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README
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README
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HIREDIS OVERVIEW
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----------------
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Hiredis is a minimalistic C client library for the Redis Database.
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It is minimalistic because it just adds minimal support for the protocol, but
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at the same time it uses an high level printf-alike API in order to make it
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much higher level than otherwise suggested by its minimal code base and the
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lack of explicit bindings for every Redis command.
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Hiredis only supports the Redis new protocol, so you can use it with any
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Redis version >= 1.2.0.
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HIREDIS API
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-----------
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Hiredis exports only three function calls:
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redisReply *redisConnect(int *fd, char *ip, int port);
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redisReply *redisCommand(int fd, char *format, ...);
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void freeReplyObject(redisReply *r);
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The first function is used in order to create a connection to the Redis server:
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redisReply *reply;
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int fd;
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reply = redisConnect(&fd,"127.0.0.1",6379);
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to test for connection errors all it is needed to do is checking if reply
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is not NULL:
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if (reply != NULL) {
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printf("Connection error: %s\n", reply->reply);
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freeReplyObject(reply);
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exit(1);
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}
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When a reply object returns an error, the reply->type is set to the value
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REDIS_REPLY_ERROR, and reply->reply points to a C string with the description
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of the error.
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In the above example we don't check for reply->type as redisConnect() can
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only return NULL or a reply object that is actually an error.
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As you can see redisConnect() will just set (by reference) the fd variable
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to the file descriptor of the open socket connected to our Redis server.
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Calls to redisCommand() will require this file descriptor as first argument.
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SENDING COMMNADS
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----------------
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Commands are sent using a printf-alike format. In the simplest form it is
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like that:
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reply = redisCommand("SET foo bar");
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But you can use "%s" and "%b" format specifiers to create commands in a
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printf-alike fashion:
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reply = redisComand("SET foo %s", somevalue);
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If your arguments are binary safe, you can use %b that receives the pointer
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to the buffer and a size_t integer with the length of the buffer.
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reply = redisCommand("SET %s %b", "foo", somevalue, somevalue_length);
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Internally Hiredis will split the command in different arguments and will
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convert it to the actual protocol used to communicate with Redis.
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Every space will separate arguments, so you can use interpolation.
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The following example is valid:
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reply = redisCommand("SET key:%s %s", myid, value);
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USING REPLIES
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-------------
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redisCommand() returns a reply object. In order to use this object you
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need to test the reply->type field, that can be one of the following types:
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REDIS_REPLY_ERROR
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The command returned an error string, that can be read accessing to
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the reply->reply field.
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REDIS_REPLY_STRING
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The command returned a string, that can be read accessing to the
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reply->reply field. The string is always nul-termined, but when you
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need to work with binary-safe strings you can obtain the exact length
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of the reply with: sdslen(reply->reply).
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REDIS_REPLY_ARRAY
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The command returned an array of reply->elements elements.
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Every element is a redisReply object, stored at redis->element[..index..]
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Redis may reply with nexted arrays but this is fully supported.
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REDIS_REPLY_INTEGER
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The command replies with an integer. It's possible to access this integer
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using the reply->integer field that is of type "long long".
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REDIS_REPLY_NIL
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The command replies with a NIL special object. There is no data to access.
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FREEING REPLIES
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---------------
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Replies should be freed using the freeReplyObject() function.
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Note that this function will take care of freeing sub-replies objects
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contained in arrays and nested arrays, so there is no need for the user to
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free the sub replies (it is actually harmful and will corrupt the memory).
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AUHTOR
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------
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Hiredis was written by Salvatore Sanfilippo (antirez at gmail) and is
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released under the BSD license.
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