#include <stdio.h>
#include "coalesce.h"
#include "block_header.h"
#include "other.h"

void * coalesce(void *ptr, heap_t *heap, allocator_t *allocator) {
    void *prev;
    int fixed_list_id, i;
    maptable_node_t *current_maptable_node;

    prev = get_previous(ptr);

    // Check if it is a block of a fixed list
    fixed_list_id = map_size_to_list(heap, get_size(prev));
    if(fixed_list_id != -1) {
        // If it is, find the fixed list and remove the block
        current_maptable_node = heap->maptable_head;
        if(fixed_list_id != 0) {
            for(i = 1; i < fixed_list_id; i++) {
                current_maptable_node = current_maptable_node->next;
            }
        }
        remove_block(ptr, current_maptable_node->fixed_list_head);
    }

    // Set the new size
    // Note: the rest of the header variables will be set on free().
    set_size(prev, get_size(prev) + get_size(ptr) + HEADER_SIZE);

    /* If the current block is the allocator's border pointer, update the
     * latter to point to the previous block.
     */
    if(allocator->border_ptr == ptr)
    {
        allocator->border_ptr = prev;
    }

    return prev;
}