Squashed '3rdparty/libfnord/' content from commit e95f046a

build

build-dbg

.DS_Store

rvm: 1.9.3

script: ./fnordmetric-core/run_specs.sh

services:

  - redis-server

### 0.11.0

* Increase the maximum multi-bulk reply depth to 7.

* Increase the read buffer size from 2k to 16k.

* Use poll(2) instead of select(2) to support large fds (>= 1024).

### 0.10.1

* Makefile overhaul. Important to check out if you override one or more

  variables using environment variables or via arguments to the "make" tool.

* Issue #45: Fix potential memory leak for a multi bulk reply with 0 elements

  being created by the default reply object functions.

* Issue #43: Don't crash in an asynchronous context when Redis returns an error

  reply after the connection has been made (this happens when the maximum

  number of connections is reached).

### 0.10.0

* See commit log.

Copyright (c) 2009-2011, Salvatore Sanfilippo <antirez at gmail dot com>

Copyright (c) 2010-2011, Pieter Noordhuis <pcnoordhuis at gmail dot com>

All rights reserved.

Redistribution and use in source and binary forms, with or without

modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice,

  this list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright notice,

  this list of conditions and the following disclaimer in the documentation

  and/or other materials provided with the distribution.

* Neither the name of Redis nor the names of its contributors may be used

  to endorse or promote products derived from this software without specific

  prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND

ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR

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[![Build Status](https://travis-ci.org/redis/hiredis.png)](https://travis-ci.org/redis/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 an 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

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:

    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 an 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:

    redisContext *c = redisConnect("127.0.0.1", 6379);

    if (c != NULL && c->err) {

        printf("Error: %s\n", c->errstr);

        // handle error

    }

### 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:

    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:

    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:

    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:

    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:

* **`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.

Replies should be freed using the `freeReplyObject()` function.

Note that this function will take care of freeing sub-replies objects

contained in arrays and nested arrays, so there is no need for the user to

free the sub replies (it is actually harmful and will corrupt the memory).

**Important:** the current version of hiredis (0.10.0) free's replies when the

asynchronous API is used. This means you should not call `freeReplyObject` when

you use this API. The reply is cleaned up by hiredis _after_ the callback

returns. This behavior will probably change in future releases, so make sure to

keep an eye on the changelog when upgrading (see issue #39).

### Cleaning up

To disconnect and free the context the following function can be used:

    void redisFree(redisContext *c);

This function immediately closes the socket and then free's the allocations done in

creating the context.

### Sending commands (cont'd)

Together with `redisCommand`, the function `redisCommandArgv` can be used to issue commands.

It has the following prototype:

    void *redisCommandArgv(redisContext *c, int argc, const char **argv, const size_t *argvlen);

It takes the number of arguments `argc`, an array of strings `argv` and the lengths of the

arguments `argvlen`. For convenience, `argvlen` may be set to `NULL` and the function will

use `strlen(3)` on every argument to determine its length. Obviously, when any of the arguments

need to be binary safe, the entire array of lengths `argvlen` should be provided.

The return value has the same semantic as `redisCommand`.

### Pipelining

To explain how Hiredis supports pipelining in a blocking connection, there needs to be

understanding of the internal execution flow.

When any of the functions in the `redisCommand` family is called, Hiredis first formats the

command according to the Redis protocol. The formatted command is then put in the output buffer

of the context. This output buffer is dynamic, so it can hold any number of commands.

After the command is put in the output buffer, `redisGetReply` is called. This function has the

following two execution paths:

1. The input buffer is non-empty:

    * Try to parse a single reply from the input buffer and return it

    * If no reply could be parsed, continue at *2*

2. The input buffer is empty:

    * Write the **entire** output buffer to the socket

    * Read from the socket until a single reply could be parsed

The function `redisGetReply` is exported as part of the Hiredis API and can be used when a reply

is expected on the socket. To pipeline commands, the only things that needs to be done is

filling up the output buffer. For this cause, two commands can be used that are identical

to the `redisCommand` family, apart from not returning a reply:

    void redisAppendCommand(redisContext *c, const char *format, ...);

    void redisAppendCommandArgv(redisContext *c, int argc, const char **argv, const size_t *argvlen);

After calling either function one or more times, `redisGetReply` can be used to receive the

subsequent replies. The return value for this function is either `REDIS_OK` or `REDIS_ERR`, where

the latter means an error occurred while reading a reply. Just as with the other commands,

the `err` field in the context can be used to find out what the cause of this error is.

