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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/distcodec.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/distcodec.go')
-rw-r--r-- | vendor/github.com/ulikunitz/xz/lzma/distcodec.go | 156 |
1 files changed, 156 insertions, 0 deletions
diff --git a/vendor/github.com/ulikunitz/xz/lzma/distcodec.go b/vendor/github.com/ulikunitz/xz/lzma/distcodec.go new file mode 100644 index 000000000..b053a2dce --- /dev/null +++ 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 +} |