/
lzss.go
430 lines (373 loc) · 10.5 KB
/
lzss.go
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package lz
import (
"bytes"
"fmt"
pb "github.com/cheggaaa/pb/v3"
"io"
"io/ioutil"
"sort"
"strconv"
"sync"
)
const (
Opening = "<"
Closing = ">"
Separator = ","
)
const MinimumSizeOfReference int = -1 // Use -1 to represent dynamic "smart" reference inclusion
type Reference struct {
value []byte
isReference bool
negativeOffset int
size int
}
type Writer struct {
windowSize int
useProgressBar bool
w io.Writer
}
const DefaultWindowSize = 4096
func NewWriter(w io.Writer) io.WriteCloser {
z, _ := NewWriterLevel(w, DefaultWindowSize)
return z
}
func NewWriterLevel(w io.Writer, level int) (*Writer, error) {
if level < 0 {
return nil, fmt.Errorf("lzss: invalid compression level: %d", level)
}
z := new(Writer)
z.windowSize = level
z.useProgressBar = true
z.w = w
return z, nil
}
func (writer *Writer) Write(data []byte) (n int, err error) {
compressed := CompressFileSync(data, writer.useProgressBar, writer.windowSize)
writer.w.Write(compressed)
return len(compressed), nil
}
func (writer *Writer) Close() error {
return nil
}
type Reader struct {
r io.Reader
compressed []byte
decompressed []byte
pos int
}
// func (r *Reader) Init(r *io.Reader) {
// }
func (r *Reader) Read(content []byte) (n int, err error) {
if r.decompressed == nil {
var compressed []byte
compressed, err = ioutil.ReadAll(r.r)
if err != nil {
return 0, err
}
r.decompressed = Decompress(compressed, true)
}
bytesToWriteOut := len(r.decompressed[r.pos:])
if len(content) < bytesToWriteOut {
bytesToWriteOut = len(content)
}
for i := 0; i < bytesToWriteOut; i++ {
content[i] = r.decompressed[r.pos:][i]
}
if len(r.decompressed[r.pos:]) <= len(content) {
err = io.EOF
} else {
r.pos += len(content)
}
return bytesToWriteOut, err
}
func NewReader(r io.Reader) io.Reader {
z := new(Reader)
z.r = r
return z
}
func (r *Reader) Close() error {
return nil
}
func Compress(fileContents []byte, useProgressBar bool, maxSearchBufferLength int) []byte {
fileContents = EncodeOpeningSymbols(fileContents)
var waitgroup sync.WaitGroup
bar := pb.New(len(fileContents))
bar.Set(pb.Bytes, true)
bar.Start()
output := make([](chan Reference), len(fileContents))
for i := 0; i < len(fileContents); i++ {
waitgroup.Add(1)
output[i] = make(chan Reference, 1)
startIndex := 0
searchBuffer := fileContents[:i]
if maxSearchBufferLength > 0 && len(searchBuffer) > maxSearchBufferLength {
startIndex = len(searchBuffer) - maxSearchBufferLength
}
go CompressorWorkerAsync(&waitgroup, output[i], searchBuffer[startIndex:], []byte{fileContents[i]}, fileContents[i:], bar)
}
waitgroup.Wait()
var finalOutput []byte
var ignoreNextChars int
for _, i := range output {
close(i)
ref := <-i
if ignoreNextChars > 0 {
ignoreNextChars--
} else if ref.isReference {
ignoreNextChars = ref.size - 1
if len(getEncoding(ref.negativeOffset, ref.size)) < ref.size {
finalOutput = append(finalOutput, getEncoding(ref.negativeOffset, ref.size)...)
} else {
finalOutput = append(finalOutput, ref.value...)
}
} else {
finalOutput = append(finalOutput, ref.value...)
