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authorDaniel J Walsh <dwalsh@redhat.com>2018-07-08 07:55:30 -0400
committerAtomic Bot <atomic-devel@projectatomic.io>2018-07-19 18:43:32 +0000
commit98703eb204923f06555605c648fc165a55214520 (patch)
treea407bae8b3489d4f9b0f0d0f228658bbfe95a38e /vendor/github.com/ulikunitz/xz/lzma/rangecodec.go
parentc020db8cd21cb221cfbe36b264e0ec02999596ed (diff)
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Vendor in latest code for storage,image, buildah
vendor in containers/storage vendor in containers/image vendor in projectatomic/buildah Signed-off-by: Daniel J Walsh <dwalsh@redhat.com> Closes: #1114 Approved by: mheon
Diffstat (limited to 'vendor/github.com/ulikunitz/xz/lzma/rangecodec.go')
-rw-r--r--vendor/github.com/ulikunitz/xz/lzma/rangecodec.go248
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diff --git a/vendor/github.com/ulikunitz/xz/lzma/rangecodec.go b/vendor/github.com/ulikunitz/xz/lzma/rangecodec.go
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+++ b/vendor/github.com/ulikunitz/xz/lzma/rangecodec.go
@@ -0,0 +1,248 @@
+// 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"
+ "io"
+)
+
+// rangeEncoder implements range encoding of single bits. The low value can
+// overflow therefore we need uint64. The cache value is used to handle
+// overflows.
+type rangeEncoder struct {
+ lbw *LimitedByteWriter
+ nrange uint32
+ low uint64
+ cacheLen int64
+ cache byte
+}
+
+// maxInt64 provides the maximal value of the int64 type
+const maxInt64 = 1<<63 - 1
+
+// newRangeEncoder creates a new range encoder.
+func newRangeEncoder(bw io.ByteWriter) (re *rangeEncoder, err error) {
+ lbw, ok := bw.(*LimitedByteWriter)
+ if !ok {
+ lbw = &LimitedByteWriter{BW: bw, N: maxInt64}
+ }
+ return &rangeEncoder{
+ lbw: lbw,
+ nrange: 0xffffffff,
+ cacheLen: 1}, nil
+}
+
+// Available returns the number of bytes that still can be written. The
+// method takes the bytes that will be currently written by Close into
+// account.
+func (e *rangeEncoder) Available() int64 {
+ return e.lbw.N - (e.cacheLen + 4)
+}
+
+// writeByte writes a single byte to the underlying writer. An error is
+// returned if the limit is reached. The written byte will be counted if
+// the underlying writer doesn't return an error.
+func (e *rangeEncoder) writeByte(c byte) error {
+ if e.Available() < 1 {
+ return ErrLimit
+ }
+ return e.lbw.WriteByte(c)
+}
+
+// DirectEncodeBit encodes the least-significant bit of b with probability 1/2.
+func (e *rangeEncoder) DirectEncodeBit(b uint32) error {
+ e.nrange >>= 1
+ e.low += uint64(e.nrange) & (0 - (uint64(b) & 1))
+
+ // normalize
+ const top = 1 << 24
+ if e.nrange >= top {
+ return nil
+ }
+ e.nrange <<= 8
+ return e.shiftLow()
+}
+
+// EncodeBit encodes the least significant bit of b. The p value will be
+// updated by the function depending on the bit encoded.
+func (e *rangeEncoder) EncodeBit(b uint32, p *prob) error {
+ bound := p.bound(e.nrange)
+ if b&1 == 0 {
+ e.nrange = bound
+ p.inc()
+ } else {
+ e.low += uint64(bound)
+ e.nrange -= bound
+ p.dec()
+ }
+
+ // normalize
+ const top = 1 << 24
+ if e.nrange >= top {
+ return nil
+ }
+ e.nrange <<= 8
+ return e.shiftLow()
+}
+
+// Close writes a complete copy of the low value.
+func (e *rangeEncoder) Close() error {
+ for i := 0; i < 5; i++ {
+ if err := e.shiftLow(); err != nil {
+ return err
+ }
+ }
+ return nil
+}
+
+// shiftLow shifts the low value for 8 bit. The shifted byte is written into
+// the byte writer. The cache value is used to handle overflows.
