Audio API

-- Audio API version 1.0 by CrazedProgrammer
-- You can find info and documentation on these pages:
--
-- You may use this in your ComputerCraft programs and modify it without asking.
-- However, you may not publish this API under your name without asking me.
-- If you have any suggestions, bug reports or questions then please send an email to:
-- crazedprogrammer@gmail.com

local _volume = 1
local _outputs = { }
local _music = { }
pitch = {fs3=0.5,g3=0.529731547179648,gs3=0.561231024154687,a3=0.594603557501361,as3=0.629960524947437,b3=0.667419927085017,c4=0.707106781186547,cs4=0.749153538438341,d4=0.7937005259841,ds4=0.840896415253715,e4=0.890898718140339,f4=0.943874312681693,fs4=1,g4=1.0594630943593,gs4=1.12246204830937,a4=1.18920711500272,as4=1.25992104989487,b4=1.33483985417003,c5=1.41421356237309,cs5=1.49830707687668,d5=1.5874010519682,ds5=1.68179283050743,e5=1.78179743628068,f5=1.88774862536339,fs5=2}
local _const = math.log(2) / 12

function setOutput(command, output)
  command = command or commands
  output = output or #_outputs + 1
  if command == commands then
    _outputs[output] = {cmd = "", setCommand = function (command) cmd = command end, runCommand = function() commands.execAsync(cmd) end}
  else
    _outputs[output] = command
  end
end

function setVolume(vol)
  _volume = vol
end

function getVolume()
  return _volume
end

function playSound(sound, pitch, vol, output)
  pitch = pitch or 1
  vol = vol or 1
  output = output or 1
  if _outputs[output] then
    _outputs[output].setCommand("/playsound "..sound.." @a ~ ~ ~ "..tostring(_volume * vol).." "..tostring(pitch))
    _outputs[output].runCommand()
  end
end

function addMusic(m)
  table.insert(_music, m)
end

function removeMusic(m)
  local index = 0
  for k,v in pairs(_music) do
    if v == m then
      index = k
    end
  end
  if index ~= 0 then
    table.remove(_music, index)
  end
end

function loadMusic(file)
  local f = fs.open(file, "r")
  if not f then return end
  local str = f.readAll()
  f.close()
  local length = tonumber(str:sub(1, 4), 16)
  local m = {length = length, volume = 1, playing = false, offset = 1, channels = { }}
  local channels = tonumber(str:sub(5, 6), 16)
  local i = 7
  for k=1,channels,1 do
    local volumeId = tonumber(str:sub(i, i), 16)
    i = i + 1
    local output = tonumber(str:sub(i, i), 16)
    i = i + 1
    local len = tonumber(str:sub(i, i + 1), 16)
    i = i + 2
    local sound = str:sub(i, i + len - 1)
    i = i + len
    local channel = {sound = sound, volumeId = volumeId, output = output, notes = { }}
    table.insert(m.channels, channel)
    for j=1,length,1 do
      if str:sub(i, i) == " " then
        i = i + 1
      else
        local pitch = tonumber(str:sub(i, i + 1), 16)
        i = i + 2
        local vol = tonumber(str:sub(i, i), 16)
        channel.notes[j * 2 - 1] = pitch
        channel.notes[j * 2] = vol
        i = i + 1
      end
    end
  end
  return m
end

function update()
  for k,v in pairs(_music) do
    if v.playing then
      for l,w in pairs(v.channels) do
        if w.notes[v.offset * 2] then
          local pitch = 0.5 * math.exp(_const * (w.notes[v.offset * 2 - 1] - 1))
          local vol = w.notes[v.offset * 2] / 15
          playSound(w.sound, pitch, v.volume * (w.volumeId / 15) * vol, w.output)
        end
      end
      v.offset = v.offset + 1
      if v.offset > v.length then
        v.playing = false
        v.offset = 1
      end
    end
  end
end