undefined: archiumwasm behoben
parent
f69d020fa8
commit
b45da3bdee
@ -0,0 +1,10 @@
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language: go
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go:
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- 1.8
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install:
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- go get -d -v github.com/stretchr/testify
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script:
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- go test -v
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@ -0,0 +1,21 @@
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MIT License
|
||||
|
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Copyright (c) 2017 Veniamin Albaev
|
||||
|
||||
Permission is hereby granted, free of charge, to any person obtaining a copy
|
||||
of this software and associated documentation files (the "Software"), to deal
|
||||
in the Software without restriction, including without limitation the rights
|
||||
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
|
||||
copies of the Software, and to permit persons to whom the Software is
|
||||
furnished to do so, subject to the following conditions:
|
||||
|
||||
The above copyright notice and this permission notice shall be included in all
|
||||
copies or substantial portions of the Software.
|
||||
|
||||
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
|
||||
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
|
||||
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
|
||||
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
|
||||
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
|
||||
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
|
||||
SOFTWARE.
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@ -0,0 +1,24 @@
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# bcd
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[](https://travis-ci.org/albenik/bcd)
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[](https://godoc.org/github.com/albenik/bcd)
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Go implementation of BCD conversion functions
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Usage
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```go
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package main
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import (
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"fmt"
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"github.com/albenik/bcd"
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)
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func main() {
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fmt.Printf("Uint32: %d", bcd.ToUint32([]byte{0x11, 0x22, 0x33, 0x44}))
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fmt.Printf("BCD: %x", bcd.FromUint32(11223344))
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}
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```
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## Documentation
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For more documentation see [package documentation](https://godoc.org/github.com/albenik/bcd)
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// Package bcd provides functions for converting integers to BCD byte array and vice versa.
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package bcd
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func pow100(power byte) uint64 {
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res := uint64(1)
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for i := byte(0); i < power; i++ {
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res *= 100
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}
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return res
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}
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|
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func FromUint(value uint64, size int) []byte {
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buf := make([]byte, size)
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if value > 0 {
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remainder := value
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for pos := size - 1; pos >= 0 && remainder > 0; pos-- {
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tail := byte(remainder % 100)
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hi, lo := tail/10, tail%10
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buf[pos] = byte(hi<<4 + lo)
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remainder = remainder / 100
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}
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}
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return buf
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}
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// Returns uint8 value in BCD format.
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//
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// If value > 99, function returns value for last two digits of source value
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// (Example: uint8(123) = uint8(0x23)).
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func FromUint8(value uint8) byte {
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return FromUint(uint64(value), 1)[0]
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}
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|
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// Returns two-bytes array with uint16 value in BCD format
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//
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// If value > 9999, function returns value for last two digits of source value
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// (Example: uint8(12345) = []byte{0x23, 0x45}).
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func FromUint16(value uint16) []byte {
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return FromUint(uint64(value), 2)
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}
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// Returns four-bytes array with uint32 value in BCD format
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//
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// If value > 99999999, function returns value for last two digits of source value
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// (Example: uint8(1234567890) = []byte{0x23, 0x45, 0x67, 0x89}).
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func FromUint32(value uint32) []byte {
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return FromUint(uint64(value), 4)
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}
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// Returns eight-bytes array with uint64 value in BCD format
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//
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// If value > 9999999999999999, function returns value for last two digits of source value
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// (Example: uint8(12233445566778899) = []byte{0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99}).
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func FromUint64(value uint64) []byte {
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return FromUint(value, 8)
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}
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func toUint(value []byte, size int) uint64 {
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vlen := len(value)
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if vlen > size {
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value = value[vlen-size:]
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}
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res := uint64(0)
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for i, b := range value {
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hi, lo := b>>4, b&0x0f
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if hi > 9 || lo > 9 {
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return 0
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}
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res += uint64(hi*10+lo) * pow100(byte(vlen-i)-1)
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}
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return res
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}
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// Returns uint8 value converted from bcd byte.
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//
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// If byte is not BCD (e.g. 0x1A), function returns zero.
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func ToUint8(value byte) uint8 {
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return uint8(toUint([]byte{value}, 1))
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}
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// Return uint16 value converted from at most last two bytes of bcd bytes array.
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//
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// If any byte of used array part is not BCD (e.g 0x1A), function returns zero.
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func ToUint16(value []byte) uint16 {
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return uint16(toUint(value, 2))
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}
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// Return uint32 value converted from at most last four bytes of bcd bytes array.
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//
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// If any byte of used array part is not BCD (e.g 0x1A), function returns zero.
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func ToUint32(value []byte) uint32 {
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return uint32(toUint(value, 4))
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}
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// Return uint64 value converted from at most last eight bytes of bcd bytes array.
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//
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// If any byte of used array part is not BCD (e.g 0x1A), function returns zero.
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func ToUint64(value []byte) uint64 {
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return toUint(value, 8)
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}
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@ -0,0 +1,304 @@
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Copyright (c) 2012 The Go Authors. All rights reserved.
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||||
Copyright (c) 2019 Klaus Post. All rights reserved.
|
||||
|
||||
Redistribution and use in source and binary forms, with or without
|
||||
modification, are permitted provided that the following conditions are
|
||||
met:
|
||||
|
||||
* Redistributions of source code must retain the above copyright
|
||||
notice, this list of conditions and the following disclaimer.
|
||||
* Redistributions in binary form must reproduce the above
|
||||
copyright notice, this list of conditions and the following disclaimer
|
||||
in the documentation and/or other materials provided with the
|
||||
distribution.
|
||||
* Neither the name of Google Inc. nor the names of its
|
||||
contributors may be used to endorse or promote products derived from
|
||||
this software without specific prior written permission.
|
||||
|
||||
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
||||
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
||||
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
|
||||
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
|
||||
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
|
||||
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
|
||||
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
||||
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
||||
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
||||
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
|
||||
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
||||
|
||||
------------------
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||||
|
||||
Files: gzhttp/*
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||||
|
||||
Apache License
|
||||
Version 2.0, January 2004
|
||||
http://www.apache.org/licenses/
|
||||
|
||||
TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
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------------------
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Files: s2/cmd/internal/readahead/*
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||||
The MIT License (MIT)
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||||
Copyright (c) 2015 Klaus Post
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Permission is hereby granted, free of charge, to any person obtaining a copy
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
|
||||
|
||||
---------------------
|
||||
Files: snappy/*
|
||||
Files: internal/snapref/*
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||||
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||||
Copyright (c) 2011 The Snappy-Go Authors. All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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|
||||
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
|
||||
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
||||
|
||||
-----------------
|
||||
|
||||
Files: s2/cmd/internal/filepathx/*
|
||||
|
||||
Copyright 2016 The filepathx Authors
|
||||
|
||||
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
|
||||
|
||||
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
|
||||
|
||||
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
|
||||
@ -0,0 +1,910 @@
|
||||
// Copyright 2009 The Go Authors. All rights reserved.
