855 lines
22 KiB
Go
855 lines
22 KiB
Go
// Copyright 2019+ Klaus Post. All rights reserved.
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// License information can be found in the LICENSE file.
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// Based on work by Yann Collet, released under BSD License.
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package zstd
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import (
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"errors"
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"fmt"
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"math"
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"math/bits"
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"github.com/klauspost/compress/huff0"
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)
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type blockEnc struct {
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size int
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literals []byte
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sequences []seq
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coders seqCoders
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litEnc *huff0.Scratch
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dictLitEnc *huff0.Scratch
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wr bitWriter
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extraLits int
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last bool
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output []byte
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recentOffsets [3]uint32
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prevRecentOffsets [3]uint32
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}
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// init should be used once the block has been created.
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// If called more than once, the effect is the same as calling reset.
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func (b *blockEnc) init() {
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if cap(b.literals) < maxCompressedLiteralSize {
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b.literals = make([]byte, 0, maxCompressedLiteralSize)
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}
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const defSeqs = 200
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b.literals = b.literals[:0]
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if cap(b.sequences) < defSeqs {
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b.sequences = make([]seq, 0, defSeqs)
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}
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if cap(b.output) < maxCompressedBlockSize {
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b.output = make([]byte, 0, maxCompressedBlockSize)
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}
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if b.coders.mlEnc == nil {
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b.coders.mlEnc = &fseEncoder{}
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b.coders.mlPrev = &fseEncoder{}
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b.coders.ofEnc = &fseEncoder{}
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b.coders.ofPrev = &fseEncoder{}
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b.coders.llEnc = &fseEncoder{}
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b.coders.llPrev = &fseEncoder{}
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}
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b.litEnc = &huff0.Scratch{WantLogLess: 4}
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b.reset(nil)
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}
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// initNewEncode can be used to reset offsets and encoders to the initial state.
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func (b *blockEnc) initNewEncode() {
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b.recentOffsets = [3]uint32{1, 4, 8}
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b.litEnc.Reuse = huff0.ReusePolicyNone
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b.coders.setPrev(nil, nil, nil)
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}
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// reset will reset the block for a new encode, but in the same stream,
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// meaning that state will be carried over, but the block content is reset.
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// If a previous block is provided, the recent offsets are carried over.
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func (b *blockEnc) reset(prev *blockEnc) {
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b.extraLits = 0
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b.literals = b.literals[:0]
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b.size = 0
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b.sequences = b.sequences[:0]
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b.output = b.output[:0]
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b.last = false
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if prev != nil {
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b.recentOffsets = prev.prevRecentOffsets
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}
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}
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// reset will reset the block for a new encode, but in the same stream,
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// meaning that state will be carried over, but the block content is reset.
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// If a previous block is provided, the recent offsets are carried over.
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func (b *blockEnc) swapEncoders(prev *blockEnc) {
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b.coders.swap(&prev.coders)
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b.litEnc, prev.litEnc = prev.litEnc, b.litEnc
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}
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// blockHeader contains the information for a block header.
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type blockHeader uint32
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// setLast sets the 'last' indicator on a block.
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func (h *blockHeader) setLast(b bool) {
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if b {
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*h = *h | 1
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} else {
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const mask = (1 << 24) - 2
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*h = *h & mask
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}
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}
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// setSize will store the compressed size of a block.
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func (h *blockHeader) setSize(v uint32) {
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const mask = 7
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*h = (*h)&mask | blockHeader(v<<3)
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}
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// setType sets the block type.
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func (h *blockHeader) setType(t blockType) {
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const mask = 1 | (((1 << 24) - 1) ^ 7)
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*h = (*h & mask) | blockHeader(t<<1)
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}
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// appendTo will append the block header to a slice.
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func (h blockHeader) appendTo(b []byte) []byte {
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return append(b, uint8(h), uint8(h>>8), uint8(h>>16))
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}
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// String returns a string representation of the block.
