mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2025-11-03 18:42:25 -06:00
585 lines
13 KiB
Go
585 lines
13 KiB
Go
// Copyright (c) 2022 Klaus Post. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package s2
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import (
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"encoding/binary"
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"errors"
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"fmt"
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)
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// LZ4Converter provides conversion from LZ4 blocks as defined here:
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// https://github.com/lz4/lz4/blob/dev/doc/lz4_Block_format.md
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type LZ4Converter struct {
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}
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// ErrDstTooSmall is returned when provided destination is too small.
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var ErrDstTooSmall = errors.New("s2: destination too small")
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// ConvertBlock will convert an LZ4 block and append it as an S2
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// block without block length to dst.
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// The uncompressed size is returned as well.
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// dst must have capacity to contain the entire compressed block.
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func (l *LZ4Converter) ConvertBlock(dst, src []byte) ([]byte, int, error) {
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if len(src) == 0 {
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return dst, 0, nil
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}
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const debug = false
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const inline = true
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const lz4MinMatch = 4
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s, d := 0, len(dst)
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dst = dst[:cap(dst)]
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if !debug && hasAmd64Asm {
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res, sz := cvtLZ4BlockAsm(dst[d:], src)
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if res < 0 {
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const (
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errCorrupt = -1
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errDstTooSmall = -2
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)
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switch res {
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case errCorrupt:
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return nil, 0, ErrCorrupt
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case errDstTooSmall:
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return nil, 0, ErrDstTooSmall
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default:
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return nil, 0, fmt.Errorf("unexpected result: %d", res)
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}
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}
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if d+sz > len(dst) {
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return nil, 0, ErrDstTooSmall
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}
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return dst[:d+sz], res, nil
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}
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dLimit := len(dst) - 10
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var lastOffset uint16
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var uncompressed int
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if debug {
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fmt.Printf("convert block start: len(src): %d, len(dst):%d \n", len(src), len(dst))
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}
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for {
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if s >= len(src) {
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return dst[:d], 0, ErrCorrupt
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}
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// Read literal info
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token := src[s]
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ll := int(token >> 4)
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ml := int(lz4MinMatch + (token & 0xf))
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// If upper nibble is 15, literal length is extended
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if token >= 0xf0 {
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for {
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s++
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if s >= len(src) {
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if debug {
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fmt.Printf("error reading ll: s (%d) >= len(src) (%d)\n", s, len(src))
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}
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return dst[:d], 0, ErrCorrupt
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}
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val := src[s]
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ll += int(val)
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if val != 255 {
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break
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}
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}
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}
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// Skip past token
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if s+ll >= len(src) {
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if debug {
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fmt.Printf("error literals: s+ll (%d+%d) >= len(src) (%d)\n", s, ll, len(src))
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}
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return nil, 0, ErrCorrupt
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}
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s++
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if ll > 0 {
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if d+ll > dLimit {
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return nil, 0, ErrDstTooSmall
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}
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if debug {
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fmt.Printf("emit %d literals\n", ll)
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}
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d += emitLiteralGo(dst[d:], src[s:s+ll])
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s += ll
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uncompressed += ll
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}
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// Check if we are done...
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if s == len(src) && ml == lz4MinMatch {
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break
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}
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// 2 byte offset
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if s >= len(src)-2 {
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if debug {
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fmt.Printf("s (%d) >= len(src)-2 (%d)", s, len(src)-2)
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}
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return nil, 0, ErrCorrupt
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}
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offset := binary.LittleEndian.Uint16(src[s:])
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s += 2
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if offset == 0 {
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if debug {
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fmt.Printf("error: offset 0, ml: %d, len(src)-s: %d\n", ml, len(src)-s)
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}
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return nil, 0, ErrCorrupt
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}
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if int(offset) > uncompressed {
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if debug {
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fmt.Printf("error: offset (%d)> uncompressed (%d)\n", offset, uncompressed)
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}
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return nil, 0, ErrCorrupt
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}
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if ml == lz4MinMatch+15 {
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for {
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if s >= len(src) {
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if debug {
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fmt.Printf("error reading ml: s (%d) >= len(src) (%d)\n", s, len(src))
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}
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return nil, 0, ErrCorrupt
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}