|
||||
// Copyright (c) 2015 Klaus Post
|
||||
// Use of this source code is governed by a BSD-style
|
||||
// license that can be found in the LICENSE file.
|
||||
|
||||
package flate
|
||||
|
||||
import (
|
||||
"encoding/binary"
|
||||
"fmt"
|
||||
"io"
|
||||
"math"
|
||||
)
|
||||
|
||||
const (
|
||||
NoCompression = 0
|
||||
BestSpeed = 1
|
||||
BestCompression = 9
|
||||
DefaultCompression = -1
|
||||
|
||||
// HuffmanOnly disables Lempel-Ziv match searching and only performs Huffman
|
||||
// entropy encoding. This mode is useful in compressing data that has
|
||||
// already been compressed with an LZ style algorithm (e.g. Snappy or LZ4)
|
||||
// that lacks an entropy encoder. Compression gains are achieved when
|
||||
// certain bytes in the input stream occur more frequently than others.
|
||||
//
|
||||
// Note that HuffmanOnly produces a compressed output that is
|
||||
// RFC 1951 compliant. That is, any valid DEFLATE decompressor will
|
||||
// continue to be able to decompress this output.
|
||||
HuffmanOnly = -2
|
||||
ConstantCompression = HuffmanOnly // compatibility alias.
|
||||
|
||||
logWindowSize = 15
|
||||
windowSize = 1 << logWindowSize
|
||||
windowMask = windowSize - 1
|
||||
logMaxOffsetSize = 15 // Standard DEFLATE
|
||||
minMatchLength = 4 // The smallest match that the compressor looks for
|
||||
maxMatchLength = 258 // The longest match for the compressor
|
||||
minOffsetSize = 1 // The shortest offset that makes any sense
|
||||
|
||||
// The maximum number of tokens we will encode at the time.
|
||||
// Smaller sizes usually creates less optimal blocks.
|
||||
// Bigger can make context switching slow.
|
||||
// We use this for levels 7-9, so we make it big.
|
||||
maxFlateBlockTokens = 1 << 15
|
||||
maxStoreBlockSize = 65535
|
||||
hashBits = 17 // After 17 performance degrades
|
||||
hashSize = 1 << hashBits
|
||||
hashMask = (1 << hashBits) - 1
|
||||
hashShift = (hashBits + minMatchLength - 1) / minMatchLength
|
||||
maxHashOffset = 1 << 28
|
||||
|
||||
skipNever = math.MaxInt32
|
||||
|
||||
debugDeflate = false
|
||||
)
|
||||
|
||||
type compressionLevel struct {
|
||||
good, lazy, nice, chain, fastSkipHashing, level int
|
||||
}
|
||||
|
||||
// Compression levels have been rebalanced from zlib deflate defaults
|
||||
// to give a bigger spread in speed and compression.
|
||||
// See https://blog.klauspost.com/rebalancing-deflate-compression-levels/
|
||||
var levels = []compressionLevel{
|
||||
{}, // 0
|
||||
// Level 1-6 uses specialized algorithm - values not used
|
||||
{0, 0, 0, 0, 0, 1},
|
||||
{0, 0, 0, 0, 0, 2},
|
||||
{0, 0, 0, 0, 0, 3},
|
||||
{0, 0, 0, 0, 0, 4},
|
||||
{0, 0, 0, 0, 0, 5},
|
||||
{0, 0, 0, 0, 0, 6},
|
||||
// Levels 7-9 use increasingly more lazy matching
|
||||
// and increasingly stringent conditions for "good enough".
|
||||
{8, 12, 16, 24, skipNever, 7},
|
||||
{16, 30, 40, 64, skipNever, 8},
|
||||
{32, 258, 258, 1024, skipNever, 9},
|
||||
}
|
||||
|
||||
// advancedState contains state for the advanced levels, with bigger hash tables, etc.
|
||||
type advancedState struct {
|
||||
// deflate state
|
||||
length int
|
||||
offset int
|
||||
maxInsertIndex int
|
||||
chainHead int
|
||||
hashOffset int
|
||||
|
||||
ii uint16 // position of last match, intended to overflow to reset.
|
||||
|
||||
// input window: unprocessed data is window[index:windowEnd]
|
||||
index int
|
||||
estBitsPerByte int
|
||||
hashMatch [maxMatchLength + minMatchLength]uint32
|
||||
|
||||
// Input hash chains
|
||||
// hashHead[hashValue] contains the largest inputIndex with the specified hash value
|
||||
// If hashHead[hashValue] is within the current window, then
|
||||
// hashPrev[hashHead[hashValue] & windowMask] contains the previous index
|
||||
// with the same hash value.
|
||||
hashHead [hashSize]uint32
|
||||
hashPrev [windowSize]uint32
|
||||
}
|
||||
|
||||
type compressor struct {
|
||||
compressionLevel
|
||||
|
||||
h *huffmanEncoder
|
||||
w *huffmanBitWriter
|
||||
|
||||
// compression algorithm
|
||||
fill func(*compressor, []byte) int // copy data to window
|
||||
step func(*compressor) // process window
|
||||
|
||||
window []byte
|
||||
windowEnd int
|
||||
blockStart int // window index where current tokens start
|
||||
err error
|
||||
|
||||
// queued output tokens
|
||||
tokens tokens
|
||||
fast fastEnc
|
||||
state *advancedState
|
||||
|
||||
sync bool // requesting flush
|
||||
byteAvailable bool // if true, still need to process window[index-1].
|
||||
}
|
||||
|
||||
func (d *compressor) fillDeflate(b []byte) int {
|
||||
s := d.state
|
||||
if s.index >= 2*windowSize-(minMatchLength+maxMatchLength) {
|
||||
// shift the window by windowSize
|
||||
//copy(d.window[:], d.window[windowSize:2*windowSize])
|
||||
*(*[windowSize]byte)(d.window) = *(*[windowSize]byte)(d.window[windowSize:])
|
||||
s.index -= windowSize
|
||||
d.windowEnd -= windowSize
|
||||
if d.blockStart >= windowSize {
|
||||
d.blockStart -= windowSize
|
||||
} else {
|
||||
d.blockStart = math.MaxInt32
|
||||
}
|
||||
s.hashOffset += windowSize
|
||||
if s.hashOffset > maxHashOffset {
|
||||
delta := s.hashOffset - 1
|
||||
s.hashOffset -= delta
|
||||
s.chainHead -= delta
|
||||
// Iterate over slices instead of arrays to avoid copying
|
||||
// the entire table onto the stack (Issue #18625).
