Platform SDK: Memory |
The PROCESS_HEAP_ENTRY structure contains information about a heap element. The HeapWalk function uses a PROCESS_HEAP_ENTRY structure to enumerate the elements of a heap.
typedef struct _PROCESS_HEAP_ENTRY { PVOID lpData; DWORD cbData; BYTE cbOverhead; BYTE iRegionIndex; WORD wFlags; union { struct { HANDLE hMem; DWORD dwReserved[ 3 ]; } Block; struct { DWORD dwCommittedSize; DWORD dwUnCommittedSize; LPVOID lpFirstBlock; LPVOID lpLastBlock; } Region; }; } PROCESS_HEAP_ENTRY, *LPPROCESS_HEAP_ENTRY;
To initiate a HeapWalk heap enumeration, set lpData to NULL.
If PROCESS_HEAP_REGION is used in the wFlags member, lpData points to the first virtual address used by the region.
If PROCESS_HEAP_UNCOMMITTED_RANGE is used in wFlags, lpData points to the beginning of the range of uncommitted memory.
If PROCESS_HEAP_REGION is used in wFlags, cbData specifies the total size, in bytes, of the address space that is reserved for this region.
If PROCESS_HEAP_UNCOMMITTED_RANGE is used in wFlags, cbData specifies the size, in bytes, of the range of uncommitted memory.
If PROCESS_HEAP_REGION is used in wFlags, cbOverhead specifies the size, in bytes, of the heap control structures that describe the region.
If PROCESS_HEAP_UNCOMMITTED_RANGE is used in wFlags, cbOverhead specifies the size, in bytes, of the control structures that describe this uncommitted range.
In the first heap entry returned for most heap regions, HeapWalk uses the PROCESS_HEAP_REGION in the wFlags member. When this value is used, the members of the Region structure contain additional information about the region.
The HeapAlloc function sometimes uses the VirtualAlloc function to allocate large blocks from a growable heap. The heap manager treats such a large block allocation as a separate region with a unique region index. HeapWalk does not use PROCESS_HEAP_REGION in the heap entry returned for a large block region, so the members of the Region structure are not valid. You can use the VirtualQuery function to get additional information about a large block region.
Value | Meaning |
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PROCESS_HEAP_REGION | The heap element is located at the beginning of a region of contiguous virtual memory in use by the heap.
The lpData member of the structure points to the first virtual address used by the region; the cbData member specifies the total size, in bytes, of the address space that is reserved for this region; and the cbOverhead member specifies the size, in bytes, of the heap control structures that describe the region. The Region structure becomes valid. The dwCommittedSize, dwUnCommittedSize, lpFirstBlock, and lpLastBlock members of the structure contain additional information about the region. |
PROCESS_HEAP_UNCOMMITTED_RANGE | The heap element is located in a range of uncommitted memory within the heap region.
The lpData member points to the beginning of the range of uncommitted memory; the cbData member specifies the size, in bytes, of the range of uncommitted memory; and the cbOverhead member specifies the size, in bytes, of the control structures that describe this uncommitted range. |
PROCESS_HEAP_ENTRY_BUSY | The heap element is an allocated block.
If PROCESS_HEAP_ENTRY_MOVEABLE is also specified, the Block structure becomes valid. The hMem member of the Block structure contains a handle to the allocated, moveable memory block. |
PROCESS_HEAP_ENTRY_MOVEABLE | This value must be used with PROCESS_HEAP_ENTRY_BUSY, indicating that the heap element is an allocated block.
The block was allocated with LMEM_MOVEABLE or GMEM_MOVEABLE, and the Block structure becomes valid. The hMem member of the Block structure contains a handle to the allocated, moveable memory block. |
PROCESS_HEAP_ENTRY_DDESHARE | This value must be used with PROCESS_HEAP_ENTRY_BUSY, indicating that the heap element is an allocated block. |
The members of the Block structure are as follows.
Member | Description |
---|---|
hMem | Contains a handle to the allocated, moveable memory block. |
dwReserved | Reserved; not used. |
The members of the Region structure are as follows.
Member | Description |
---|---|
dwCommittedSize | Specifies the number of bytes in the heap region that are currently committed as free memory blocks, busy memory blocks, or heap control structures.
This is an optional field that is set to zero if the number of committed bytes is not available. |
dwUnCommittedSize | Specifies the number of bytes in the heap region that are currently uncommitted.
This is an optional field that is set to zero if the number of uncommitted bytes is not available. |
lpFirstBlock | Pointer to the first valid memory block in this heap region. |
lpLastBlock | Pointer to the first invalid memory block in this heap region. |
Windows NT/2000: Requires Windows NT 3.5 or later.
Windows 95/98: Unsupported.
Header: Declared in Winbase.h; include Windows.h.
Memory Management Overview, Memory Management Structures, GlobalAlloc, HeapAlloc, HeapWalk, VirtualAlloc, VirtualQuery