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func (h blockHeader) String() string {
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return fmt.Sprintf("Type: %d, Size: %d, Last:%t", (h>>1)&3, h>>3, h&1 == 1)
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}
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// literalsHeader contains literals header information.
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type literalsHeader uint64
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// setType can be used to set the type of literal block.
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func (h *literalsHeader) setType(t literalsBlockType) {
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const mask = math.MaxUint64 - 3
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*h = (*h & mask) | literalsHeader(t)
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}
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// setSize can be used to set a single size, for uncompressed and RLE content.
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func (h *literalsHeader) setSize(regenLen int) {
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inBits := bits.Len32(uint32(regenLen))
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// Only retain 2 bits
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const mask = 3
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lh := uint64(*h & mask)
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switch {
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case inBits < 5:
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lh |= (uint64(regenLen) << 3) | (1 << 60)
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if debug {
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got := int(lh>>3) & 0xff
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if got != regenLen {
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panic(fmt.Sprint("litRegenSize = ", regenLen, "(want) != ", got, "(got)"))
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}
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}
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case inBits < 12:
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lh |= (1 << 2) | (uint64(regenLen) << 4) | (2 << 60)
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case inBits < 20:
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lh |= (3 << 2) | (uint64(regenLen) << 4) | (3 << 60)
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default:
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panic(fmt.Errorf("internal error: block too big (%d)", regenLen))
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}
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*h = literalsHeader(lh)
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}
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// setSizes will set the size of a compressed literals section and the input length.
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func (h *literalsHeader) setSizes(compLen, inLen int, single bool) {
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compBits, inBits := bits.Len32(uint32(compLen)), bits.Len32(uint32(inLen))
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// Only retain 2 bits
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const mask = 3
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lh := uint64(*h & mask)
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switch {
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case compBits <= 10 && inBits <= 10:
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if !single {
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lh |= 1 << 2
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}
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lh |= (uint64(inLen) << 4) | (uint64(compLen) << (10 + 4)) | (3 << 60)
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if debug {
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const mmask = (1 << 24) - 1
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n := (lh >> 4) & mmask
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if int(n&1023) != inLen {
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panic(fmt.Sprint("regensize:", int(n&1023), "!=", inLen, inBits))
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}
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if int(n>>10) != compLen {
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panic(fmt.Sprint("compsize:", int(n>>10), "!=", compLen, compBits))
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}
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}
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case compBits <= 14 && inBits <= 14:
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lh |= (2 << 2) | (uint64(inLen) << 4) | (uint64(compLen) << (14 + 4)) | (4 << 60)
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if single {
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panic("single stream used with more than 10 bits length.")
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}
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case compBits <= 18 && inBits <= 18:
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lh |= (3 << 2) | (uint64(inLen) << 4) | (uint64(compLen) << (18 + 4)) | (5 << 60)
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if single {
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panic("single stream used with more than 10 bits length.")
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}
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default:
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panic("internal error: block too big")
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}
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*h = literalsHeader(lh)
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}
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// appendTo will append the literals header to a byte slice.
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func (h literalsHeader) appendTo(b []byte) []byte {
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size := uint8(h >> 60)
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switch size {
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case 1:
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b = append(b, uint8(h))
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case 2:
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b = append(b, uint8(h), uint8(h>>8))
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case 3:
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b = append(b, uint8(h), uint8(h>>8), uint8(h>>16))
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case 4:
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b = append(b, uint8(h), uint8(h>>8), uint8(h>>16), uint8(h>>24))
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case 5:
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b = append(b, uint8(h), uint8(h>>8), uint8(h>>16), uint8(h>>24), uint8(h>>32))
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default:
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panic(fmt.Errorf("internal error: literalsHeader has invalid size (%d)", size))
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}
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return b
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}
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// size returns the output size with currently set values.
