# sysvmq

`sysvmq` is a C extension that wraps SysV IPC Message Queues. It's similar to
the [POSIX MQ Ruby wrapper](https://github.com/Sirupsen/posix-mqueue). Message
queues are handy for interprocess communication where you want to be able to
take down either endpoint easily. The main disadvantage of SysV message queues
over POSIX MQs (on Linux) is that SysV doesn't expose a file descriptor to do
e.g. `select(2)` on.

## Installation

Add `sysvm` to your Gemfile.

`gem 'sysvmq'`

Currently known to work on Linux (MRI >= 2.0).

## Usage

```ruby
# Create a message queue with a 1024 byte buffer.
require 'sysvmq'
mq = SysVMQ.new(0xDEADC0DE, 1024, SysVMQ::IPC_CREAT | 0666)

mq.send "Hellø Wårld!"
assert_equal 1, mq.stats[:count]

assert_equal "Hellø Wårld!", mq.receive

# Raise an exception instead of blocking until a message is available
mq.receive(0, SysVMQ::IPC_NOWAIT)

ensure
# Delete queue
mq.destroy
```

## Todo

* Explain messages types
* Add named params for flags (e.g. `mq.receive(:front, blocking: false)`)
  instead of ORing flags directly.
* Add `IPC_INFO` on Linux
* Add all of `IPC_STAT`