利用函数指针实现C的回调函数，实现调用者和底层驱动的解耦

女爷i 2022-12-11 07:59 80阅读 0赞

1.  新建空项目，命名为RF\_Drive,这个作为底层的驱动。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hoaGhoaGhoaGh3d3d3d3d3d3d3_size_16_color_FFFFFF_t_70][]

1.  添加MyDrive.c文件，向文件中添加代码，模拟驱动一些函数，代码如下：

思路：

EncData和DecData实现信息的加密和解密，由于不同厂家的设备，加密和解密的方式不同，所以不能在底层驱动中实现，需要不同的厂家在自己的函数库中实现。厂家和驱动约定好相同的接口，将函数通过指针传进来，实现函数的回调。

#define  _CRT_SECURE_NO_WARNINGS
    
    #include <stdlib.h>
    
    #include <string.h>
    
    #include <stdio.h>
    
    //完成发送报文的时候,进行数据加密
    
    //定义函数指针类型  通过函数指针类型 来约定 厂商 去实现 加密解密函数的原型
    
    typedef int(*EncData)(unsigned char *in, int inlen, unsigned char *out, int *outlen);
    
    
    
    typedef int(*DecData)(unsigned char *in, int inlen, unsigned char *out, int *outlen);
    
    
    
    typedef struct _Sck_Handle
    
    {
    
        char    version[16];
    
        char    ip[16];
    
        int     port;
    
        unsigned char *p;
    
        int         len;
    
        char        *p2;
    
    }Sck_Handle;
    
    
    
    int socketclient_sendAndEnc1(void *handle, unsigned char *buf, int buflen, EncData encDataCallback)
    
    {
    
        int     ret = 0;
    
        unsigned char cryptbuf[4096];
    
        int             cryptbuflen = 4096;
    
        Sck_Handle  *tmpHandle = NULL;
    
        if (handle == NULL || buf == NULL || encDataCallback == NULL)
    
        {
    
            ret = -1;
    
            printf("func socketclient_sendAndEnc1() err :%d  check handle == NULL err \n", ret);
    
            return ret;
    
        }
    
        ret = encDataCallback(buf, buflen, cryptbuf, &cryptbuflen); //间接的调用子任务
    
        if (ret != 0)
    
        {
    
            ret = -2;
    
            printf("func socketclient_sendAndEnc1() err :%d  check handle == NULL err \n", ret);
    
            return ret;
    
        }
    
        tmpHandle = (Sck_Handle *)handle;
    
        tmpHandle->len = cryptbuflen;
    
        tmpHandle->p = (unsigned char *)malloc(cryptbuflen);
    
        if (tmpHandle->p == NULL)
    
        {
    
            ret = -3;
    
            printf("func socketclient_sendAndEnc1() err :%d  mallocerr \n", ret);
    
            return ret;
    
        }
    
        //把加密的明文  缓存到 内存中
    
        memcpy(tmpHandle->p, cryptbuf, cryptbuflen);
    
        return 0;
    
    }
    
    //socket客户端环境初始化
    
    int socketclient_init(void **handle)
    
    {
    
        int         ret = 0;
    
        Sck_Handle  *tmpHandle = NULL;
    
        if (handle == NULL)
    
        {
    
            ret = -1;
    
            printf("func socketclient_init() err :%d  check handle == NULL err \n", ret);
    
            return ret;
    
        }
    
        tmpHandle = (Sck_Handle *)malloc(sizeof(Sck_Handle));
    
        if (tmpHandle == NULL)
    
        {
    
            ret = -2;
    
            printf("func socketclient_init() err :%d  malloc err \n", ret);
    
            return ret;
    
        }
    
        memset(tmpHandle, 0, sizeof(Sck_Handle));
    
        strcpy(tmpHandle->version, "1.0.0.1");
    
        strcpy(tmpHandle->ip, "192.168.12.12");
    
        tmpHandle->port = 8081;
    
