一、Redis数据库简介

Redis(REmote DIctionary Server)是一个高性能的key-value数据库。
Redis是一个开源的使用ANSI C语言编写、遵守BSD协议、支持网络、可基于内存亦可持久化的日志型、Key-Value数据库，并提供多种语言的API。它通常被称为数据结构服务器，因为值（value）可以是字符串(String), 哈希(Map), 列表(list), 集合(sets) 和有序集合(sorted sets)等类型。
Redis的使用，请参考如下网址：
https://www.runoob.com/redis/redis-tutorial.html
Redis
Redis 特点

性能极高 – Redis能读的速度是110000次/s,写的速度是81000次/s 。
丰富的数据类型 – Redis支持二进制案例的 Strings, Lists, Hashes, Sets 及 Ordered Sets 数据类型操作。
原子性 – Redis的所有操作都是原子性的，意思就是要么成功执行要么失败完全不执行。单个操作是原子性的。多个操作也支持事务，即原子性，通过MULTI和EXEC指令包起来。
丰富的特性 – Redis还支持 publish/subscribe, 通知, key 过期等等特性。
二、Redia的基本操作

三、C语言常用API

Hiredis是Redis数据库的一个极简C客户端库，只是对Redis协议的最小支持。源码地址：https://github.com/redis/hiredis。前面已经详介绍如何安装和配置，这里就不在描述。

1、常用API

建立连接：与Redis server建立连接，返回一个redisContext结构指针

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

发送命令：向Redis server发送命令；成功：返回redisReply结构指针，失败：返回NULL

void *redisCommand(redisContext *c, const char *format, ...); // 同步执行redis命令，和printf()用法类似
// argc：argv数组元素个数；argv：参数数组（指针数组）；argvlen：数组首地址，每个元素是argv数组中相应参数的长度。
// 传入命令是字符串形式时，argvlen可以指定为NULL，这个时候使用strlen()计算argv中每个字符串长度；传入命令是二进制形式时，argvlen必须指定，用于指示argv中每个元素的长度void *redisCommandArgv(redisContext *c, int argc, const char **argv, const size_t *argvlen);
使用hiredis连接带密码的redis服务
c = redisConnect((char*)redis_host, redis_port); 
if (c->err) {    /* Error flags, 0 when there is no error */ 
printf("连接Redis失败: %s\n", c->errstr); 
exit(1); 
} 
else  
{ 
 printf("连接Redis成功！\n"); 
} 

reply = (redisReply *)redisCommand(c, "AUTH %s", redis_password); 
if (reply->type == REDIS_REPLY_ERROR) { 
 printf("Redis认证失败！\n"); 
} 
else 
{ 
 printf("Redis认证成功！\n"); 
} 
freeReplyObject(reply);

释放redisReply结构指针
```
void freeReplyObject(void *reply);
```
释放redisContext结构指针
```
void redisFree(redisContext *c);
```
2、主要数据结构

redisContext：管理连接上下文的结构体，由redisConnect()函数创建并返回。

//* Context for a connection to Redis */
typedef struct redisContext {
  int err; /* Error flags, 0 when there is no error */
  char errstr[128]; /* String representation of error when applicable */
  int fd;
  int flags;
  char *obuf; /* Write buffer */
  redisReader *reader; /* Protocol reader */
  enum redisConnectionType connection_type;
  struct timeval *timeout;
  struct {
      char *host;
      char *source_addr;
      int port;
  } tcp;
  struct {
      char *path;
  } unix_sock;
/* For non-blocking connect */
  struct sockadr *saddr;
  size_t addrlen;
} redisContext;

redisReply：响应结构体，由redisCommand()函数创建并返回。

/* This is the reply object returned by redisCommand() */
typedef struct redisReply {
  int type; /* REDIS_REPLY_* */
  long long integer; /* The integer when type is REDIS_REPLY_INTEGER */
  size_t len; /* Length of string */
  char *str; /* Used for both REDIS_REPLY_ERROR and REDIS_REPLY_STRING */
  size_t elements; /* number of elements, for REDIS_REPLY_ARRAY */
  struct redisReply **element; /* elements vector for REDIS_REPLY_ARRAY */
} redisReply;

3、Redis二进制操作（安全操作）

参考资料：https://github.com/redis/hiredis#sending-commands-contd ```bash int toredis(int runmode, redisContext conn_redis,char ReidsKey,unsigned char* sendbuf,int SendBufElemnets)//数组传给函数作参数后,在函数中运算不包含数组长度 { if (runmode)

   printf("Toredis...\n");
 /* Set a key using binary safe API */

char* RedisCommand=”LPUSH”;

redisReply *reply=NULL;
const char* command_argv_set[3] = {RedisCommand, ReidsKey, (char*)sendbuf};//指针数组，存放Command所使用的字节的地址；
const size_t command_argv_set_len[3]={strlen(RedisCommand),strlen(ReidsKey),SendBufElemnets};//
int CommandElements =  sizeof(command_argv_set_len)/sizeof(size_t);//元素个数由数组长度除以每个元素的长度
if(runmode)
{
    printf("SendBuf Elements:%d\n",SendBufElemnets);
     printf("CommandElements Size: %d \n",CommandElements);//打印命令中的元素个数
}
//执行命令
reply = (redisReply *)redisCommandArgv(conn_redis,CommandElements, (const char**)&command_argv_set, command_argv_set_len);
if (reply->type == REDIS_REPLY_ERROR)        //操作失败
{
    if(runmode)
    {
        printf("Toredis: Message to Redis Fail!\n");
         printf("Toredis: %s\n",reply->str);
    }
    freeReplyObject(reply);
    return -1;
}

else //操作成功 {

  if(runmode)
  {
       printf( "reply->type：%d\n",reply->type);//确定是list类型
       printf("Toredis:");
       for(int i=0;i<SendBufElemnets; i++)
           printf("%02x ",sendbuf[i]);
       printf("\n");
       printf("This List has %lld elements!\n", reply->integer);//查看列表中有多少元素
  }