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func (h literalsHeader) size() int {
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return int(h >> 60)
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}
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func (h literalsHeader) String() string {
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return fmt.Sprintf("Type: %d, SizeFormat: %d, Size: 0x%d, Bytes:%d", literalsBlockType(h&3), (h>>2)&3, h&((1<<60)-1)>>4, h>>60)
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}
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// pushOffsets will push the recent offsets to the backup store.
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func (b *blockEnc) pushOffsets() {
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b.prevRecentOffsets = b.recentOffsets
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}
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// pushOffsets will push the recent offsets to the backup store.
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func (b *blockEnc) popOffsets() {
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b.recentOffsets = b.prevRecentOffsets
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}
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// matchOffset will adjust recent offsets and return the adjusted one,
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// if it matches a previous offset.
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func (b *blockEnc) matchOffset(offset, lits uint32) uint32 {
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// Check if offset is one of the recent offsets.
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// Adjusts the output offset accordingly.
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// Gives a tiny bit of compression, typically around 1%.
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if true {
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if lits > 0 {
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switch offset {
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case b.recentOffsets[0]:
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offset = 1
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case b.recentOffsets[1]:
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b.recentOffsets[1] = b.recentOffsets[0]
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b.recentOffsets[0] = offset
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offset = 2
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case b.recentOffsets[2]:
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b.recentOffsets[2] = b.recentOffsets[1]
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b.recentOffsets[1] = b.recentOffsets[0]
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b.recentOffsets[0] = offset
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offset = 3
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default:
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b.recentOffsets[2] = b.recentOffsets[1]
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b.recentOffsets[1] = b.recentOffsets[0]
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b.recentOffsets[0] = offset
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offset += 3
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}
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} else {
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switch offset {
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case b.recentOffsets[1]:
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b.recentOffsets[1] = b.recentOffsets[0]
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b.recentOffsets[0] = offset
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offset = 1
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case b.recentOffsets[2]:
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b.recentOffsets[2] = b.recentOffsets[1]
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b.recentOffsets[1] = b.recentOffsets[0]
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b.recentOffsets[0] = offset
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offset = 2
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case b.recentOffsets[0] - 1:
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b.recentOffsets[2] = b.recentOffsets[1]
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b.recentOffsets[1] = b.recentOffsets[0]
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b.recentOffsets[0] = offset
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offset = 3
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default:
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b.recentOffsets[2] = b.recentOffsets[1]
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b.recentOffsets[1] = b.recentOffsets[0]
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b.recentOffsets[0] = offset
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offset += 3
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}
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}
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} else {
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offset += 3
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}
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return offset
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}
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// encodeRaw can be used to set the output to a raw representation of supplied bytes.
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func (b *blockEnc) encodeRaw(a []byte) {
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var bh blockHeader
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bh.setLast(b.last)
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bh.setSize(uint32(len(a)))
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bh.setType(blockTypeRaw)
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b.output = bh.appendTo(b.output[:0])
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b.output = append(b.output, a...)
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if debug {
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println("Adding RAW block, length", len(a), "last:", b.last)
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}
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}
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// encodeRaw can be used to set the output to a raw representation of supplied bytes.
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func (b *blockEnc) encodeRawTo(dst, src []byte) []byte {
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var bh blockHeader
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bh.setLast(b.last)
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bh.setSize(uint32(len(src)))
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bh.setType(blockTypeRaw)
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dst = bh.appendTo(dst)
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dst = append(dst, src...)
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if debug {
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println("Adding RAW block, length", len(src), "last:", b.last)
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}
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return dst
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}
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// encodeLits can be used if the block is only litLen.
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func (b *blockEnc) encodeLits(lits []byte, raw bool) error {
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var bh blockHeader
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bh.setLast(b.last)
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bh.setSize(uint32(len(lits)))
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// Don't compress extremely small blocks
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if len(lits) < 8 || (len(lits) < 32 && b.dictLitEnc == nil) || raw {
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if debug {
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println("Adding RAW block, length", len(lits), "last:", b.last)
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}
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bh.setType(blockTypeRaw)
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b.output = bh.appendTo(b.output)
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b.output = append(b.output, lits...)
