ml
85 lines
1.7 KiB
Go
85 lines
1.7 KiB
Go
package compression
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import (
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"io"
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"github.com/inkyblackness/hacked/ss1/serial"
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)
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type compressor struct {
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coder serial.Coder
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writer *WordWriter
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dictBuffer dictEntryBuffer
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overtime int
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dictionary *dictEntry
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dictionarySize int
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curEntry *dictEntry
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}
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// NewCompressor creates a new compressor instance over a writer.
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func NewCompressor(target io.Writer) io.WriteCloser {
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coder := serial.NewEncoder(target)
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obj := &compressor{
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coder: coder,
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writer: NewWordWriter(coder),
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dictionary: rootDictEntry(),
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dictionarySize: 0,
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overtime: 0}
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obj.resetDictionary()
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return obj
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}
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func (obj *compressor) resetDictionary() {
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obj.dictionarySize = 0
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for i := 0; i < 0x100; i++ {
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obj.dictionary.Add(byte(i), Word(i), obj.dictBuffer.entry(Word(i)))
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}
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obj.curEntry = obj.dictionary
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}
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func (obj *compressor) Close() error {
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obj.writer.Write(obj.curEntry.key)
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obj.writer.Close()
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return obj.coder.FirstError()
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}
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func (obj *compressor) Write(p []byte) (n int, err error) {
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for _, input := range p {
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obj.addByte(input)
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}
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return len(p), obj.coder.FirstError()
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}
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func (obj *compressor) addByte(value byte) {
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nextEntry := obj.curEntry.next[int(value)]
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if nextEntry != nil {
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obj.curEntry = nextEntry
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} else {
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obj.writer.Write(obj.curEntry.key)
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key := Word(int(literalLimit) + obj.dictionarySize)
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if key < Reset {
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obj.curEntry.Add(value, key, obj.dictBuffer.entry(key))
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obj.dictionarySize++
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} else {
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obj.onKeySaturation()
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}
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obj.curEntry = obj.dictionary.next[value]
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}
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}
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func (obj *compressor) onKeySaturation() {
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obj.overtime++
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if obj.overtime > 1000 {
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obj.writer.Write(Reset)
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obj.resetDictionary()
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obj.overtime = 0
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}
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}
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