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<H1><A NAME="SECTION0011200000000000000000"></A><A NAME="memoryInterface"></A>
<BR>
9.2 Memory Interface
</H1>

<P>
The following function sets, modeled after the ANSI C standard,
but specifying  behavior when requesting zero bytes,
are available for allocating and releasing memory from the Python heap:

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>void*&nbsp;<b><tt id='l2h-899' xml:id='l2h-899' class="cfunction">PyMem_Malloc</tt></b>(</nobr></td><td>size_t <var>n</var>)</td></tr></table></dt>
<dd>
  Allocates <var>n</var> bytes and returns a pointer of type <tt class="ctype">void*</tt>
  to the allocated memory, or <tt class="constant">NULL</tt> if the request fails.
  Requesting zero bytes returns a distinct non-<tt class="constant">NULL</tt> pointer if
  possible, as if <tt class="cfunction">PyMem_Malloc(1)</tt> had been called instead.
  The memory will not have been initialized in any way.
</dd></dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>void*&nbsp;<b><tt id='l2h-900' xml:id='l2h-900' class="cfunction">PyMem_Realloc</tt></b>(</nobr></td><td>void *<var>p</var>, size_t <var>n</var>)</td></tr></table></dt>
<dd>
  Resizes the memory block pointed to by <var>p</var> to <var>n</var> bytes.
  The contents will be unchanged to the minimum of the old and the new
  sizes. If <var>p</var> is <tt class="constant">NULL</tt>, the call is equivalent to
  <tt class="cfunction">PyMem_Malloc(<var>n</var>)</tt>; else if <var>n</var> is equal to zero, the
  memory block is resized but is not freed, and the returned pointer
  is non-<tt class="constant">NULL</tt>.  Unless <var>p</var> is <tt class="constant">NULL</tt>, it must have been
  returned by a previous call to <tt class="cfunction">PyMem_Malloc()</tt> or
  <tt class="cfunction">PyMem_Realloc()</tt>.
</dd></dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>void&nbsp;<b><tt id='l2h-901' xml:id='l2h-901' class="cfunction">PyMem_Free</tt></b>(</nobr></td><td>void *<var>p</var>)</td></tr></table></dt>
<dd>
  Frees the memory block pointed to by <var>p</var>, which must have been
  returned by a previous call to <tt class="cfunction">PyMem_Malloc()</tt> or
  <tt class="cfunction">PyMem_Realloc()</tt>.  Otherwise, or if
  <tt class="cfunction">PyMem_Free(p)</tt> has been called before, undefined
  behavior occurs. If <var>p</var> is <tt class="constant">NULL</tt>, no operation is performed.
</dd></dl>

<P>
The following type-oriented macros are provided for convenience.  Note
that <var>TYPE</var> refers to any C type.

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr><var>TYPE</var>*&nbsp;<b><tt id='l2h-902' xml:id='l2h-902' class="cfunction">PyMem_New</tt></b>(</nobr></td><td>TYPE, size_t <var>n</var>)</td></tr></table></dt>
<dd>
  Same as <tt class="cfunction">PyMem_Malloc()</tt>, but allocates <code>(<var>n</var> *
  sizeof(<var>TYPE</var>))</code> bytes of memory.  Returns a pointer cast to
  <tt class="ctype"><var>TYPE</var>*</tt>.  The memory will not have been initialized in
  any way.
</dd></dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr><var>TYPE</var>*&nbsp;<b><tt id='l2h-903' xml:id='l2h-903' class="cfunction">PyMem_Resize</tt></b>(</nobr></td><td>void *<var>p</var>, TYPE, size_t <var>n</var>)</td></tr></table></dt>
<dd>
  Same as <tt class="cfunction">PyMem_Realloc()</tt>, but the memory block is resized
  to <code>(<var>n</var> * sizeof(<var>TYPE</var>))</code> bytes.  Returns a pointer
  cast to <tt class="ctype"><var>TYPE</var>*</tt>.
</dd></dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>void&nbsp;<b><tt id='l2h-904' xml:id='l2h-904' class="cfunction">PyMem_Del</tt></b>(</nobr></td><td>void *<var>p</var>)</td></tr></table></dt>
<dd>
  Same as <tt class="cfunction">PyMem_Free()</tt>.
</dd></dl>

<P>
In addition, the following macro sets are provided for calling the
Python memory allocator directly, without involving the C API functions
listed above. However, note that their use does not preserve binary
compatibility across Python versions and is therefore deprecated in
extension modules.

<P>
<tt class="cfunction">PyMem_MALLOC()</tt>, <tt class="cfunction">PyMem_REALLOC()</tt>, <tt class="cfunction">PyMem_FREE()</tt>.

<P>
<tt class="cfunction">PyMem_NEW()</tt>, <tt class="cfunction">PyMem_RESIZE()</tt>, <tt class="cfunction">PyMem_DEL()</tt>.

<P>

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<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
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