}
}
return finalOutput
}
func CompressorWorkerAsync(waitgroup *sync.WaitGroup, output chan<- Reference, searchBuffer []byte, scanBytes []byte, nextBytes []byte, bar *pb.ProgressBar) {
defer waitgroup.Done()
out := CompressorWorker(searchBuffer, scanBytes, nextBytes[1:], bar)
output <- out
bar.Increment()
}
func CompressorWorker(searchBuffer []byte, scanBytes []byte, nextBytes []byte, bar *pb.ProgressBar) Reference {
index, found := FindReverseSlice(searchBuffer, scanBytes)
if found {
negativeOffset := len(searchBuffer) - index
if len(nextBytes) > 0 {
checkNextByte := CompressorWorker(searchBuffer, append(scanBytes, nextBytes[0]), nextBytes[1:], bar)
if checkNextByte.isReference {
return checkNextByte
} else {
return Reference{value: scanBytes, isReference: true, negativeOffset: negativeOffset, size: len(scanBytes)}
}
} else {
return Reference{value: scanBytes, isReference: true, negativeOffset: negativeOffset, size: len(scanBytes)}
}
} else {
return Reference{value: scanBytes}
}
}
func CompressFileSync2(fileContents []byte, _ bool, maxSearchBufferLength int) []byte {
fileContents = EncodeOpeningSymbols(fileContents)
var output []byte
bar := pb.New(len(fileContents))
bar.Set(pb.Bytes, true)
bar.Start()
var ignoreNextChars int
for i, fileByte := range fileContents {
windowStart := 0
if i > maxSearchBufferLength {
windowStart = len(fileContents[:i]) - maxSearchBufferLength
}
ref := CompressorWorker(fileContents[windowStart:i], []byte{fileByte}, fileContents[i:], bar)
if ignoreNextChars > 0 {
ignoreNextChars--
} else if ref.isReference {
ignoreNextChars = ref.size - 1
if len(getEncoding(ref.negativeOffset, ref.size)) < ref.size {
output = append(output, getEncoding(ref.negativeOffset, ref.size)...)
} else {
output = append(output, ref.value...)
}
} else {
output = append(output, ref.value...)
}
bar.Increment()
}
return output
}
func CompressFileSync(fileContents []byte, useProgressBar bool, maxSearchBufferLength int) []byte {
fileContents = EncodeOpeningSymbols(fileContents)
var searchBuffer []byte
var output []byte
pointer := 0
checkNextByte := false
checkStartPointer := 0
checkOffset := 0
checkBytesToAdd := make([]byte, 0)
bar := pb.New(len(fileContents))
if useProgressBar {
bar.Set(pb.Bytes, true)
bar.Start()
}
for _, fileByte := range fileContents {
if useProgressBar {
bar.Increment()
}
index, found := 0, false
if !checkNextByte {
index, found = FindReverse(searchBuffer, fileByte)
} else {
diminishingReturns := 0
if maxSearchBufferLength > 0 && len(searchBuffer) > maxSearchBufferLength {
diminishingReturns = len(searchBuffer) - maxSearchBufferLength
}
index, found = FindReverseSlice(searchBuffer[diminishingReturns:], append(checkBytesToAdd, fileByte))
}
if found && checkNextByte {
pointer = len(searchBuffer) - index
checkStartPointer = pointer
checkOffset++
checkBytesToAdd = append(checkBytesToAdd, fileByte)
} else if found && !checkNextByte {
pointer = len(searchBuffer) - index
checkStartPointer = pointer
checkOffset = 1
checkNextByte = true
checkBytesToAdd = append(checkBytesToAdd, fileByte)
} else {
if checkNextByte {
shouldAdd := true
if MinimumSizeOfReference == -1 {
if len(getEncoding(checkStartPointer, checkOffset)) > len(checkBytesToAdd) {
shouldAdd = false
}
}
if len(checkBytesToAdd) > MinimumSizeOfReference && shouldAdd {
output = append(output, getEncoding(checkStartPointer, checkOffset)...)
} else {
output = append(output, checkBytesToAdd...)
}
checkStartPointer = 0
checkOffset = 0
checkNextByte = false
searchBuffer = append(searchBuffer, checkBytesToAdd...)
