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50 lines
1.4 KiB
Go
50 lines
1.4 KiB
Go
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// Copyright 2014-2017 Ulrich Kunitz. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package lzma
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import "fmt"
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// directCodec allows the encoding and decoding of values with a fixed number
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// of bits. The number of bits must be in the range [1,32].
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type directCodec byte
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// makeDirectCodec creates a directCodec. The function panics if the number of
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// bits is not in the range [1,32].
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func makeDirectCodec(bits int) directCodec {
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if !(1 <= bits && bits <= 32) {
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panic(fmt.Errorf("bits=%d out of range", bits))
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}
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return directCodec(bits)
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}
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// Bits returns the number of bits supported by this codec.
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func (dc directCodec) Bits() int {
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return int(dc)
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}
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// Encode uses the range encoder to encode a value with the fixed number of
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// bits. The most-significant bit is encoded first.
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func (dc directCodec) Encode(e *rangeEncoder, v uint32) error {
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for i := int(dc) - 1; i >= 0; i-- {
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if err := e.DirectEncodeBit(v >> uint(i)); err != nil {
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return err
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}
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}
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return nil
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}
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// Decode uses the range decoder to decode a value with the given number of
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// given bits. The most-significant bit is decoded first.
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func (dc directCodec) Decode(d *rangeDecoder) (v uint32, err error) {
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for i := int(dc) - 1; i >= 0; i-- {
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x, err := d.DirectDecodeBit()
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if err != nil {
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return 0, err
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}
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v = (v << 1) | x
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}
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return v, nil
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}
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