smalloc.c

来自「source code of armboot for s3c4510」· C语言 代码 · 共 61 行

/* smalloc.c: simple malloc using a heap that grows down
 *
 */

#ifdef DEBUG
#define dprintf(arg...) printf(arg)
#else
#define dprintf(arg...)
#endif

/* very simple.  At the beginning of the block is the size.
   That's all.  We keep track of the bottom and the absolute
   bottom.  A zero size block marks the top, size -ve is free */

int * last_block;
int * bottom;

int smalloc_init(void * mem, int size)
{
	bottom = (int *)(((int)mem + 3) & ~0x3);
	last_block = (int *)(((int)mem + size - 1) & ~0x3);
	*last_block = 0;
}

void *
smalloc_malloc(int size)
{
  int * p;

  for (p=last_block; *p; p += (*p < 0) ? -*p : *p) {

    if (*p > 0) continue;
    if (size > (-*p)<<1 && (size + 4) <= ((-*p) << 2)) { /* up to 2 times */
      *p = -(*p);
      dprintf("reuse of %d(%d)\n",size,*p*4);
      return p+1;
    }
  }
  /* nothing matches */

  p = last_block - ((size + 3) >> 2) - 1;
  *p = last_block - p;

  last_block = p;
  dprintf("new of %d.  %d free\n", size, (int)(last_block - bottom) * 4);

  return p+1;
}

int
smalloc_free(void *ptr)
{
  int * p = ptr;
  if (!ptr) return 0;
  p--;

  dprintf("free %d\n",*p * 4);
  *p = -(*p);
}