        //间接赋值
    
        *handle = tmpHandle;
    
        return ret;
    
    }
    
    //socket报文发送
    
    int socketclient_send(void *handle, unsigned char *buf, int buflen)
    
    {
    
        int         ret = 0;
    
        Sck_Handle  *tmpHandle = NULL;
    
        if (handle == NULL || buf == NULL || buflen <= 0)
    
        {
    
            ret = -2;
    
            printf("func socketclient_send() err :%d  (handle == NULL ||  buf==NULL || buflen <=0 ) \n", ret);
    
            return ret;
    
        }
    
        tmpHandle = (Sck_Handle *)handle;
    
        tmpHandle->len = buflen;
    
        tmpHandle->p = (unsigned char *)malloc(buflen);
    
        if (tmpHandle->p == NULL)
    
        {
    
            ret = -2;
    
            printf("func socketclient_send() err :%d  malloc len:%d \n", ret, buflen);
    
            return ret;
    
        }
    
        memcpy(tmpHandle->p, buf, buflen); //数据的缓存到内存
    
        return ret;
    
    }
    
    //socket报文接受
    
    int socketclient_recv(void *handle, unsigned char *buf, int *buflen)
    
    {
    
        int         ret = 0;
    
        Sck_Handle  *tmpHandle = NULL;
    
        if (handle == NULL || buf == NULL || buflen == NULL)
    
        {
    
            ret = -2;
    
            printf("func socketclient_recv() err :%d  (handle == NULL ||  buf==NULL || buflen==NULL ) \n", ret);
    
            return ret;
    
        }
    
        tmpHandle = (Sck_Handle *)handle;
    
        memcpy(buf, tmpHandle->p, tmpHandle->len);
    
        *buflen = tmpHandle->len; //间接赋值  告诉调用者 收到的数据的长度
    
        return ret;
    
    }
    
    //socket环境释放
    
    
    
    int socketclient_destory(void *handle)
    
    {
    
        int         ret = 0;
    
        Sck_Handle  *tmpHandle = NULL;
    
        if (handle == NULL)
    
        {
    
            return -1;
    
        }
    
        tmpHandle = (Sck_Handle *)handle;
    
        if (tmpHandle->p != NULL)
    
        {
    
            free(tmpHandle->p); //释放结构体 成员域的 指针所指向的内存空间
    
        }
    
        free(tmpHandle); //释放结构体内存
    
        return 0;
    
    }

1.  添加MyDrive.h文件。

完成后，右键项目，将配置类型改为dll动态链接库。

1.  新建TestDrive工程，测试底层dll。将生成的RF\_Drive.dll、RF\_Drive.lib和MyDrive.h文件放到工程目录下面。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hoaGhoaGhoaGh3d3d3d3d3d3d3_size_16_color_FFFFFF_t_70 1][]

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1.  将RF\_Drive链接到TestDrive。选择输入，然后选择附加依赖项，将RF\_Drive.lib添加进去，然后点击确定。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hoaGhoaGhoaGh3d3d3d3d3d3d3_size_16_color_FFFFFF_t_70 3][]

1.  将MyDrive.h包含到项目，然后新建Test.c文件，在Test.c中写入测试代码。代码如下：

#ifndef _INC_MYDRIVE_H__
    
    #define _INC_MYDRIVE_H__
    
    
    
    #define Import_SSS
    
    
    
    #ifdef Import_SSS
    
    #define API _declspec(dllexport)
    
    #else
    
    #define API _declspec(dllimport)
    
    
    
    #endif
    
    
    
    #ifdef  __cplusplus
    
    extern "C" {
    
    #endif
    
    
    
        //1 数据类型的封装
    
        //2 handle的概念:  底层库的内存资源,记录着函数运行的上下文信息..
    
