rle.coffee

module.exports =
  parseRLE: ->
    @byteCounts = @parseByteCounts()
    @parseChannelData()

  parseByteCounts: ->
    @file.readShort() for i in [0...(@channels() * @height())]

  parseChannelData: ->
    @chanPos = 0
    @lineIndex = 0

    for i in [0...@channels()]
      @decodeRLEChannel()
      @lineIndex += @height()

  decodeRLEChannel: ->
    for j in [0...@height()]
      byteCount = @byteCounts[@lineIndex + j]
      finish = @file.tell() + byteCount

      while @file.tell() < finish
        len = @file.read(1)[0]

        if len < 128
          len += 1
          @channelData.splice @chanPos, 0, @file.read(len)...
          @chanPos += len
        else if len > 128
          len ^= 0xff
          len += 2

          val = @file.read(1)[0]
          @channelData[@chanPos++] = val for i in [0...len]