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val := src[s]
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s++
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ml += int(val)
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if val != 255 {
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if s >= len(src) {
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if debug {
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fmt.Printf("error reading ml: s (%d) >= len(src) (%d)\n", s, len(src))
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}
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return nil, 0, ErrCorrupt
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}
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break
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}
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}
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}
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if offset == lastOffset {
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if debug {
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fmt.Printf("emit repeat, length: %d, offset: %d\n", ml, offset)
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}
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if !inline {
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d += emitRepeat16(dst[d:], offset, ml)
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} else {
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length := ml
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dst := dst[d:]
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for len(dst) > 5 {
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// Repeat offset, make length cheaper
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length -= 4
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if length <= 4 {
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dst[0] = uint8(length)<<2 | tagCopy1
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dst[1] = 0
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d += 2
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break
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}
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if length < 8 && offset < 2048 {
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// Encode WITH offset
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dst[1] = uint8(offset)
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dst[0] = uint8(offset>>8)<<5 | uint8(length)<<2 | tagCopy1
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d += 2
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break
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}
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if length < (1<<8)+4 {
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length -= 4
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dst[2] = uint8(length)
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dst[1] = 0
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dst[0] = 5<<2 | tagCopy1
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d += 3
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break
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}
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if length < (1<<16)+(1<<8) {
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length -= 1 << 8
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dst[3] = uint8(length >> 8)
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dst[2] = uint8(length >> 0)
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dst[1] = 0
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dst[0] = 6<<2 | tagCopy1
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d += 4
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break
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}
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const maxRepeat = (1 << 24) - 1
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length -= 1 << 16
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left := 0
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if length > maxRepeat {
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left = length - maxRepeat + 4
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length = maxRepeat - 4
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}
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dst[4] = uint8(length >> 16)
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dst[3] = uint8(length >> 8)
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dst[2] = uint8(length >> 0)
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dst[1] = 0
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dst[0] = 7<<2 | tagCopy1
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if left > 0 {
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d += 5 + emitRepeat16(dst[5:], offset, left)
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break
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}
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d += 5
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break
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}
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}
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} else {
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if debug {
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fmt.Printf("emit copy, length: %d, offset: %d\n", ml, offset)
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}
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if !inline {
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d += emitCopy16(dst[d:], offset, ml)
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} else {
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length := ml
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dst := dst[d:]
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for len(dst) > 5 {
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// Offset no more than 2 bytes.
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if length > 64 {
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off := 3
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if offset < 2048 {
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// emit 8 bytes as tagCopy1, rest as repeats.
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dst[1] = uint8(offset)
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dst[0] = uint8(offset>>8)<<5 | uint8(8-4)<<2 | tagCopy1
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length -= 8
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off = 2
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} else {
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// Emit a length 60 copy, encoded as 3 bytes.
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// Emit remaining as repeat value (minimum 4 bytes).
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dst[2] = uint8(offset >> 8)
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dst[1] = uint8(offset)
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dst[0] = 59<<2 | tagCopy2
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length -= 60
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}
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// Emit remaining as repeats, at least 4 bytes remain.
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d += off + emitRepeat16(dst[off:], offset, length)
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break
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}
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if length >= 12 || offset >= 2048 {
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// Emit the remaining copy, encoded as 3 bytes.
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dst[2] = uint8(offset >> 8)
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dst[1] = uint8(offset)
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dst[0] = uint8(length-1)<<2 | tagCopy2
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d += 3
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break
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}
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// Emit the remaining copy, encoded as 2 bytes.
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dst[1] = uint8(offset)
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dst[0] = uint8(offset>>8)<<5 | uint8(length-4)<<2 | tagCopy1
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d += 2
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break
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}
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}
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lastOffset = offset
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}
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uncompressed += ml
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if d > dLimit {
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return nil, 0, ErrDstTooSmall
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}
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}
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return dst[:d], uncompressed, nil
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}
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// ConvertBlockSnappy will convert an LZ4 block and append it
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// as a Snappy block without block length to dst.
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// The uncompressed size is returned as well.
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// dst must have capacity to contain the entire compressed block.
