Now with generalised lazy buffer.

play.lua

local general = 	require"general"
local len = general.len

local decode = 		require"decode"
local new_fifo = 	require"fifo"
local lazybuffer = 	require"lazybuffer"


local empty_item = { source = "silent" , from = 0 , to = math.huge }

local function setup ( outputbuffers )
	local queue = new_fifo ( )
	queue:setempty ( function ( f ) return empty_item end )

	local current_offset
	local get = function ( )
		local item = queue:pop()
		current_offset = item.from
		local left = item.to - current_offset
		return item , left
	end
	local put = function ( r , item , len )
		decode ( r , item.source , current_offset , len )
		current_offset = current_offset + len
		return r + len
	end
	fill = lazybuffer ( get, put )

	local current_outputbuffer = 1

	local step = function ( )
		local buff = outputbuffers [ current_outputbuffer ]
		fill ( buff , len(buff) )
		current_outputbuffer = ( current_outputbuffer % len(outputbuffers) ) + 1
	end

	return {
		queue = queue ;
		step = step ;
	}
end

return setup