}

freeReplyObject(reply);
return 0;

}

size_t fromredis(int runmode, redisContext conn_redis,char ReidsKey,unsigned char* recvbuf,int RecvBufElements,int timeout) { if (runmode)

    printf("Fromredis...\n");

redisReply reply=NULL; size_t ReceiveLen=0; char RedisCommand=”BRPOP”;//取最旧的一个数据 reply = (redisReply *)redisCommand(conn_redis,”%s %s %d”,RedisCommand,ReidsKey,timeout);//获取最下面的元素，旧的 if (runmode)

   printf( "reply->type：%d\n",reply->type);

if(reply->type == REDIS_REPLY_ARRAY) //操作成功 {

   ReceiveLen=reply->element[1]->len;
   memcpy(recvbuf,reply->element[1]->str,ReceiveLen);    //把读取的消息放入recvbuf
   if(runmode)
   {
       printf( "reply->elements：%lu\n",reply->elements);
       printf( "reply->element[0]->len: %lu\n",(unsigned long)reply->element[0]->len);
       printf(    "reply->element[0]->str: %s\n",reply->element[0]->str);
       printf( "reply->element[1]->len: %lu\n",ReceiveLen);
       printf( "reply->element[1]: ");
       for(int i=0;i<reply->element[1]->len;i++)//element[0]的内容是ListBit
       {
           printf("%dth:%02x ",i,recvbuf[i]);
       }
       printf("\n");
   }

} else if (reply->type == REDIS_REPLY_ERROR)//操作redis失败 {

   printf("Toredis: %s\n",reply->str);
   freeReplyObject(reply);
   return -1;

} freeReplyObject(reply); return ReceiveLen; }

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# 四、C语言访问与操作Redis数据库
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##### Hiredis源码中提供的一个例子，包含了常用API和Redis的基本操作
```c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <hiredis.h>           //这个头文件一般是#include <hiredis/hiredis.h>   前面已经说明了
int main(int argc, char **argv) 
{
    unsigned int j, isunix = 0;
    redisContext *c;
    redisReply *reply;
    const char *hostname = (argc > 1) ? argv[1] : "127.0.0.1";
    if (argc > 2) {
        if (*argv[2] == 'u' || *argv[2] == 'U') {
            isunix = 1;
            /* in this case, host is the path to the unix socket */
            printf("Will connect to unix socket @%s\n", hostname);
        }
    }
    int port = (argc > 2) ? atoi(argv[2]) : 6379;
    struct timeval timeout = { 1, 500000 }; // 1.5 seconds
    if (isunix) {
            c = redisConnectUnixWithTimeout(hostname, timeout);
    } else {
        c = redisConnectWithTimeout(hostname, port, timeout);
    }
    if (c == NULL || c->err) {
        if (c) {
             printf("Connection error: %s\n", c->errstr);
            redisFree(c);
        } else {
             printf("Connection error: can't allocate redis context\n");
        }
        exit(1);
    }
    /* PING server */
    reply = redisCommand(c,"PING");
    printf("PING: %s\n", reply->str);
    freeReplyObject(reply);
    /* Set a key */
    reply = redisCommand(c,"SET %s %s", "foo", "hello world");
    printf("SET: %s\n", reply->str);
    freeReplyObject(reply);
    /* Set a key using binary safe API */
    reply = redisCommand(c,"SET %b %b", "bar", (size_t) 3, "hello", (size_t) 5);
    printf("SET (binary API): %s\n", reply->str);
    freeReplyObject(reply);
    /* Try a GET and two INCR */
    reply = redisCommand(c,"GET foo");
    printf("GET foo: %s\n", reply->str);
    freeReplyObject(reply);
    reply = redisCommand(c,"INCR counter");
    printf("INCR counter: %lld\n", reply->integer);
    freeReplyObject(reply);
    /* again ... */
    reply = redisCommand(c,"INCR counter");
    printf("INCR counter: %lld\n", reply->integer);
    freeReplyObject(reply);
    /* Create a list of numbers, from 0 to 9 */
    reply = redisCommand(c,"DEL mylist");
    freeReplyObject(reply);
    for (j = 0; j < 10; j++) {
        char buf[64];
        sprintf(buf,64,"%u",j);
        reply = redisCommand(c,"LPUSH mylist element-%s", buf);
        freeReplyObject(reply);
    }
    /* Let's check what we have inside the list */
    reply = redisCommand(c,"LRANGE mylist 0 -1");
    if (reply->type == REDIS_REPLY_ARRAY) {
        for (j = 0; j < reply->elements; j++) {
             printf("%u) %s\n", j, reply->element[j]->str);
        }
    }
    freeReplyObject(reply);//释放返回结构体
    /* Disconnects and frees the context */
    redisFree(c);//释放redis连接
    return 0;
}

Linux系统/服务器基础操作

Redis数据库使用

一、Redis数据库简介

二、Redia的基本操作

三、C语言常用API

1、常用API

2、主要数据结构

3、Redis二进制操作（安全操作）