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func (l *LZ4Converter) ConvertBlockSnappy(dst, src []byte) ([]byte, int, error) {
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if len(src) == 0 {
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return dst, 0, nil
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}
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const debug = false
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const lz4MinMatch = 4
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s, d := 0, len(dst)
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dst = dst[:cap(dst)]
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// Use assembly when possible
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if !debug && hasAmd64Asm {
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res, sz := cvtLZ4BlockSnappyAsm(dst[d:], src)
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if res < 0 {
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const (
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errCorrupt = -1
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errDstTooSmall = -2
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)
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switch res {
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case errCorrupt:
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return nil, 0, ErrCorrupt
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case errDstTooSmall:
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return nil, 0, ErrDstTooSmall
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default:
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return nil, 0, fmt.Errorf("unexpected result: %d", res)
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}
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}
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if d+sz > len(dst) {
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return nil, 0, ErrDstTooSmall
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}
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return dst[:d+sz], res, nil
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}
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dLimit := len(dst) - 10
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var uncompressed int
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if debug {
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fmt.Printf("convert block start: len(src): %d, len(dst):%d \n", len(src), len(dst))
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}
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for {
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if s >= len(src) {
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return nil, 0, ErrCorrupt
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}
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// Read literal info
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token := src[s]
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ll := int(token >> 4)
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ml := int(lz4MinMatch + (token & 0xf))
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// If upper nibble is 15, literal length is extended
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if token >= 0xf0 {
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for {
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s++
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if s >= len(src) {
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if debug {
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fmt.Printf("error reading ll: s (%d) >= len(src) (%d)\n", s, len(src))
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}
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return nil, 0, ErrCorrupt
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}
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val := src[s]
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ll += int(val)
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if val != 255 {
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break
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}
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}
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}
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// Skip past token
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if s+ll >= len(src) {
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if debug {
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fmt.Printf("error literals: s+ll (%d+%d) >= len(src) (%d)\n", s, ll, len(src))
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}
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return nil, 0, ErrCorrupt
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}
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s++
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if ll > 0 {
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if d+ll > dLimit {
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return nil, 0, ErrDstTooSmall
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}
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if debug {
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fmt.Printf("emit %d literals\n", ll)
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}
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d += emitLiteralGo(dst[d:], src[s:s+ll])
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s += ll
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uncompressed += ll
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}
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// Check if we are done...
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if s == len(src) && ml == lz4MinMatch {
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break
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}
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// 2 byte offset
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if s >= len(src)-2 {
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if debug {
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fmt.Printf("s (%d) >= len(src)-2 (%d)", s, len(src)-2)
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}
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return nil, 0, ErrCorrupt
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}
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offset := binary.LittleEndian.Uint16(src[s:])
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s += 2
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if offset == 0 {
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if debug {
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fmt.Printf("error: offset 0, ml: %d, len(src)-s: %d\n", ml, len(src)-s)
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}
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return nil, 0, ErrCorrupt
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}
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if int(offset) > uncompressed {
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if debug {
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fmt.Printf("error: offset (%d)> uncompressed (%d)\n", offset, uncompressed)
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}
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return nil, 0, ErrCorrupt
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}
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if ml == lz4MinMatch+15 {
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for {
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if s >= len(src) {
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if debug {
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fmt.Printf("error reading ml: s (%d) >= len(src) (%d)\n", s, len(src))
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}
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return nil, 0, ErrCorrupt
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}
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val := src[s]
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s++
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ml += int(val)
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if val != 255 {
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if s >= len(src) {
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if debug {
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fmt.Printf("error reading ml: s (%d) >= len(src) (%d)\n", s, len(src))
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}
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return nil, 0, ErrCorrupt
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}
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break
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}
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}
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}
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if debug {
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fmt.Printf("emit copy, length: %d, offset: %d\n", ml, offset)
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}
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length := ml
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// d += emitCopyNoRepeat(dst[d:], int(offset), ml)
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for length > 0 {
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if d >= dLimit {
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return nil, 0, ErrDstTooSmall
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}
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// Offset no more than 2 bytes.
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if length > 64 {
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// Emit a length 64 copy, encoded as 3 bytes.
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dst[d+2] = uint8(offset >> 8)
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dst[d+1] = uint8(offset)
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dst[d+0] = 63<<2 | tagCopy2
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length -= 64
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d += 3
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continue
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}
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if length >= 12 || offset >= 2048 || length < 4 {
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// Emit the remaining copy, encoded as 3 bytes.
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dst[d+2] = uint8(offset >> 8)
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dst[d+1] = uint8(offset)
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dst[d+0] = uint8(length-1)<<2 | tagCopy2
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d += 3
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break
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}
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// Emit the remaining copy, encoded as 2 bytes.
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dst[d+1] = uint8(offset)
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dst[d+0] = uint8(offset>>8)<<5 | uint8(length-4)<<2 | tagCopy1
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d += 2
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break
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}
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uncompressed += ml
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if d > dLimit {
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return nil, 0, ErrDstTooSmall
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}
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}
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return dst[:d], uncompressed, nil
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}
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// emitRepeat writes a repeat chunk and returns the number of bytes written.
