majek / lua-channels

Go style channels in pure Lua

Lua-Channels

Go style Channels for Lua

This code is derived from libtask library by Russ Cox, mainly from channel.c. Semantically channels as implemented here are quite similar to channels from the Go language.

Usage

This is an example of using an unbuffered channel:

local task = require('lua-channels')

local function counter(channel)
   local i = 1
   while true do
       channel:send(i)
       i = i + 1
   end
end

local function main()
    local channel = task.Channel:new()
    task.spawn(counter, channel)
    assert(channel:recv() == 1)
    assert(channel:recv() == 2)
    assert(channel:recv() == 3)
end

task.spawn(main)
task.scheduler()

lua-channels exposes:

• task.spawn(fun, [...]) - run fun as a coroutine with given parameters. You should use this instead of coroutine.create()

• task.scheduler() - can be run only from the main thread, executes all the stuff, resumes the coroutines that are blocked on channels that became available. You can only do non-blocking sends / receives from the main thread.

• task.Channel:new([buffer size]) - create a new channel with given size

• task.chanalt(alts, can_block) - run alt / select / multiplex over the alts structure. For example:

• task.chanalt({{c = channel_1, op = task.RECV}, {c = channel_2, op = task.SEND, p = "hello"}}, true)

This will block current coroutine until it's possible to receive from channel_1 or send to channel_2. chanalt returns a number of statement from alts that succeeded (1 or 2 here) and a received value if executed statement was RECV.

Finally, if two alt statements can be fulfilled at the same time, we use math.random() to decide which one should go first. So it makes sense to initialize seed with something random. If you don't have access to an entropy source you can do:

  math.randomseed(os.time())

but beware, the results of random() will predictable to a attacker.

Installing

You may simply require src/lua-channels.lua from the source, or install lua-channels from luarocks.