stdlib中的xmalloc,xfree,xinit_mempool

1.xinit_mempool

 

Summary

#include <stdlib.h>void xinit_mempool (  void xhuge *p,           /* start of memory pool */  unsigned long size);     /* length of memory pool */

Description

The xinit_mempool function initializes the memory management routines and provides the starting address and size of the memory pool. The p argument points to a memory area in xdata which is managed using the xcalloc, xfree, xmalloc, and xrealloc library functions. The size argument specifies the number of bytes to use for the memory pool.

Note

• This function must be used to setup the memory pool before any other memory management functions (xcalloc, xfree, xmalloc, xrealloc) can be called. Call the xinit_mempool function only once at the beginning of your program.
• Source code for this routine is provide in the LIB folder. You may modify the source to customize this function for your particular hardware environment.
• This function uses xhuge pointers to objects and may be used in any memory model other than Tiny Model.
• Each memory block needs 8 bytes overhead to handle the allocation information. In addition another 8 bytes are required for init_mempool itself. Therefore if you want to allocate 2 blocks with 100 bytes each, the memory pool size must be 224 bytes.

Return Value

None.

See Also

xcalloc, xfree, xmalloc, xrealloc

Example

#include <stdlib.h>void tst_init_mempool (void) {  xdata void *p;  int i;/* initialize memory pool at xdata 0x2000 for 4096 bytes */  xinit_mempool (&XBYTE [0x2000], 0x1000);  p = xmalloc (100);  for (i = 0; i < 100; i++)    ((char *) p)[i] = i;  xfree (p);}

2.xmalloc

 

Summary

#include <stdlib.h>void xhuge *xmalloc (  unsigned long size);      /* block size to allocate */

Description

The xmalloc function allocates a memory block from the memory pool of size bytes in length.

Note

• Source code for this routine is provide in the LIB folder. You may modify the source to customize this function for your particular hardware environment.
• This function uses xhuge pointers to objects and may be used in any memory model other than Tiny Model.

Return Value

The xmalloc function returns a pointer to the allocated block or a null pointer if there is not enough memory to satisfy the allocation request.

See Also

xcalloc, xfree, xinit_mempool, xrealloc

Example

#include <stdlib.h>#include <stdio.h> /* for printf */void tst_malloc (void) {  void xhuge *p;  p = xmalloc (1000); /* allocate 1000 bytes */  if (p == NULL)    printf ("Not enough memory space/n");  else    printf ("Memory allocated/n");

 

3.xfree

Summary

#include <stdlib.h>void xfree (  void xhuge *p);      /* block to free */

Description

The xfree function returns a memory block to the memory pool. The p argument points to a memory block that was previously allocated with the xcalloc, xmalloc, or xrealloc functions. Once it has been returned to the memory pool by the free function, the block is available for subsequent allocation.

If p is a null pointer, it is ignored.

Note

• Source code for this routine is provide in the LIB folder. You may modify the source to customize this function for your particular hardware environment.
• This function uses xhuge pointers to objects and may be used in any memory model other than Tiny Model.

Return Value

None.

See Also

xcalloc, xinit_mempool, xmalloc, xrealloc

Example

#include <stdlib.h>#include <stdio.h> /* for printf */void tst_free (void) {  void xhuge *mbuf;  printf ("Allocating memory/n");  mbuf = xmalloc (1000);  if (mbuf == NULL) {    printf ("Unable to allocate memory/n");  }  else {    xfree (mbuf);    printf ("Memory free/n");  }}

 

 

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