　hiredis是redis官方推荐的C/C++客户端代码库。使用hiredis库很简易方便的进行redis的相关开发。

同步方式

不过大多数情况下，我们采用的都是同步的调用方式。

/* 和redis服务器建立TCP连接 */

redisContext *redisConnectWithTimeout(const char *ip, int port, const struct timeval tv);

/* 发送指令到redis服务器，并取得结果 */

void *redisCommand(redisContext *c, const char *format, ...);

/* 处理完结果后，释放内存 */

void freeReplyObject(void *reply);

/* 释放和redis服务器的连接 */

void redisFree(redisContext *c);

没错，同步的方式就是这么简单易用。

异步方式

不过说到了同步，那必然得说异步。同步简单，异步性能高。为了性能，或者说为了装B，必须得用一下异步调用方式才能显示得出高大上。

当然，本文不是描述基于libevent，或者基于redis本身得ae网络库的异步方式。而是基于公司（或者自己）已有的异步服务器框架上，我们需要：

将发送redis的请求按照redis的既有协议打包到一个buffer。

将这个buffer丢给异步服务器框架，由框架负责和redis服务器建立（维护）连接，发送请求buffer，并取得redis返回的数据buffer。框架保证这个过程是异步高性能的。

然后框架会给出redis的回包buffer。我们需要按照redis的既有协议解开这个包，并得到结果。

redis的既有协议，这里先不展开描述。回到上面的需求，我们怎么才能打包redis的请求，解包redis的返回数据呢？用习惯了同步的方式，还曾经抱怨hiredis为什么不提供一个打包的函数和一个解包的函数呢。原来是自己眼拙，没看出hiredis库的打包和解包的使用方式。

打包函数系列：

/* Functions to format a command according to the protocol. */

int redisvFormatCommand(char **target, const char *format, va_list ap);

int redisFormatCommand(char **target, const char *format, ...);

int redisFormatCommandArgv(char **target, int argc, const char **argv, const size_t *argvlen);

解包是通过一个redisReader来完成的。

/* State for the protocol parser */

typedef struct redisReader {

int err; /* Error flags, 0 when there is no error */

char errstr[128]; /* String representation of error when applicable */

char *buf; /* Read buffer */

size_t pos; /* Buffer cursor */

size_t len; /* Buffer length */

size_t maxbuf; /* Max length of unused buffer */

redisReadTask rstack[9];

int ridx; /* Index of current read task */

void *reply; /* Temporary reply pointer */

redisReplyObjectFunctions *fn;

void *privdata;

} redisReader;

/* Public API for the protocol parser. */

redisReader *redisReaderCreate(void);

void redisReaderFree(redisReader *r);

int redisReaderFeed(redisReader *r, const char *buf, size_t len);

int redisReaderGetReply(redisReader *r, void **reply);

呵呵，打包和解包看来不是一个简单的函数搞定的，就原谅自己的眼拙了。哈哈。

实战演习

来一个简单的例子（demo.c），假设实例里面的函数

int asyncFrameWork(const uint8_t* sendBuf, int sendBufLen, uint8_t* recvBuf, int* recvBufLen);

就是公司高大上的异步服务器框架了啊。（汗颜一下。。。）

或者把这个asyncFrameWork替换为目前很前沿的微线程（协程）技术，那性能也是相当高的。

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#include "hiredis.h"

#include <stdio.h>

#include <string.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <netinet/in.h>

#include <errno.h>

#include <unistd.h>

#include <stdint.h>

int asyncFrameWork(const uint8_t* sendBuf, int sendBufLen, uint8_t* recvBuf, int* recvBufLen)

{

if (sendBuf == NULL || recvBuf == NULL || sendBufLen < 1 || *recvBufLen < 1) {

printf("asyncFrameWork param error.\n");

return -1;

}

int fd = socket(AF_INET, SOCK_STREAM, 0);

if (fd < 0) {

printf("socket error : %d\n", errno);

return -1;

