The following program shows how you might create and use a heap.
#include <windows.h>
#include <stdlib.h>
#include <stdio.h>
#include <umalloc.h>
static void *get_fn(Heap_t usrheap, size_t *length, int *clean)
{
void *p;
/* Round up to the next chunk size */
*length = ((*length) / 65536) * 65536 + 65536;
*clean = _BLOCK_CLEAN;
P = VirtualAlloc( NULL, *length,
MEM_COMMIT|MEM_RESERVE, PAGE_READWRITE);
return (p);
}
static void release_fn(Heap_t usrheap, void *p, size_t size)
{
VirtualFree( p, 0, MEM_RELEASE );
return;
}
int main(void)
{
void *initial_block;
DWORD rc;
Heap_t myheap;
char *ptr;
/* Call VirtualAlloc to get the initial block of memory */
if((initial_block == VirtualAlloc( NULL, 65536, MEM_COMMIT|RESERVE,
PAGE_READWRITE)) == NULL) {
printf("VirtualAlloc error", GetLastError());
}
/* Create an expandable heap starting with the block declared earlier */
if (NULL == (myheap = _ucreate(initial_block, 65536, _BLOCK_CLEAN,
_HEAP_REGULAR, get_fn, release_fn))) {
puts("_ucreate failed.");
exit(EXIT_FAILURE);
}
if (0 != _uopen(myheap)) {
puts("_uopen failed.");
exit(EXIT_FAILURE);
}
/* Force user heap to grow */
ptr = _umalloc(myheap, 100000);
_uclose(myheap);
if (0 != _udestroy(myheap, _FORCE)) {
puts("_udestroy failed.");
exit(EXIT_FAILURE);
}
if (FALSE == VirtualFree( initial_block, 0, MEM_RELEASE)){
printf("VirtualAlloc error", GetLastError());
}
return 0;
}
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Create a
Fixed-Size Heap
Create an
Expandable Heap
Use a
User-Defined Heap
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Example of Sharing a User
Heap