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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/distcodec.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/distcodec.go')
-rw-r--r--vendor/github.com/ulikunitz/xz/lzma/distcodec.go156
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diff --git a/vendor/github.com/ulikunitz/xz/lzma/distcodec.go b/vendor/github.com/ulikunitz/xz/lzma/distcodec.go
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+++ b/vendor/github.com/ulikunitz/xz/lzma/distcodec.go
@@ -0,0 +1,156 @@
+// 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
+
+// Constants used by the distance codec.
+const (
+ // minimum supported distance
+ minDistance = 1
+ // maximum supported distance, value is used for the eos marker.
+ maxDistance = 1 << 32
+ // number of the supported len states
+ lenStates = 4
+ // start for the position models
+ startPosModel = 4
+ // first index with align bits support
+ endPosModel = 14
+ // bits for the position slots
+ posSlotBits = 6
+ // number of align bits
+ alignBits = 4
+ // maximum position slot
+ maxPosSlot = 63
+)
+
+// distCodec provides encoding and decoding of distance values.
+type distCodec struct {
+ posSlotCodecs [lenStates]treeCodec
+ posModel [endPosModel - startPosModel]treeReverseCodec
+ alignCodec treeReverseCodec
+}
+
+// deepcopy initializes dc as deep copy of the source.
+func (dc *distCodec) deepcopy(src *distCodec) {
+ if dc == src {
+ return
+ }
+ for i := range dc.posSlotCodecs {
+ dc.posSlotCodecs[i].deepcopy(&src.posSlotCodecs[i])
+ }
+ for i := range dc.posModel {
+ dc.posModel[i].deepcopy(&src.posModel[i])
+ }
+ dc.alignCodec.deepcopy(&src.alignCodec)
+}
+
+// distBits returns the number of bits required to encode dist.
+func distBits(dist uint32) int {
+ if dist < startPosModel {
+ return 6
+ }
+ // slot s > 3, dist d
+ // s = 2(bits(d)-1) + bit(d, bits(d)-2)
+ // s>>1 = bits(d)-1
+ // bits(d) = 32-nlz32(d)
+ // s>>1=31-nlz32(d)
+ // n = 5 + (s>>1) = 36 - nlz32(d)
+ return 36 - nlz32(dist)
+}
+
+// newDistCodec creates a new distance codec.
+func (dc *distCodec) init() {
+ for i := range dc.posSlotCodecs {
+ dc.posSlotCodecs[i] = makeTreeCodec(posSlotBits)
+ }
+ for i := range dc.posModel {
+ posSlot := startPosModel + i
+ bits := (posSlot >> 1) - 1
+ dc.posModel[i] = makeTreeReverseCodec(bits)
+ }
+ dc.alignCodec = makeTreeReverseCodec(alignBits)
+}
+
+// lenState converts the value l to a supported lenState value.
+func lenState(l uint32) uint32 {
+ if l >= lenStates {
+ l = lenStates - 1
+ }
+ return l
+}
+
+// Encode encodes the distance using the parameter l. Dist can have values from
+// the full range of uint32 values. To get the distance offset the actual match
+// distance has to be decreased by 1. A distance offset of 0xffffffff (eos)
+// indicates the end of the stream.
+func (dc *distCodec) Encode(e *rangeEncoder, dist uint32, l uint32) (err error) {
+ // Compute the posSlot using nlz32
+ var posSlot uint32
+ var bits uint32
+ if dist < startPosModel {
+ posSlot = dist
+ } else {
+ bits = uint32(30 - nlz32(dist))
+ posSlot = startPosModel - 2 + (bits << 1)
+ posSlot += (dist >> uint(bits)) & 1
+ }
+
+ if err = dc.posSlotCodecs[lenState(l)].Encode(e, posSlot); err != nil {
+ return
+ }
+
+ switch {
+ case posSlot < startPosModel:
+ return nil
+ case posSlot < endPosModel:
+ tc := &dc.posModel[posSlot-startPosModel]
+ return tc.Encode(dist, e)
+ }
+ dic := directCodec(bits - alignBits)
+ if err = dic.Encode(e, dist>>alignBits); err != nil {
+ return
+ }
+ return dc.alignCodec.Encode(dist, e)
+}
+
+// Decode decodes the distance offset using the parameter l. The dist value
+// 0xffffffff (eos) indicates the end of the stream. Add one to the distance
+// offset to get the actual match distance.
+func (dc *distCodec) Decode(d *rangeDecoder, l uint32) (dist uint32, err error) {
+ posSlot, err := dc.posSlotCodecs[lenState(l)].Decode(d)
+ if err != nil {
+ return
+ }
+
+ // posSlot equals distance
+ if posSlot < startPosModel {
+ return posSlot, nil
+ }
+
+ // posSlot uses the individual models
+ bits := (posSlot >> 1) - 1
+ dist = (2 | (posSlot & 1)) << bits
+ var u uint32
+ if posSlot < endPosModel {
+ tc := &dc.posModel[posSlot-startPosModel]
+ if u, err = tc.Decode(d); err != nil {
+ return 0, err
+ }
+ dist += u
+ return dist, nil
+ }
+
+ // posSlots use direct encoding and a single model for the four align
+ // bits.
+ dic := directCodec(bits - alignBits)
+ if u, err = dic.Decode(d); err != nil {
+ return 0, err
+ }
+ dist += u << alignBits
+ if u, err = dc.alignCodec.Decode(d); err != nil {
+ return 0, err
+ }
+ dist += u
+ return dist, nil
+}