}

struct sockaddr_in addr;

memset(&addr, 0x00, sizeof(addr));

addr.sin_family = AF_INET;

addr.sin_port = htons(6379);

addr.sin_addr.s_addr = inet_addr("127.0.0.1");

int ret = connect(fd, (struct sockaddr*)&addr, sizeof(addr));

if (ret) {

printf("connect error : %d\n", errno);

close(fd);

return -2;

}

ret = send(fd, sendBuf, sendBufLen, 0);

if (ret < 0) {

printf("send error : %d\n", errno);

close(fd);

return -3;

}

ret = recv(fd, recvBuf, *recvBufLen, 0);

if (ret <= 0) {

printf("recv error : %d\n", errno);

close(fd);

return -4;

}

*recvBufLen = ret;

printf("asyncFrameWork recv len = %d\n", ret);

close(fd);

return 0;

}

int setCmd(const char* key, const char* value)

{

char* cmdBuf = NULL;

int len = 0;

len = redisFormatCommand(&cmdBuf, "SET %s %s", key, value);

if (len < 0) {

printf("redisFormatCommand error! len = %d\n", len);

return -1;

}

printf("redisFormatCommand result: len = %d, cmdBuf = %s\n", len, cmdBuf);

int ret = 0;

char recvBuf[1024] = {

0};

int recvBufLen = sizeof(recvBuf);

ret = asyncFrameWork((const uint8_t*)cmdBuf, len, (uint8_t*)recvBuf, &recvBufLen);

if (ret) {

printf("asyncFrameWork error:%d!\n", ret);

free(cmdBuf);

cmdBuf = NULL;

return -2;

}

printf("asyncFrameWork return : recvBuf = %s, recvBufLen = %d\n", recvBuf, recvBufLen);

free(cmdBuf);

cmdBuf = NULL;

redisReader *reader = NULL;

void *reply = NULL;

reader = redisReaderCreate();

if (reader == NULL) {

printf("redisReaderCreate error!\n");

return -3;

}

redisReaderFeed(reader, recvBuf, recvBufLen);

ret = redisReaderGetReply(reader, &reply);

if (ret != REDIS_OK) {

printf("redisReaderGetReply error:%d!\n", ret);

redisReaderFree(reader);

reader = NULL;

return -4;

}

if (reply == NULL) {

printf("redisReply is NULL!\n");

redisReaderFree(reader);

reader = NULL;

return -5;

}

printf("redisReader get reply : %d\n", *((int*)reply));

struct redisReply *r = (struct redisReply*)reply;

printf("r->type = %d\n", r->type);

if (REDIS_REPLY_ERROR == r->type) {

printf("redisReply return REDIS_REPLY_ERROR!\n");

freeReplyObject(reply);

redisReaderFree(reader);

reader = NULL;

return -6;

}

if (REDIS_REPLY_STATUS != r->type) {

printf("redisReply return is't REDIS_REPLY_STATUS!\n");

freeReplyObject(reply);

redisReaderFree(reader);

reader = NULL;

return -7;

}

printf("-------------------------------------\n");

if (r->integer == REDIS_OK)

printf("set key(%s) OK\n", key);

else

printf("set key(%s) FAIL\n", key);

printf("-------------------------------------\n");

freeReplyObject(reply);

redisReaderFree(reader);

return 0;

}

int getCmd(const char* key)

{

char* cmdBuf = NULL;

int len = 0;

len = redisFormatCommand(&cmdBuf, "GET %s", key);

if (len < 0) {

printf("redisFormatCommand error! len = %d\n", len);

return -1;

}

printf("redisFormatCommand result: len = %d, cmdBuf = %s\n", len, cmdBuf);

int ret = 0;

char recvBuf[1024] = {

0};

int recvBufLen = sizeof(recvBuf);

ret = asyncFrameWork((const uint8_t*)cmdBuf, len, (uint8_t*)recvBuf, &recvBufLen);

if (ret) {

printf("asyncFrameWork error:%d!\n", ret);

free(cmdBuf);

cmdBuf = NULL;

return -2;

