kolibrios/programs/develop/ktcc/trunk/libc.obj/source/stdlib/free.c

#include <stdlib.h>
#include <stdbool.h>
#include <sys/ksys.h>
#include "_mem.h"

void free(void* ptr)
{
    // Handle NULL pointer.
    if (ptr == NULL)
        return;

    // Get a pointer to the mem_node header from the user data pointer.
    struct mem_node* node = GET_MEM_NODE_HEADER(ptr);

    // Mark the memory node as free.
    node->free = node->size;

    if (__last_biggest_mem_node == node) {
        if (node->last) {
            __last_biggest_mem_node = node->last; // anyway node will be merged with next
                                                  // and last and last will have size = last + node + next(if its free too)
        }
    }

    // Merge with the next node if possible.
    if (node->next != NULL)
        __mem_MERGE_MEM_NODES(node, node->next);

    // Merge with the previous node if possible.
    if (node->last != NULL)
        node = __mem_MERGE_MEM_NODES(node->last, node);

    if (node) {

        // If the current node is not adjacent to either the next or previous node,
        // it might be a separate block that can be freed.
        if (MEM_NODE_IS_FREE(node) // check it because node maybe was merged with last
            && (node->last == NULL || !MEM_NODES_ARE_IN_ONE_BLOCK(node, node->next))
            && (node->next == NULL || !MEM_NODES_ARE_IN_ONE_BLOCK(node->last, node))) {

            // Get a pointer to the mem_block header from the mem_node header.
            struct mem_block* block = (struct mem_block*)(((char*)node) - sizeof(struct mem_block));

            // Check if the block size matches the node size.
            if (block->size == node->size + sizeof(struct mem_block) + sizeof(struct mem_node)) {

                // Update the linked list pointers to remove the current node.
                if (node->last != NULL)
                    node->last->next = node->next;

                if (node->next != NULL)
                    node->next->last = node->last;

                // Update the head of the linked list if necessary.
                if (__mem_node == node) {
                    if (node->last != NULL) {
                        __mem_node = node->last;
                    } else if (node->next != NULL) {
                        __mem_node = node->next;
                    } else {
                        __mem_node = NULL;
                    }
                }

                struct mem_node* a = node->next;
                struct mem_node* b = node->last;

                if (!a && !b) {
                    __last_biggest_mem_node = NULL;
                } else if (a && !b) {
                    __last_biggest_mem_node = a;
                } else if (!a && b) {
                    __last_biggest_mem_node = b;
                } else if (a && b) {
                    __last_biggest_mem_node = (a->free > b->free) ? a : b;
                }

                if (__last_biggest_mem_node == node) {
                    if (node->next && !(node->last)) {
                        __last_biggest_mem_node = node->next;
                    } else if (node->last && !(node->next)) {
                        __last_biggest_mem_node = node->last;
                    } else if (node->next && node->last) {
                        if (node->last->free > node->next->free) {
                            __last_biggest_mem_node = node->last;
                        } else {
                            __last_biggest_mem_node = node->next;
                        }
                    }
                }

                // Free the memory block using the ksys_free function.
                _ksys_free(block);
            }
        }
    }
}