|
||||
for i, v := range s.hashPrev[:] {
|
||||
if int(v) > delta {
|
||||
s.hashPrev[i] = uint32(int(v) - delta)
|
||||
} else {
|
||||
s.hashPrev[i] = 0
|
||||
}
|
||||
}
|
||||
for i, v := range s.hashHead[:] {
|
||||
if int(v) > delta {
|
||||
s.hashHead[i] = uint32(int(v) - delta)
|
||||
} else {
|
||||
s.hashHead[i] = 0
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
n := copy(d.window[d.windowEnd:], b)
|
||||
d.windowEnd += n
|
||||
return n
|
||||
}
|
||||
|
||||
func (d *compressor) writeBlock(tok *tokens, index int, eof bool) error {
|
||||
if index > 0 || eof {
|
||||
var window []byte
|
||||
if d.blockStart <= index {
|
||||
window = d.window[d.blockStart:index]
|
||||
}
|
||||
d.blockStart = index
|
||||
//d.w.writeBlock(tok, eof, window)
|
||||
d.w.writeBlockDynamic(tok, eof, window, d.sync)
|
||||
return d.w.err
|
||||
}
|
||||
return nil
|
||||
}
|
||||
|
||||
// writeBlockSkip writes the current block and uses the number of tokens
|
||||
// to determine if the block should be stored on no matches, or
|
||||
// only huffman encoded.
|
||||
func (d *compressor) writeBlockSkip(tok *tokens, index int, eof bool) error {
|
||||
if index > 0 || eof {
|
||||
if d.blockStart <= index {
|
||||
window := d.window[d.blockStart:index]
|
||||
// If we removed less than a 64th of all literals
|
||||
// we huffman compress the block.
|
||||
if int(tok.n) > len(window)-int(tok.n>>6) {
|
||||
d.w.writeBlockHuff(eof, window, d.sync)
|
||||
} else {
|
||||
// Write a dynamic huffman block.
|
||||
d.w.writeBlockDynamic(tok, eof, window, d.sync)
|
||||
}
|
||||
} else {
|
||||
d.w.writeBlock(tok, eof, nil)
|
||||
}
|
||||
d.blockStart = index
|
||||
return d.w.err
|
||||
}
|
||||
return nil
|
||||
}
|
||||
|
||||
// fillWindow will fill the current window with the supplied
|
||||
// dictionary and calculate all hashes.
|
||||
// This is much faster than doing a full encode.
|
||||
// Should only be used after a start/reset.
|
||||
func (d *compressor) fillWindow(b []byte) {
|
||||
// Do not fill window if we are in store-only or huffman mode.
|
||||
if d.level <= 0 {
|
||||
return
|
||||
}
|
||||
if d.fast != nil {
|
||||
// encode the last data, but discard the result
|
||||
if len(b) > maxMatchOffset {
|
||||
b = b[len(b)-maxMatchOffset:]
|
||||
}
|
||||
d.fast.Encode(&d.tokens, b)
|
||||
d.tokens.Reset()
|
||||
return
|
||||
}
|
||||
s := d.state
|
||||
// If we are given too much, cut it.
|
||||
if len(b) > windowSize {
|
||||
b = b[len(b)-windowSize:]
|
||||
}
|
||||
// Add all to window.
|
||||
n := copy(d.window[d.windowEnd:], b)
|
||||
|
||||
// Calculate 256 hashes at the time (more L1 cache hits)
|
||||
loops := (n + 256 - minMatchLength) / 256
|
||||
for j := 0; j < loops; j++ {
|
||||
startindex := j * 256
|
||||
end := startindex + 256 + minMatchLength - 1
|
||||
if end > n {
|
||||
end = n
|
||||
}
|
||||
tocheck := d.window[startindex:end]
|
||||
dstSize := len(tocheck) - minMatchLength + 1
|
||||
|
||||
if dstSize <= 0 {
|
||||
continue
|
||||
}
|
||||
|
||||
dst := s.hashMatch[:dstSize]
|
||||
bulkHash4(tocheck, dst)
|
||||
var newH uint32
|
||||
for i, val := range dst {
|
||||
di := i + startindex
|
||||
newH = val & hashMask
|
||||
// Get previous value with the same hash.
|
||||
// Our chain should point to the previous value.
|
||||
s.hashPrev[di&windowMask] = s.hashHead[newH]
|
||||
// Set the head of the hash chain to us.
|
||||
s.hashHead[newH] = uint32(di + s.hashOffset)
|
||||
}
|
||||
}
|
||||
// Update window information.
|
||||
d.windowEnd += n
|
||||
s.index = n
|
||||
}
|
||||
|
||||
// Try to find a match starting at index whose length is greater than prevSize.
|
||||
// We only look at chainCount possibilities before giving up.
|
||||
// pos = s.index, prevHead = s.chainHead-s.hashOffset, prevLength=minMatchLength-1, lookahead
|
||||
func (d *compressor) findMatch(pos int, prevHead int, lookahead int) (length, offset int, ok bool) {
|
||||
minMatchLook := maxMatchLength
|
||||
if lookahead < minMatchLook {
|
||||
minMatchLook = lookahead
|
||||
}
|
||||
|
||||
win := d.window[0 : pos+minMatchLook]
|
||||
|
||||
// We quit when we get a match that's at least nice long
|
||||
nice := len(win) - pos
|
||||
if d.nice < nice {
|
||||
nice = d.nice
|
||||
}
|
||||
|
||||
// If we've got a match that's good enough, only look in 1/4 the chain.
|
||||
tries := d.chain
|
||||
length = minMatchLength - 1
|
||||
|
||||
wEnd := win[pos+length]
|
||||
wPos := win[pos:]
|
||||
minIndex := pos - windowSize
|
||||
if minIndex < 0 {
|
||||
minIndex = 0
|
||||
}
|
||||
offset = 0
|
||||
|
||||
cGain := 0
|
||||
if d.chain < 100 {
|
||||
for i := prevHead; tries > 0; tries-- {
|
||||
if wEnd == win[i+length] {
|
||||
n := matchLen(win[i:i+minMatchLook], wPos)
|
||||
if n > length {
|
||||
length = n
|
||||
offset = pos - i
|
||||
ok = true
|
||||
if n >= nice {
|
||||
// The match is good enough that we don't try to find a better one.
|
||||
break
|
||||
}
|
||||
wEnd = win[pos+n]
|
||||
}
|
||||
}
|
||||
if i <= minIndex {
|
||||
// hashPrev[i & windowMask] has already been overwritten, so stop now.
|
||||
break
|
||||
}
|
||||
i = int(d.state.hashPrev[i&windowMask]) - d.state.hashOffset
|
||||
if i < minIndex {
|
||||
break
|
||||
}
|
||||
}
|
||||
return
|
||||
}
|
||||
|
||||
// Some like it higher (CSV), some like it lower (JSON)
|
||||
const baseCost = 6
|
||||
// Base is 4 bytes at with an additional cost.
|
||||
// Matches must be better than this.