// SortByteArray(searchBuffer)
checkBytesToAdd = make([]byte, 0)
}
output = append(output, fileByte)
}
if !checkNextByte {
searchBuffer = append(searchBuffer, fileByte)
// SortByteArray(searchBuffer)
}
}
if checkNextByte {
shouldAdd := true
if MinimumSizeOfReference == -1 {
if len([]byte(Opening+strconv.Itoa(checkStartPointer)+Separator+strconv.Itoa(checkOffset)+Closing)) > len(checkBytesToAdd) {
shouldAdd = false
}
}
if len(checkBytesToAdd) > MinimumSizeOfReference && shouldAdd {
output = append(output, []byte(Opening+strconv.Itoa(checkStartPointer)+Separator+strconv.Itoa(checkOffset)+Closing)...)
} else {
output = append(output, checkBytesToAdd...)
}
}
if useProgressBar {
bar.Finish()
}
return output
}
func getEncoding(relativePointer int, relativeOffset int) []byte {
return []byte(Opening + strconv.Itoa(relativePointer) + Separator + strconv.Itoa(relativeOffset) + Closing)
}
func Decompress(fileContents []byte, useProgressBar bool) []byte {
searchBuffer := make([]byte, 0)
output := make([]byte, 0)
pointer := 0
pointerBytes := make([]byte, 0)
offset := 0
offsetBytes := make([]byte, 0)
lookingFor := Opening
for _, fileByte := range fileContents {
if lookingFor == Opening && string(fileByte) == Opening {
lookingFor = Separator
} else if lookingFor == Separator {
if string(fileByte) == Separator {
lookingFor = Closing
pointer, _ = strconv.Atoi(string(pointerBytes))
pointerBytes = make([]byte, 0)
} else {
pointerBytes = append(pointerBytes, fileByte)
}
} else if lookingFor == Closing {
if string(fileByte) == Closing {
lookingFor = Opening
offset, _ = strconv.Atoi(string(offsetBytes))
offsetBytes = make([]byte, 0)
absolutePointer := len(searchBuffer) - pointer
slice := searchBuffer[absolutePointer : absolutePointer+offset]
output = append(output, slice...)
searchBuffer = append(searchBuffer, slice...)
} else {
offsetBytes = append(offsetBytes, fileByte)
}
} else {
output = append(output, fileByte)
searchBuffer = append(searchBuffer, fileByte)
}
}
output = DecodeOpeningSymbols(output)
return output
}
const EncodedOpening = 0xff
const EscapeByte = 0x5c
func EncodeOpeningSymbols(bytes []byte) []byte {
encoded := make([]byte, 0)
foundEscape := false
for _, val := range bytes {
if string(val) == Opening {
if foundEscape {
encoded = append(encoded, EscapeByte)
}
val = EncodedOpening
} else if val == EncodedOpening || val == EscapeByte {
encoded = append(encoded, EscapeByte)
} else if val == EscapeByte {
if foundEscape {
encoded = append(encoded, EscapeByte)
}
foundEscape = true
}
encoded = append(encoded, val)
}
return encoded
}
func DecodeOpeningSymbols(bytes []byte) []byte {
decoded := make([]byte, 0)
foundEscape := false
for _, val := range bytes {
if val == EncodedOpening && !foundEscape {
newVal := []byte(Opening)
decoded = append(decoded, newVal...)
} else if val == EscapeByte && !foundEscape {
foundEscape = true
} else {
foundEscape = false
decoded = append(decoded, val)
}
}
return decoded
}
func FindSequential(slice []byte, val byte) (int, bool) {
// Find
for i, item := range slice {
if item == val {
return i, true
}
}
return -1, false
}
func FindReverseSlice(input []byte, val []byte) (int, bool) {
index := bytes.Index(input, val)
return index, index != -1
}
func FindReverse(slice []byte, val byte) (int, bool) {
// Find
for i := len(slice) - 1; i >= 0; i-- {
item := slice[i]
if item == val {
return i, true
}
i--
}
return -1, false
}
func SortByteArray(src []byte) {
sort.Slice(src, func(i, j int) bool { return src[i] < src[j] })
}