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return nil
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}
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var (
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out []byte
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reUsed, single bool
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err error
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)
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if b.dictLitEnc != nil {
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b.litEnc.TransferCTable(b.dictLitEnc)
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b.litEnc.Reuse = huff0.ReusePolicyAllow
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b.dictLitEnc = nil
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}
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if len(lits) >= 1024 {
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// Use 4 Streams.
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out, reUsed, err = huff0.Compress4X(lits, b.litEnc)
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} else if len(lits) > 32 {
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// Use 1 stream
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single = true
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out, reUsed, err = huff0.Compress1X(lits, b.litEnc)
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} else {
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err = huff0.ErrIncompressible
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}
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switch err {
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case huff0.ErrIncompressible:
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if debug {
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println("Adding RAW block, length", len(lits), "last:", b.last)
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}
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bh.setType(blockTypeRaw)
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b.output = bh.appendTo(b.output)
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b.output = append(b.output, lits...)
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return nil
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case huff0.ErrUseRLE:
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if debug {
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println("Adding RLE block, length", len(lits))
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}
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bh.setType(blockTypeRLE)
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b.output = bh.appendTo(b.output)
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b.output = append(b.output, lits[0])
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return nil
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default:
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return err
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case nil:
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}
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// Compressed...
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// Now, allow reuse
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b.litEnc.Reuse = huff0.ReusePolicyAllow
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bh.setType(blockTypeCompressed)
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var lh literalsHeader
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if reUsed {
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if debug {
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println("Reused tree, compressed to", len(out))
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}
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lh.setType(literalsBlockTreeless)
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} else {
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if debug {
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println("New tree, compressed to", len(out), "tree size:", len(b.litEnc.OutTable))
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}
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lh.setType(literalsBlockCompressed)
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}
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// Set sizes
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lh.setSizes(len(out), len(lits), single)
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bh.setSize(uint32(len(out) + lh.size() + 1))
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// Write block headers.
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b.output = bh.appendTo(b.output)
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b.output = lh.appendTo(b.output)
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// Add compressed data.
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b.output = append(b.output, out...)
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// No sequences.
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b.output = append(b.output, 0)
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return nil
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}
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// fuzzFseEncoder can be used to fuzz the FSE encoder.
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func fuzzFseEncoder(data []byte) int {
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if len(data) > maxSequences || len(data) < 2 {
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return 0
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}
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enc := fseEncoder{}
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hist := enc.Histogram()[:256]
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maxSym := uint8(0)
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for i, v := range data {
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v = v & 63
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data[i] = v
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hist[v]++
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if v > maxSym {
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maxSym = v
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}
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}
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if maxSym == 0 {
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// All 0
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return 0
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}
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maxCount := func(a []uint32) int {
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var max uint32
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for _, v := range a {
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if v > max {
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max = v
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}
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}
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return int(max)
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}
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cnt := maxCount(hist[:maxSym])
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if cnt == len(data) {
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// RLE
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return 0
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}
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enc.HistogramFinished(maxSym, cnt)
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err := enc.normalizeCount(len(data))
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if err != nil {
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return 0
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}
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_, err = enc.writeCount(nil)
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if err != nil {
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panic(err)
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}
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return 1
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}
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// encode will encode the block and append the output in b.output.
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// Previous offset codes must be pushed if more blocks are expected.
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func (b *blockEnc) encode(org []byte, raw, rawAllLits bool) error {
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if len(b.sequences) == 0 {
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return b.encodeLits(b.literals, rawAllLits)
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}
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// We want some difference to at least account for the headers.
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saved := b.size - len(b.literals) - (b.size >> 5)
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if saved < 16 {
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if org == nil {
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return errIncompressible
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}
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b.popOffsets()
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return b.encodeLits(org, rawAllLits)
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}
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var bh blockHeader
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var lh literalsHeader
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bh.setLast(b.last)
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bh.setType(blockTypeCompressed)
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// Store offset of the block header. Needed when we know the size.
