C基础 redis缓存访问详解

Linux version 4.4.0-22-generic (buildd@lgw01-41) 
(gcc version 5.3.1 20160413 (Ubuntu 5.3.1-14ubuntu2) ) 
#40-Ubuntu SMP Thu May 12 22:03:46 UTC 2016

wget http://download.redis.io/releases/redis-3.0.6.tar.gz
tar xzf redis-3.0.6.tar.gz
cd redis-3.0.6
make

mkdir -p /usr/local/include/hiredis /usr/local/lib
cp -a hiredis.h async.h read.h sds.h adapters /usr/local/include/hiredis
cp -a libhiredis.so /usr/local/lib/libhiredis.so.0.13
cd /usr/local/lib && ln -sf libhiredis.so.0.13 libhiredis.so
cp -a libhiredis.a /usr/local/lib
mkdir -p /usr/local/lib/pkgconfig
cp -a hiredis.pc /usr/local/lib/pkgconfig

/*
 * redis链接函数, 返回redis上下文.
 * ip  : 链接地址的ip
 * port  : 链接端口
 *     : 返回 redis上下文, NULL表示获取失败
 */
redisContext *redisConnect(const char *ip, int port)


/*
 * 执行redis操作命令, 返回得到的结果集
 *  context  : redisConnect 返回的redis上下文对象
 *  format  : 等同于 printf格式控制符
 *  ...    : 后面可变参数, 需要和 format中格式符对应
 *      : 返回 得到的结果集
 */
void *redisCommand(redisContext *context, const char *format, ...);

/*
 * 释放redis命令操作返回过来的结果集
 * reply  : redisCommand返回的结果集
 */
void freeReplyObject(void *reply);

/*
 * 释放链接上下文
 * context  : redisConnect返回的链接上下文
 */
void redisFree(redisContext *context);

第一个是 redisConnect 返回的 redisContext上下文结构
/* 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;
} redisContext;

还有一个是 redisCommand 返回的命令集
/* 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 */
  int 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;

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

/*
 * 请求 redis网络缓存服务器内存.
 */
int main(int argc, char* argv[]) {
  redisContext *conn = redisConnect("127.0.0.1", 6379);
  if(NULL == conn) {
    fprintf(stderr, "redisConnect 127.0.0.1:6379 error!\n");
    exit(EXIT_FAILURE);
  }  
  if(conn->err) {
    fprintf(stderr, "redisConect error:%d\n", conn->err);
    redisFree(conn);
    exit(EXIT_FAILURE);
  }  
  
  // 这里redisConnect 链接对象创建完毕了
  redisReply *reply = redisCommand(conn, "get foo");
  if(reply && reply->type == REDIS_REPLY_STRING) {
    printf("get foo => %s\n", reply->str);
  }  
  printf("reply->type = %d\n", reply->type);

  // 释放这个对象
  freeReplyObject(reply);
  // 释放hiredis 上下文对象  
  redisFree(conn);

  return 0;
}

#define REDIS_REPLY_STRING 1
#define REDIS_REPLY_ARRAY 2
#define REDIS_REPLY_INTEGER 3
#define REDIS_REPLY_NIL 4
#define REDIS_REPLY_STATUS 5
#define REDIS_REPLY_ERROR 6

#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <hiredis/hiredis.h>

/*
 * 请求 redis网络缓存服务器内存.
 */
int main(int argc, char* argv[]) {
  // 忽略服务器退出,导致当前进程退出
  signal(SIGPIPE, SIG_IGN);

  redisContext *conn = redisConnect("127.0.0.1", 6379);
  if(NULL == conn) {
    fprintf(stderr, "redisConnect 127.0.0.1:6379 error!\n");
    exit(EXIT_FAILURE);
  }  
  if(conn->err) {
    fprintf(stderr, "redisConect error:%d\n", conn->err);
    redisFree(conn);
    exit(EXIT_FAILURE);
  }  
  
  // 这里redisConnect 链接对象创建完毕了
  freeReplyObject(redisCommand(conn, "lpush mylist foo"));
  freeReplyObject(redisCommand(conn, "lpush mylist bar"));
  redisReply *reply = redisCommand(conn, "lrange mylist 0 -1");
  if(reply && reply->type == REDIS_REPLY_ARRAY && reply->elements == 2) {
    printf("%s %s\n", reply->element[0]->str, reply->element[1]->str);
  }  
  else {
    printf("redisCommand [lrange mylist 0 -1] error:%d. %s\n", reply->type, reply->str);
  }  

  // 释放这个对象
  freeReplyObject(reply);
  // 释放hiredis 上下文对象  
  redisFree(conn);

  return 0;
}