redis使用c++ API 的hiredis连接详解

素颜马尾好姑娘i 2022-05-08 15:40 267阅读 0赞

Redis是一个NoSQL数据库，本文将实现一个用c++ API接口连接的例子，来实现对Redis数据库的写入和读出功能，具体将从Redis的安装，Redis的c++接口hiredis安装，代码演示三部分组成。

## 一、Redis的安装和配置 ##

由于源中已有Redis的相关组件，这里就不进行源码编译而直接使用apt-get （ubuntu环境）下载和安装

1.redis的安装和配置
    sudo apt-cache search redis        //根据结果列表找到需要安装的软件包：redis-server
    sudo apt-get install redis-server  //安装软件
    
    2.配置文件
    whereis resids                    //查看redis位置: /etc/redis
    cd  /etc/redis                    //进入文件夹
    /etc/redis$ ls -l                 //显示文件，其中redis.conf为配置文件
    总用量 60
    -rw-r----- 1 redis redis 41623 12月 19  2015 redis.conf
    drwxr-xr-x 2 root  root   4096 9月  21 10:47 redis-server.post-down.d
    drwxr-xr-x 2 root  root   4096 9月  21 10:47 redis-server.post-up.d
    drwxr-xr-x 2 root  root   4096 9月  21 10:47 redis-server.pre-down.d
    drwxr-xr-x 2 root  root   4096 9月  21 10:47 redis-server.pre-up.d
    
    3.启动
    服务端：redis-server (使用默认端口) (--port 6599 加端口)
    客户端：redis-cli    (连接之前测试启动指令 redis-cli ping 返回PONG启动成功)
    
    4.关闭：redis-cli    (-p 6380 可指定端口)shutdown

## 二、redis的c++api接口 hiredis安装 ##

实际上hiredis是一个c的接口，同样使用apt-get安装hiredis，**[GitHub上有他的完整工程项目，点此转到][GitHub]**。

sudo apt-cache search hiredis // 查看发现c语言开发库为libhiredis-dev
    libhiredis-dbg - minimalistic C client library for Redis (debug)
    libhiredis-dev - minimalistic C client library for Redis (development files)
    libhiredis0.13 - minimalistic C client library for Redis
    python-hiredis - redis protocol reader for Python 2.X using hiredis
    
    sudo apt-get install libhiredis-dev  //选择并安装

hiredis库目录的位置为默认的 /usr/lib/x86\_64-linux-gnu/下，头文件在 /usr/include/hiredis 下，hiredis头文件中定义了Redis的连接的方式redisConnect()等方法，连接信息存储在上下文redisContext的结构体对象中，通过redisCommand()等方法进行具体的数据库存取指令操作并返回相关信息在redisReply的结构体对象中，不要忘了freeReplyObject(void \*reply)释放redisReply连接响应对象，redisFree()函数释放redisContext上下文对象，具体的定义和方法请看以下代码。

#ifndef __HIREDIS_H
    #define __HIREDIS_H
    #include "read.h"
    #include <stdarg.h> /* for va_list */
    #include <sys/time.h> /* for struct timeval */
    #include <stdint.h> /* uintXX_t, etc */
    #include "sds.h" /* for sds */
    
    #define HIREDIS_MAJOR 0
    #define HIREDIS_MINOR 13
    #define HIREDIS_PATCH 3
    #define HIREDIS_SONAME 0.13
    
    #ifdef __cplusplus
    extern "C" {
    #endif
    
    /* This is the reply object returned by redisCommand()
    执行redis数据库指令操作的响应信息封装在redisReply的结构体中
     */
    typedef struct redisReply {
        int type; /* REDIS_REPLY_* */
        long long integer; /* The integer when type is REDIS_REPLY_INTEGER */
        int len; /* Length of string 存储字符串长度 */
        char *str; /* Used for both REDIS_REPLY_ERROR and REDIS_REPLY_STRING 错误信息和返回的string类型*/
        size_t elements; /* number of elements, for REDIS_REPLY_ARRAY 如果为数组存储数组长度*/
        struct redisReply **element; /* elements vector for REDIS_REPLY_ARRAY 存储数组元素向量*/
    } redisReply;
    
    redisReader *redisReaderCreate(void);
    
    /* Function to free the reply objects hiredis returns by default.
       释放响应对象
     */
    void freeReplyObject(void *reply);
    
    /* Functions to format a command according to the protocol.
       数据库操作相关语句
     */
    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);
    int redisFormatSdsCommandArgv(sds *target, int argc, const char ** argv, const size_t *argvlen);
    void redisFreeCommand(char *cmd);
    void redisFreeSdsCommand(sds cmd);
    
    enum redisConnectionType {
        REDIS_CONN_TCP,
        REDIS_CONN_UNIX,
    };
    
