Redis (redis-6.2.10.tar.gz)

[](https://travis-ci.org/redis/hiredis) **This Readme reflects the latest changed in the master branch. See [v1.0.0](https://github.com/redis/hiredis/tree/v1.0.0) for the Readme and documentation for the latest release ([API/ABI history](https://abi-laboratory.pro/?view=timeline&l=hiredis)).** # HIREDIS Hiredis is a minimalistic C client library for the [Redis](http://redis.io/) database. It is minimalistic because it just adds minimal support for the protocol, but at the same time it uses a high level printf-alike API in order to make it much higher level than otherwise suggested by its minimal code base and the lack of explicit bindings for every Redis command. Apart from supporting sending commands and receiving replies, it comes with a reply parser that is decoupled from the I/O layer. It is a stream parser designed for easy reusability, which can for instance be used in higher level language bindings for efficient reply parsing. Hiredis only supports the binary-safe Redis protocol, so you can use it with any Redis version >= 1.2.0. The library comes with multiple APIs. There is the *synchronous API*, the *asynchronous API* and the *reply parsing API*. ## Upgrading to `1.0.0` Version 1.0.0 marks the first stable release of Hiredis. It includes some minor breaking changes, mostly to make the exposed API more uniform and self-explanatory. It also bundles the updated `sds` library, to sync up with upstream and Redis. For code changes see the [Changelog](CHANGELOG.md). _Note: As described below, a few member names have been changed but most applications should be able to upgrade with minor code changes and recompiling._ ## IMPORTANT: Breaking changes from `0.14.1` -> `1.0.0` * `redisContext` has two additional members (`free_privdata`, and `privctx`). * `redisOptions.timeout` has been renamed to `redisOptions.connect_timeout`, and we've added `redisOptions.command_timeout`. * `redisReplyObjectFunctions.createArray` now takes `size_t` instead of `int` for its length parameter. ## IMPORTANT: Breaking changes when upgrading from 0.13.x -> 0.14.x Bulk and multi-bulk lengths less than -1 or greater than `LLONG_MAX` are now protocol errors. This is consistent with the RESP specification. On 32-bit platforms, the upper bound is lowered to `SIZE_MAX`. Change `redisReply.len` to `size_t`, as it denotes the the size of a string User code should compare this to `size_t` values as well. If it was used to compare to other values, casting might be necessary or can be removed, if casting was applied before. ## Upgrading from `<0.9.0` 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. ## Synchronous API To consume the synchronous API, there are only a few function calls that need to be introduced: ```c redisContext *redisConnect(const char *ip, int port); void *redisCommand(redisContext *c, const char *format, ...); void freeReplyObject(void *reply); ``` ### Connecting 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) { if (c) { printf("Error: %s\n", c->errstr); // handle error } else { printf("Can't allocate redis context\n"); } } ``` *Note: A `redisContext` is not thread-safe.* ### Sending commands There are several ways to issue commands to Redis. The first that will be introduced is `redisCommand`. This function takes a format similar to printf. In the simplest form, it is used like this: ```c reply = redisCommand(context, "SET foo bar"); ``` The specifier `%s` interpolates a string in the command, and uses `strlen` to determine the length of the string: ```c reply = redisCommand(context, "SET foo %s", value); ``` When you need to pass binary safe strings in a command, the `%b` specifier can be used. Together with a pointer to the string, it requires a `size_t` length argument of the string: ```c reply = redisCommand(context, "SET foo %b", value, (size_t) valuelen); ``` Internally, Hiredis splits the command in different arguments and will convert it to the protocol used to communicate with Redis. One or more spaces separates arguments, so you can use the specifiers anywhere in an argument: ```c reply = redisCommand(context, "SET key:%s %s", myid, value); ``` ### Using replies The return value of `redisCommand` holds a reply when the command was successfully executed. When an error occurs, the return value is `NULL` and the `err` field in the context will be set (see section on **Errors**). Once an error is returned the context cannot be reused and you should set up a new connection. The standard replies that `redisCommand` are of the type `redisReply`. The `type` field in the `redisReply` should be used to test what kind of reply was received: ### RESP2 * **`REDIS_REPLY_STATUS`**: * The command replied with a status reply. The status string can be accessed using `reply->str`. The length of this string can be accessed using `reply->len`. * **`REDIS_REPLY_ERROR`**: * The command replied with an error. The error string can be accessed identical to `REDIS_REPLY_STATUS`. * **`REDIS_REPLY_INTEGER`**: * The command replied with an integer. The integer value can be accessed using the `reply->integer` field of type `long long`. * **`REDIS_REPLY_NIL`**: * The command replied with a **nil** object. There is no data to access. * **`REDIS_REPLY_STRING`**: * A bulk (string) reply. The value of the reply can be accessed using `reply->str`. The length of this string can be accessed using `reply->len`. * **`REDIS_REPLY_ARRAY`**: * A multi bulk reply. The number of elements in the multi bulk reply is stored in `reply->elements`. Every element in the multi bulk reply is a `redisReply` object as well and can be accessed via `reply->element[..index..]`. Redis may reply with nested arrays but this is fully supported. ### RESP3 Hiredis also supports every new `RESP3` data type which are as follows. For more information about the protocol see the `RESP3` [specification.](https://github.com/antirez/RESP3/blob/master/spec.md) * **`REDIS_REPLY_DOUBLE`**: * The command replied with a double-precision floating point number. The value is stored as a string in the `str` member, and can be converted with `strtod` or similar. * **`REDIS_REPLY_BOOL`**: * A boolean true/false reply. The value is stored in the `integer` member and will be either `0` or `1`. * **`REDIS_REPLY_MAP`**: * An array with the added invariant that there will always be an even number of elements. The MAP is functionally equivelant to `REDIS_REPLY_ARRAY` except for the previously mentioned invariant. * **`REDIS_REPLY_SET`**: * An array response where each entry is unique. Like the MAP type, the data is identical to an array response except there are no duplicate values. * **`REDIS_REPLY_PUSH`**: * An array that can be generated spontaneously by Redis. This array response will always contain at least two subelements. The first contains the type of `PUSH` message (e.g. `message`, or `invalidate`), and the second being a sub-array with the `PUSH` payload itself.