mirror of
https://codeberg.org/superseriousbusiness/gotosocial.git
synced 2024-12-30 04:48:18 +03:00
331 lines
8.9 KiB
Go
331 lines
8.9 KiB
Go
// Copyright (c) 2022+ Klaus Post. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package s2
|
|
|
|
import (
|
|
"bytes"
|
|
"encoding/binary"
|
|
"sync"
|
|
)
|
|
|
|
const (
|
|
// MinDictSize is the minimum dictionary size when repeat has been read.
|
|
MinDictSize = 16
|
|
|
|
// MaxDictSize is the maximum dictionary size when repeat has been read.
|
|
MaxDictSize = 65536
|
|
|
|
// MaxDictSrcOffset is the maximum offset where a dictionary entry can start.
|
|
MaxDictSrcOffset = 65535
|
|
)
|
|
|
|
// Dict contains a dictionary that can be used for encoding and decoding s2
|
|
type Dict struct {
|
|
dict []byte
|
|
repeat int // Repeat as index of dict
|
|
|
|
fast, better, best sync.Once
|
|
fastTable *[1 << 14]uint16
|
|
|
|
betterTableShort *[1 << 14]uint16
|
|
betterTableLong *[1 << 17]uint16
|
|
|
|
bestTableShort *[1 << 16]uint32
|
|
bestTableLong *[1 << 19]uint32
|
|
}
|
|
|
|
// NewDict will read a dictionary.
|
|
// It will return nil if the dictionary is invalid.
|
|
func NewDict(dict []byte) *Dict {
|
|
if len(dict) == 0 {
|
|
return nil
|
|
}
|
|
var d Dict
|
|
// Repeat is the first value of the dict
|
|
r, n := binary.Uvarint(dict)
|
|
if n <= 0 {
|
|
return nil
|
|
}
|
|
dict = dict[n:]
|
|
d.dict = dict
|
|
if cap(d.dict) < len(d.dict)+16 {
|
|
d.dict = append(make([]byte, 0, len(d.dict)+16), d.dict...)
|
|
}
|
|
if len(dict) < MinDictSize || len(dict) > MaxDictSize {
|
|
return nil
|
|
}
|
|
d.repeat = int(r)
|
|
if d.repeat > len(dict) {
|
|
return nil
|
|
}
|
|
return &d
|
|
}
|
|
|
|
// Bytes will return a serialized version of the dictionary.
|
|
// The output can be sent to NewDict.
|
|
func (d *Dict) Bytes() []byte {
|
|
dst := make([]byte, binary.MaxVarintLen16+len(d.dict))
|
|
return append(dst[:binary.PutUvarint(dst, uint64(d.repeat))], d.dict...)
|
|
}
|
|
|
|
// MakeDict will create a dictionary.
|
|
// 'data' must be at least MinDictSize.
|
|
// If data is longer than MaxDictSize only the last MaxDictSize bytes will be used.
|
|
// If searchStart is set the start repeat value will be set to the last
|
|
// match of this content.
|
|
// If no matches are found, it will attempt to find shorter matches.
|
|
// This content should match the typical start of a block.
|
|
// If at least 4 bytes cannot be matched, repeat is set to start of block.
|
|
func MakeDict(data []byte, searchStart []byte) *Dict {
|
|
if len(data) == 0 {
|
|
return nil
|
|
}
|
|
if len(data) > MaxDictSize {
|
|
data = data[len(data)-MaxDictSize:]
|
|
}
|
|
var d Dict
|
|
dict := data
|
|
d.dict = dict
|
|
if cap(d.dict) < len(d.dict)+16 {
|
|
d.dict = append(make([]byte, 0, len(d.dict)+16), d.dict...)
|
|
}
|
|
if len(dict) < MinDictSize {
|
|
return nil
|
|
}
|
|
|
|
// Find the longest match possible, last entry if multiple.
|
|
for s := len(searchStart); s > 4; s-- {
|
|
if idx := bytes.LastIndex(data, searchStart[:s]); idx >= 0 && idx <= len(data)-8 {
|
|
d.repeat = idx
|
|
break
|
|
}
|
|
}
|
|
|
|
return &d
|
|
}
|
|
|
|
// Encode returns the encoded form of src. The returned slice may be a sub-
|
|
// slice of dst if dst was large enough to hold the entire encoded block.
|
|
// Otherwise, a newly allocated slice will be returned.
|
|
//
|
|
// The dst and src must not overlap. It is valid to pass a nil dst.
