klish/lub/heap/heap_extend_downwards.c

#include "private.h"

/*--------------------------------------------------------- */
bool_t
lub_heap_extend_downwards(lub_heap_t * this,
			  lub_heap_block_t ** ptr_block, const words_t words)
{
	lub_heap_block_t *block = *ptr_block;
	lub_heap_free_block_t *prev_block =
	    (lub_heap_free_block_t *) lub_heap_block_getprevious(block);
	bool_t result = BOOL_FALSE;

	if (NULL != prev_block) {
		/* Do we have a free block below us? */
		if (1 == prev_block->tag.free) {
			int segment;
			void *tmp;

			/* work out how many extra words we need */
			words_t delta = words - block->alloc.tag.words;

			/* remove the block from the tree */
			lub_bintree_remove(&this->free_tree, prev_block);

			/* remember the segment status */
			segment = prev_block->tag.segment;

			/* try and slice off a chunk of memory */
			tmp =
			    lub_heap_slice_from_top(this, &prev_block, &delta,
						    BOOL_FALSE);

			if (NULL != prev_block) {
				/* put the modified free block back into the tree */
				lub_bintree_insert(&this->free_tree,
						   prev_block);

				/* there is still a block below us */
				segment = 0;
			}
			if (NULL != tmp) {
				/* we managed to extend downwards */
				lub_heap_tag_t *tail =
				    lub_heap_block__get_tail(block);
				lub_heap_block_t *new_block = tmp;

				/* get ready to copy the data down accounts for the header */
				words_t old_words = tail->words;
				const unsigned int *src = (unsigned int *)block;
				unsigned int *dst = (unsigned int *)new_block;

				/* copy the old data to the new location */
				while (old_words--) {
					*dst++ = *src++;
				}
				/* taint the extra memory */
				lub_heap_taint_memory(((char *)tail) -
						      (delta << 2),
						      LUB_HEAP_TAINT_ALLOC,
						      (delta << 2));

				/* fill out the new block details */
				tail->words += delta;
				this->stats.alloc_bytes += (delta << 2);
				this->stats.alloc_total_bytes += (delta << 2);

				new_block->alloc.tag.segment = segment;
				new_block->alloc.tag.free = 0;
				new_block->alloc.tag.words = tail->words;

				/* update the clients pointer */
				*ptr_block = new_block;

				result = BOOL_TRUE;
			}
		}
	}
	return result;
}

/*--------------------------------------------------------- */