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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
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<h1>Lua-System</h1>
<ul>
<li><a href="../index.html">Index</a></li>
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<h2>Contents</h2>
<ul>
<li><a href="#Bit_flags">Bit flags </a></li>
</ul>
<h2>Classes</h2>
<ul class="nowrap">
<li><strong>bitflags</strong></li>
</ul>
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<li><a href="../modules/system.html">system</a></li>
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<li><a href="../topics/01-introduction.md.html">1. Introduction</a></li>
<li><a href="../topics/02-development.md.html">2. Development</a></li>
<li><a href="../topics/03-terminal.md.html">3. Terminal functionality</a></li>
<li><a href="../topics/CHANGELOG.md.html">CHANGELOG</a></li>
<li><a href="../topics/LICENSE.md.html">MIT License</a></li>
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<li><a href="../examples/compat.lua.html">compat.lua</a></li>
<li><a href="../examples/flag_debugging.lua.html">flag_debugging.lua</a></li>
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<li><a href="../examples/readline.lua.html">readline.lua</a></li>
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<li><a href="../examples/spiral_snake.lua.html">spiral_snake.lua</a></li>
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<h1>Class <code>bitflags</code></h1>
<p>Bitflags module.</p>
<p> The bitflag object makes it easy to manipulate flags in a bitmask.</p>
<p> It has metamethods that do the hard work, adding flags sets them, substracting
unsets them. Comparing flags checks if all flags in the second set are also set
in the first set. The <code>has</code> method checks if all flags in the second set are
also set in the first set, but behaves slightly different.</p>
<p> Indexing allows checking values or setting them by bit index (eg. 0-7 for flags
in the first byte).</p>
<p> <em>NOTE</em>: unavailable flags (eg. Windows flags on a Posix system) should not be
omitted, but be assigned a value of 0. This is because the <code>has</code> method will
return <code>false</code> if the flags are checked and the value is 0.</p>
<p> See <a href="../classes/bitflags.html#system.bitflag">system.bitflag</a> (the constructor) for extensive examples on usage.</p>
<h2><a href="#Bit_flags">Bit flags </a></h2>
<table class="function_list">
<tr>
<td class="name" nowrap><a href="#bitflag:has_all_of">bitflag:has_all_of (subset)</a></td>
<td class="summary">Checks if all the flags in the given subset are set.</td>
</tr>
<tr>
<td class="name" nowrap><a href="#bitflag:has_any_of">bitflag:has_any_of (subset)</a></td>
<td class="summary">Checks if any of the flags in the given subset are set.</td>
</tr>
<tr>
<td class="name" nowrap><a href="#bitflag:value">bitflag:value ()</a></td>
<td class="summary">Retrieves the numeric value of the bitflag object.</td>
</tr>
<tr>
<td class="name" nowrap><a href="#system.bitflag">system.bitflag ([value=0])</a></td>
<td class="summary">Creates a new bitflag object from the given value.</td>
</tr>
</table>
<br/>
<br/>
<h2 class="section-header has-description"><a name="Bit_flags"></a>Bit flags </h2>
<div class="section-description">
Bitflag objects can be used to easily manipulate and compare bit flags.
These are primarily for use with the terminal functions, but can be used
in other places as well.
</div>
<dl class="function">
<dt>
<a name = "bitflag:has_all_of"></a>
<strong>bitflag:has_all_of (subset)</strong>
</dt>
<dd>
Checks if all the flags in the given subset are set.
If the flags to check has a value <code>0</code>, it will always return <code>false</code>. So if there are flags that are
unsupported on a platform, they can be set to 0 and the <a href="../classes/bitflags.html#bitflag:has_all_of">has_all_of</a> function will
return <code>false</code> if the flags are checked.
<h3>Parameters:</h3>
<ul>
<li><span class="parameter">subset</span>
<span class="types"><a class="type" href="../classes/bitflags.html#system.bitflag">bitflag</a></span>
the flags to check for.
