typedef struct MemoryBlock{
    void *data;//內(nèi)存塊起始地址
    struct MemoryBlock *next;//下一個內(nèi)存塊的地址
}MemoryBlock;

typedef struct MemoryPool{
    MemoryBlock *freeList;//空閑內(nèi)存塊鏈表
    MemoryBlock *usedList;//占用內(nèi)存塊鏈表
    int freeCount;//空閑內(nèi)存塊數(shù)量
    int usedCount;//占用內(nèi)存塊數(shù)量
    int blockCount;//內(nèi)存塊總數(shù)量
}MemoryPool;

MemoryPool *InitMemoryPool(int blockSize, int blockCount)
{
    MemoryPool *pool = NULL;


    pool = (MemoryPool *)malloc(sizeof(MemoryPool));//為內(nèi)存池分配空間
    pool->freeList = NULL;
    pool->usedList = NULL;
    for(int i = 0; i < blockCount; i++)
    {
        //創(chuàng)建內(nèi)存塊節(jié)點，插入到空閑鏈表
        MemoryBlock * block = (MemoryBlock *)malloc(sizeof(MemoryBlock));
        block->data = malloc(blockSize);
        block->next = pool->freeList;
        pool->freeList = block;
    }
    //初始化狀態(tài)
    pool->freeCount = blockCount;
    pool->usedList = 0;
    pool->blockCount = blockCount;

    return pool;
}

void *AllocateBlock(MemoryPool *pool)
{
    if(pool->freeList == NULL || pool->freeCount == 0)
        return NULL;
    MemoryBlock *node = pool->freeList;
    //該內(nèi)存塊從空閑鏈表刪除
    pool->freeList = node->next;
    //該內(nèi)存塊插入到占用鏈表
    node->next = pool->usedList;
    pool->usedList = node;
    //更新空閑，占用狀態(tài)
    pool->usedCount++;
    pool->freeCount--;

    return node->data;
}

void FreeBlock(MemoryPool *pool, void *data)
{
    MemoryBlock *cur = pool->usedList;
    MemoryBlock *pre = NULL;

    //尋找給內(nèi)存塊的節(jié)點
    while(pre != NULL && cur->data != data)
    {
        pre = cur;
        cur = cur->next;
    }
    if(cur == NULL)
        return;
    //將該內(nèi)存塊從占用鏈表刪除
    if(pre != NULL)
        pre->next = cur->next;
    else
        pool->usedList = cur->next;
    //將該內(nèi)存塊插入到空閑鏈表
    cur->next = pool->freeList;
    pool->freeList = cur;

    pool->freeCount++;
    pool->usedCount--;

   return;
}

void DestroyMemoryPool(MemoryPool *pool)
{
    MemoryBlock *pre = NULL;
    //釋放所有空閑內(nèi)存塊空間
    while(pool->freeList != NULL)
    {
        pre = pool->freeList;
        free(pool->freeList->data);
        pool->freeList = pool->freeList->next;
        free(pre);
    }
    //釋放所有占用內(nèi)存塊空間
    while(pool->usedList != NULL)
    {
        pre = pool->usedList;
        free(pool->usedList->data);
        pool->usedList = pool->usedList->next;
        free(pre);
    }
    //釋放內(nèi)存池空間
    free(pool);

    pool->freeList = NULL;
    pool->usedList = NULL;
    pool->freeCount = 0;
    pool->usedCount = 0;

    return;
}

int main(void)
{
    MemoryPool *pool;

    pool = InitMemoryPool(10, 5);

    int *str = (int *)AllocateBlock(pool);
    *str = 2;
    int *ptr = (int *)AllocateBlock(pool);
    *ptr = 3;
    printf("free block : %d, used block : %d\n", pool->freeCount, pool->usedCount);
    FreeBlock(pool, ptr);
    printf("free block : %d, used block : %d\n", pool->freeCount, pool->usedCount);

    DestroyMemoryPool(pool);

    return 0;
}