bitfield</strong> (char const* b, int bits);
void <strong>assign</strong> (char const* b, int bits);
bool <strong>operator[]</strong> (int index) const;
bool <strong>get_bit</strong> (int index) const;
void <strong>clear_bit</strong> (int index);
void <strong>set_bit</strong> (int index);
bool <strong>all_set</strong> () const;
bool <strong>none_set</strong> () const;
int <strong>size</strong> () const;
int <strong>num_words</strong> () const;
bool <strong>empty</strong> () const;
char const* <strong>data</strong> () const;
bitfield& <strong>operator=</strong> (bitfield const& rhs);
int <strong>count</strong> () const;
};
</pre>
<a name="bitfield()"></a><div class="section" id="id5">
<h3>bitfield()</h3>
<pre class="literal-block">
<strong>bitfield</strong> (int bits);
<strong>bitfield</strong> (bitfield const& rhs);
<strong>bitfield</strong> (bitfield&& rhs);
<strong>bitfield</strong> (int bits, bool val);
<strong>bitfield</strong> ();
<strong>bitfield</strong> (char const* b, int bits);
</pre>
<p>constructs a new <a class="reference external" href="reference-Utility.html#bitfield">bitfield</a>. The default constructor creates an empty
<a class="reference external" href="reference-Utility.html#bitfield">bitfield</a>. <tt class="docutils literal">bits</tt> is the size of the <a class="reference external" href="reference-Utility.html#bitfield">bitfield</a> (specified in bits).
<tt class="docutils literal">val</tt> is the value to initialize the bits to. If not specified
all bits are initialized to 0.</p>
<p>The constructor taking a pointer <tt class="docutils literal">b</tt> and <tt class="docutils literal">bits</tt> copies a <a class="reference external" href="reference-Utility.html#bitfield">bitfield</a>
from the specified buffer, and <tt class="docutils literal">bits</tt> number of bits (rounded up to
the nearest byte boundary).</p>
<a name="assign()"></a></div>
<div class="section" id="assign">
<h3>assign()</h3>
<pre class="literal-block">
void <strong>assign</strong> (char const* b, int bits);
</pre>
<p>copy <a class="reference external" href="reference-Utility.html#bitfield">bitfield</a> from buffer <tt class="docutils literal">b</tt> of <tt class="docutils literal">bits</tt> number of bits, rounded up to
the nearest byte boundary.</p>
<a name="operator[]()"></a></div>
<div class="section" id="operator">
<h3>operator[]()</h3>
<pre class="literal-block">
bool <strong>operator[]</strong> (int index) const;
</pre>
<p>query bit at <tt class="docutils literal">index</tt>. Returns true if bit is 1, otherwise false.</p>
<a name="set_bit()"></a>
<a name="clear_bit()"></a></div>
<div class="section" id="set-bit-clear-bit">
<h3>set_bit() clear_bit()</h3>
<pre class="literal-block">
void <strong>clear_bit</strong> (int index);
void <strong>set_bit</strong> (int index);
</pre>
<p>set bit at <tt class="docutils literal">index</tt> to 0 (clear_bit) or 1 (set_bit).</p>
<a name="all_set()"></a></div>
<div class="section" id="all-set">
<h3>all_set()</h3>
<pre class="literal-block">
bool <strong>all_set</strong> () const;
</pre>
<p>returns true if all bits in the <a class="reference external" href="reference-Utility.html#bitfield">bitfield</a> are set</p>
<a name="size()"></a></div>
<div class="section" id="size">
<h3>size()</h3>
<pre class="literal-block">
int <strong>size</strong> () const;
</pre>
<p>returns the size of the <a class="reference external" href="reference-Utility.html#bitfield">bitfield</a> in bits.</p>
<a name="empty()"></a></div>
<div class="section" id="empty">
<h3>empty()</h3>
<pre class="literal-block">
bool <strong>empty</strong> () const;
</pre>
<p>returns true if the <a class="reference external" href="reference-Utility.html#bitfield">bitfield</a> has zero size.</p>
<a name="data()"></a></div>
<div class="section" id="data">
<h3>data()</h3>
<pre class="literal-block">
char const* <strong>data</strong> () const;
</pre>
<p>returns a pointer to the internal buffer of the <a class="reference external" href="reference-Utility.html#bitfield">bitfield</a>.</p>
<a name="operator=()"></a></div>