|
||||
for i := prevHead; tries > 0; tries-- {
|
||||
if wEnd == win[i+length] {
|
||||
n := matchLen(win[i:i+minMatchLook], wPos)
|
||||
if n > length {
|
||||
// Calculate gain. Estimate
|
||||
newGain := d.h.bitLengthRaw(wPos[:n]) - int(offsetExtraBits[offsetCode(uint32(pos-i))]) - baseCost - int(lengthExtraBits[lengthCodes[(n-3)&255]])
|
||||
|
||||
//fmt.Println(n, "gain:", newGain, "prev:", cGain, "raw:", d.h.bitLengthRaw(wPos[:n]))
|
||||
if newGain > cGain {
|
||||
length = n
|
||||
offset = pos - i
|
||||
cGain = newGain
|
||||
ok = true
|
||||
if n >= nice {
|
||||
// The match is good enough that we don't try to find a better one.
|
||||
break
|
||||
}
|
||||
wEnd = win[pos+n]
|
||||
}
|
||||
}
|
||||
}
|
||||
if i <= minIndex {
|
||||
// hashPrev[i & windowMask] has already been overwritten, so stop now.
|
||||
break
|
||||
}
|
||||
i = int(d.state.hashPrev[i&windowMask]) - d.state.hashOffset
|
||||
if i < minIndex {
|
||||
break
|
||||
}
|
||||
}
|
||||
return
|
||||
}
|
||||
|
||||
func (d *compressor) writeStoredBlock(buf []byte) error {
|
||||
if d.w.writeStoredHeader(len(buf), false); d.w.err != nil {
|
||||
return d.w.err
|
||||
}
|
||||
d.w.writeBytes(buf)
|
||||
return d.w.err
|
||||
}
|
||||
|
||||
// hash4 returns a hash representation of the first 4 bytes
|
||||
// of the supplied slice.
|
||||
// The caller must ensure that len(b) >= 4.
|
||||
func hash4(b []byte) uint32 {
|
||||
return hash4u(binary.LittleEndian.Uint32(b), hashBits)
|
||||
}
|
||||
|
||||
// hash4 returns the hash of u to fit in a hash table with h bits.
|
||||
// Preferably h should be a constant and should always be <32.
|
||||
func hash4u(u uint32, h uint8) uint32 {
|
||||
return (u * prime4bytes) >> (32 - h)
|
||||
}
|
||||
|
||||
// bulkHash4 will compute hashes using the same
|
||||
// algorithm as hash4
|
||||
func bulkHash4(b []byte, dst []uint32) {
|
||||
if len(b) < 4 {
|
||||
return
|
||||
}
|
||||
hb := binary.LittleEndian.Uint32(b)
|
||||
|
||||
dst[0] = hash4u(hb, hashBits)
|
||||
end := len(b) - 4 + 1
|
||||
for i := 1; i < end; i++ {
|
||||
hb = (hb >> 8) | uint32(b[i+3])<<24
|
||||
dst[i] = hash4u(hb, hashBits)
|
||||
}
|
||||
}
|
||||
|
||||
func (d *compressor) initDeflate() {
|
||||
d.window = make([]byte, 2*windowSize)
|
||||
d.byteAvailable = false
|
||||
d.err = nil
|
||||
if d.state == nil {
|
||||
return
|
||||
}
|
||||
s := d.state
|
||||
s.index = 0
|
||||
s.hashOffset = 1
|
||||
s.length = minMatchLength - 1
|
||||
s.offset = 0
|
||||
s.chainHead = -1
|
||||
}
|
||||
|
||||
// deflateLazy is the same as deflate, but with d.fastSkipHashing == skipNever,
|
||||
// meaning it always has lazy matching on.
|
||||
func (d *compressor) deflateLazy() {
|
||||
s := d.state
|
||||
// Sanity enables additional runtime tests.
|
||||
// It's intended to be used during development
|
||||
// to supplement the currently ad-hoc unit tests.
|
||||
const sanity = debugDeflate
|
||||
|
||||
if d.windowEnd-s.index < minMatchLength+maxMatchLength && !d.sync {
|
||||
return
|
||||
}
|
||||
if d.windowEnd != s.index && d.chain > 100 {
|
||||
// Get literal huffman coder.
|
||||
if d.h == nil {
|
||||
d.h = newHuffmanEncoder(maxFlateBlockTokens)
|
||||
}
|
||||
var tmp [256]uint16
|
||||
for _, v := range d.window[s.index:d.windowEnd] {
|
||||
tmp[v]++
|
||||
}
|
||||
d.h.generate(tmp[:], 15)
|
||||
}
|
||||
|
||||
s.maxInsertIndex = d.windowEnd - (minMatchLength - 1)
|
||||
|
||||
for {
|
||||
if sanity && s.index > d.windowEnd {
|
||||
panic("index > windowEnd")
|
||||
}
|
||||
lookahead := d.windowEnd - s.index
|
||||
if lookahead < minMatchLength+maxMatchLength {
|
||||
if !d.sync {
|
||||
return
|
||||
}
|
||||
if sanity && s.index > d.windowEnd {
|
||||
panic("index > windowEnd")
|
||||
}
|
||||
if lookahead == 0 {
|
||||
// Flush current output block if any.
|
||||
if d.byteAvailable {
|
||||
// There is still one pending token that needs to be flushed
|
||||
d.tokens.AddLiteral(d.window[s.index-1])
|
||||
d.byteAvailable = false
|
||||
}
|
||||
if d.tokens.n > 0 {
|
||||
if d.err = d.writeBlock(&d.tokens, s.index, false); d.err != nil {
|
||||
return
|
||||
}
|
||||
d.tokens.Reset()
|
||||
}
|
||||
return
|
||||
}
|
||||
}
|
||||
if s.index < s.maxInsertIndex {
|
||||
// Update the hash
|
||||
hash := hash4(d.window[s.index:])
|
||||
ch := s.hashHead[hash]
|
||||
s.chainHead = int(ch)
|
||||
s.hashPrev[s.index&windowMask] = ch
|
||||
s.hashHead[hash] = uint32(s.index + s.hashOffset)
|
||||
}
|
||||
prevLength := s.length
|
||||
prevOffset := s.offset
|
||||
s.length = minMatchLength - 1
|
||||
s.offset = 0
|
||||
minIndex := s.index - windowSize
|
||||
if minIndex < 0 {
|
||||
minIndex = 0
|
||||
}
|
||||
|
||||
if s.chainHead-s.hashOffset >= minIndex && lookahead > prevLength && prevLength < d.lazy {
|
||||
if newLength, newOffset, ok := d.findMatch(s.index, s.chainHead-s.hashOffset, lookahead); ok {
|
||||
s.length = newLength
|
||||
s.offset = newOffset
|
||||
}
|
||||
}
|
||||
|
||||
if prevLength >= minMatchLength && s.length <= prevLength {
|
||||
// Check for better match at end...
|
||||
//
|
||||
// checkOff must be >=2 since we otherwise risk checking s.index
|
||||
// Offset of 2 seems to yield best results.