    /* Context for a connection to Redis
        建立上下文连接对象的结构体
     */
    typedef struct redisContext {
        int err; /* Error flags, 0 when there is no error错误标志，0表示没有错误 */
        char errstr[128]; /* String representation of error when applicable 错误声明 */
        int fd;
        int flags;
        char *obuf; /* Write buffer */
        redisReader *reader; /* Protocol reader */
    
        enum redisConnectionType connection_type;
        struct timeval *timeout;  //设置连接等待时间
    
        struct {
            char *host;
            char *source_addr;
            int port;
        } tcp;
    
        struct {
            char *path;
        } unix_sock;
    
    } redisContext;
    
    //建立上下文连接
    redisContext *redisConnect(const char *ip, int port);
    redisContext *redisConnectWithTimeout(const char *ip, int port, const struct timeval tv);
    redisContext *redisConnectNonBlock(const char *ip, int port);
    redisContext *redisConnectBindNonBlock(const char *ip, int port,
                                           const char *source_addr);
    redisContext *redisConnectBindNonBlockWithReuse(const char *ip, int port,
                                                    const char *source_addr);
    redisContext *redisConnectUnix(const char *path);
    redisContext *redisConnectUnixWithTimeout(const char *path, const struct timeval tv);
    redisContext *redisConnectUnixNonBlock(const char *path);
    redisContext *redisConnectFd(int fd);
    
    /**
     * Reconnect the given context using the saved information.
     *
     * This re-uses the exact same connect options as in the initial connection.
     * host, ip (or path), timeout and bind address are reused,
     * flags are used unmodified from the existing context.
     *
     * Returns REDIS_OK on successfull connect or REDIS_ERR otherwise.
     */
    int redisReconnect(redisContext *c);
    
    int redisSetTimeout(redisContext *c, const struct timeval tv);
    int redisEnableKeepAlive(redisContext *c);
    void redisFree(redisContext *c);
    int redisFreeKeepFd(redisContext *c);
    int redisBufferRead(redisContext *c);
    int redisBufferWrite(redisContext *c, int *done);
    
    /* In a blocking context, this function first checks if there are unconsumed
     * replies to return and returns one if so. Otherwise, it flushes the output
     * buffer to the socket and reads until it has a reply. In a non-blocking
     * context, it will return unconsumed replies until there are no more. */
    int redisGetReply(redisContext *c, void **reply);
    int redisGetReplyFromReader(redisContext *c, void **reply);
    
    /* Write a formatted command to the output buffer. Use these functions in blocking mode
     * to get a pipeline of commands. */
    int redisAppendFormattedCommand(redisContext *c, const char *cmd, size_t len);
    
    /* Write a command to the output buffer. Use these functions in blocking mode
     * to get a pipeline of commands. */
    int redisvAppendCommand(redisContext *c, const char *format, va_list ap);
    int redisAppendCommand(redisContext *c, const char *format, ...);
    int redisAppendCommandArgv(redisContext *c, int argc, const char **argv, const size_t *argvlen);
    
    /* Issue a command to Redis. In a blocking context, it is identical to calling
     * redisAppendCommand, followed by redisGetReply. The function will return
     * NULL if there was an error in performing the request, otherwise it will
     * return the reply. In a non-blocking context, it is identical to calling
     * only redisAppendCommand and will always return NULL. */
    void *redisvCommand(redisContext *c, const char *format, va_list ap);
    void *redisCommand(redisContext *c, const char *format, ...);
    void *redisCommandArgv(redisContext *c, int argc, const char **argv, const size_t *argvlen);
    
    #ifdef __cplusplus
    }
    #endif
    
    #endif

在read.h文件中有redisReply结构体宏的定义，int type的类型：

#ifndef __HIREDIS_READ_H
    #define __HIREDIS_READ_H
    
    #define REDIS_ERR -1
    #define REDIS_OK 0
    
    #define REDIS_ERR_IO 1 /* Error in read or write */
    #define REDIS_ERR_EOF 3 /* End of file */
    #define REDIS_ERR_PROTOCOL 4 /* Protocol error */
    #define REDIS_ERR_OOM 5 /* Out of memory */
    #define REDIS_ERR_OTHER 2 /* Everything else... */
    
    #define REDIS_REPLY_STRING 1    //存放在char *str
    #define REDIS_REPLY_ARRAY 2
    #define REDIS_REPLY_INTEGER 3   //integer存储为数据条数
    #define REDIS_REPLY_NIL 4
    #define REDIS_REPLY_STATUS 5   //成功状态码为："OK"  存放在char *str
    #define REDIS_REPLY_ERROR 6    //存放在char *str

![70][]