<div class="section" id="id15">
<h3>operator=()</h3>
<pre class="literal-block">
bitfield& <strong>operator=</strong> (bitfield const& rhs);
</pre>
<p>copy operator</p>
<a name="count()"></a></div>
<div class="section" id="count">
<h3>count()</h3>
<pre class="literal-block">
int <strong>count</strong> () const;
</pre>
<p>count the number of bits in the <a class="reference external" href="reference-Utility.html#bitfield">bitfield</a> that are set to 1.</p>
<a name="hasher"></a></div>
</div>
<div class="section" id="hasher">
<h2>hasher</h2>
<p>Declared in "<a class="reference external" href="../include/libtorrent/hasher.hpp">libtorrent/hasher.hpp</a>"</p>
<p>this is a SHA-1 hash class.</p>
<p>You use it by first instantiating it, then call <tt class="docutils literal">update()</tt> to feed it
with data. i.e. you don't have to keep the entire buffer of which you want to
create the hash in memory. You can feed the <a class="reference external" href="reference-Utility.html#hasher">hasher</a> parts of it at a time. When
You have fed the <a class="reference external" href="reference-Utility.html#hasher">hasher</a> with all the data, you call <tt class="docutils literal">final()</tt> and it
will return the sha1-hash of the data.</p>
<p>The constructor that takes a <tt class="docutils literal">char const*</tt> and an integer will construct the
sha1 context and feed it the data passed in.</p>
<p>If you want to reuse the <a class="reference external" href="reference-Utility.html#hasher">hasher</a> object once you have created a hash, you have to
call <tt class="docutils literal">reset()</tt> to reinitialize it.</p>
<p>The sha1-algorithm used was implemented by Steve Reid and released as public domain.
For more info, see <tt class="docutils literal">src/sha1.cpp</tt>.</p>
<pre class="literal-block">
class hasher
{
<strong>hasher</strong> ();
<strong>hasher</strong> (const char* data, int len);
hasher& <strong>operator=</strong> (hasher const& h);
<strong>hasher</strong> (hasher const& h);
hasher& <strong>update</strong> (std::string const& data);
hasher& <strong>update</strong> (const char* data, int len);
sha1_hash <strong>final</strong> ();
void <strong>reset</strong> ();
<strong>~hasher</strong> ();
};
</pre>
<a name="hasher()"></a><div class="section" id="id21">
<h3>hasher()</h3>
<pre class="literal-block">
<strong>hasher</strong> (const char* data, int len);
</pre>
<p>this is the same as default constructing followed by a call to
<tt class="docutils literal">update(data, len)</tt>.</p>
<a name="update()"></a></div>
<div class="section" id="update">
<h3>update()</h3>
<pre class="literal-block">
hasher& <strong>update</strong> (std::string const& data);
hasher& <strong>update</strong> (const char* data, int len);
</pre>
<p>append the following bytes to what is being hashed</p>
<a name="final()"></a></div>
<div class="section" id="final">
<h3>final()</h3>
<pre class="literal-block">
sha1_hash <strong>final</strong> ();
</pre>
<p>returns the SHA-1 digest of the buffers previously passed to
<a class="reference external" href="reference-Utility.html#update()">update()</a> and the <a class="reference external" href="reference-Utility.html#hasher">hasher</a> constructor.</p>
<a name="reset()"></a></div>
<div class="section" id="reset">
<h3>reset()</h3>
<pre class="literal-block">
void <strong>reset</strong> ();
</pre>
<p>restore the <a class="reference external" href="reference-Utility.html#hasher">hasher</a> state to be as if the <a class="reference external" href="reference-Utility.html#hasher">hasher</a> has just been
default constructed.</p>
<a name="sha1_hash"></a></div>
</div>
<div class="section" id="sha1-hash">
<h2>sha1_hash</h2>
<p>Declared in "<a class="reference external" href="../include/libtorrent/sha1_hash.hpp">libtorrent/sha1_hash.hpp</a>"</p>
<p>This type holds a SHA-1 digest or any other kind of 20 byte
sequence. It implements a number of convenience functions, such
as bit operations, comparison operators etc.</p>
<p>In libtorrent it is primarily used to hold info-hashes, piece-hashes,
peer IDs, node IDs etc.</p>