</li>
</ul>
<h3>Returns:</h3>
<ol>
<span class="types"><span class="type">boolean</span></span>
true if all the flags are set, false otherwise.
</ol>
<h3>Usage:</h3>
<ul>
<pre class="example"><span class="keyword">local</span> sys = <span class="global">require</span> <span class="string">'system'</span>
<span class="keyword">local</span> flags = sys.<span class="function-name">bitflag</span>(<span class="number">12</span>) <span class="comment">-- b1100
</span><span class="keyword">local</span> myflags = sys.<span class="function-name">bitflag</span>(<span class="number">15</span>) <span class="comment">-- b1111
</span><span class="global">print</span>(flags:<span class="function-name">has_all_of</span>(myflags)) <span class="comment">-- false, not all bits in myflags are set in flags
</span><span class="global">print</span>(myflags:<span class="function-name">has_all_of</span>(flags)) <span class="comment">-- true, all bits in flags are set in myflags</span></pre>
</ul>
</dd>
<dt>
<a name = "bitflag:has_any_of"></a>
<strong>bitflag:has_any_of (subset)</strong>
</dt>
<dd>
Checks if any of the flags in the given subset are set.
If the flags to check has a value <code>0</code>, it will always return <code>false</code>. So if there are flags that are
unsupported on a platform, they can be set to 0 and the <a href="../classes/bitflags.html#bitflag:has_any_of">has_any_of</a> function will
return <code>false</code> if the flags are checked.
<h3>Parameters:</h3>
<ul>
<li><span class="parameter">subset</span>
<span class="types"><a class="type" href="../classes/bitflags.html#system.bitflag">bitflag</a></span>
the flags to check for.
</li>
</ul>
<h3>Returns:</h3>
<ol>
<span class="types"><span class="type">boolean</span></span>
true if any of the flags are set, false otherwise.
</ol>
<h3>Usage:</h3>
<ul>
<pre class="example"><span class="keyword">local</span> sys = <span class="global">require</span> <span class="string">'system'</span>
<span class="keyword">local</span> flags = sys.<span class="function-name">bitflag</span>(<span class="number">12</span>) <span class="comment">-- b1100
</span><span class="keyword">local</span> myflags = sys.<span class="function-name">bitflag</span>(<span class="number">7</span>) <span class="comment">-- b0111
</span><span class="global">print</span>(flags:<span class="function-name">has_any_of</span>(myflags)) <span class="comment">-- true, some bits in myflags are set in flags
</span><span class="global">print</span>(myflags:<span class="function-name">has_any_of</span>(flags)) <span class="comment">-- true, some bits in flags are set in myflags</span></pre>
</ul>
</dd>
<dt>
<a name = "bitflag:value"></a>
<strong>bitflag:value ()</strong>
</dt>
<dd>
Retrieves the numeric value of the bitflag object.
<h3>Returns:</h3>
<ol>
<span class="types"><span class="type">number</span></span>
the numeric value of the bitflags.
</ol>
<h3>Usage:</h3>
<ul>
<pre class="example"><span class="keyword">local</span> sys = <span class="global">require</span> <span class="string">'system'</span>
<span class="keyword">local</span> flags = sys.<span class="function-name">bitflag</span>() <span class="comment">-- b0000
</span>flags[<span class="number">0</span>] = <span class="keyword">true</span> <span class="comment">-- b0001
</span>flags[<span class="number">2</span>] = <span class="keyword">true</span> <span class="comment">-- b0101
</span><span class="global">print</span>(flags:<span class="function-name">value</span>()) <span class="comment">-- 5</span></pre>
</ul>
</dd>
<dt>
<a name = "system.bitflag"></a>
<strong>system.bitflag ([value=0])</strong>
</dt>
<dd>
Creates a new bitflag object from the given value.
