81 lines
1.8 KiB
Go
81 lines
1.8 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 (
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"errors"
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"fmt"
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"unicode"
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)
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// operation represents an operation on the dictionary during encoding or
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// decoding.
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type operation interface {
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Len() int
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}
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// rep represents a repetition at the given distance and the given length
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type match struct {
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// supports all possible distance values, including the eos marker
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distance int64
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// length
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n int
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}
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// verify checks whether the match is valid. If that is not the case an
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// error is returned.
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func (m match) verify() error {
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if !(minDistance <= m.distance && m.distance <= maxDistance) {
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return errors.New("distance out of range")
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}
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if !(1 <= m.n && m.n <= maxMatchLen) {
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return errors.New("length out of range")
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}
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return nil
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}
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// l return the l-value for the match, which is the difference of length
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// n and 2.
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func (m match) l() uint32 {
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return uint32(m.n - minMatchLen)
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}
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// dist returns the dist value for the match, which is one less of the
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// distance stored in the match.
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func (m match) dist() uint32 {
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return uint32(m.distance - minDistance)
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}
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// Len returns the number of bytes matched.
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func (m match) Len() int {
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return m.n
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}
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// String returns a string representation for the repetition.
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func (m match) String() string {
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return fmt.Sprintf("M{%d,%d}", m.distance, m.n)
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}
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// lit represents a single byte literal.
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type lit struct {
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b byte
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}
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// Len returns 1 for the single byte literal.
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func (l lit) Len() int {
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return 1
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}
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// String returns a string representation for the literal.
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func (l lit) String() string {
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var c byte
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if unicode.IsPrint(rune(l.b)) {
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c = l.b
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} else {
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c = '.'
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}
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return fmt.Sprintf("L{%c/%02x}", c, l.b)
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}
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