<pre class="literal-block">
class sha1_hash
{
<strong>sha1_hash</strong> ();
static sha1_hash <strong>max</strong> ();
static sha1_hash <strong>min</strong> ();
explicit <strong>sha1_hash</strong> (char const* s);
void <strong>assign</strong> (char const* str);
explicit <strong>sha1_hash</strong> (std::string const& s);
void <strong>assign</strong> (std::string const& s);
char* <strong>data</strong> ();
char const* <strong>data</strong> () const;
void <strong>clear</strong> ();
bool <strong>is_all_zeros</strong> () const;
sha1_hash& <strong>operator<<=</strong> (int n);
sha1_hash& <strong>operator>>=</strong> (int n);
bool <strong>operator!=</strong> (sha1_hash const& n) const;
bool <strong>operator<</strong> (sha1_hash const& n) const;
bool <strong>operator==</strong> (sha1_hash const& n) const;
sha1_hash <strong>operator~</strong> () const;
sha1_hash <strong>operator^</strong> (sha1_hash const& n) const;
sha1_hash& <strong>operator^=</strong> (sha1_hash const& n);
sha1_hash <strong>operator&</strong> (sha1_hash const& n) const;
sha1_hash& <strong>operator&=</strong> (sha1_hash const& n);
sha1_hash& <strong>operator|=</strong> (sha1_hash const& n);
boost::uint8_t& <strong>operator[]</strong> (int i);
boost::uint8_t const& <strong>operator[]</strong> (int i) const;
const_iterator <strong>begin</strong> () const;
iterator <strong>begin</strong> ();
iterator <strong>end</strong> ();
const_iterator <strong>end</strong> () const;
std::string <strong>to_string</strong> () const;
};
</pre>
<a name="sha1_hash()"></a><div class="section" id="id27">
<h3>sha1_hash()</h3>
<pre class="literal-block">
<strong>sha1_hash</strong> ();
</pre>
<p>constructs an all-zero sha1-hash</p>
<a name="max()"></a></div>
<div class="section" id="max">
<h3>max()</h3>
<pre class="literal-block">
static sha1_hash <strong>max</strong> ();
</pre>
<p>returns an all-F sha1-hash. i.e. the maximum value
representable by a 160 bit number (20 bytes). This is
a static member function.</p>
<a name="min()"></a></div>
<div class="section" id="min">
<h3>min()</h3>
<pre class="literal-block">
static sha1_hash <strong>min</strong> ();
</pre>
<p>returns an all-zero sha1-hash. i.e. the minimum value
representable by a 160 bit number (20 bytes). This is
a static member function.</p>
<a name="assign()"></a>
<a name="sha1_hash()"></a></div>
<div class="section" id="assign-sha1-hash">
<h3>assign() sha1_hash()</h3>
<pre class="literal-block">
explicit <strong>sha1_hash</strong> (char const* s);
void <strong>assign</strong> (char const* str);
explicit <strong>sha1_hash</strong> (std::string const& s);
void <strong>assign</strong> (std::string const& s);
</pre>
<p>copies 20 bytes from the pointer provided, into the sha1-hash.
The passed in string MUST be at least 20 bytes. NULL terminators
are ignored, <tt class="docutils literal">s</tt> is treated like a raw memory buffer.</p>
<a name="clear()"></a></div>
<div class="section" id="clear">
<h3>clear()</h3>
<pre class="literal-block">
void <strong>clear</strong> ();
</pre>
<p>set the sha1-hash to all zeros.</p>
<a name="is_all_zeros()"></a></div>
<div class="section" id="is-all-zeros">
<h3>is_all_zeros()</h3>
<pre class="literal-block">
bool <strong>is_all_zeros</strong> () const;
</pre>
<p>return true if the sha1-hash is all zero.</p>
<a name="operator<<=()"></a></div>
<div class="section" id="id28">
<h3>operator<<=()</h3>
<pre class="literal-block">
sha1_hash& <strong>operator<<=</strong> (int n);
</pre>
<p>shift left <tt class="docutils literal">n</tt> bits.</p>
<a name="operator>>=()"></a></div>
<div class="section" id="id29">
<h3>operator>>=()</h3>
<pre class="literal-block">
sha1_hash& <strong>operator>>=</strong> (int n);
</pre>
<p>shift r <tt class="docutils literal">n</tt> bits.</p>
<a name="operator!=()"></a>
<a name="operator<()"></a>
<a name="operator==()"></a></div>
<div class="section" id="operator-operator-operator">
<h3>operator!=() operator<() operator==()</h3>
<pre class="literal-block">
bool <strong>operator!=</strong> (sha1_hash const& n) const;
bool <strong>operator<</strong> (sha1_hash const& n) const;