<h3>Parameters:</h3>
<ul>
<li><span class="parameter">value</span>
<span class="types"><span class="type">number</span></span>
the value to create the bitflag object from.
(<em>default</em> 0)
</li>
</ul>
<h3>Returns:</h3>
<ol>
<span class="types"><a class="type" href="../classes/bitflags.html#system.bitflag">bitflag</a></span>
bitflag object with the given values set.
</ol>
<h3>Usage:</h3>
<ul>
<pre class="example"><span class="keyword">local</span> sys = <span class="global">require</span> <span class="string">'system'</span>
<span class="keyword">local</span> flags = sys.<span class="function-name">bitflag</span>(<span class="number">2</span>) <span class="comment">-- b0010
</span>
<span class="comment">-- get state of individual bits
</span><span class="global">print</span>(flags[<span class="number">0</span>]) <span class="comment">-- false
</span><span class="global">print</span>(flags[<span class="number">1</span>]) <span class="comment">-- true
</span>
<span class="comment">-- set individual bits
</span>flags[<span class="number">0</span>] = <span class="keyword">true</span> <span class="comment">-- b0011
</span><span class="global">print</span>(flags:<span class="function-name">value</span>()) <span class="comment">-- 3
</span><span class="global">print</span>(flags) <span class="comment">-- "bitflags: 3"
</span>
<span class="comment">-- adding flags (bitwise OR)
</span><span class="keyword">local</span> flags1 = sys.<span class="function-name">bitflag</span>(<span class="number">1</span>) <span class="comment">-- b0001
</span><span class="keyword">local</span> flags2 = sys.<span class="function-name">bitflag</span>(<span class="number">2</span>) <span class="comment">-- b0010
</span><span class="keyword">local</span> flags3 = flags1 + flags2 <span class="comment">-- b0011
</span>
<span class="comment">-- substracting flags (bitwise AND NOT)
</span><span class="global">print</span>(flags3:<span class="function-name">value</span>()) <span class="comment">-- 3
</span>flag3 = flag3 - flag3 <span class="comment">-- b0000
</span><span class="global">print</span>(flags3:<span class="function-name">value</span>()) <span class="comment">-- 0
</span>
<span class="comment">-- comparing flags
</span><span class="keyword">local</span> flags4 = sys.<span class="function-name">bitflag</span>(<span class="number">7</span>) <span class="comment">-- b0111
</span><span class="keyword">local</span> flags5 = sys.<span class="function-name">bitflag</span>(<span class="number">255</span>) <span class="comment">-- b11111111
</span><span class="global">print</span>(flags5 ~= flags4) <span class="comment">-- true, not the same flags
</span><span class="keyword">local</span> flags6 = sys.<span class="function-name">bitflag</span>(<span class="number">7</span>) <span class="comment">-- b0111
</span><span class="global">print</span>(flags6 == flags4) <span class="comment">-- true, same flags
</span>
<span class="comment">-- comparison of subsets
</span><span class="keyword">local</span> flags7 = sys.<span class="function-name">bitflag</span>(<span class="number">0</span>) <span class="comment">-- b0000
</span><span class="keyword">local</span> flags8 = sys.<span class="function-name">bitflag</span>(<span class="number">3</span>) <span class="comment">-- b0011
</span><span class="keyword">local</span> flags9 = sys.<span class="function-name">bitflag</span>(<span class="number">7</span>) <span class="comment">-- b0111
</span><span class="global">print</span>(flags9:<span class="function-name">has_all_of</span>(flags8)) <span class="comment">-- true, flags8 bits are all set in flags9
</span><span class="global">print</span>(flags8:<span class="function-name">has_any_of</span>(flags9)) <span class="comment">-- true, some of flags9 bits are set in flags8
</span><span class="global">print</span>(flags8:<span class="function-name">has_all_of</span>(flags7)) <span class="comment">-- false, flags7 (== 0) is not set in flags8</span></pre>
</ul>
</dd>
</dl>
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