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bhOffset := len(b.output)
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b.output = bh.appendTo(b.output)
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var (
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out []byte
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reUsed, single bool
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err error
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)
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if b.dictLitEnc != nil {
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b.litEnc.TransferCTable(b.dictLitEnc)
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b.litEnc.Reuse = huff0.ReusePolicyAllow
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b.dictLitEnc = nil
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}
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if len(b.literals) >= 1024 && !raw {
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// Use 4 Streams.
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out, reUsed, err = huff0.Compress4X(b.literals, b.litEnc)
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} else if len(b.literals) > 32 && !raw {
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// Use 1 stream
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single = true
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out, reUsed, err = huff0.Compress1X(b.literals, b.litEnc)
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} else {
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err = huff0.ErrIncompressible
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}
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switch err {
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case huff0.ErrIncompressible:
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lh.setType(literalsBlockRaw)
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lh.setSize(len(b.literals))
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b.output = lh.appendTo(b.output)
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b.output = append(b.output, b.literals...)
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|
if debug {
|
|
println("Adding literals RAW, length", len(b.literals))
|
|
}
|
|
case huff0.ErrUseRLE:
|
|
lh.setType(literalsBlockRLE)
|
|
lh.setSize(len(b.literals))
|
|
b.output = lh.appendTo(b.output)
|
|
b.output = append(b.output, b.literals[0])
|
|
if debug {
|
|
println("Adding literals RLE")
|
|
}
|
|
default:
|
|
if debug {
|
|
println("Adding literals ERROR:", err)
|
|
}
|
|
return err
|
|
case nil:
|
|
// Compressed litLen...
|
|
if reUsed {
|
|
if debug {
|
|
println("reused tree")
|
|
}
|
|
lh.setType(literalsBlockTreeless)
|
|
} else {
|
|
if debug {
|
|
println("new tree, size:", len(b.litEnc.OutTable))
|
|
}
|
|
lh.setType(literalsBlockCompressed)
|
|
if debug {
|
|
_, _, err := huff0.ReadTable(out, nil)
|
|
if err != nil {
|
|
panic(err)
|
|
}
|
|
}
|
|
}
|
|
lh.setSizes(len(out), len(b.literals), single)
|
|
if debug {
|
|
printf("Compressed %d literals to %d bytes", len(b.literals), len(out))
|
|
println("Adding literal header:", lh)
|
|
}
|
|
b.output = lh.appendTo(b.output)
|
|
b.output = append(b.output, out...)
|
|
b.litEnc.Reuse = huff0.ReusePolicyAllow
|
|
if debug {
|
|
println("Adding literals compressed")
|
|
}
|
|
}
|
|
// Sequence compression
|
|
|
|
// Write the number of sequences
|
|
switch {
|
|
case len(b.sequences) < 128:
|
|
b.output = append(b.output, uint8(len(b.sequences)))
|
|
case len(b.sequences) < 0x7f00: // TODO: this could be wrong
|
|
n := len(b.sequences)
|
|
b.output = append(b.output, 128+uint8(n>>8), uint8(n))
|
|
default:
|
|
n := len(b.sequences) - 0x7f00
|
|
b.output = append(b.output, 255, uint8(n), uint8(n>>8))
|
|
}
|
|
if debug {
|
|
println("Encoding", len(b.sequences), "sequences")
|
|
}
|
|
b.genCodes()
|
|
llEnc := b.coders.llEnc
|
|
ofEnc := b.coders.ofEnc
|
|
mlEnc := b.coders.mlEnc
|
|
err = llEnc.normalizeCount(len(b.sequences))
|
|
if err != nil {
|
|
return err
|
|
}
|
|
err = ofEnc.normalizeCount(len(b.sequences))
|
|
if err != nil {
|
|
return err
|
|
}
|
|
err = mlEnc.normalizeCount(len(b.sequences))
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
// Choose the best compression mode for each type.