|
||||
const checkOff = 2
|
||||
prevIndex := s.index - 1
|
||||
if prevIndex+prevLength+checkOff < s.maxInsertIndex {
|
||||
end := lookahead
|
||||
if lookahead > maxMatchLength {
|
||||
end = maxMatchLength
|
||||
}
|
||||
end += prevIndex
|
||||
idx := prevIndex + prevLength - (4 - checkOff)
|
||||
h := hash4(d.window[idx:])
|
||||
ch2 := int(s.hashHead[h]) - s.hashOffset - prevLength + (4 - checkOff)
|
||||
if ch2 > minIndex {
|
||||
length := matchLen(d.window[prevIndex:end], d.window[ch2:])
|
||||
// It seems like a pure length metric is best.
|
||||
if length > prevLength {
|
||||
prevLength = length
|
||||
prevOffset = prevIndex - ch2
|
||||
}
|
||||
}
|
||||
}
|
||||
// There was a match at the previous step, and the current match is
|
||||
// not better. Output the previous match.
|
||||
d.tokens.AddMatch(uint32(prevLength-3), uint32(prevOffset-minOffsetSize))
|
||||
|
||||
// Insert in the hash table all strings up to the end of the match.
|
||||
// index and index-1 are already inserted. If there is not enough
|
||||
// lookahead, the last two strings are not inserted into the hash
|
||||
// table.
|
||||
newIndex := s.index + prevLength - 1
|
||||
// Calculate missing hashes
|
||||
end := newIndex
|
||||
if end > s.maxInsertIndex {
|
||||
end = s.maxInsertIndex
|
||||
}
|
||||
end += minMatchLength - 1
|
||||
startindex := s.index + 1
|
||||
if startindex > s.maxInsertIndex {
|
||||
startindex = s.maxInsertIndex
|
||||
}
|
||||
tocheck := d.window[startindex:end]
|
||||
dstSize := len(tocheck) - minMatchLength + 1
|
||||
if dstSize > 0 {
|
||||
dst := s.hashMatch[:dstSize]
|
||||
bulkHash4(tocheck, dst)
|
||||
var newH uint32
|
||||
for i, val := range dst {
|
||||
di := i + startindex
|
||||
newH = val & hashMask
|
||||
// Get previous value with the same hash.
|
||||
// Our chain should point to the previous value.
|
||||
s.hashPrev[di&windowMask] = s.hashHead[newH]
|
||||
// Set the head of the hash chain to us.
|
||||
s.hashHead[newH] = uint32(di + s.hashOffset)
|
||||
}
|
||||
}
|
||||
|
||||
s.index = newIndex
|
||||
d.byteAvailable = false
|
||||
s.length = minMatchLength - 1
|
||||
if d.tokens.n == maxFlateBlockTokens {
|
||||
// The block includes the current character
|
||||
if d.err = d.writeBlock(&d.tokens, s.index, false); d.err != nil {
|
||||
return
|
||||
}
|
||||
d.tokens.Reset()
|
||||
}
|
||||
s.ii = 0
|
||||
} else {
|
||||
// Reset, if we got a match this run.
|
||||
if s.length >= minMatchLength {
|
||||
s.ii = 0
|
||||
}
|
||||
// We have a byte waiting. Emit it.
|
||||
if d.byteAvailable {
|
||||
s.ii++
|
||||
d.tokens.AddLiteral(d.window[s.index-1])
|
||||
if d.tokens.n == maxFlateBlockTokens {
|
||||
if d.err = d.writeBlock(&d.tokens, s.index, false); d.err != nil {
|
||||
return
|
||||
}
|
||||
d.tokens.Reset()
|
||||
}
|
||||
s.index++
|
||||
|
||||
// If we have a long run of no matches, skip additional bytes
|
||||
// Resets when s.ii overflows after 64KB.
|
||||
if n := int(s.ii) - d.chain; n > 0 {
|
||||
n = 1 + int(n>>6)
|
||||
for j := 0; j < n; j++ {
|
||||
if s.index >= d.windowEnd-1 {
|
||||
break
|
||||
}
|
||||
d.tokens.AddLiteral(d.window[s.index-1])
|
||||
if d.tokens.n == maxFlateBlockTokens {
|
||||
if d.err = d.writeBlock(&d.tokens, s.index, false); d.err != nil {
|
||||
return
|
||||
}
|
||||
d.tokens.Reset()
|
||||
}
|
||||
// Index...
|
||||
if s.index < s.maxInsertIndex {
|
||||
h := hash4(d.window[s.index:])
|
||||
ch := s.hashHead[h]
|
||||
s.chainHead = int(ch)
|
||||
s.hashPrev[s.index&windowMask] = ch
|
||||
s.hashHead[h] = uint32(s.index + s.hashOffset)
|
||||
}
|
||||
s.index++
|
||||
}
|
||||
// Flush last byte
|
||||
d.tokens.AddLiteral(d.window[s.index-1])
|
||||
d.byteAvailable = false
|
||||
// s.length = minMatchLength - 1 // not needed, since s.ii is reset above, so it should never be > minMatchLength
|
||||
if d.tokens.n == maxFlateBlockTokens {
|
||||
if d.err = d.writeBlock(&d.tokens, s.index, false); d.err != nil {
|
||||
return
|
||||
}
|
||||
d.tokens.Reset()
|
||||
}
|
||||
}
|
||||
} else {
|
||||
s.index++
|
||||
d.byteAvailable = true
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
func (d *compressor) store() {
|
||||
if d.windowEnd > 0 && (d.windowEnd == maxStoreBlockSize || d.sync) {
|
||||
d.err = d.writeStoredBlock(d.window[:d.windowEnd])
|
||||
d.windowEnd = 0
|
||||
}
|
||||
}
|
||||
|
||||
// fillWindow will fill the buffer with data for huffman-only compression.
|
||||
// The number of bytes copied is returned.
|
||||
func (d *compressor) fillBlock(b []byte) int {
|
||||
n := copy(d.window[d.windowEnd:], b)
|
||||
d.windowEnd += n
|
||||
return n
|
||||
}
|
||||
|
||||
// storeHuff will compress and store the currently added data,
|
||||
// if enough has been accumulated or we at the end of the stream.
|
||||
// Any error that occurred will be in d.err
|
||||
func (d *compressor) storeHuff() {
|
||||
if d.windowEnd < len(d.window) && !d.sync || d.windowEnd == 0 {
|
||||
return
|
||||
}
|
||||
d.w.writeBlockHuff(false, d.window[:d.windowEnd], d.sync)
|
||||
d.err = d.w.err
|
||||
d.windowEnd = 0
|
||||
}
|
||||
|
||||
// storeFast will compress and store the currently added data,
|
||||
// if enough has been accumulated or we at the end of the stream.
|
||||
// Any error that occurred will be in d.err
|
||||
func (d *compressor) storeFast() {
|
||||
// We only compress if we have maxStoreBlockSize.
