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author | Daniel J Walsh <dwalsh@redhat.com> | 2018-07-08 07:55:30 -0400 |
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committer | Atomic Bot <atomic-devel@projectatomic.io> | 2018-07-19 18:43:32 +0000 |
commit | 98703eb204923f06555605c648fc165a55214520 (patch) | |
tree | a407bae8b3489d4f9b0f0d0f228658bbfe95a38e /vendor/github.com/ulikunitz/xz/lzma/rangecodec.go | |
parent | c020db8cd21cb221cfbe36b264e0ec02999596ed (diff) | |
download | podman-98703eb204923f06555605c648fc165a55214520.tar.gz podman-98703eb204923f06555605c648fc165a55214520.tar.bz2 podman-98703eb204923f06555605c648fc165a55214520.zip |
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.go | 248 |
1 files changed, 248 insertions, 0 deletions
diff --git a/vendor/github.com/ulikunitz/xz/lzma/rangecodec.go b/vendor/github.com/ulikunitz/xz/lzma/rangecodec.go new file mode 100644 index 000000000..6361c5e7c --- /dev/null +++ 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 +} |