The following examples shows a simple pipeline (resulting in only a single call to `write(2)` and

a single call to `read(2)`):

    redisReply *reply;

    redisAppendCommand(context,"SET foo bar");

    redisAppendCommand(context,"GET foo");

    redisGetReply(context,&reply); // reply for SET

    freeReplyObject(reply);

    redisGetReply(context,&reply); // reply for GET

    freeReplyObject(reply);

This API can also be used to implement a blocking subscriber:

    reply = redisCommand(context,"SUBSCRIBE foo");

    freeReplyObject(reply);

    while(redisGetReply(context,&reply) == REDIS_OK) {

        // consume message

        freeReplyObject(reply);

    }

### Errors

When a function call is not successful, depending on the function either `NULL` or `REDIS_ERR` is

returned. The `err` field inside the context will be non-zero and set to one of the

following constants:

* **`REDIS_ERR_IO`**:

    There was an I/O error while creating the connection, trying to write

    to the socket or read from the socket. If you included `errno.h` in your

    application, you can use the global `errno` variable to find out what is

    wrong.

* **`REDIS_ERR_EOF`**:

    The server closed the connection which resulted in an empty read.

* **`REDIS_ERR_PROTOCOL`**:

    There was an error while parsing the protocol.

* **`REDIS_ERR_OTHER`**:

    Any other error. Currently, it is only used when a specified hostname to connect

    to cannot be resolved.

In every case, the `errstr` field in the context will be set to hold a string representation

of the error.

## Asynchronous API

Hiredis comes with an asynchronous API that works easily with any event library.

Examples are bundled that show using Hiredis with [libev](http://software.schmorp.de/pkg/libev.html)

and [libevent](http://monkey.org/~provos/libevent/).

### Connecting

The function `redisAsyncConnect` can be used to establish a non-blocking connection to

Redis. It returns a pointer to the newly created `redisAsyncContext` struct. The `err` field

should be checked after creation to see if there were errors creating the connection.

Because the connection that will be created is non-blocking, the kernel is not able to

instantly return if the specified host and port is able to accept a connection.

    redisAsyncContext *c = redisAsyncConnect("127.0.0.1", 6379);

    if (c->err) {

        printf("Error: %s\n", c->errstr);

        // handle error

    }

The asynchronous context can hold a disconnect callback function that is called when the

connection is disconnected (either because of an error or per user request). This function should

have the following prototype:

    void(const redisAsyncContext *c, int status);

On a disconnect, the `status` argument is set to `REDIS_OK` when disconnection was initiated by the

user, or `REDIS_ERR` when the disconnection was caused by an error. When it is `REDIS_ERR`, the `err`

field in the context can be accessed to find out the cause of the error.

The context object is always free'd after the disconnect callback fired. When a reconnect is needed,

the disconnect callback is a good point to do so.

Setting the disconnect callback can only be done once per context. For subsequent calls it will

return `REDIS_ERR`. The function to set the disconnect callback has the following prototype:

    int redisAsyncSetDisconnectCallback(redisAsyncContext *ac, redisDisconnectCallback *fn);

### Sending commands and their callbacks

In an asynchronous context, commands are automatically pipelined due to the nature of an event loop.

Therefore, unlike the synchronous API, there is only a single way to send commands.

Because commands are sent to Redis asynchronously, issuing a command requires a callback function

that is called when the reply is received. Reply callbacks should have the following prototype:

    void(redisAsyncContext *c, void *reply, void *privdata);

The `privdata` argument can be used to curry arbitrary data to the callback from the point where

the command is initially queued for execution.

