mythslove / coil

A tiny cooperative threading module for Lua

coil

A tiny cooperative threading module for Lua. Coil is based around coroutines, allowing many cooperative threads to run simultaneously.

Usage

The coil.lua file should be dropped into an existing project and required by it.

coil = require "coil"

At the start of each frame coil.update() should be called and given the delta time since the last call as its argument.

coil.update(deltatime)

Coil refers to each cooperative thread as a task; new tasks can be created by using the coil.add() function.

-- prints the word "hello" each second for 5 seconds
coil.add(function()
  for i = 1, 5 do
    print("hello")
    coil.wait(1)
  end
end)

coil.wait()

As tasks are cooperative, they must be manually yielded to allow other parts of the program to continue. This is done by calling the coil.wait() function. The function can be used to wait for different events before continuing.

• If wait is called with a number as its argument then it waits for that number of seconds before resuming.
• If wait is called with a callback created by coil.callback() it will wait until that callback function is called before resuming; it will return the arguments passed to the callback when it was called.
• If wait is called with no arguments it waits until the next frame (coil.update() call) before resuming; it returns the time that has passed since the last frame.

coil.callback()

The coil.callback() function can be used to create a special callback which, if passed to the coil.wait() function, will cause the task to wait until the callback is called.

-- Prints "Hello world" when `cb()` is called.
coil.add(function()
  cb = coil.callback()
  coil.wait(cb)
  print("Hello world")
end)

coil.update(dt)

This should be called at the start of each frame. Updates all the tasks, running those which aren't waiting or paused. dt should be the amount of time in seconds which has passed since the function was last called.

coil.add(fn)

Adds a new task, the task will begin running on the next call to coil.update().

-- prints "hello world" every 2 seconds
coil.add(function()
  while 1 do
    print("hello world")
    coil.wait(2)
  end
end)

Stopping a task

A task can be stopped and removed at any point by calling its :stop() method. To do this the task must be assigned to a variable when it is created.

-- Adds a new task
local t = coil.add(function()
  coil.wait(1)
  print("hello")
end)

-- Removes the task before it has a chance to run
t:stop()

Groups

Coil provides the ability to create task groups; these are objects which can have tasks added to them, and which are in charge of updating and handling their contained tasks. A group is created by calling the coil.group() function.

local group = coil.group()

Once a group is created it acts independently of the coil object, and must be updated each frame using its own update method.

group:update(deltatime)

To add a task to a group, the group's add() method should be used.

group:add(function()
  coil.wait(10)
  print("10 seconds have passed")
end)

A good example of where groups are useful is for games where you may have a set of tasks which effect objects in the game world and which you want to pause when the game is paused. A group's tasks can be paused by simply neglecting to call its update() method; when a group is destroyed its tasks are also destroyed.

License

This library is free software; you can redistribute it and/or modify it under the terms of the MIT license. See LICENSE for details.