tiny-malloc.c

Newlib 嵌入式 C库 标准实现代码

  if (old_real_size - real_size >= sizeof (struct freelist_entry))
    {
      fle newblock = (fle)((size_t)block + real_size);
      block->size = real_size;
      newblock->size = old_real_size - real_size;
      free (&newblock->next);
    }
  return block_p;
}
#endif

#ifdef DEFINE_CALLOC
void *
calloc (size_t n, size_t elem_size)
{
  void *result;
  size_t sz = n * elem_size;
  result = malloc (sz);
  if (result != NULL)
    memset (result, 0, sz);
  return result;
}
#endif

#ifdef DEFINE_CFREE
void
cfree (void *p)
{
  free (p);
}
#endif

#ifdef DEFINE_MEMALIGN
void *
memalign (size_t align, size_t sz)
{
  fle *nextfree;
  fle block;

  /* real_size is the size we actually have to allocate, allowing for
     overhead and alignment.  */
  size_t real_size = REAL_SIZE (sz);

  /* Some sanity checking on 'align'. */
  if ((align & (align - 1)) != 0
      || align <= 0)
    return NULL;

  /* Look for the first block on the freelist that is large enough.  */
  /* One tricky part is this: We want the result to be a valid pointer
     to free.  That means that there has to be room for a size_t
     before the block.  If there's additional space before the block,
     it should go on the freelist, or it'll be lost---we could add it
     to the size of the block before it in memory, but finding the
     previous block is expensive.  */
  for (nextfree = &__malloc_freelist; 
       ; 
       nextfree = &(*nextfree)->next)  
    {
      size_t before_size;
      size_t old_size;

      /* If we've run out of free blocks, allocate more space.  */
      if (! *nextfree)
	{
	  old_size = real_size;
	  if (MALLOC_DIRECTION < 0)
	    {
	      old_size += M_ALIGN_SUB (((size_t)__malloc_end 
					- old_size + sizeof (size_t)),
				       align);
	      if (! CAN_ALLOC_P (old_size))
		return NULL;
	      block = __malloc_end = (void *)((size_t)__malloc_end - old_size);
	    }
	  else
	    {
	      block = __malloc_end;
	      old_size += M_ALIGN ((size_t)__malloc_end + sizeof (size_t),
				   align);
	      if (! CAN_ALLOC_P (old_size))
		return NULL;
	      __malloc_end = (void *)((size_t)__malloc_end + old_size);
	    }
	  *nextfree = block;
	  block->size = old_size;
	  block->next = NULL;
	}
      else
	{
	  block = *nextfree;
	  old_size = block->size;
	}
      

      before_size = M_ALIGN (&block->next, align);
      if (before_size != 0)
	before_size = sizeof (*block) + M_ALIGN (&(block+1)->next, align);

      /* If this is the last block on the freelist, and it is too small,
	 enlarge it.  */
      if (! block->next
	  && old_size < real_size + before_size
	  && __malloc_end == (void *)((size_t)block + block->size))
	{
	  if (MALLOC_DIRECTION < 0)
	    {
	      size_t moresize = real_size - block->size;
	      moresize += M_ALIGN_SUB ((size_t)&block->next - moresize, align);
	      if (! CAN_ALLOC_P (moresize))
		return NULL;
	      block = __malloc_end = (void *)((size_t)block - moresize);
	      block->next = NULL;
	      block->size = old_size = old_size + moresize;
	      before_size = 0;
	    }
	  else
	    {
	      if (! CAN_ALLOC_P (before_size + real_size - block->size))
		return NULL;
	      __malloc_end = (void *)((size_t)block + before_size + real_size);
	      block->size = old_size = before_size + real_size;
	    }

	  /* Two out of the four cases below will now be possible; which
	     two depends on MALLOC_DIRECTION.  */
	}

      if (old_size >= real_size + before_size)
	{
	  /* This block will do.  If there needs to be space before it, 
	     split the block.  */
	  if (before_size != 0)
	    {
	      fle old_block = block;

	      old_block->size = before_size;
	      block = (fle)((size_t)block + before_size);
	      
