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// Copyright 2014-2021 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 (
"errors"
"fmt"
)
// maximum and minimum values for the LZMA properties.
const (
minPB = 0
maxPB = 4
)
// maxPropertyCode is the possible maximum of a properties code byte.
const maxPropertyCode = (maxPB+1)*(maxLP+1)*(maxLC+1) - 1
// Properties contains the parameters LC, LP and PB. The parameter LC
// defines the number of literal context bits; parameter LP the number
// of literal position bits and PB the number of position bits.
type Properties struct {
LC int
LP int
PB int
}
// String returns the properties in a string representation.
func (p *Properties) String() string {
return fmt.Sprintf("LC %d LP %d PB %d", p.LC, p.LP, p.PB)
}
// PropertiesForCode converts a properties code byte into a Properties value.
func PropertiesForCode(code byte) (p Properties, err error) {
if code > maxPropertyCode {
return p, errors.New("lzma: invalid properties code")
}
p.LC = int(code % 9)
code /= 9
p.LP = int(code % 5)
code /= 5
p.PB = int(code % 5)
return p, err
}
// verify checks the properties for correctness.
func (p *Properties) verify() error {
if p == nil {
return errors.New("lzma: properties are nil")
}
if !(minLC <= p.LC && p.LC <= maxLC) {
return errors.New("lzma: lc out of range")
}
if !(minLP <= p.LP && p.LP <= maxLP) {
return errors.New("lzma: lp out of range")
}
if !(minPB <= p.PB && p.PB <= maxPB) {
return errors.New("lzma: pb out of range")
}
return nil
}
// Code converts the properties to a byte. The function assumes that
// the properties components are all in range.
func (p Properties) Code() byte {
return byte((p.PB*5+p.LP)*9 + p.LC)
}
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