klish/lub/heap/heap_block_getprevious.c

#include "private.h"

/*--------------------------------------------------------- */
lub_heap_block_t *lub_heap_block_getprevious(lub_heap_block_t * this)
{
	lub_heap_block_t *result = NULL;

	/* only go back if this is not the first block in the segment */
	if (0 == this->alloc.tag.segment) {
		/* get the tag from the previous block */
		lub_heap_tag_t *tag = &(&this->alloc.tag)[-1];

		/* get a pointer to the previous block 
		 * +1 required to account for header tag
		 */
		tag = &tag[1 - tag->words];

		/* now point to the start of the previous block */
		result = (lub_heap_block_t *) tag;
	}
	return result;
}

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