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// Length must be at least 4 and < 1<<24
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func emitRepeat16(dst []byte, offset uint16, length int) int {
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// Repeat offset, make length cheaper
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length -= 4
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if length <= 4 {
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dst[0] = uint8(length)<<2 | tagCopy1
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dst[1] = 0
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return 2
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}
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if length < 8 && offset < 2048 {
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// Encode WITH offset
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dst[1] = uint8(offset)
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dst[0] = uint8(offset>>8)<<5 | uint8(length)<<2 | tagCopy1
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return 2
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}
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if length < (1<<8)+4 {
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length -= 4
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dst[2] = uint8(length)
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dst[1] = 0
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dst[0] = 5<<2 | tagCopy1
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return 3
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}
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if length < (1<<16)+(1<<8) {
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length -= 1 << 8
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dst[3] = uint8(length >> 8)
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dst[2] = uint8(length >> 0)
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dst[1] = 0
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dst[0] = 6<<2 | tagCopy1
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return 4
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}
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const maxRepeat = (1 << 24) - 1
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length -= 1 << 16
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left := 0
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if length > maxRepeat {
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left = length - maxRepeat + 4
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length = maxRepeat - 4
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}
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dst[4] = uint8(length >> 16)
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dst[3] = uint8(length >> 8)
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dst[2] = uint8(length >> 0)
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dst[1] = 0
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dst[0] = 7<<2 | tagCopy1
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if left > 0 {
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return 5 + emitRepeat16(dst[5:], offset, left)
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}
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return 5
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}
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// emitCopy writes a copy chunk and returns the number of bytes written.
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//
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// It assumes that:
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//
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// dst is long enough to hold the encoded bytes
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// 1 <= offset && offset <= math.MaxUint16
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// 4 <= length && length <= math.MaxUint32
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func emitCopy16(dst []byte, offset uint16, length int) int {
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// Offset no more than 2 bytes.
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if length > 64 {
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off := 3
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if offset < 2048 {
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// emit 8 bytes as tagCopy1, rest as repeats.
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dst[1] = uint8(offset)
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dst[0] = uint8(offset>>8)<<5 | uint8(8-4)<<2 | tagCopy1
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length -= 8
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off = 2
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} else {
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// Emit a length 60 copy, encoded as 3 bytes.
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// Emit remaining as repeat value (minimum 4 bytes).
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dst[2] = uint8(offset >> 8)
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dst[1] = uint8(offset)
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dst[0] = 59<<2 | tagCopy2
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length -= 60
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}
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// Emit remaining as repeats, at least 4 bytes remain.
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return off + emitRepeat16(dst[off:], offset, length)
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}
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if length >= 12 || offset >= 2048 {
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// Emit the remaining copy, encoded as 3 bytes.
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dst[2] = uint8(offset >> 8)
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dst[1] = uint8(offset)
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dst[0] = uint8(length-1)<<2 | tagCopy2
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return 3
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}
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// Emit the remaining copy, encoded as 2 bytes.
|
|
dst[1] = uint8(offset)
|
|
dst[0] = uint8(offset>>8)<<5 | uint8(length-4)<<2 | tagCopy1
|
|
return 2
|
|
}
|
|
|
|
// emitLiteral writes a literal chunk and returns the number of bytes written.
|
|
//
|
|
// It assumes that:
|
|
//
|
|
// dst is long enough to hold the encoded bytes
|
|
// 0 <= len(lit) && len(lit) <= math.MaxUint32
|
|
func emitLiteralGo(dst, lit []byte) int {
|
|
if len(lit) == 0 {
|
|
return 0
|
|
}
|
|
i, n := 0, uint(len(lit)-1)
|
|
switch {
|
|
case n < 60:
|
|
dst[0] = uint8(n)<<2 | tagLiteral
|
|
i = 1
|
|
case n < 1<<8:
|
|
dst[1] = uint8(n)
|
|
dst[0] = 60<<2 | tagLiteral
|
|
i = 2
|
|
case n < 1<<16:
|
|
dst[2] = uint8(n >> 8)
|
|
dst[1] = uint8(n)
|
|
dst[0] = 61<<2 | tagLiteral
|
|
i = 3
|
|
case n < 1<<24:
|
|
dst[3] = uint8(n >> 16)
|
|
dst[2] = uint8(n >> 8)
|
|
dst[1] = uint8(n)
|
|
dst[0] = 62<<2 | tagLiteral
|
|
i = 4
|
|
default:
|
|
dst[4] = uint8(n >> 24)
|
|
dst[3] = uint8(n >> 16)
|
|
dst[2] = uint8(n >> 8)
|
|
dst[1] = uint8(n)
|
|
dst[0] = 63<<2 | tagLiteral
|
|
i = 5
|
|
}
|
|
return i + copy(dst[i:], lit)
|
|
}
|