The functions that can be used to issue commands in an asynchronous context are:

    int redisAsyncCommand(

      redisAsyncContext *ac, redisCallbackFn *fn, void *privdata,

      const char *format, ...);

    int redisAsyncCommandArgv(

      redisAsyncContext *ac, redisCallbackFn *fn, void *privdata,

      int argc, const char **argv, const size_t *argvlen);

Both functions work like their blocking counterparts. The return value is `REDIS_OK` when the command

was successfully added to the output buffer and `REDIS_ERR` otherwise. Example: when the connection

is being disconnected per user-request, no new commands may be added to the output buffer and `REDIS_ERR` is

returned on calls to the `redisAsyncCommand` family.

If the reply for a command with a `NULL` callback is read, it is immediately free'd. When the callback

for a command is non-`NULL`, the memory is free'd immediately following the callback: the reply is only

valid for the duration of the callback.

All pending callbacks are called with a `NULL` reply when the context encountered an error.

### Disconnecting

An asynchronous connection can be terminated using:

    void redisAsyncDisconnect(redisAsyncContext *ac);

When this function is called, the connection is **not** immediately terminated. Instead, new

commands are no longer accepted and the connection is only terminated when all pending commands

have been written to the socket, their respective replies have been read and their respective

callbacks have been executed. After this, the disconnection callback is executed with the

`REDIS_OK` status and the context object is free'd.

### Hooking it up to event library *X*

There are a few hooks that need to be set on the context object after it is created.

See the `adapters/` directory for bindings to *libev* and *libevent*.

## Reply parsing API

Hiredis comes with a reply parsing API that makes it easy for writing higher

level language bindings.

The reply parsing API consists of the following functions:

    redisReader *redisReaderCreate(void);

    void redisReaderFree(redisReader *reader);

    int redisReaderFeed(redisReader *reader, const char *buf, size_t len);

    int redisReaderGetReply(redisReader *reader, void **reply);

The same set of functions are used internally by hiredis when creating a

normal Redis context, the above API just exposes it to the user for a direct

usage.

### Usage

The function `redisReaderCreate` creates a `redisReader` structure that holds a

buffer with unparsed data and state for the protocol parser.

Incoming data -- most likely from a socket -- can be placed in the internal

buffer of the `redisReader` using `redisReaderFeed`. This function will make a

copy of the buffer pointed to by `buf` for `len` bytes. This data is parsed

when `redisReaderGetReply` is called. This function returns an integer status

and a reply object (as described above) via `void **reply`. The returned status

can be either `REDIS_OK` or `REDIS_ERR`, where the latter means something went

wrong (either a protocol error, or an out of memory error).

The parser limits the level of nesting for multi bulk payloads to 7. If the

multi bulk nesting level is higher than this, the parser returns an error.

### Customizing replies

The function `redisReaderGetReply` creates `redisReply` and makes the function

argument `reply` point to the created `redisReply` variable. For instance, if

the response of type `REDIS_REPLY_STATUS` then the `str` field of `redisReply`

will hold the status as a vanilla C string. However, the functions that are

responsible for creating instances of the `redisReply` can be customized by

setting the `fn` field on the `redisReader` struct. This should be done

immediately after creating the `redisReader`.

For example, [hiredis-rb](https://github.com/pietern/hiredis-rb/blob/master/ext/hiredis_ext/reader.c)

uses customized reply object functions to create Ruby objects.

### Reader max buffer

Both when using the Reader API directly or when using it indirectly via a

normal Redis context, the redisReader structure uses a buffer in order to

accumulate data from the server.

Usually this buffer is destroyed when it is empty and is larger than 16

kb in order to avoid wasting memory in unused buffers

However when working with very big payloads destroying the buffer may slow

down performances considerably, so it is possible to modify the max size of

an idle buffer changing the value of the `maxbuf` field of the reader structure

to the desired value. The special value of 0 means that there is no maximum

value for an idle buffer, so the buffer will never get freed.

For instance if you have a normal Redis context you can set the maximum idle

buffer to zero (unlimited) just with:

    context->reader->maxbuf = 0;

This should be done only in order to maximize performances when working with

large payloads. The context should be set back to `REDIS_READER_MAX_BUF` again

as soon as possible in order to prevent allocation of useless memory.

## AUTHORS

Hiredis was written by Salvatore Sanfilippo (antirez at gmail) and

Pieter Noordhuis (pcnoordhuis at gmail) and is released under the BSD license.