_uaddmem - Add Memory to a Heap

Syntax

#include <umalloc.h>
Heap_t _uaddmem(Heap_t heap, void *block, size_t size, int clean);

uaddmem adds a block of memory of size bytes into the specified user heap (created with _ucreate). Before calling _uaddmem, you must first get the block from the operating system, typically by using an OS/2 function like DosAllocMem or by allocating it statically. (See the Control Program Guide and Reference for details on OS/2 functions for memory management.)
If the memory block has been initialized to 0, specify _BLOCK_CLEAN for the clean parameter. If not, specify !_BLOCK_CLEAN. (This information makes calloc and _ucalloc more efficient).
Note: Memory returned by DosAllocMem is initialized to 0.

For fixed-size heaps, you must return all the blocks you added with _uaddmem to the system. (For expandable heaps, these blocks are returned by your release_fn when you call _udestroy.)
For more information about creating and using heaps, see "Managing Memory" in the VisualAge C++ Programming Guide.
Note: For every block of memory you add, a small number of bytes from it are used to store internal information. To reduce the total amount of overhead, it is better to add a few large blocks of memory than many small blocks.

uaddmem returns a pointer to the heap the memory was added to. If the heap specified is not valid, _uaddmem returns NULL.

The following example creates a heap myheap, and then uses _uaddmem to add memory to it.

#define  INCL_DOSMEMMGR             /* Memory Manager values */
#include <os2.h>
#include <bsememf.h>                /* Get flags for memory management  */
#include <stdlib.h>
#include <stdio.h>
#include <umalloc.h>

int main(void)
{
   void    *initial_block, *extra_chunk;
   APIRET  rc;
   Heap_t  myheap;
   char    *p1, *p2;

   /* Call DosAllocMem to get the initial block of memory */
   if (0 != (rc = DosAllocMem(&initial_block, 65536,
                              PAG_WRITE | PAG_READ | PAG_COMMIT))) {
      printf("DosAllocMem for initial block failed: return code = %ld\n", rc);
      exit(EXIT_FAILURE);
   }
   /* Create a fixed size heap starting with the block declared earlier */
   if (NULL == (myheap = _ucreate(initial_block, 65536, _BLOCK_CLEAN,
                                  _HEAP_REGULAR, NULL, NULL))) {
      puts("_ucreate failed.");
      exit(EXIT_FAILURE);
   }
   if (0 != _uopen(myheap)) {
      puts("_uopen failed.");
      exit(EXIT_FAILURE);
   }
   p1 = _umalloc(myheap, 100);
   /* Call DosAllocMem to get another block of memory */
   if (0 != (rc = DosAllocMem(&extra_chunk, 10 * 65536,
                              PAG_WRITE | PAG_READ | PAG_COMMIT))) {
      printf("DosAllocMem for extra chunk failed: return code = %ld\n", rc);
      exit(EXIT_FAILURE);
   }
   /* Add the second chunk of memory to user heap */
   if (myheap != _uaddmem(myheap, extra_chunk, 10 * 65536, _BLOCK_CLEAN)) {
      puts("_uaddmem failed.");
      exit(EXIT_FAILURE);
   }
   p2 = _umalloc(myheap, 100000);
   free(p1);
   free(p2);
   if (0 != _uclose(myheap)) {
      puts("_uclose failed");
      exit(EXIT_FAILURE);
   }
   if (0 != DosFreeMem(initial_block) || 0 != DosFreeMem(extra_chunk)) {
      puts("DosFreeMem error.");
      exit(EXIT_FAILURE);
   }
   return 0;
}

ucreate
udestroy
uheapmin
Differentiating between Memory Management Functions
Managing Memory" in the VisualAge C++ Programming Guide

[Back: tzset - Set Time Zone Information]

[Next: _ucalloc - Reserve and Initialize Memory from User Heap]