1// Copyright 2014-2022 Ulrich Kunitz. All rights reserved.
 2// Use of this source code is governed by a BSD-style
 3// license that can be found in the LICENSE file.
 4
 5package lzma
 6
 7// directCodec allows the encoding and decoding of values with a fixed number
 8// of bits. The number of bits must be in the range [1,32].
 9type directCodec byte
10
11// Bits returns the number of bits supported by this codec.
12func (dc directCodec) Bits() int {
13	return int(dc)
14}
15
16// Encode uses the range encoder to encode a value with the fixed number of
17// bits. The most-significant bit is encoded first.
18func (dc directCodec) Encode(e *rangeEncoder, v uint32) error {
19	for i := int(dc) - 1; i >= 0; i-- {
20		if err := e.DirectEncodeBit(v >> uint(i)); err != nil {
21			return err
22		}
23	}
24	return nil
25}
26
27// Decode uses the range decoder to decode a value with the given number of
28// given bits. The most-significant bit is decoded first.
29func (dc directCodec) Decode(d *rangeDecoder) (v uint32, err error) {
30	for i := int(dc) - 1; i >= 0; i-- {
31		x, err := d.DirectDecodeBit()
32		if err != nil {
33			return 0, err
34		}
35		v = (v << 1) | x
36	}
37	return v, nil
38}