链表管理内存

//mem.h
#include <stdio.h>
#include <stdlib.h>


void *mymalloc(size_t size);

void myfree(void *p);

void *myrealloc(void *p, size_t size);

//记录分配的内存地址的大小,地址
struct MEM
{
    void *p;
    int size;
};

typedef struct LinkNode
{
    struct MEM *pmem;//保存指针
    struct LinkNode *pNext;//指向下一个节点
}node,*PNODE;

struct LinkNode *phead;


PNODE addback(PNODE phead, struct MEM *pmem);
PNODE change(PNODE phead, void *pfind, struct MEM *pnewmem);
PNODE findit(PNODE phead, void *pfind);
PNODE deletenode(PNODE phead, void *paddr);
PNODE deleteall(PNODE phead);
void showall(PNODE phead);

void getinfo(PNODE phead);



//mem.c
#include "mem.h"
struct LinkNode *phead = NULL;


void *mymalloc(size_t size)
{

    void *p = malloc(size);
    //printf("分配内存地址%p,大小%d
", p, size);
    struct MEM *pmem = malloc(sizeof(struct MEM));
    pmem->p = p;
    pmem->size = size;
    phead = addback(phead, pmem);
    return p;
}

void myfree(void *p)
{
    PNODE *px = findit(phead, p);
    if (px == NULL)
    {
        return;
    }
    else
    {
        phead = deletenode(phead, p);
        free(p);
    }
}

void *myrealloc(void *p, size_t size)
{
    
    void *pt = realloc(p, size);
    struct MEM mymem;
    mymem.p = pt;
    mymem.size = size;
    change(phead, p, &mymem);
    return pt;
}


PNODE addback(PNODE phead, struct MEM *pmem)
{
    PNODE pnew = malloc(sizeof(node));
    pnew->pmem = pmem;
    pnew->pNext = NULL;

    if (phead == NULL)
    {
        phead = pnew;
    }
    else
    {
        PNODE ptemp = phead;
        while (ptemp->pNext != NULL)
        {
            ptemp = ptemp->pNext;
        }
        ptemp->pNext = pnew;
    }
    return phead;
}

PNODE change(PNODE phead, void *pfind, struct MEM *pnewmem)
{
    for (PNODE p = phead; p != NULL; p = p->pNext)
    {
        if (p->pmem->p == pfind)
        {
            p->pmem->p = pnewmem->p;
            p->pmem->size = pnewmem->size;
            return phead;
        }
    }
    return phead;
}

PNODE deletenode(PNODE phead, void *paddr)
{
    PNODE p1, p2;
    p1 = p2 = NULL;
    p1 = phead;
    while (p1 != NULL)
    {
        if (p1->pmem->p == paddr)
        {
            break;
        }
        else
        {
            p2 = p1;
            p1 = p1->pNext;
        }
    }

    if (p1 != NULL)
    {
        if (p1 != phead)
        {
            p2->pNext = p1->pNext;
            free(p1);
        }
        else
        {
            phead = phead->pNext;
            free(p1);
        }
    }
    

    return phead;
}
void showall(PNODE phead)
{
    if (phead == NULL)
    {
        return;
    }
    else
    {
        printf("memaddr=%p,size=%d
", phead->pmem->p, phead->pmem->size);
        showall(phead->pNext);
    }
}

PNODE findit(PNODE phead, void *pfind)
{
    for (PNODE p = phead; p != NULL; p = p->pNext)
    {
        if (p->pmem->p == pfind)
        {
            return p;
        }
    }
    return NULL;
}

void getinfo(PNODE phead)
{
    int i = 0;//多少个地址
    int j = 0;//多少个字节内存
    for (PNODE p = phead; p != NULL; p = p->pNext)
    {
        i++;
        j += p->pmem->size;;
    }
    printf("目前一共%d个地址在使用,一共消耗%d内存
",i,j);
}

PNODE deleteall(PNODE phead)
{
    PNODE p1, *p2;
    p1 = NULL;
    p2 = NULL;
    if (phead == NULL)
    {
        return;
    }
    else
    {
        p1 = phead;
        while (p1->pNext != NULL)
        {
            p2 = p1->pNext;
            printf("内存%p被删除
", p1->pmem->p);
            free(p1->pmem->p);
            free(p1);
            p1 = p2;

        }
        printf("内存%p被删除
", p1->pmem->p);
        free(p1->pmem->p);
        free(p1);
    }
    return NULL;
}


//main.c
#include "mem.h"
#define malloc mymalloc
#define free myfree
#define realloc myrealloc


void main()
{
    void *p1 = malloc(10);
    void *p2 = malloc(11);
    void *p3 = malloc(12);
    void *p4 = malloc(13);
    showall(phead);
    printf("


");
    p1 = realloc(p1, 100);
    showall(phead);
    printf("


");
    free(p1);
    showall(phead);
    printf("


");
    printf("


");
    phead = deleteall(phead);
    showall(phead);
    system("pause");
}

 //指针的副本机制   在函数参数中 如果传递的是指针，当改变的是指针所指向的地址，则改变的是作为参数的指针所指向的内存，原来的指针所指向的地址不变，改变的是这片内存所储存的内容 要改变一个n级指针需要n+1级指针