|
|
//
|
|
// The blocks will require the same amount of memory to decode as encoding,
|
|
// and does not make for concurrent decoding.
|
|
// Also note that blocks do not contain CRC information, so corruption may be undetected.
|
|
//
|
|
// If you need to encode larger amounts of data, consider using
|
|
// the streaming interface which gives all of these features.
|
|
func (d *Dict) Encode(dst, src []byte) []byte {
|
|
if n := MaxEncodedLen(len(src)); n < 0 {
|
|
panic(ErrTooLarge)
|
|
} else if cap(dst) < n {
|
|
dst = make([]byte, n)
|
|
} else {
|
|
dst = dst[:n]
|
|
}
|
|
|
|
// The block starts with the varint-encoded length of the decompressed bytes.
|
|
dstP := binary.PutUvarint(dst, uint64(len(src)))
|
|
|
|
if len(src) == 0 {
|
|
return dst[:dstP]
|
|
}
|
|
if len(src) < minNonLiteralBlockSize {
|
|
dstP += emitLiteral(dst[dstP:], src)
|
|
return dst[:dstP]
|
|
}
|
|
n := encodeBlockDictGo(dst[dstP:], src, d)
|
|
if n > 0 {
|
|
dstP += n
|
|
return dst[:dstP]
|
|
}
|
|
// Not compressible
|
|
dstP += emitLiteral(dst[dstP:], src)
|
|
return dst[:dstP]
|
|
}
|
|
|
|
// EncodeBetter returns the encoded form of src. The returned slice may be a sub-
|
|
// slice of dst if dst was large enough to hold the entire encoded block.
|
|
// Otherwise, a newly allocated slice will be returned.
|
|
//
|
|
// EncodeBetter compresses better than Encode but typically with a
|
|
// 10-40% speed decrease on both compression and decompression.
|
|
//
|
|
// The dst and src must not overlap. It is valid to pass a nil dst.
|
|
//
|
|
// The blocks will require the same amount of memory to decode as encoding,
|
|
// and does not make for concurrent decoding.
|
|
// Also note that blocks do not contain CRC information, so corruption may be undetected.
|
|
//
|
|
// If you need to encode larger amounts of data, consider using
|
|
// the streaming interface which gives all of these features.
|
|
func (d *Dict) EncodeBetter(dst, src []byte) []byte {
|
|
if n := MaxEncodedLen(len(src)); n < 0 {
|
|
panic(ErrTooLarge)
|
|
} else if len(dst) < n {
|
|
dst = make([]byte, n)
|
|
}
|
|
|
|
// The block starts with the varint-encoded length of the decompressed bytes.
|
|
dstP := binary.PutUvarint(dst, uint64(len(src)))
|
|
|
|
if len(src) == 0 {
|
|
return dst[:dstP]
|
|
}
|
|
if len(src) < minNonLiteralBlockSize {
|
|
dstP += emitLiteral(dst[dstP:], src)
|
|
return dst[:dstP]
|
|
}
|
|
n := encodeBlockBetterDict(dst[dstP:], src, d)
|
|
if n > 0 {
|
|
dstP += n
|
|
return dst[:dstP]
|
|
}
|
|
// Not compressible
|
|
dstP += emitLiteral(dst[dstP:], src)
|
|
return dst[:dstP]
|
|
}
|
|
|
|
// EncodeBest returns the encoded form of src. The returned slice may be a sub-
|
|
// slice of dst if dst was large enough to hold the entire encoded block.
|
|
// Otherwise, a newly allocated slice will be returned.
|
|
//
|
|
// EncodeBest compresses as good as reasonably possible but with a
|
|
// big speed decrease.
|
|
//
|
|
// The dst and src must not overlap. It is valid to pass a nil dst.
|
|
//
|
|
// The blocks will require the same amount of memory to decode as encoding,
|
|
// and does not make for concurrent decoding.
|
|
// Also note that blocks do not contain CRC information, so corruption may be undetected.
|
|
//
|
|
// If you need to encode larger amounts of data, consider using
|
|
// the streaming interface which gives all of these features.
|
|
func (d *Dict) EncodeBest(dst, src []byte) []byte {
|
|
if n := MaxEncodedLen(len(src)); n < 0 {
|
|
panic(ErrTooLarge)
|
|
} else if len(dst) < n {
|
|
dst = make([]byte, n)
|
|
}
|
|
|
|
// The block starts with the varint-encoded length of the decompressed bytes.