|
||||
if d.windowEnd < len(d.window) {
|
||||
if !d.sync {
|
||||
return
|
||||
}
|
||||
// Handle extremely small sizes.
|
||||
if d.windowEnd < 128 {
|
||||
if d.windowEnd == 0 {
|
||||
return
|
||||
}
|
||||
if d.windowEnd <= 32 {
|
||||
d.err = d.writeStoredBlock(d.window[:d.windowEnd])
|
||||
} else {
|
||||
d.w.writeBlockHuff(false, d.window[:d.windowEnd], true)
|
||||
d.err = d.w.err
|
||||
}
|
||||
d.tokens.Reset()
|
||||
d.windowEnd = 0
|
||||
d.fast.Reset()
|
||||
return
|
||||
}
|
||||
}
|
||||
|
||||
d.fast.Encode(&d.tokens, d.window[:d.windowEnd])
|
||||
// If we made zero matches, store the block as is.
|
||||
if d.tokens.n == 0 {
|
||||
d.err = d.writeStoredBlock(d.window[:d.windowEnd])
|
||||
// If we removed less than 1/16th, huffman compress the block.
|
||||
} else if int(d.tokens.n) > d.windowEnd-(d.windowEnd>>4) {
|
||||
d.w.writeBlockHuff(false, d.window[:d.windowEnd], d.sync)
|
||||
d.err = d.w.err
|
||||
} else {
|
||||
d.w.writeBlockDynamic(&d.tokens, false, d.window[:d.windowEnd], d.sync)
|
||||
d.err = d.w.err
|
||||
}
|
||||
d.tokens.Reset()
|
||||
d.windowEnd = 0
|
||||
}
|
||||
|
||||
// write will add input byte to the stream.
|
||||
// Unless an error occurs all bytes will be consumed.
|
||||
func (d *compressor) write(b []byte) (n int, err error) {
|
||||
if d.err != nil {
|
||||
return 0, d.err
|
||||
}
|
||||
n = len(b)
|
||||
for len(b) > 0 {
|
||||
if d.windowEnd == len(d.window) || d.sync {
|
||||
d.step(d)
|
||||
}
|
||||
b = b[d.fill(d, b):]
|
||||
if d.err != nil {
|
||||
return 0, d.err
|
||||
}
|
||||
}
|
||||
return n, d.err
|
||||
}
|
||||
|
||||
func (d *compressor) syncFlush() error {
|
||||
d.sync = true
|
||||
if d.err != nil {
|
||||
return d.err
|
||||
}
|
||||
d.step(d)
|
||||
if d.err == nil {
|
||||
d.w.writeStoredHeader(0, false)
|
||||
d.w.flush()
|
||||
d.err = d.w.err
|
||||
}
|
||||
d.sync = false
|
||||
return d.err
|
||||
}
|
||||
|
||||
func (d *compressor) init(w io.Writer, level int) (err error) {
|
||||
d.w = newHuffmanBitWriter(w)
|
||||
|
||||
switch {
|
||||
case level == NoCompression:
|
||||
d.window = make([]byte, maxStoreBlockSize)
|
||||
d.fill = (*compressor).fillBlock
|
||||
d.step = (*compressor).store
|
||||
case level == ConstantCompression:
|
||||
d.w.logNewTablePenalty = 10
|
||||
d.window = make([]byte, 32<<10)
|
||||
d.fill = (*compressor).fillBlock
|
||||
d.step = (*compressor).storeHuff
|
||||
case level == DefaultCompression:
|
||||
level = 5
|
||||
fallthrough
|
||||
case level >= 1 && level <= 6:
|
||||
d.w.logNewTablePenalty = 7
|
||||
d.fast = newFastEnc(level)
|
||||
d.window = make([]byte, maxStoreBlockSize)
|
||||
d.fill = (*compressor).fillBlock
|
||||
d.step = (*compressor).storeFast
|
||||
case 7 <= level && level <= 9:
|
||||
d.w.logNewTablePenalty = 8
|
||||
d.state = &advancedState{}
|
||||
d.compressionLevel = levels[level]
|
||||
d.initDeflate()
|
||||
d.fill = (*compressor).fillDeflate
|
||||
d.step = (*compressor).deflateLazy
|
||||
default:
|
||||
return fmt.Errorf("flate: invalid compression level %d: want value in range [-2, 9]", level)
|
||||
}
|
||||
d.level = level
|
||||
return nil
|
||||
}
|
||||
|
||||
// reset the state of the compressor.
|
||||
func (d *compressor) reset(w io.Writer) {
|
||||
d.w.reset(w)
|
||||
d.sync = false
|
||||
d.err = nil
|
||||
// We only need to reset a few things for Snappy.
|
||||
if d.fast != nil {
|
||||
d.fast.Reset()
|
||||
d.windowEnd = 0
|
||||
d.tokens.Reset()
|
||||
return
|
||||
}
|
||||
switch d.compressionLevel.chain {
|
||||
case 0:
|
||||
// level was NoCompression or ConstantCompresssion.
|
||||
d.windowEnd = 0
|
||||
default:
|
||||
s := d.state
|
||||
s.chainHead = -1
|
||||
for i := range s.hashHead {
|
||||
s.hashHead[i] = 0
|
||||
}
|
||||
for i := range s.hashPrev {
|
||||
s.hashPrev[i] = 0
|
||||
}
|
||||
s.hashOffset = 1
|
||||
s.index, d.windowEnd = 0, 0
|
||||
d.blockStart, d.byteAvailable = 0, false
|
||||
d.tokens.Reset()
|
||||
s.length = minMatchLength - 1
|
||||
s.offset = 0
|
||||
s.ii = 0
|
||||
s.maxInsertIndex = 0
|
||||
}
|
||||
}
|
||||
|
||||
func (d *compressor) close() error {
|
||||
if d.err != nil {
|
||||
return d.err
|
||||
}
|
||||
d.sync = true
|
||||
d.step(d)
|
||||
if d.err != nil {
|
||||
return d.err
|
||||
}
|
||||
if d.w.writeStoredHeader(0, true); d.w.err != nil {
|
||||
return d.w.err
|
||||
}
|
||||
d.w.flush()
|
||||
d.w.reset(nil)
|
||||
return d.w.err
|
||||
}
|
||||
|
||||
// NewWriter returns a new Writer compressing data at the given level.
|
||||
// Following zlib, levels range from 1 (BestSpeed) to 9 (BestCompression);
|
||||
// higher levels typically run slower but compress more.
|
||||
// Level 0 (NoCompression) does not attempt any compression; it only adds the
|
||||
// necessary DEFLATE framing.
|
||||
// Level -1 (DefaultCompression) uses the default compression level.
|
||||
// Level -2 (ConstantCompression) will use Huffman compression only, giving
|
||||
// a very fast compression for all types of input, but sacrificing considerable
|
||||
// compression efficiency.
|
||||
//
|
||||
// If level is in the range [-2, 9] then the error returned will be nil.
