@@ -116,6 +116,92 @@ const size_t argvlen[] = {3, 8, 5};
116116redisReply *reply = redisCommandArgv(c, argc, argv, argvlen);
117117```
118118
119+ ## Construct asynchronous commands
120+
121+ Use the ` redisAsyncCommand() ` and ` redisAsyncCommandArgv() `
122+ functions to send commands to the server asynchronously:
123+
124+ ``` c
125+ int redisAsyncCommand (
126+ redisAsyncContext * ac, redisCallbackFn * fn, void * privdata,
127+ const char * format, ...);
128+ int redisAsyncCommandArgv(
129+ redisAsyncContext * ac, redisCallbackFn * fn, void * privdata,
130+ int argc, const char ** argv, const size_t * argvlen);
131+ ```
132+
133+ These work the same way as `redisCommand()` and `redisCommandArgv()`
134+ (see [Construct synchronous commands](#construct-synchronous-commands)
135+ above) but they have two extra parameters. The first is a pointer to
136+ a optional callback function and the second is a pointer to your own
137+ custom data, which will be passed to the callback when it
138+ executes. Pass `NULL` for both of these pointers if you don't need
139+ to use them.
140+
141+ The callback has the following signature:
142+
143+ ```c
144+ void(redisAsyncContext *c, void *reply, void *privdata);
145+ ```
146+
147+ The first parameter is the asynchronous connection context and
148+ the second is a pointer to the reply object. Use a cast to
149+ ` (redisReply *) ` to access the reply in the usual way (see
150+ [ Handle command replies] ({{< relref "/develop/clients/hiredis/handle-replies" >}})
151+ for a full description of ` redisReply ` ). The last parameter
152+ is the custom data pointer that you supplied during the
153+ ` redisAsyncCommand() ` call. This is passed to your function
154+ without any modification.
155+
156+ The example below shows how you can use ` redisAsyncCommand() ` with
157+ or without a reply callback:
158+
159+ ``` c
160+ // The callback expects the key for the data in the `privdata`
161+ // custom data parameter.
162+ void getCallback (redisAsyncContext * c, void * r, void * privdata) {
163+ redisReply * reply = r;
164+ char * key = privdata;
165+
166+ if (reply == NULL) {
167+ if (c->errstr) {
168+ printf("errstr: %s\n", c->errstr);
169+ }
170+ return;
171+ }
172+
173+ printf("Key: %s, value: %s\n", key, reply->str);
174+
175+ /* Disconnect after receiving the reply to GET */
176+ redisAsyncDisconnect(c);
177+ }
178+ .
179+ .
180+ .
181+
182+ // Key and string value to pass to ` SET ` .
183+ char * key = "testkey";
184+ char * value = "testvalue";
185+
186+ // We aren't interested in the simple status reply for
187+ // ` SET ` , so use NULL for the callback and custom data
188+ // pointers.
189+ redisAsyncCommand(c, NULL, NULL, "SET %s %s", key, value);
190+
191+ // The reply from ` GET ` is essential, so set a callback
192+ // to retrieve it. Also, pass the key to the callback
193+ // as the custom data.
194+ redisAsyncCommand(c, getCallback, key, "GET %s", key);
195+ ```
196+
197+ Note that you should normally disconnect asynchronously from a
198+ callback when you have finished using the connection.
199+ Use `redisAsyncDisconnect()` to disconnect gracefully, letting
200+ pending commands execute and activate their callbacks.
201+ Use `redisAsyncFree()` to disconnect immediately. If you do this then
202+ any pending callbacks from commands that have already executed will be
203+ called with a `NULL` reply pointer.
204+
119205## Command replies
120206
121207The information in the `redisReply` object has several formats,
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