/*************************************************
* function: implement memory free
**************************************************/

static void _mem_free(MNG_NODE* pNode)
{
    MNG_NODE* pPreNode;

    if(pNode == pAllocList)
    {
        pAllocList = pAllocList->next;
        add_node_into_list_head(pNode, &pFreeList);
        return;
    }   

    pPreNode = find_previous_node_in_list(pNode, pAllocList);
    if(NULL == pPreNode)
        return;

    pPreNode->next = pNode->next;
    add_node_into_list_head(pNode, &pFreeList);
    return;
}

/*************************************************
* function: free memory function
**************************************************/

void mem_free(void* pData)
{
    if(NULL == pData)
        return;

    if(pData < pGlbData || pData >= (void*)((char*)pGlbData + MEM_BUFFER_LENGTH))
        return;

    _mem_free((MNG_NODE*)((char*)pData - sizeof(MNG_NODE)));
}

/*************************************************
* function: get memory buffer
**************************************************/

void mem_init()
{
    pGlbData = (void*)malloc(MEM_BUFFER_LENGTH);
    if(NULL == pGlbData)
        return;

    memset(pGlbData, 0, MEM_BUFFER_LENGTH);
    pFreeList = (MNG_NODE*)pGlbData;
    pFreeList->size = MEM_BUFFER_LENGTH - sizeof(MNG_NODE);
    pAllocList = NULL;
}

/*************************************************
* function: free memory buffer
**************************************************/

void mem_exit()
{
    if(NULL != pGlbData)
        free(pGlbData);  

    pFreeList = NULL;
    pAllocList = NULL;
}

/*************************************************
* function: file starts here
**************************************************/

int main(int argc, char* argv[])
{
    mem_init();
    mem_exit();
    return 1;
}