PROCESS_HEAP_ENTRY structure (minwinbase.h)

Contains information about a heap element. The HeapWalk function uses a PROCESS_HEAP_ENTRY structure to enumerate the elements of a heap.

Syntax

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;
  } DUMMYUNIONNAME;
} PROCESS_HEAP_ENTRY, *LPPROCESS_HEAP_ENTRY, *PPROCESS_HEAP_ENTRY;

Members

lpData

A pointer to the data portion of the heap element.

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.

cbData

The size of the data portion of the heap element, in bytes.

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.

cbOverhead

The size of the data used by the system to maintain information about the heap element, in bytes. These overhead bytes are in addition to the cbData bytes of the data portion of the heap element.

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.

iRegionIndex

A handle to the heap region that contains the heap element. A heap consists of one or more regions of virtual memory, each with a unique region index.

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.

wFlags

The properties of the heap element. Some values affect the meaning of other members of this PROCESS_HEAP_ENTRY data structure. The following values are defined.

DUMMYUNIONNAME

DUMMYUNIONNAME.Block

This structure is valid only if both the PROCESS_HEAP_ENTRY_BUSY and PROCESS_HEAP_ENTRY_MOVEABLE are specified in wFlags.

DUMMYUNIONNAME.Block.hMem

Handle to the allocated, moveable memory block.

DUMMYUNIONNAME.Block.dwReserved[3]

Reserved; not used.

DUMMYUNIONNAME.Region

This structure is valid only if the wFlags member specifies PROCESS_HEAP_REGION.

DUMMYUNIONNAME.Region.dwCommittedSize

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.

DUMMYUNIONNAME.Region.dwUnCommittedSize

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.

DUMMYUNIONNAME.Region.lpFirstBlock

Pointer to the first valid memory block in this heap region.

DUMMYUNIONNAME.Region.lpLastBlock

Pointer to the first invalid memory block in this heap region.

Requirements

See also

GlobalAlloc

HeapAlloc

HeapWalk

VirtualAlloc

VirtualQuery