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 <h5 class="subsubsection">3.2.4.3 Allocation in an Obstack</h5>

 <p><a name="index-allocation-_0028obstacks_0029-307"></a>
 The most direct way to allocate an object in an obstack is with
 <code>obstack_alloc</code>, which is invoked almost like <code>malloc</code>.

 <!-- obstack.h -->
 <!-- GNU -->
 <div class="defun">
 &mdash; Function: void * <b>obstack_alloc</b> (<var>struct obstack *obstack-ptr, int size</var>)<var><a name="index-obstack_005falloc-308"></a></var><br>
 <blockquote><p>This allocates an uninitialized block of <var>size</var> bytes in an obstack
 and returns its address.  Here <var>obstack-ptr</var> specifies which obstack
 to allocate the block in; it is the address of the <code>struct obstack</code>
 object which represents the obstack.  Each obstack function or macro
 requires you to specify an <var>obstack-ptr</var> as the first argument.

         <p>This function calls the obstack's <code>obstack_chunk_alloc</code> function if
 it needs to allocate a new chunk of memory; it calls
 <code>obstack_alloc_failed_handler</code> if allocation of memory by
 <code>obstack_chunk_alloc</code> failed.
 </p></blockquote></div>

    <p>For example, here is a function that allocates a copy of a string <var>str</var>
 in a specific obstack, which is in the variable <code>string_obstack</code>:

 <pre class="smallexample">     struct obstack string_obstack;

      char *
      copystring (char *string)
      {
        size_t len = strlen (string) + 1;
        char *s = (char *) obstack_alloc (&amp;string_obstack, len);
        memcpy (s, string, len);
        return s;
      }
 </pre>
    <p>To allocate a block with specified contents, use the function
 <code>obstack_copy</code>, declared like this:

 <!-- obstack.h -->
 <!-- GNU -->
 <div class="defun">
 &mdash; Function: void * <b>obstack_copy</b> (<var>struct obstack *obstack-ptr, void *address, int size</var>)<var><a name="index-obstack_005fcopy-309"></a></var><br>
 <blockquote><p>This allocates a block and initializes it by copying <var>size</var>
 bytes of data starting at <var>address</var>.  It calls
 <code>obstack_alloc_failed_handler</code> if allocation of memory by
 <code>obstack_chunk_alloc</code> failed.
 </p></blockquote></div>

 <!-- obstack.h -->
 <!-- GNU -->
 <div class="defun">
 &mdash; Function: void * <b>obstack_copy0</b> (<var>struct obstack *obstack-ptr, void *address, int size</var>)<var><a name="index-obstack_005fcopy0-310"></a></var><br>
 <blockquote><p>Like <code>obstack_copy</code>, but appends an extra byte containing a null
 character.  This extra byte is not counted in the argument <var>size</var>.
 </p></blockquote></div>

    <p>The <code>obstack_copy0</code> function is convenient for copying a sequence
 of characters into an obstack as a null-terminated string.  Here is an
 example of its use:

 <pre class="smallexample">     char *
      obstack_savestring (char *addr, int size)
      {
        return obstack_copy0 (&amp;myobstack, addr, size);
      }
 </pre>
    <p class="noindent">Contrast this with the previous example of <code>savestring</code> using
 <code>malloc</code> (see <a href="Basic-Allocation.html#Basic-Allocation">Basic Allocation</a>).

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	Previous: <a rel="previous" accesskey="p" href="Preparing-for-Obstacks.html#Preparing-for-Obstacks">Preparing for Obstacks</a>,
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	<hr>
	</div>

	<h5 class="subsubsection">3.2.4.3 Allocation in an Obstack</h5>

	<p><a name="index-allocation-_0028obstacks_0029-307"></a>
	The most direct way to allocate an object in an obstack is with
	<code>obstack_alloc</code>, which is invoked almost like <code>malloc</code>.

	<!-- obstack.h -->
	<!-- GNU -->
	<div class="defun">
	— Function: void * <b>obstack_alloc</b> (<var>struct obstack *obstack-ptr, int size</var>)<var><a name="index-obstack_005falloc-308"></a></var><br>
	<blockquote><p>This allocates an uninitialized block of <var>size</var> bytes in an obstack
	and returns its address. Here <var>obstack-ptr</var> specifies which obstack
	to allocate the block in; it is the address of the <code>struct obstack</code>
	object which represents the obstack. Each obstack function or macro
	requires you to specify an <var>obstack-ptr</var> as the first argument.

	<p>This function calls the obstack's <code>obstack_chunk_alloc</code> function if
	it needs to allocate a new chunk of memory; it calls
	<code>obstack_alloc_failed_handler</code> if allocation of memory by
	<code>obstack_chunk_alloc</code> failed.
	</p></blockquote></div>

	<p>For example, here is a function that allocates a copy of a string <var>str</var>
	in a specific obstack, which is in the variable <code>string_obstack</code>:

	<pre class="smallexample"> struct obstack string_obstack;

	char *
	copystring (char *string)
	{
	size_t len = strlen (string) + 1;
	char s = (char ) obstack_alloc (&string_obstack, len);
	memcpy (s, string, len);
	return s;
	}
	</pre>
	<p>To allocate a block with specified contents, use the function
	<code>obstack_copy</code>, declared like this:

	<!-- obstack.h -->
	<!-- GNU -->
	<div class="defun">
	— Function: void * <b>obstack_copy</b> (<var>struct obstack obstack-ptr, void address, int size</var>)<var><a name="index-obstack_005fcopy-309"></a></var><br>
	<blockquote><p>This allocates a block and initializes it by copying <var>size</var>
	bytes of data starting at <var>address</var>. It calls
	<code>obstack_alloc_failed_handler</code> if allocation of memory by
	<code>obstack_chunk_alloc</code> failed.
	</p></blockquote></div>

	<!-- obstack.h -->
	<!-- GNU -->
	<div class="defun">
	— Function: void * <b>obstack_copy0</b> (<var>struct obstack obstack-ptr, void address, int size</var>)<var><a name="index-obstack_005fcopy0-310"></a></var><br>
	<blockquote><p>Like <code>obstack_copy</code>, but appends an extra byte containing a null
	character. This extra byte is not counted in the argument <var>size</var>.
	</p></blockquote></div>

	<p>The <code>obstack_copy0</code> function is convenient for copying a sequence
	of characters into an obstack as a null-terminated string. Here is an
	example of its use:

	<pre class="smallexample"> char *
	obstack_savestring (char *addr, int size)
	{
	return obstack_copy0 (&myobstack, addr, size);
	}
	</pre>
	<p class="noindent">Contrast this with the previous example of <code>savestring</code> using
	<code>malloc</code> (see <a href="Basic-Allocation.html#Basic-Allocation">Basic Allocation</a>).

	</body></html>