/*!
* Free memory chunk
* \param mpool Memory pool to be used (if NULL default pool is used)
* \param chunk Chunk location (starting address)
* \return 0 if successful, -1 otherwise
*/
int ffs_free ( ffs_mpool_t *mpool, void *chunk_to_be_freed )
{
ffs_hdr_t *chunk, *before, *after;
ASSERT ( mpool && chunk_to_be_freed );
chunk = chunk_to_be_freed - sizeof (size_t);
MARK_FREE ( chunk ); /* mark it as free */
/* join with left? */
before = ( (void *) chunk ) - sizeof(size_t);
if ( CHECK_FREE ( before ) )
{
before = GET_HDR ( before );
ffs_remove_chunk ( mpool, before );
before->size += chunk->size; /* join */
chunk = before;
}
/* join with right? */
after = GET_AFTER ( chunk );
if ( CHECK_FREE ( after ) )
{
ffs_remove_chunk ( mpool, after );
chunk->size += after->size; /* join */
}
/* insert chunk in free list */
ffs_insert_chunk ( mpool, chunk );
/* set chunk tail */
CLONE_SIZE_TO_TAIL ( chunk );
return 0;
}
/*!
* Get free chunk with required size (or slightly bigger)
* \param mpool Memory pool to be used (if NULL default pool is used)
* \param size Requested chunk size
* \return Block address, NULL if can't find adequate free chunk
*/
void *ffs_alloc ( ffs_mpool_t *mpool, size_t size )
{
ffs_hdr_t *iter, *chunk;
ASSERT ( mpool );
size += sizeof (size_t) * 2; /* add header and tail size */
if ( size < HEADER_SIZE )
size = HEADER_SIZE;
/* align request size to higher 'size_t' boundary */
ALIGN_FW ( size );
iter = mpool->first;
while ( iter != NULL && iter->size < size )
iter = iter->next;
if ( iter == NULL )
return NULL; /* no adequate free chunk found */
if ( iter->size >= size + HEADER_SIZE )
{
/* split chunk */
/* first part remains in free list, just update size */
iter->size -= size;
CLONE_SIZE_TO_TAIL ( iter );
chunk = GET_AFTER ( iter );
chunk->size = size;
}
else { /* give whole chunk */
chunk = iter;
/* remove it from free list */
ffs_remove_chunk ( mpool, chunk );
}
MARK_USED ( chunk );
CLONE_SIZE_TO_TAIL ( chunk );
return ( (void *) chunk ) + sizeof (size_t);
}
