package rle

func decompress4(output *[]uint8, width, height int, input []uint8, size int) bool {
	var (
		code             int
		onceBytes, total int
	)

	code = CVAL(&input)
	rle := code&0x10 != 0
	noAlpha := code&0x20 != 0

	if !rle {
		return false
	}

	total = 1
	out := *output

	if noAlpha {
		// No alpha plane in the stream; fill alpha channel with 0xFF.
		for i := 3; i < len(out); i += 4 {
			out[i] = 0xFF
		}
	} else {
		var ok bool
		onceBytes, ok = processPlane(&input, width, height, output, 3)
		if !ok {
			return false
		}
		total += onceBytes
	}

	var ok bool
	onceBytes, ok = processPlane(&input, width, height, output, 2)
	if !ok {
		return false
	}
	total += onceBytes

	onceBytes, ok = processPlane(&input, width, height, output, 1)
	if !ok {
		return false
	}
	total += onceBytes

	onceBytes, ok = processPlane(&input, width, height, output, 0)
	if !ok {
		return false
	}
	total += onceBytes

	return true
}

// DecompressInto decompresses bitmap data into dst, reusing dst if it has
// sufficient capacity (size = width*height*bpp). If dst is nil or too small
// a new slice is allocated. Returns the (re)used output slice.