如hiredis.c文件中看freeReplyObject函数对以上响应状态的处理：

/* Free a reply object 
    redisReply的类型有：REDIS_REPLY_INTEGER：
    REDIS_REPLY_ERROR：
    REDIS_REPLY_STATUS：
    REDIS_REPLY_STRING：这三个都是返回字符串
    */
    void freeReplyObject(void *reply) {
        redisReply *r = reply;
        size_t j;
    
        if (r == NULL)
            return;
    
        switch(r->type) {
        case REDIS_REPLY_INTEGER:
            break; /* Nothing to free */
        case REDIS_REPLY_ARRAY:
            if (r->element != NULL) {
                for (j = 0; j < r->elements; j++)
                    freeReplyObject(r->element[j]);
                free(r->element);
            }
            break;
        case REDIS_REPLY_ERROR:
        case REDIS_REPLY_STATUS:
        case REDIS_REPLY_STRING:
            free(r->str);
            break;
        }
        free(r);
    }

## 三、Redis使用hiredis API连接 ##

代码结构如图所示：

![70 1][]

具体代码如下：配置文件

#ifndef REDISCONFIG_H
    #define REDISCONFIG_H
    #include <string>
    
    class RedisConfig
    {
    public:
        RedisConfig();
        std::string getRedisIP();//获取ip
        int getRedisPort();//获取端口号
    
    };
    
    #endif

#include "RedisConfig.h"
    #include <sstream>
    
    RedisConfig::RedisConfig()
    {
    
    }
    
    std::string RedisConfig::getRedisIP()
    {
        return "127.0.0.1";//设置为本机ip
    }
    
    int RedisConfig::getRedisPort()
    {
        return 6379;
    }

具体处理代码：包含了string类型和list类型的存取代码，根据redisReply响应的信息来进行信息的处理，对于其他类型对响应状态的判断可以通过命令行操作来确定，如图1所示。

#ifndef _H_REDIS_TOOLS_
    #define _H_REDIS_TOOLS_
    #include <iostream>
    #include <vector>
    #include <hiredis/hiredis.h>
    #include <RedisConfig.h>
    
    using namespace std;
    
    class RedisTool
    {
    public:
        RedisTool();
        ~RedisTool();
        int setString(string key, string value);
        string getString(string key);
    
        int setList(string key,vector<int> value);
        vector<int> getList(string key);
    
    private:
        void init();
        redisContext *m_redis;
        RedisConfig m_config;
    };
    
    #endif

#include <RedisTools.h>
    #include <RedisConfig.h>
    #include <stdio.h>
    #include <string.h>
    #include <sstream>
    
    RedisTool::RedisTool()
    {
        m_redis = NULL;
    	init();
    }
    RedisTool::~RedisTool()
    {
        if(m_redis != NULL)
    	{
            redisFree(m_redis);//析构函数释放资源
    		cout << "~RedisTool :: free redis connection " << endl;
    	}
    }
    
    void RedisTool::init()
    {
        struct timeval timeout = { 1, 500000 }; // 1.5 seconds 设置连接等待时间
    	char ip[255];	
        strcpy(ip, m_config.getRedisIP().c_str());
    	cout << "init : ip = " << ip << endl;
        m_redis = redisConnectWithTimeout(ip, m_config.getRedisPort(), timeout);//建立连接
        if (m_redis->err) {
            printf("RedisTool : Connection error: %s\n", m_redis->errstr);
        }	
    	else
    	{
    		cout << "init redis tool success " << endl;
            //REDIS_REPLY响应的类型type
            cout << "#define REDIS_REPLY_STRING 1"<< endl;
            cout << "#define REDIS_REPLY_ARRAY 2"<< endl;
            cout << "#define REDIS_REPLY_INTEGER 3"<< endl;
            cout << "#define REDIS_REPLY_NIL 4"<< endl;
            cout << "#define REDIS_REPLY_STATUS 5"<< endl;
            cout << "#define REDIS_REPLY_ERROR 6"<< endl;
    	}
    }
    
    //向数据库写入string类型数据
    int RedisTool::setString(string key, string value)
    {
        if(m_redis == NULL || m_redis->err)//int err; /* Error flags, 错误标识，0表示无错误 */
        {
            cout << "Redis init Error !!!" << endl;
            init();
            return -1;
        }
        redisReply *reply;
        reply = (redisReply *)redisCommand(m_redis,"SET %s %s", key.c_str(), value.c_str());//执行写入命令
        cout<<"set string type = "<<reply->type<<endl;//获取响应的枚举类型
        int result = 0;
        if(reply == NULL)
        {
            redisFree(m_redis);
            m_redis = NULL;
            result = -1;
            cout << "set string fail : reply->str = NULL " << endl;
            //pthread_spin_unlock(&m_redis_flock);
            return -1;
        }
        else if(strcmp(reply->str, "OK") == 0)//根据不同的响应类型进行判断获取成功与否
        {
            result = 1;
        }
        else
        {
            result = -1;
            cout << "set string fail :" << reply->str << endl;
        }
        freeReplyObject(reply);//释放响应信息
    