|
||||
// Otherwise the error returned will be non-nil.
|
||||
func NewWriter(w io.Writer, level int) (*Writer, error) {
|
||||
var dw Writer
|
||||
if err := dw.d.init(w, level); err != nil {
|
||||
return nil, err
|
||||
}
|
||||
return &dw, nil
|
||||
}
|
||||
|
||||
// NewWriterDict is like NewWriter but initializes the new
|
||||
// Writer with a preset dictionary. The returned Writer behaves
|
||||
// as if the dictionary had been written to it without producing
|
||||
// any compressed output. The compressed data written to w
|
||||
// can only be decompressed by a Reader initialized with the
|
||||
// same dictionary.
|
||||
func NewWriterDict(w io.Writer, level int, dict []byte) (*Writer, error) {
|
||||
zw, err := NewWriter(w, level)
|
||||
if err != nil {
|
||||
return nil, err
|
||||
}
|
||||
zw.d.fillWindow(dict)
|
||||
zw.dict = append(zw.dict, dict...) // duplicate dictionary for Reset method.
|
||||
return zw, err
|
||||
}
|
||||
|
||||
// A Writer takes data written to it and writes the compressed
|
||||
// form of that data to an underlying writer (see NewWriter).
|
||||
type Writer struct {
|
||||
d compressor
|
||||
dict []byte
|
||||
}
|
||||
|
||||
// Write writes data to w, which will eventually write the
|
||||
// compressed form of data to its underlying writer.
|
||||
func (w *Writer) Write(data []byte) (n int, err error) {
|
||||
return w.d.write(data)
|
||||
}
|
||||
|
||||
// Flush flushes any pending data to the underlying writer.
|
||||
// It is useful mainly in compressed network protocols, to ensure that
|
||||
// a remote reader has enough data to reconstruct a packet.
|
||||
// Flush does not return until the data has been written.
|
||||
// Calling Flush when there is no pending data still causes the Writer
|
||||
// to emit a sync marker of at least 4 bytes.
|
||||
// If the underlying writer returns an error, Flush returns that error.
|
||||
//
|
||||
// In the terminology of the zlib library, Flush is equivalent to Z_SYNC_FLUSH.
|
||||
func (w *Writer) Flush() error {
|
||||
// For more about flushing:
|
||||
// http://www.bolet.org/~pornin/deflate-flush.html
|
||||
return w.d.syncFlush()
|
||||
}
|
||||
|
||||
// Close flushes and closes the writer.
|
||||
func (w *Writer) Close() error {
|
||||
return w.d.close()
|
||||
}
|
||||
|
||||
// Reset discards the writer's state and makes it equivalent to
|
||||
// the result of NewWriter or NewWriterDict called with dst
|
||||
// and w's level and dictionary.
|
||||
func (w *Writer) Reset(dst io.Writer) {
|
||||
if len(w.dict) > 0 {
|
||||
// w was created with NewWriterDict
|
||||
w.d.reset(dst)
|
||||
if dst != nil {
|
||||
w.d.fillWindow(w.dict)
|
||||
}
|
||||
} else {
|
||||
// w was created with NewWriter
|
||||
w.d.reset(dst)
|
||||
}
|
||||
}
|
||||
|
||||
// ResetDict discards the writer's state and makes it equivalent to
|
||||
// the result of NewWriter or NewWriterDict called with dst
|
||||
// and w's level, but sets a specific dictionary.
|
||||
func (w *Writer) ResetDict(dst io.Writer, dict []byte) {
|
||||
w.dict = dict
|
||||
w.d.reset(dst)
|
||||
w.d.fillWindow(w.dict)
|
||||
}
|
||||
@ -0,0 +1,184 @@
|
||||
// Copyright 2016 The Go Authors. All rights reserved.
|
||||
// Use of this source code is governed by a BSD-style
|
||||
// license that can be found in the LICENSE file.
|
||||
|
||||
package flate
|
||||
|
||||
// dictDecoder implements the LZ77 sliding dictionary as used in decompression.
|
||||
// LZ77 decompresses data through sequences of two forms of commands:
|
||||
//
|
||||
// - Literal insertions: Runs of one or more symbols are inserted into the data
|
||||
// stream as is. This is accomplished through the writeByte method for a
|
||||
// single symbol, or combinations of writeSlice/writeMark for multiple symbols.
|
||||
// Any valid stream must start with a literal insertion if no preset dictionary
|
||||
// is used.
|
||||
//
|
||||
// - Backward copies: Runs of one or more symbols are copied from previously
|
||||
// emitted data. Backward copies come as the tuple (dist, length) where dist
|
||||
// determines how far back in the stream to copy from and length determines how
|
||||
// many bytes to copy. Note that it is valid for the length to be greater than
|
||||
// the distance. Since LZ77 uses forward copies, that situation is used to
|
||||
// perform a form of run-length encoding on repeated runs of symbols.
|
||||
// The writeCopy and tryWriteCopy are used to implement this command.
|
||||
//
|
||||
// For performance reasons, this implementation performs little to no sanity
|
||||
// checks about the arguments. As such, the invariants documented for each
|
||||
// method call must be respected.
|
||||
type dictDecoder struct {
|
||||
hist []byte // Sliding window history
|
||||
|
||||
// Invariant: 0 <= rdPos <= wrPos <= len(hist)
|
||||
wrPos int // Current output position in buffer
|
||||
rdPos int // Have emitted hist[:rdPos] already
|
||||
full bool // Has a full window length been written yet?
|
||||
}
|
||||
|
||||
// init initializes dictDecoder to have a sliding window dictionary of the given
|
||||
// size. If a preset dict is provided, it will initialize the dictionary with
|
||||
// the contents of dict.
|
||||
func (dd *dictDecoder) init(size int, dict []byte) {
|
||||
*dd = dictDecoder{hist: dd.hist}
|
||||
|
||||
if cap(dd.hist) < size {
|
||||
dd.hist = make([]byte, size)
|
||||
}
|
||||
dd.hist = dd.hist[:size]
|
||||
|
||||
if len(dict) > len(dd.hist) {
|
||||
dict = dict[len(dict)-len(dd.hist):]
|
||||
}
|
||||
dd.wrPos = copy(dd.hist, dict)
|
||||
if dd.wrPos == len(dd.hist) {
|
||||
dd.wrPos = 0
|
||||
dd.full = true
|
||||
}
|
||||
dd.rdPos = dd.wrPos
|
||||
}
|
||||
|
||||
// histSize reports the total amount of historical data in the dictionary.
|
||||
func (dd *dictDecoder) histSize() int {
|
||||
if dd.full {
|
||||
return len(dd.hist)
|
||||
}
|
||||
return dd.wrPos
|
||||
}
|
||||
|
||||
// availRead reports the number of bytes that can be flushed by readFlush.