|
|
dstP := binary.PutUvarint(dst, uint64(len(src)))
|
|
|
|
if len(src) == 0 {
|
|
return dst[:dstP]
|
|
}
|
|
if len(src) < minNonLiteralBlockSize {
|
|
dstP += emitLiteral(dst[dstP:], src)
|
|
return dst[:dstP]
|
|
}
|
|
n := encodeBlockBest(dst[dstP:], src, d)
|
|
if n > 0 {
|
|
dstP += n
|
|
return dst[:dstP]
|
|
}
|
|
// Not compressible
|
|
dstP += emitLiteral(dst[dstP:], src)
|
|
return dst[:dstP]
|
|
}
|
|
|
|
// Decode returns the decoded form of src. The returned slice may be a sub-
|
|
// slice of dst if dst was large enough to hold the entire decoded block.
|
|
// Otherwise, a newly allocated slice will be returned.
|
|
//
|
|
// The dst and src must not overlap. It is valid to pass a nil dst.
|
|
func (d *Dict) Decode(dst, src []byte) ([]byte, error) {
|
|
dLen, s, err := decodedLen(src)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
if dLen <= cap(dst) {
|
|
dst = dst[:dLen]
|
|
} else {
|
|
dst = make([]byte, dLen)
|
|
}
|
|
if s2DecodeDict(dst, src[s:], d) != 0 {
|
|
return nil, ErrCorrupt
|
|
}
|
|
return dst, nil
|
|
}
|
|
|
|
func (d *Dict) initFast() {
|
|
d.fast.Do(func() {
|
|
const (
|
|
tableBits = 14
|
|
maxTableSize = 1 << tableBits
|
|
)
|
|
|
|
var table [maxTableSize]uint16
|
|
// We stop so any entry of length 8 can always be read.
|
|
for i := 0; i < len(d.dict)-8-2; i += 3 {
|
|
x0 := load64(d.dict, i)
|
|
h0 := hash6(x0, tableBits)
|
|
h1 := hash6(x0>>8, tableBits)
|
|
h2 := hash6(x0>>16, tableBits)
|
|
table[h0] = uint16(i)
|
|
table[h1] = uint16(i + 1)
|
|
table[h2] = uint16(i + 2)
|
|
}
|
|
d.fastTable = &table
|
|
})
|
|
}
|
|
|
|
func (d *Dict) initBetter() {
|
|
d.better.Do(func() {
|
|
const (
|
|
// Long hash matches.
|
|
lTableBits = 17
|
|
maxLTableSize = 1 << lTableBits
|
|
|
|
// Short hash matches.
|
|
sTableBits = 14
|
|
maxSTableSize = 1 << sTableBits
|
|
)
|
|
|
|
var lTable [maxLTableSize]uint16
|
|
var sTable [maxSTableSize]uint16
|
|
|
|
// We stop so any entry of length 8 can always be read.
|
|
for i := 0; i < len(d.dict)-8; i++ {
|
|
cv := load64(d.dict, i)
|
|
lTable[hash7(cv, lTableBits)] = uint16(i)
|
|
sTable[hash4(cv, sTableBits)] = uint16(i)
|
|
}
|
|
d.betterTableShort = &sTable
|
|
d.betterTableLong = &lTable
|
|
})
|
|
}
|
|
|
|
func (d *Dict) initBest() {
|
|
d.best.Do(func() {
|
|
const (
|
|
// Long hash matches.
|
|
lTableBits = 19
|
|
maxLTableSize = 1 << lTableBits
|
|
|
|
// Short hash matches.
|
|
sTableBits = 16
|
|
maxSTableSize = 1 << sTableBits
|
|
)
|
|
|
|
var lTable [maxLTableSize]uint32
|
|
var sTable [maxSTableSize]uint32
|
|
|
|
// We stop so any entry of length 8 can always be read.
|
|
for i := 0; i < len(d.dict)-8; i++ {
|
|
cv := load64(d.dict, i)
|
|
hashL := hash8(cv, lTableBits)
|
|
hashS := hash4(cv, sTableBits)
|
|
candidateL := lTable[hashL]
|
|
candidateS := sTable[hashS]
|
|
lTable[hashL] = uint32(i) | candidateL<<16
|
|
sTable[hashS] = uint32(i) | candidateS<<16
|
|
}
|
|
d.bestTableShort = &sTable
|
|
d.bestTableLong = &lTable
|
|
})
|
|
}
|