|
|
// Will evaluate the new vs predefined and previous.
|
|
chooseComp := func(cur, prev, preDef *fseEncoder) (*fseEncoder, seqCompMode) {
|
|
// See if predefined/previous is better
|
|
hist := cur.count[:cur.symbolLen]
|
|
nSize := cur.approxSize(hist) + cur.maxHeaderSize()
|
|
predefSize := preDef.approxSize(hist)
|
|
prevSize := prev.approxSize(hist)
|
|
|
|
// Add a small penalty for new encoders.
|
|
// Don't bother with extremely small (<2 byte gains).
|
|
nSize = nSize + (nSize+2*8*16)>>4
|
|
switch {
|
|
case predefSize <= prevSize && predefSize <= nSize || forcePreDef:
|
|
if debug {
|
|
println("Using predefined", predefSize>>3, "<=", nSize>>3)
|
|
}
|
|
return preDef, compModePredefined
|
|
case prevSize <= nSize:
|
|
if debug {
|
|
println("Using previous", prevSize>>3, "<=", nSize>>3)
|
|
}
|
|
return prev, compModeRepeat
|
|
default:
|
|
if debug {
|
|
println("Using new, predef", predefSize>>3, ". previous:", prevSize>>3, ">", nSize>>3, "header max:", cur.maxHeaderSize()>>3, "bytes")
|
|
println("tl:", cur.actualTableLog, "symbolLen:", cur.symbolLen, "norm:", cur.norm[:cur.symbolLen], "hist", cur.count[:cur.symbolLen])
|
|
}
|
|
return cur, compModeFSE
|
|
}
|
|
}
|
|
|
|
// Write compression mode
|
|
var mode uint8
|
|
if llEnc.useRLE {
|
|
mode |= uint8(compModeRLE) << 6
|
|
llEnc.setRLE(b.sequences[0].llCode)
|
|
if debug {
|
|
println("llEnc.useRLE")
|
|
}
|
|
} else {
|
|
var m seqCompMode
|
|
llEnc, m = chooseComp(llEnc, b.coders.llPrev, &fsePredefEnc[tableLiteralLengths])
|
|
mode |= uint8(m) << 6
|
|
}
|
|
if ofEnc.useRLE {
|
|
mode |= uint8(compModeRLE) << 4
|
|
ofEnc.setRLE(b.sequences[0].ofCode)
|
|
if debug {
|
|
println("ofEnc.useRLE")
|
|
}
|
|
} else {
|
|
var m seqCompMode
|
|
ofEnc, m = chooseComp(ofEnc, b.coders.ofPrev, &fsePredefEnc[tableOffsets])
|
|
mode |= uint8(m) << 4
|
|
}
|
|
|
|
if mlEnc.useRLE {
|
|
mode |= uint8(compModeRLE) << 2
|
|
mlEnc.setRLE(b.sequences[0].mlCode)
|
|
if debug {
|
|
println("mlEnc.useRLE, code: ", b.sequences[0].mlCode, "value", b.sequences[0].matchLen)
|
|
}
|
|
} else {
|
|
var m seqCompMode
|
|
mlEnc, m = chooseComp(mlEnc, b.coders.mlPrev, &fsePredefEnc[tableMatchLengths])
|
|
mode |= uint8(m) << 2
|
|
}
|
|
b.output = append(b.output, mode)
|
|
if debug {
|
|
printf("Compression modes: 0b%b", mode)
|
|
}
|
|
b.output, err = llEnc.writeCount(b.output)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
start := len(b.output)
|
|
b.output, err = ofEnc.writeCount(b.output)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
if false {
|
|
println("block:", b.output[start:], "tablelog", ofEnc.actualTableLog, "maxcount:", ofEnc.maxCount)
|
|
fmt.Printf("selected TableLog: %d, Symbol length: %d\n", ofEnc.actualTableLog, ofEnc.symbolLen)
|
|
for i, v := range ofEnc.norm[:ofEnc.symbolLen] {
|
|
fmt.Printf("%3d: %5d -> %4d \n", i, ofEnc.count[i], v)
|
|
}
|
|
}
|
|
b.output, err = mlEnc.writeCount(b.output)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
// Maybe in block?