}

printf("asyncFrameWork return : recvBuf = %s, recvBufLen = %d\n", recvBuf, recvBufLen);

free(cmdBuf);

cmdBuf = NULL;

redisReader *reader = NULL;

void *reply = NULL;

reader = redisReaderCreate();

if (reader == NULL) {

printf("redisReaderCreate error!\n");

return -3;

}

redisReaderFeed(reader, recvBuf, recvBufLen);

ret = redisReaderGetReply(reader, &reply);

if (ret != REDIS_OK) {

printf("redisReaderGetReply error:%d!\n", ret);

redisReaderFree(reader);

reader = NULL;

return -4;

}

if (reply == NULL) {

printf("redisReply is NULL!\n");

redisReaderFree(reader);

reader = NULL;

return -5;

}

printf("redisReader get reply : %d\n", *((int*)reply));

struct redisReply *r = (struct redisReply*)reply;

printf("r->type = %d\n", r->type);

if (REDIS_REPLY_ERROR == r->type) {

printf("redisReply return REDIS_REPLY_ERROR!\n");

freeReplyObject(reply);

redisReaderFree(reader);

reader = NULL;

return -6;

}

if (REDIS_REPLY_STRING != r->type) {

if (REDIS_REPLY_NIL == r->type) {

printf("-------------------------------------\n");

printf("key(%s) not exists!\n", key);

printf("-------------------------------------\n");

}

else

printf("redisReply return is't REDIS_REPLY_STRING!\n");

freeReplyObject(reply);

redisReaderFree(reader);

reader = NULL;

return -7;

}

printf("r->len = %d\n", r->len);

printf("r->str = %s\n", r->str);

printf("-------------------------------------\n");

printf("key(%s), value=(%s)\n", key, r->str);

printf("-------------------------------------\n");

freeReplyObject(reply);

redisReaderFree(reader);

return 0;

}

int main(int argc, char** argv)

{

setCmd("company", "leoox");

getCmd("company..");

getCmd("company");

return 0;

}

编译

1	gcc -o demo -I/home/leoox/soft/hiredis-master demo.c /home/leoox/soft/hiredis-master/libhiredis.a

执行

用valgrind执行一下，看结果是否正确的同时，也顺便看看是否有内存泄露。

[amcool@leoox redisDemo]$ valgrind –leak-check=full –tool=memcheck ./demo

==3868== Memcheck, a memory error detector.

==3868== Using LibVEX rev 1658, a library for dynamic binary translation.

==3868== Using valgrind-3.2.1, a dynamic binary instrumentation framework.

==3868== For more details, rerun with: -v

==3868==

redisFormatCommand result: len = 37, cmdBuf = *3

SET

company

leoox

asyncFrameWork recv len = 5

asyncFrameWork return : recvBuf = +OK

, recvBufLen = 5

redisReader get reply : 5

r->type = 5

————————————-

set key(company) OK

————————————-

redisFormatCommand result: len = 28, cmdBuf = *2

GET

company..

asyncFrameWork recv len = 5

asyncFrameWork return : recvBuf = $-1

, recvBufLen = 5

redisReader get reply : 4

r->type = 4

————————————-

key(company..) not exists!

————————————-

redisFormatCommand result: len = 26, cmdBuf = *2

GET

company

asyncFrameWork recv len = 11

asyncFrameWork return : recvBuf = $5

leoox

, recvBufLen = 11

redisReader get reply : 1

r->type = 1

r->len = 5

r->str = leoox

————————————-

key(company), value=(leoox)

————————————-

==3868==

==3868== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 5 from 1)

==3868== malloc/free: in use at exit: 0 bytes in 0 blocks.

==3868== malloc/free: 41 allocs, 41 frees, 2,352 bytes allocated.

==3868== For counts of detected errors, rerun with: -v

==3868== All heap blocks were freed — no leaks are possible.

结果正确，并且没有内存泄露。perfect！哦，圣诞过完了，那提前说元旦快乐，新的一年要任性！

谋胆并重