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<title>9.2 Memory Interface
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<H1><A NAME=
"SECTION0011200000000000000000"></A><A NAME=
"memoryInterface"></A>
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:
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline"><td><nobr>void*
<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>
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.
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline"><td><nobr>void*
<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>
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>.
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline"><td><nobr>void
<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>
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.
The following type-oriented macros are provided for convenience. Note
that
<var>TYPE
</var> refers to any C type.
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline"><td><nobr><var>TYPE
</var>*
<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>
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
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline"><td><nobr><var>TYPE
</var>*
<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>
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>.
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline"><td><nobr>void
<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>
Same as
<tt class=
"cfunction">PyMem_Free()
</tt>.
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
<tt class=
"cfunction">PyMem_MALLOC()
</tt>,
<tt class=
"cfunction">PyMem_REALLOC()
</tt>,
<tt class=
"cfunction">PyMem_FREE()
</tt>.
<tt class=
"cfunction">PyMem_NEW()
</tt>,
<tt class=
"cfunction">PyMem_RESIZE()
</tt>,
<tt class=
"cfunction">PyMem_DEL()
</tt>.
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<span class=
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2.4.2, documentation updated on
28 September
2005.
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