|
|
wr := &b.wr
|
|
wr.reset(b.output)
|
|
|
|
var ll, of, ml cState
|
|
|
|
// Current sequence
|
|
seq := len(b.sequences) - 1
|
|
s := b.sequences[seq]
|
|
llEnc.setBits(llBitsTable[:])
|
|
mlEnc.setBits(mlBitsTable[:])
|
|
ofEnc.setBits(nil)
|
|
|
|
llTT, ofTT, mlTT := llEnc.ct.symbolTT[:256], ofEnc.ct.symbolTT[:256], mlEnc.ct.symbolTT[:256]
|
|
|
|
// We have 3 bounds checks here (and in the loop).
|
|
// Since we are iterating backwards it is kinda hard to avoid.
|
|
llB, ofB, mlB := llTT[s.llCode], ofTT[s.ofCode], mlTT[s.mlCode]
|
|
ll.init(wr, &llEnc.ct, llB)
|
|
of.init(wr, &ofEnc.ct, ofB)
|
|
wr.flush32()
|
|
ml.init(wr, &mlEnc.ct, mlB)
|
|
|
|
// Each of these lookups also generates a bounds check.
|
|
wr.addBits32NC(s.litLen, llB.outBits)
|
|
wr.addBits32NC(s.matchLen, mlB.outBits)
|
|
wr.flush32()
|
|
wr.addBits32NC(s.offset, ofB.outBits)
|
|
if debugSequences {
|
|
println("Encoded seq", seq, s, "codes:", s.llCode, s.mlCode, s.ofCode, "states:", ll.state, ml.state, of.state, "bits:", llB, mlB, ofB)
|
|
}
|
|
seq--
|
|
if llEnc.maxBits+mlEnc.maxBits+ofEnc.maxBits <= 32 {
|
|
// No need to flush (common)
|
|
for seq >= 0 {
|
|
s = b.sequences[seq]
|
|
wr.flush32()
|
|
llB, ofB, mlB := llTT[s.llCode], ofTT[s.ofCode], mlTT[s.mlCode]
|
|
// tabelog max is 8 for all.
|
|
of.encode(ofB)
|
|
ml.encode(mlB)
|
|
ll.encode(llB)
|
|
wr.flush32()
|
|
|
|
// We checked that all can stay within 32 bits
|
|
wr.addBits32NC(s.litLen, llB.outBits)
|
|
wr.addBits32NC(s.matchLen, mlB.outBits)
|
|
wr.addBits32NC(s.offset, ofB.outBits)
|
|
|
|
if debugSequences {
|
|
println("Encoded seq", seq, s)
|
|
}
|
|
|
|
seq--
|
|
}
|
|
} else {
|
|
for seq >= 0 {
|
|
s = b.sequences[seq]
|
|
wr.flush32()
|
|
llB, ofB, mlB := llTT[s.llCode], ofTT[s.ofCode], mlTT[s.mlCode]
|
|
// tabelog max is below 8 for each.
|
|
of.encode(ofB)
|
|
ml.encode(mlB)
|
|
ll.encode(llB)
|
|
wr.flush32()
|
|
|
|
// ml+ll = max 32 bits total
|
|
wr.addBits32NC(s.litLen, llB.outBits)
|
|
wr.addBits32NC(s.matchLen, mlB.outBits)
|
|
wr.flush32()
|
|
wr.addBits32NC(s.offset, ofB.outBits)
|
|
|
|
if debugSequences {
|
|
println("Encoded seq", seq, s)
|
|
}
|
|
|
|
seq--
|
|
}
|
|
}
|
|
ml.flush(mlEnc.actualTableLog)
|
|
of.flush(ofEnc.actualTableLog)
|
|
ll.flush(llEnc.actualTableLog)
|
|
err = wr.close()
|
|
if err != nil {
|
|
return err
|
|
}
|
|
b.output = wr.out
|
|
|
|
if len(b.output)-3-bhOffset >= b.size {
|
|
// Maybe even add a bigger margin.