|
||||
func (dd *dictDecoder) availRead() int {
|
||||
return dd.wrPos - dd.rdPos
|
||||
}
|
||||
|
||||
// availWrite reports the available amount of output buffer space.
|
||||
func (dd *dictDecoder) availWrite() int {
|
||||
return len(dd.hist) - dd.wrPos
|
||||
}
|
||||
|
||||
// writeSlice returns a slice of the available buffer to write data to.
|
||||
//
|
||||
// This invariant will be kept: len(s) <= availWrite()
|
||||
func (dd *dictDecoder) writeSlice() []byte {
|
||||
return dd.hist[dd.wrPos:]
|
||||
}
|
||||
|
||||
// writeMark advances the writer pointer by cnt.
|
||||
//
|
||||
// This invariant must be kept: 0 <= cnt <= availWrite()
|
||||
func (dd *dictDecoder) writeMark(cnt int) {
|
||||
dd.wrPos += cnt
|
||||
}
|
||||
|
||||
// writeByte writes a single byte to the dictionary.
|
||||
//
|
||||
// This invariant must be kept: 0 < availWrite()
|
||||
func (dd *dictDecoder) writeByte(c byte) {
|
||||
dd.hist[dd.wrPos] = c
|
||||
dd.wrPos++
|
||||
}
|
||||
|
||||
// writeCopy copies a string at a given (dist, length) to the output.
|
||||
// This returns the number of bytes copied and may be less than the requested
|
||||
// length if the available space in the output buffer is too small.
|
||||
//
|
||||
// This invariant must be kept: 0 < dist <= histSize()
|
||||
func (dd *dictDecoder) writeCopy(dist, length int) int {
|
||||
dstBase := dd.wrPos
|
||||
dstPos := dstBase
|
||||
srcPos := dstPos - dist
|
||||
endPos := dstPos + length
|
||||
if endPos > len(dd.hist) {
|
||||
endPos = len(dd.hist)
|
||||
}
|
||||
|
||||
// Copy non-overlapping section after destination position.
|
||||
//
|
||||
// This section is non-overlapping in that the copy length for this section
|
||||
// is always less than or equal to the backwards distance. This can occur
|
||||
// if a distance refers to data that wraps-around in the buffer.
|
||||
// Thus, a backwards copy is performed here; that is, the exact bytes in
|
||||
// the source prior to the copy is placed in the destination.
|
||||
if srcPos < 0 {
|
||||
srcPos += len(dd.hist)
|
||||
dstPos += copy(dd.hist[dstPos:endPos], dd.hist[srcPos:])
|
||||
srcPos = 0
|
||||
}
|
||||
|
||||
// Copy possibly overlapping section before destination position.
|
||||
//
|
||||
// This section can overlap if the copy length for this section is larger
|
||||
// than the backwards distance. This is allowed by LZ77 so that repeated
|
||||
// strings can be succinctly represented using (dist, length) pairs.
|
||||
// Thus, a forwards copy is performed here; that is, the bytes copied is
|
||||
// possibly dependent on the resulting bytes in the destination as the copy
|
||||
// progresses along. This is functionally equivalent to the following:
|
||||
//
|
||||
// for i := 0; i < endPos-dstPos; i++ {
|
||||
// dd.hist[dstPos+i] = dd.hist[srcPos+i]
|
||||
// }
|
||||
// dstPos = endPos
|
||||
//
|
||||
for dstPos < endPos {
|
||||
dstPos += copy(dd.hist[dstPos:endPos], dd.hist[srcPos:dstPos])
|
||||
}
|
||||
|
||||
dd.wrPos = dstPos
|
||||
return dstPos - dstBase
|
||||
}
|
||||
|
||||
// tryWriteCopy tries to copy a string at a given (distance, length) to the
|
||||
// output. This specialized version is optimized for short distances.
|
||||
//
|
||||
// This method is designed to be inlined for performance reasons.
|
||||
//
|
||||
// This invariant must be kept: 0 < dist <= histSize()
|
||||
func (dd *dictDecoder) tryWriteCopy(dist, length int) int {
|
||||
dstPos := dd.wrPos
|
||||
endPos := dstPos + length
|
||||
if dstPos < dist || endPos > len(dd.hist) {
|
||||
return 0
|
||||
}
|
||||
dstBase := dstPos
|
||||
srcPos := dstPos - dist
|
||||
|
||||
// Copy possibly overlapping section before destination position.
|
||||
loop:
|
||||
dstPos += copy(dd.hist[dstPos:endPos], dd.hist[srcPos:dstPos])
|
||||
if dstPos < endPos {
|
||||
goto loop // Avoid for-loop so that this function can be inlined
|
||||
}
|
||||
|
||||
dd.wrPos = dstPos
|
||||
return dstPos - dstBase
|
||||
}
|
||||
|
||||
// readFlush returns a slice of the historical buffer that is ready to be
|
||||
// emitted to the user. The data returned by readFlush must be fully consumed
|
||||
// before calling any other dictDecoder methods.
|
||||
func (dd *dictDecoder) readFlush() []byte {
|
||||
toRead := dd.hist[dd.rdPos:dd.wrPos]
|
||||
dd.rdPos = dd.wrPos
|
||||
if dd.wrPos == len(dd.hist) {
|
||||
dd.wrPos, dd.rdPos = 0, 0
|
||||
dd.full = true
|
||||
}
|
||||
return toRead
|
||||
}
|
||||
@ -0,0 +1,216 @@
|
||||
// Copyright 2011 The Snappy-Go Authors. All rights reserved.
|
||||
// Modified for deflate by Klaus Post (c) 2015.
|
||||
// Use of this source code is governed by a BSD-style
|
||||
// license that can be found in the LICENSE file.
|
||||
|
||||
package flate
|
||||
|
||||
import (
|
||||
"encoding/binary"
|
||||
"fmt"
|
||||
"math/bits"
|
||||
)
|
||||
|
||||
type fastEnc interface {
|
||||
Encode(dst *tokens, src []byte)
|
||||
Reset()
|
||||
}
|
||||
|
||||
func newFastEnc(level int) fastEnc {
|
||||
switch level {
|
||||
case 1:
|
||||
return &fastEncL1{fastGen: fastGen{cur: maxStoreBlockSize}}
|
||||
case 2:
|
||||
return &fastEncL2{fastGen: fastGen{cur: maxStoreBlockSize}}
|
||||
case 3:
|
||||
return &fastEncL3{fastGen: fastGen{cur: maxStoreBlockSize}}
|
||||
case 4:
|
||||
return &fastEncL4{fastGen: fastGen{cur: maxStoreBlockSize}}
|
||||
case 5:
|
||||
return &fastEncL5{fastGen: fastGen{cur: maxStoreBlockSize}}
|
||||
case 6:
|
||||
return &fastEncL6{fastGen: fastGen{cur: maxStoreBlockSize}}
|
||||
default:
|
||||
panic("invalid level specified")
|
||||
}
|
||||
}
|
||||
|
||||