        //3 底层库提供的是一种机制, 而不是满足某一个人的策略
    
    
    
        //完成发送报文的时候,进行数据加密
    
        //定义函数指针类型  通过函数指针类型 来约定 厂商 去实现 加密解密函数的原型
    
        typedef int(*EncData)(unsigned char *in, int inlen, unsigned char *out, int *outlen);
    
        typedef int(*DecData)(unsigned char *in, int inlen, unsigned char *out, int *outlen);
    
        API
    
            int socketclient_init(void **handle);
    
        API
    
            int socketclient_send(void *handle, unsigned char *buf, int buflen);
    
        API
    
            int socketclient_sendAndEnc1(void *handle, unsigned char *buf, int buflen, EncData encDataCallback);
    
        API
    
            int socketclient_recv(void *handle, unsigned char *buf, int *buflen);
    
        API
    
            int socketclient_destory(void *handle);
    
    
    
    #ifdef  __cplusplus
    
     }
    
    #endif
    
    
    
    #endif

思路：

在调用者实现加密算法Hw\_EncData，不同的调用者，实现加密算法的方式不同，需要调用者自己实现，然后将函数的指针传递给底层驱动。

#define  _CRT_SECURE_NO_WARNINGS
    
    #include <stdlib.h>
    
    #include <string.h>
    
    #include <stdio.h>
    
    #include "MyDrive.h"
    
    
    
    int Hw_EncData(unsigned char *in, int inlen, unsigned char *out, int *outlen)
    
    {
    
        printf("func Hw_EncData begin....\n ");
    
        strcpy((char *)out, "123456789");
    
        *outlen = 9;
    
        printf("func Hw_EncData end....\n ");
    
        return 0;
    
    }
    
    
    
    void main()
    
    {
    
        unsigned char buf[1024];
    
        int buflen;
    
        unsigned char out[1024];
    
        int outlen;
    
        void *handle = NULL;
    
        int ret = 0;
    
        strcpy((char *)buf, "aaaaaaaaaffffffffdddddddd");
    
        buflen = 9;
    
        //客户端初始化 获取handle上下
    
        ret = socketclient_init(&handle /*out*/);
    
        if (ret != 0)
    
        {
    
            printf("func socketclient_init() err:%d \n ", ret);
    
            goto End;
    
        }
    
        //客户端发报文
    
        //ret = socketclient_send(handle /*in*/, buf /*in*/,  buflen /*in*/);
    
        ret = socketclient_sendAndEnc1(handle, buf, buflen, Hw_EncData);
    
        if (ret != 0)
    
        {
    
            printf("func socketclient_send() err:%d \n ", ret);
    
            goto End;
    
        }
    
        //客户端收报文
    
        ret = socketclient_recv(handle /*in*/, out /*in*/, &outlen/*in out*/);
    
        if (ret != 0)
    
        {
    
            printf("func socketclient_recv() err:%d \n ", ret);
    
            goto End;
    
        }
    
    End:
    
        //客户端释放资源
    
        ret = socketclient_destory(handle/*in*/);
    
        printf("hello...\n");
    
        system("pause");
    
        printf("hello...\n");
    
        system("pause");
    
        return;
    
    }

运行结果如下：

![20200929162052526.png][]

代码：[https://download.csdn.net/download/hhhhhhhhhhwwwwwwwwww/12898322][https_download.csdn.net_download_hhhhhhhhhhwwwwwwwwww_12898322]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hoaGhoaGhoaGh3d3d3d3d3d3d3_size_16_color_FFFFFF_t_70]: /images/20221123/5bb9e5dd19584c9e83250659da6e0510.png
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hoaGhoaGhoaGh3d3d3d3d3d3d3_size_16_color_FFFFFF_t_70 3]: /images/20221123/b6c8ffb604874365a42cca8c4dcaa9ff.png
[20200929162052526.png]: /images/20221123/190f873b1b6f465695b4456379a70f54.png
[https_download.csdn.net_download_hhhhhhhhhhwwwwwwwwww_12898322]: https://download.csdn.net/download/hhhhhhhhhhwwwwwwwwww/12898322