989489096e
This commit implements a massive refactor of the repository, and moves the build system over to use Mage (magefile.org) which should allow seamless building across multiple platforms.
54 lines
1.5 KiB
Go
54 lines
1.5 KiB
Go
// 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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// movebits defines the number of bits used for the updates of probability
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// values.
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const movebits = 5
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// probbits defines the number of bits of a probability value.
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const probbits = 11
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// probInit defines 0.5 as initial value for prob values.
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const probInit prob = 1 << (probbits - 1)
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// Type prob represents probabilities. The type can also be used to encode and
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// decode single bits.
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type prob uint16
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// Dec decreases the probability. The decrease is proportional to the
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// probability value.
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func (p *prob) dec() {
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*p -= *p >> movebits
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}
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// Inc increases the probability. The Increase is proportional to the
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// difference of 1 and the probability value.
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func (p *prob) inc() {
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*p += ((1 << probbits) - *p) >> movebits
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}
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// Computes the new bound for a given range using the probability value.
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func (p prob) bound(r uint32) uint32 {
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return (r >> probbits) * uint32(p)
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}
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// Bits returns 1. One is the number of bits that can be encoded or decoded
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// with a single prob value.
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func (p prob) Bits() int {
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return 1
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}
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// Encode encodes the least-significant bit of v. Note that the p value will be
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// changed.
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func (p *prob) Encode(e *rangeEncoder, v uint32) error {
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return e.EncodeBit(v, p)
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}
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// Decode decodes a single bit. Note that the p value will change.
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func (p *prob) Decode(d *rangeDecoder) (v uint32, err error) {
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return d.DecodeBit(p)
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}
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