void mm_addfreechunk(FAR struct mm_heap_s *heap, FAR struct mm_freenode_s *node)
{
FAR struct mm_freenode_s *next;
FAR struct mm_freenode_s *prev;
/* Convert the size to a nodelist index */
int ndx = mm_size2ndx(node->size);
/* Now put the new node int the next */
for (prev = &heap->mm_nodelist[ndx], next = heap->mm_nodelist[ndx].flink;
next && next->size && next->size < node->size;
prev = next, next = next->flink);
/* Does it go in mid next or at the end? */
prev->flink = node;
node->blink = prev;
node->flink = next;
if (next)
{
/* The new node goes between prev and next */
next->blink = node;
}
}
FAR void *mm_malloc(FAR struct mm_heap_s *heap, size_t size)
{
FAR struct mm_freenode_s *node;
void *ret = NULL;
int ndx;
/* Handle bad sizes */
if (size <= 0)
{
return NULL;
}
/* Adjust the size to account for (1) the size of the allocated node and
* (2) to make sure that it is an even multiple of our granule size.
*/
size = MM_ALIGN_UP(size + SIZEOF_MM_ALLOCNODE);
/* We need to hold the MM semaphore while we muck with the nodelist. */
mm_takesemaphore(heap);
/* Get the location in the node list to start the search. Special case
* really big allocations
*/
if (size >= MM_MAX_CHUNK)
{
ndx = MM_NNODES-1;
}
else
{
/* Convert the request size into a nodelist index */
ndx = mm_size2ndx(size);
}
/* Search for a large enough chunk in the list of nodes. This list is
* ordered by size, but will have occasional zero sized nodes as we visit
* other mm_nodelist[] entries.
*/
for (node = heap->mm_nodelist[ndx].flink;
node && node->size < size;
node = node->flink);
/* If we found a node with non-zero size, then this is one to use. Since
* the list is ordered, we know that is must be best fitting chunk
* available.
*/
if (node)
{
FAR struct mm_freenode_s *remainder;
FAR struct mm_freenode_s *next;
size_t remaining;
/* Remove the node. There must be a predecessor, but there may not be
* a successor node.
*/
DEBUGASSERT(node->blink);
node->blink->flink = node->flink;
if (node->flink)
{
node->flink->blink = node->blink;
}
/* Check if we have to split the free node into one of the allocated
* size and another smaller freenode. In some cases, the remaining
* bytes can be smaller (they may be SIZEOF_MM_ALLOCNODE). In that
* case, we will just carry the few wasted bytes at the end of the
* allocation.
*/
remaining = node->size - size;
if (remaining >= SIZEOF_MM_FREENODE)
{
/* Get a pointer to the next node in physical memory */
next = (FAR struct mm_freenode_s*)(((char*)node) + node->size);
/* Create the remainder node */
remainder = (FAR struct mm_freenode_s*)(((char*)node) + size);
remainder->size = remaining;
remainder->preceding = size;
/* Adjust the size of the node under consideration */
node->size = size;
/* Adjust the 'preceding' size of the (old) next node, preserving
* the allocated flag.
*/
next->preceding = remaining | (next->preceding & MM_ALLOC_BIT);
/* Add the remainder back into the nodelist */
mm_addfreechunk(heap, remainder);
}
/* Handle the case of an exact size match */
node->preceding |= MM_ALLOC_BIT;
ret = (void*)((char*)node + SIZEOF_MM_ALLOCNODE);
}
mm_givesemaphore(heap);
/* If CONFIG_DEBUG_MM is defined, then output the result of the allocation
* to the SYSLOG.
*/
#ifdef CONFIG_DEBUG_MM
if (!ret)
{
mdbg("Allocation failed, size %d\n", size);
}
else
{
mvdbg("Allocated %p, size %d\n", ret, size);
}
#endif
return ret;
}