	      /* If there's no space after the block, we're now nearly
                 done; just make a note of the size required.  
	         Otherwise, we need to create a new free space block.  */
	      if (old_size - before_size 
		  <= real_size + sizeof (struct freelist_entry))
		{
		  block->size = old_size - before_size;
		  return (void *)&block->next;
		}
	      else 
		{
		  fle new_block;
		  new_block = (fle)((size_t)block + real_size);
		  new_block->size = old_size - before_size - real_size;
		  if (MALLOC_DIRECTION > 0)
		    {
		      new_block->next = old_block->next;
		      old_block->next = new_block;
		    }
		  else
		    {
		      new_block->next = old_block;
		      *nextfree = new_block;
		    }
		  goto done;
		}
	    }
	  else
	    {
	      /* If the block found is just the right size, remove it from
		 the free list.  Otherwise, split it.  */
	      if (old_size <= real_size + sizeof (struct freelist_entry))
		{
		  *nextfree = block->next;
		  return (void *)&block->next;
		}
	      else
		{
		  size_t newsize = old_size - real_size;
		  fle newnext = block->next;
		  *nextfree = (fle)((size_t)block + real_size);
		  (*nextfree)->size = newsize;
		  (*nextfree)->next = newnext;
		  goto done;
		}
	    }
	}
    }

 done:
  block->size = real_size;
  return (void *)&block->next;
}
#endif

#ifdef DEFINE_VALLOC
void *
valloc (size_t sz)
{
  return memalign (128, sz);
}
#endif
#ifdef DEFINE_PVALLOC
void *
pvalloc (size_t sz)
{
  return memalign (128, sz + M_ALIGN (sz, 128));
}
#endif

#ifdef DEFINE_MALLINFO
#include "malloc.h"

struct mallinfo 
mallinfo (void)
{
  struct mallinfo r;
  fle fr;
  size_t free_size;
  size_t total_size;
  size_t free_blocks;

  memset (&r, 0, sizeof (r));

  free_size = 0;
  free_blocks = 0;
  for (fr = __malloc_freelist; fr; fr = fr->next)
    {
      free_size += fr->size;
      free_blocks++;
      if (! fr->next)
	{
	  int atend;
	  if (MALLOC_DIRECTION > 0)
	    atend = (void *)((size_t)fr + fr->size) == __malloc_end;
	  else
	    atend = (void *)fr == __malloc_end;
	  if (atend)
	    r.keepcost = fr->size;
	}
    }

  if (MALLOC_DIRECTION > 0)
    total_size = (char *)__malloc_end - (char *)&__malloc_start;
  else
    total_size = (char *)&__malloc_start - (char *)__malloc_end;
  
#ifdef DEBUG
  /* Fixme: should walk through all the in-use blocks and see if
     they're valid.  */
#endif

  r.arena = total_size;
  r.fordblks = free_size;
  r.uordblks = total_size - free_size;
  r.ordblks = free_blocks;
  return r;
}
#endif

#ifdef DEFINE_MALLOC_STATS
#include "malloc.h"
#include <stdio.h>

void 
malloc_stats(void)
{
  struct mallinfo i;
  FILE *fp;
  
  fp = stderr;
  i = mallinfo();
  fprintf (fp, "malloc has reserved %u bytes between %p and %p\n",
	   i.arena, &__malloc_start, __malloc_end);
  fprintf (fp, "there are %u bytes free in %u chunks\n",
	   i.fordblks, i.ordblks);
  fprintf (fp, "of which %u bytes are at the end of the reserved space\n",
	   i.keepcost);
  fprintf (fp, "and %u bytes are in use.\n", i.uordblks);
}
#endif

#ifdef DEFINE_MALLOC_USABLE_SIZE
size_t 
malloc_usable_size (void *block_p)
{
  fle block = (fle)((size_t) block_p - offsetof (struct freelist_entry, next));
  return block->size - sizeof (size_t);
}
#endif

#ifdef DEFINE_MALLOPT
int
mallopt (int n, int v)
{
  (void)n; (void)v;
  return 0;
}
#endif