GlobalReAlloc
The GlobalReAlloc
function changes the size or attributes of a specified global memory object.
The size can increase or decrease.
HGLOBAL GlobalReAlloc(
|
HGLOBAL hMem, |
// handle to the
global memory object |
|
DWORD dwBytes, |
// new size of the
block |
|
UINT uFlags |
// how to
reallocate object |
|
); |
|
Parameters
hMem
Identifies
the global memory object to be reallocated. This handle is returned by either
the GlobalAlloc
or GlobalReAlloc function.
dwBytes
Specifies the
new size, in bytes, of the memory block. If this parameter is zero and the uFlags
parameter specifies the GMEM_MOVEABLE flag, the function returns the handle of
a memory object that is marked as discarded. If uFlags specifies the
GMEM_MODIFY flag, this parameter is ignored.
uFlags
Specifies how
to reallocate the global memory object. If the GMEM_MODIFY flag is specified,
this parameter modifies the attributes of the memory object, and the dwBytes
parameter is ignored. Otherwise, this parameter controls the reallocation of
the memory object.
The
GMEM_MODIFY flag can be combined with either or both of the following flags:
|
Flag |
Meaning |
|
GMEM_DISCARDABLE |
Allocates
discardable memory if the GMEM_MODIFY flag is also specified. This flag is ignored,
unless the object was previously allocated as movable or the GMEM_MOVEABLE
flag is also specified. |
|
GMEM_MOVEABLE |
Windows
NT only: Changes a fixed memory object
to a movable memory object if the GMEM_MODIFY flag is also specified. |
If this
parameter does not specify GMEM_MODIFY, it can be any combination of the
following flags:
|
Flag |
Meaning |
|
GMEM_MOVEABLE |
If dwBytes
is zero, discards a previously movable and discardable memory block. If the
lock count of the object is not zero or if the block is not movable and
discardable, the function fails. If dwBytes
is nonzero, enables the system to move the reallocated block to a new
location without changing the movable or fixed attribute of the memory
object. If the object is fixed, the handle returned may be different from the
handle specified by the hMem parameter. If the object is movable, the
block can be moved without invalidating the handle, even if the object is
currently locked by a previous call to the GlobalLock function. To get the new
address of the memory block, use GlobalLock. |
|
GMEM_NOCOMPACT |
Prevents
memory from being compacted or discarded to satisfy the allocation request. |
|
GMEM_ZEROINIT |
Causes the
additional memory contents to be initialized to zero if the memory object is
growing in size. |
Return Values
If the
function succeeds, the return value is the handle of the reallocated memory
object.
If the function
fails, the return value is NULL. To get extended error information, call GetLastError.
Remarks
If GlobalReAlloc
reallocates a movable object, the return value is the handle of the memory
object. To convert the handle to a pointer, use the GlobalLock function.
If GlobalReAlloc
reallocates a fixed object, the value of the handle returned is the address of
the first byte of the memory block. To access the memory, a process can simply
cast the return value to a pointer.
If GlobalReAlloc
fails, the original memory is not freed, and the original handle and pointer
are still valid.
See Also