        return result;
    }
    
    //从数据库读出string类型数据
    string RedisTool::getString(string key)
    {
        if(m_redis == NULL || m_redis->err)
    	{
    		cout << "Redis init Error !!!" << endl;
    		init();
            return NULL;
    	}
    	redisReply *reply;
        reply = (redisReply *)redisCommand(m_redis,"GET %s", key.c_str());
        cout<<"get string type = "<<reply->type<<endl;
    
    	if(reply == NULL)
    	{
            redisFree(m_redis);
            m_redis = NULL;
            cout << "ERROR getString: reply = NULL!!!!!!!!!!!! maybe redis server is down" << endl;
            return NULL;
    	}
        else if(reply->len <= 0)
    	{		
            freeReplyObject(reply);
            return NULL;
    	}
    	else
    	{
            stringstream ss;
            ss << reply->str;
            freeReplyObject(reply);
            return ss.str();
        }
    }
    
    //向数据库写入vector（list）类型数据
    int RedisTool::setList(string key,vector<int> value)
    {
        if(m_redis == NULL || m_redis->err)
        {
            cout << "Redis init Error !!!" << endl;
            init();
            return -1;
        }
    
        redisReply *reply;
    
        int valueSize = value.size();
        int result = 0;
    
        for(int i=0; i<valueSize; i++)
        {
            reply = (redisReply*)redisCommand(m_redis,"RPUSH %s %d", key.c_str(),value.at(i));
            cout<<"set list type = "<<reply->type<<" ";
            int old = reply->integer;
            if(reply == NULL)
            {
                redisFree(m_redis);
                m_redis = NULL;
                result = -1;
                cout << "set list fail : reply->str = NULL " << endl;
                //pthread_spin_unlock(&m_redis_flock);
                return -1;
            }
            else if(reply->integer == old++)
            {
                result = 1;
                cout<<"rpush list ok"<<endl;
                continue;
            }
            else
            {
                result = -1;
                cout << "set list fail ,reply->integer = " << reply->integer << endl;
                return -1;
            }
    
        }
    
        freeReplyObject(reply);
        cout<<"set List  success"<<endl;
        return result;
    
    }
    
    //从数据库读出vector（list）类型数据
    vector<int> RedisTool::getList(string key)
    {
    
        if(m_redis == NULL || m_redis->err)
        {
            cout << "Redis init Error !!!" << endl;
            init();
            return vector<int>{};//返回空的向量
        }
    
        redisReply *reply;
        reply = (redisReply*)redisCommand(m_redis,"LLEN %s", key.c_str());
        int valueSize = reply->integer;
        cout<<"List size is :"<<reply->integer<<endl;
    
        reply = (redisReply*)redisCommand(m_redis,"LRANGE %s %d %d", key.c_str(),0,valueSize-1);
        cout<<"get list type = "<<reply->type<<endl;
        cout<<"get list size = "<<reply->elements<<endl;//对于数组类型可以用elements元素获取数组长度
    
        redisReply** replyVector = reply->element;//获取数组指针
        vector<int> result;
        for(int i=0;i<valueSize;i++)
        {
            string temp =(*replyVector)->str;//遍历redisReply*数组,存入vector向量
            int a =atoi(temp.c_str());
            result.push_back(a);
            replyVector++;
        }
    
        cout<<"result size:"<<result.size()<<endl;
        return result;
    
    }

main函数：

#include <iostream>
    #include <vector>
    #include <RedisTools.h>
    
    using namespace std;
    
    
    int main()
    {
        RedisTool redis;
        //测试 string
        redis.setString("wangbaojia","test1");
        string result = redis.getString("wangbaojia");
        cout<<"result="<<result<<endl;
        //测试list
        vector<int> vec ={1,2,3,4};
        redis.setList("bao",vec);
        vector<int> vecResult = redis.getList("bao");
        for(int i=0;i<vecResult.size();i++)
        {
            cout<<vecResult[i]<<" ";
        }
    
        return 0;
    }

运行结果：

![70 2][]

##  四、完整代码下载    ##

[点击下载][Link 1]

[GitHub]: https://github.com/redis/hiredis
[70]: /images/20220506/8834f87c267146d89cd74fbe8078ab04.png
[70 1]: /images/20220506/c1d398a186a74ef6a87b432786965d28.png
[70 2]: /images/20220506/82be6f80885d4bf98318bcc8a2ecfe1b.png
[Link 1]: https://download.csdn.net/download/bwangk/10730753