ev in redisAsyncContext - asynchronous

Question

In redisAsyncContext, stuct ev was defined:
struct {
void *data;
void (*addRead)(void *privdata);
void (*delRead)(void *privdata);
void (*addWrite)(void *privdata);
void (*delWrite)(void *privdata);
void (*cleanup)(void *privdata);
} ev;
There is a function:
void CleanUpEvent()
{
if (m_pstContext->ev.delRead)
{
m_pstContext->ev.delRead(m_pstContext->ev.data);
}
if (m_pstContext->ev.delWrite)
{
m_pstContext->ev.delWrite(m_pstContext->ev.data);
}
}
How it works? When should I use ev?

Answer 1

Basically you need to provide only connect and disconnect callbacks, rest of things hiredis will do for you alone.
#include <hiredis.h>
#include <async.h>
#include <adapters/libuv.h>
void connectCallback(const redisAsyncContext *c, int status);
void disconnectCallback(const redisAsyncContext *c, int status);
void getCallback(redisAsyncContext *c, void *r, void *privdata);
int main (int argc, char **argv) {
//make a async context
redisAsyncContext *c = redisAsyncConnect("127.0.0.1", 6379);
if (c->err) {
/* Let *c leak for now... */
printf("Error: %s\n", c->errstr);
return 1;
}
//now, you need to attach hiredis to your event loop, its depends on event lib that you are using
//example for libuv
redisLibuvAttach(c, uv_default_loop());
//now we setup callbacks
redisAsyncSetConnectCallback(c, connectCallback);
redisAsyncSetDisconnectCallback(c, disconnectCallback);
//enquee "SET foo bar" without callback
redisAsyncCommand(c, NULL, NULL, "SET foo %b", "bar", strlen("bar"));
//enquee "GET foo" with callback and privdata "end-1"
redisAsyncCommand(c, getCallback, (char*)"end-1", "GET foo");
//run your event loop
uv_run(loop, UV_RUN_DEFAULT);
return 0;
}
void connectCallback(const redisAsyncContext *c, int status) {
if (status != REDIS_OK) {
printf("Error: %s\n", c->errstr);
return;
}
printf("Connected...\n");
}
void disconnectCallback(const redisAsyncContext *c, int status) {
if (status != REDIS_OK) {
printf("Error: %s\n", c->errstr);
return;
}
printf("Disconnected...\n");
}
void getCallback(redisAsyncContext *c, void *r, void *privdata) {
redisReply *reply = r;
if (reply == NULL) return;
printf("argv[%s]: %s\n", (char*)privdata, reply->str);
/* Disconnect after receiving the reply to GET */
redisAsyncDisconnect(c);
}
Check https://github.com/redis/hiredis/tree/master/examples for more examples on different event libraries.