bool <strong>operator==</strong> (sha1_hash const& n) const;
</pre>
<p>standard comparison operators</p>
<a name="operator~()"></a></div>
<div class="section" id="id30">
<h3>operator~()</h3>
<pre class="literal-block">
sha1_hash <strong>operator~</strong> () const;
</pre>
<p>returns a bit-wise negated copy of the sha1-hash</p>
<a name="operator^()"></a></div>
<div class="section" id="id31">
<h3>operator^()</h3>
<pre class="literal-block">
sha1_hash <strong>operator^</strong> (sha1_hash const& n) const;
</pre>
<p>returns the bit-wise XOR of the two sha1-hashes.</p>
<a name="operator^=()"></a></div>
<div class="section" id="id32">
<h3>operator^=()</h3>
<pre class="literal-block">
sha1_hash& <strong>operator^=</strong> (sha1_hash const& n);
</pre>
<p>in-place bit-wise XOR with the passed in <a class="reference external" href="reference-Utility.html#sha1_hash">sha1_hash</a>.</p>
<a name="operator&()"></a></div>
<div class="section" id="id34">
<h3>operator&()</h3>
<pre class="literal-block">
sha1_hash <strong>operator&</strong> (sha1_hash const& n) const;
</pre>
<p>returns the bit-wise AND of the two sha1-hashes.</p>
<a name="operator&=()"></a></div>
<div class="section" id="id35">
<h3>operator&=()</h3>
<pre class="literal-block">
sha1_hash& <strong>operator&=</strong> (sha1_hash const& n);
</pre>
<p>in-place bit-wise AND of the passed in <a class="reference external" href="reference-Utility.html#sha1_hash">sha1_hash</a></p>
<a name="operator|=()"></a></div>
<div class="section" id="id37">
<h3>operator|=()</h3>
<pre class="literal-block">
sha1_hash& <strong>operator|=</strong> (sha1_hash const& n);
</pre>
<p>in-place bit-wise OR of the two sha1-hash.</p>
<a name="operator[]()"></a></div>
<div class="section" id="id38">
<h3>operator[]()</h3>
<pre class="literal-block">
boost::uint8_t& <strong>operator[]</strong> (int i);
boost::uint8_t const& <strong>operator[]</strong> (int i) const;
</pre>
<p>accessors for specific bytes</p>
<a name="begin()"></a>
<a name="end()"></a></div>
<div class="section" id="begin-end">
<h3>begin() end()</h3>
<pre class="literal-block">
const_iterator <strong>begin</strong> () const;
iterator <strong>begin</strong> ();
iterator <strong>end</strong> ();
const_iterator <strong>end</strong> () const;
</pre>
<p>start and end iterators for the hash. The value type
of these iterators is <tt class="docutils literal"><span class="pre">boost::uint8_t</span></tt>.</p>
<a name="to_string()"></a></div>
<div class="section" id="to-string">
<h3>to_string()</h3>
<pre class="literal-block">
std::string <strong>to_string</strong> () const;
</pre>
<p>return a copy of the 20 bytes representing the sha1-hash as a std::string.
It's still a binary string with 20 binary characters.</p>
<a name="hash_value()"></a></div>
</div>
<div class="section" id="hash-value">
<h2>hash_value()</h2>
<p>Declared in "<a class="reference external" href="../include/libtorrent/sha1_hash.hpp">libtorrent/sha1_hash.hpp</a>"</p>
<pre class="literal-block">
inline std::size_t <strong>hash_value</strong> (sha1_hash const& b);
</pre>
<a name="operator<<()"></a></div>
<div class="section" id="id40">
<h2>operator<<()</h2>
<p>Declared in "<a class="reference external" href="../include/libtorrent/sha1_hash.hpp">libtorrent/sha1_hash.hpp</a>"</p>
<pre class="literal-block">
inline std::ostream& <strong>operator<<</strong> (std::ostream& os, sha1_hash const& peer);
</pre>
<p>print a <a class="reference external" href="reference-Utility.html#sha1_hash">sha1_hash</a> object to an ostream as 40 hexadecimal digits</p>
<a name="operator>>()"></a></div>
<div class="section" id="id43">
<h2>operator>>()</h2>
<p>Declared in "<a class="reference external" href="../include/libtorrent/sha1_hash.hpp">libtorrent/sha1_hash.hpp</a>"</p>
<pre class="literal-block">
inline std::istream& <strong>operator>></strong> (std::istream& is, sha1_hash& peer);
</pre>
<p>read 40 hexadecimal digits from an istream into a <a class="reference external" href="reference-Utility.html#sha1_hash">sha1_hash</a></p>
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