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// Copyright 2014-2019 Ulrich Kunitz. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package lzma
import "fmt"
// directCodec allows the encoding and decoding of values with a fixed number
// of bits. The number of bits must be in the range [1,32].
type directCodec byte
// makeDirectCodec creates a directCodec. The function panics if the number of
// bits is not in the range [1,32].
func makeDirectCodec(bits int) directCodec {
if !(1 <= bits && bits <= 32) {
panic(fmt.Errorf("bits=%d out of range", bits))
}
return directCodec(bits)
}
// Bits returns the number of bits supported by this codec.
func (dc directCodec) Bits() int {
return int(dc)
}
// Encode uses the range encoder to encode a value with the fixed number of
// bits. The most-significant bit is encoded first.
func (dc directCodec) Encode(e *rangeEncoder, v uint32) error {
for i := int(dc) - 1; i >= 0; i-- {
if err := e.DirectEncodeBit(v >> uint(i)); err != nil {
return err
}
}
return nil
}
// Decode uses the range decoder to decode a value with the given number of
// given bits. The most-significant bit is decoded first.
func (dc directCodec) Decode(d *rangeDecoder) (v uint32, err error) {
for i := int(dc) - 1; i >= 0; i-- {
x, err := d.DirectDecodeBit()
if err != nil {
return 0, err
}
v = (v << 1) | x
}
return v, nil
}
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