technical/api-allocation-growing.html - external/gitster/git-htmldocs - Git at Google

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 <div id="header">
 <h1>allocation growing API</h1>
 </div>
 <div id="content">
 <div id="preamble">
 <div class="sectionbody">
 <div class="paragraph"><p>Dynamically growing an array using realloc() is error prone and boring.</p></div>
 <div class="paragraph"><p>Define your array with:</p></div>
 <div class="ulist"><ul>
 <li>
 <p>
 a pointer (<code>item</code>) that points at the array, initialized to <code>NULL</code>
  (although please name the variable based on its contents, not on its
  type);
 </p>
 </li>
 <li>
 <p>
 an integer variable (<code>alloc</code>) that keeps track of how big the current
  allocation is, initialized to <code>0</code>;
 </p>
 </li>
 <li>
 <p>
 another integer variable (<code>nr</code>) to keep track of how many elements the
  array currently has, initialized to <code>0</code>.
 </p>
 </li>
 </ul></div>
 <div class="paragraph"><p>Then before adding <code>n`th element to the item, call `ALLOC_GROW(item, n,
 alloc)</code>. This ensures that the array can hold at least <code>n</code> elements by
 calling <code>realloc(3)</code> and adjusting <code>alloc</code> variable.</p></div>
 <div class="listingblock">
 <div class="content">
 <pre><code>sometype *item;
 size_t nr;
 size_t alloc

 for (i = 0; i &lt; nr; i++)
  if (we like item[i] already)
  return;

 /* we did not like any existing one, so add one */
 ALLOC_GROW(item, nr + 1, alloc);
 item[nr++] = value you like;</code></pre>
 </div></div>
 <div class="paragraph"><p>You are responsible for updating the <code>nr</code> variable.</p></div>
 <div class="paragraph"><p>If you need to specify the number of elements to allocate explicitly
 then use the macro <code>REALLOC_ARRAY(item, alloc)</code> instead of <code>ALLOC_GROW</code>.</p></div>
 </div>
 </div>
 </div>
 <div id="footnotes"><hr /></div>
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 Last updated 2014-09-26 15:36:58 PDT
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	<body class="article">
	<div id="header">
	<h1>allocation growing API</h1>
	</div>
	<div id="content">
	<div id="preamble">
	<div class="sectionbody">
	<div class="paragraph"><p>Dynamically growing an array using realloc() is error prone and boring.</p></div>
	<div class="paragraph"><p>Define your array with:</p></div>
	<div class="ulist"><ul>
	<li>
	<p>
	a pointer (<code>item</code>) that points at the array, initialized to <code>NULL</code>
	(although please name the variable based on its contents, not on its
	type);
	</p>
	</li>
	<li>
	<p>
	an integer variable (<code>alloc</code>) that keeps track of how big the current
	allocation is, initialized to <code>0</code>;
	</p>
	</li>
	<li>
	<p>
	another integer variable (<code>nr</code>) to keep track of how many elements the
	array currently has, initialized to <code>0</code>.
	</p>
	</li>
	</ul></div>
	<div class="paragraph"><p>Then before adding <code>n`th element to the item, call `ALLOC_GROW(item, n,
	alloc)</code>. This ensures that the array can hold at least <code>n</code> elements by
	calling <code>realloc(3)</code> and adjusting <code>alloc</code> variable.</p></div>
	<div class="listingblock">
	<div class="content">
	<pre><code>sometype *item;
	size_t nr;
	size_t alloc

	for (i = 0; i < nr; i++)
	if (we like item[i] already)
	return;

	/* we did not like any existing one, so add one */
	ALLOC_GROW(item, nr + 1, alloc);
	item[nr++] = value you like;</code></pre>
	</div></div>
	<div class="paragraph"><p>You are responsible for updating the <code>nr</code> variable.</p></div>
	<div class="paragraph"><p>If you need to specify the number of elements to allocate explicitly
	then use the macro <code>REALLOC_ARRAY(item, alloc)</code> instead of <code>ALLOC_GROW</code>.</p></div>
	</div>
	</div>
	</div>
	<div id="footnotes"><hr /></div>
	<div id="footer">
	<div id="footer-text">
	Last updated 2014-09-26 15:36:58 PDT
	</div>
	</div>
	</body>
	</html>