diff options
Diffstat (limited to 'vendor/github.com/ulikunitz/xz/lzma/properties.go')
-rw-r--r-- | vendor/github.com/ulikunitz/xz/lzma/properties.go | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/vendor/github.com/ulikunitz/xz/lzma/properties.go b/vendor/github.com/ulikunitz/xz/lzma/properties.go new file mode 100644 index 000000000..23418e25d --- /dev/null +++ b/vendor/github.com/ulikunitz/xz/lzma/properties.go @@ -0,0 +1,69 @@ +// Copyright 2014-2017 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) +} |