+func (e *rangeEncoder) shiftLow() error {
+ if uint32(e.low) < 0xff000000 || (e.low>>32) != 0 {
+ tmp := e.cache
+ for {
+ err := e.writeByte(tmp + byte(e.low>>32))
+ if err != nil {
+ return err
+ }
+ tmp = 0xff
+ e.cacheLen--
+ if e.cacheLen <= 0 {
+ if e.cacheLen < 0 {
+ panic("negative cacheLen")
+ }
+ break
+ }
+ }
+ e.cache = byte(uint32(e.low) >> 24)
+ }
+ e.cacheLen++
+ e.low = uint64(uint32(e.low) << 8)
+ return nil
+}
+
+// rangeDecoder decodes single bits of the range encoding stream.
+type rangeDecoder struct {
+ br io.ByteReader
+ nrange uint32
+ code uint32
+}
+
+// init initializes the range decoder, by reading from the byte reader.
+func (d *rangeDecoder) init() error {
+ d.nrange = 0xffffffff
+ d.code = 0
+
+ b, err := d.br.ReadByte()
+ if err != nil {
+ return err
+ }
+ if b != 0 {
+ return errors.New("newRangeDecoder: first byte not zero")
+ }
+
+ for i := 0; i < 4; i++ {
+ if err = d.updateCode(); err != nil {
+ return err
+ }
+ }
+
+ if d.code >= d.nrange {
+ return errors.New("newRangeDecoder: d.code >= d.nrange")
+ }
+
+ return nil
+}
+
+// newRangeDecoder initializes a range decoder. It reads five bytes from the
+// reader and therefore may return an error.
+func newRangeDecoder(br io.ByteReader) (d *rangeDecoder, err error) {
+ d = &rangeDecoder{br: br, nrange: 0xffffffff}
+
+ b, err := d.br.ReadByte()
+ if err != nil {
+ return nil, err
+ }
+ if b != 0 {
+ return nil, errors.New("newRangeDecoder: first byte not zero")
+ }
+
+ for i := 0; i < 4; i++ {
+ if err = d.updateCode(); err != nil {
+ return nil, err
+ }
+ }
+
+ if d.code >= d.nrange {
+ return nil, errors.New("newRangeDecoder: d.code >= d.nrange")
+ }
+
+ return d, nil
+}
+
+// possiblyAtEnd checks whether the decoder may be at the end of the stream.
+func (d *rangeDecoder) possiblyAtEnd() bool {
+ return d.code == 0
+}
+
+// DirectDecodeBit decodes a bit with probability 1/2. The return value b will
+// contain the bit at the least-significant position. All other bits will be
+// zero.
+func (d *rangeDecoder) DirectDecodeBit() (b uint32, err error) {
+ d.nrange >>= 1
+ d.code -= d.nrange
+ t := 0 - (d.code >> 31)
+ d.code += d.nrange & t
+ b = (t + 1) & 1
+
+ // d.code will stay less then d.nrange
+
+ // normalize
+ // assume d.code < d.nrange
+ const top = 1 << 24
+ if d.nrange >= top {
+ return b, nil
+ }
+ d.nrange <<= 8
+ // d.code < d.nrange will be maintained
+ return b, d.updateCode()
+}
+
+// decodeBit decodes a single bit. The bit will be returned at the
+// least-significant position. All other bits will be zero. The probability
+// value will be updated.
+func (d *rangeDecoder) DecodeBit(p *prob) (b uint32, err error) {
+ bound := p.bound(d.nrange)
+ if d.code < bound {
+ d.nrange = bound
+ p.inc()
+ b = 0
+ } else {
+ d.code -= bound
+ d.nrange -= bound
+ p.dec()
+ b = 1
+ }
+ // normalize
+ // assume d.code < d.nrange
+ const top = 1 << 24
+ if d.nrange >= top {
+ return b, nil
+ }
+ d.nrange <<= 8
+ // d.code < d.nrange will be maintained
+ return b, d.updateCode()
+}
+
+// updateCode reads a new byte into the code.
+func (d *rangeDecoder) updateCode() error {
+ b, err := d.br.ReadByte()
+ if err != nil {
+ return err
+ }
+ d.code = (d.code << 8) | uint32(b)
+ return nil
+}