第一 基本的连接与添加数据
在redis中使用如下结构来保存状态，README里有这样一段话
Version 0.9.0 is a major overhaul of hiredis in every aspect. However, upgrading existing
code using hiredis should not be a big pain. The key thing to keep in mind when
upgrading is that hiredis >= 0.9.0 uses a `redisContext*` to keep state, in contrast to
the stateless 0.0.1 that only has a file descriptor to work with.
以前是直接用文件描述符来操作的，现在使用redisContext，下面是这个结构的定义。
/* 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 */
} redisContext;
下面先来练习连接，在README中是这样说的：
The function `redisConnect` is used to create a so-called `redisContext`. The
context is where Hiredis holds state for a connection. The `redisContext`
struct has an integer `err` field that is non-zero when the connection is in
an error state. The field `errstr` will contain a string with a description of
the error. More information on errors can be found in the **Errors** section.
After trying to connect to Redis using `redisConnect` you should
check the `err` field to see if establishing the connection was successful:
```c
redisContext *c = redisConnect("127.0.0.1", 6379);
if (c != NULL && c->err) {
printf("Error: %s\n", c->errstr);
// handle error
}
这里有一个代码介绍，下面就按照这个来写一下。
A#include <hiredis.h> #include <stdio.h> #include <stdlib.h>
int main(int argc, char *argv[])
{
redisContext *c;
redisReply *reply;
//1. redisContext *redisConnect(const char *ip, int port);
#if 0
c = redisConnect("127.0.0.1", 6379);
if (c == NULL || c->err) {
if (c) {
printf("redisConnect() error: %s\n", c->errstr);
redisFree(c);
} else {
printf("redisConnect() error: can't allocate redis context\n");
}
exit(1);
}
#endif
#if 0
//2. redisContext *redisConnectWithTimeout(const char *ip, int port, const struct timeval tv);
struct timeval timeout = {1, 500 * 1000}; // 1.5s
c = redisConnectWithTimeout("127.0.0.1", 6379, timeout);
if (c == NULL || c->err) {
if (c) {
printf("redisConnectWithTimeout() error: %s\n", c->errstr);
redisFree(c);
} else {
printf("redisConnectWithTimeout() error: can't allocate redis context\n");
}
exit(1);
}
#endif
#if 1
//3. redisContext *redisConnectNonBlock(const char *ip, int port);
c = redisConnectNonBlock("127.0.0.1", 6379);
if (c == NULL || c->err) {
if (c) {
printf("redisConnectNonBlock() error: %s\n", c->errstr);
redisFree(c);
} else {
printf("redisConnectNonBlock() error: can't allocate redis context\n");
}
exit(1);
}
#endif
#if 0
//4. redisContext *redisConnectBindNonBlock(const char *ip, int port, const char *source_addr);
c = redisConnectBindNonBlock("127.0.0.1", 6379, "192.168.22.114");
if (c == NULL || c->err) {
if (c) {
printf("redisConnectBindNonBlock() error: %s\n", c->errstr);
redisFree(c);
} else {
printf("BindNonBlock() error: can't allocate redis context\n");
}
exit(1);
}
#endif
//5. redisContext *redisConnectBindNonBlockWithReuse(const char *ip, int port, const char *source_addr);
//6. redisContext *redisConnectUnix(const char *path);
//7. redisContext *redisConnectUnixWithTimeout(const char *path, const struct timeval tv);
//8. redisContext *redisConnectUnixNonBlock(const char *path);
//9. redisContext *redisConnectFd(int fd);
//
//
reply = redisCommand(c, "PING");
printf("PING: %s\n", reply->str);
freeReplyObject(reply);
return 0; }
这里有这么多连接的函数，我用头几个可以，但是如果是NonBlock的就会出现“段错误”，应该是有不一样的用法。
去查一查。