|
|
b.litEnc.Reuse = huff0.ReusePolicyNone
|
|
return errIncompressible
|
|
}
|
|
|
|
// Size is output minus block header.
|
|
bh.setSize(uint32(len(b.output)-bhOffset) - 3)
|
|
if debug {
|
|
println("Rewriting block header", bh)
|
|
}
|
|
_ = bh.appendTo(b.output[bhOffset:bhOffset])
|
|
b.coders.setPrev(llEnc, mlEnc, ofEnc)
|
|
return nil
|
|
}
|
|
|
|
var errIncompressible = errors.New("incompressible")
|
|
|
|
func (b *blockEnc) genCodes() {
|
|
if len(b.sequences) == 0 {
|
|
// nothing to do
|
|
return
|
|
}
|
|
|
|
if len(b.sequences) > math.MaxUint16 {
|
|
panic("can only encode up to 64K sequences")
|
|
}
|
|
// No bounds checks after here:
|
|
llH := b.coders.llEnc.Histogram()[:256]
|
|
ofH := b.coders.ofEnc.Histogram()[:256]
|
|
mlH := b.coders.mlEnc.Histogram()[:256]
|
|
for i := range llH {
|
|
llH[i] = 0
|
|
}
|
|
for i := range ofH {
|
|
ofH[i] = 0
|
|
}
|
|
for i := range mlH {
|
|
mlH[i] = 0
|
|
}
|
|
|
|
var llMax, ofMax, mlMax uint8
|
|
for i, seq := range b.sequences {
|
|
v := llCode(seq.litLen)
|
|
seq.llCode = v
|
|
llH[v]++
|
|
if v > llMax {
|
|
llMax = v
|
|
}
|
|
|
|
v = ofCode(seq.offset)
|
|
seq.ofCode = v
|
|
ofH[v]++
|
|
if v > ofMax {
|
|
ofMax = v
|
|
}
|
|
|
|
v = mlCode(seq.matchLen)
|
|
seq.mlCode = v
|
|
mlH[v]++
|
|
if v > mlMax {
|
|
mlMax = v
|
|
if debugAsserts && mlMax > maxMatchLengthSymbol {
|
|
panic(fmt.Errorf("mlMax > maxMatchLengthSymbol (%d), matchlen: %d", mlMax, seq.matchLen))
|
|
}
|
|
}
|
|
b.sequences[i] = seq
|
|
}
|
|
maxCount := func(a []uint32) int {
|
|
var max uint32
|
|
for _, v := range a {
|
|
if v > max {
|
|
max = v
|
|
}
|
|
}
|
|
return int(max)
|
|
}
|
|
if debugAsserts && mlMax > maxMatchLengthSymbol {
|
|
panic(fmt.Errorf("mlMax > maxMatchLengthSymbol (%d)", mlMax))
|
|
}
|
|
if debugAsserts && ofMax > maxOffsetBits {
|
|
panic(fmt.Errorf("ofMax > maxOffsetBits (%d)", ofMax))
|
|
}
|
|
if debugAsserts && llMax > maxLiteralLengthSymbol {
|
|
panic(fmt.Errorf("llMax > maxLiteralLengthSymbol (%d)", llMax))
|
|
}
|
|
|
|
b.coders.mlEnc.HistogramFinished(mlMax, maxCount(mlH[:mlMax+1]))
|
|
b.coders.ofEnc.HistogramFinished(ofMax, maxCount(ofH[:ofMax+1]))
|
|
b.coders.llEnc.HistogramFinished(llMax, maxCount(llH[:llMax+1]))
|
|
}
|