func()

in wim/lzx/lzx.go [263:326]

• 59 lines of code
• 17 McCabe index (conditional complexity)

func (f *decompressor) readTree(lens []byte) error {
	// Get the pre-tree for the main tree.
	var pretreeLen [20]byte
	for i := range pretreeLen {
		pretreeLen[i] = byte(f.getBits(4))
	}
	if f.err != nil {
		return f.err
	}
	h := buildTable(pretreeLen[:])

	// The lengths are encoded as a series of huffman codes
	// encoded by the pre-tree.
	for i := 0; i < len(lens); {
		c := byte(f.getCode(h))
		if f.err != nil {
			return f.err
		}
		switch {
		case c <= 16: // length is delta from previous length
			lens[i] = (lens[i] + 17 - c) % 17
			i++
		case c == 17: // next n + 4 lengths are zero
			zeroes := int(f.getBits(4)) + 4
			if i+zeroes > len(lens) {
				return errCorrupt
			}
			for j := 0; j < zeroes; j++ {
				lens[i+j] = 0
			}
			i += zeroes
		case c == 18: // next n + 20 lengths are zero
			zeroes := int(f.getBits(5)) + 20
			if i+zeroes > len(lens) {
				return errCorrupt
			}
			for j := 0; j < zeroes; j++ {
				lens[i+j] = 0
			}
			i += zeroes
		case c == 19: // next n + 4 lengths all have the same value
			same := int(f.getBits(1)) + 4
			if i+same > len(lens) {
				return errCorrupt
			}
			c = byte(f.getCode(h))
			if c > 16 {
				return errCorrupt
			}
			l := (lens[i] + 17 - c) % 17
			for j := 0; j < same; j++ {
				lens[i+j] = l
			}
			i += same
		default:
			return errCorrupt
		}
	}

	if f.err != nil {
		return f.err
	}
	return nil
}