85 lines
1.6 KiB
Go
85 lines
1.6 KiB
Go
package rle
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import (
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"bytes"
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"errors"
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"github.com/ethereum/go-ethereum/crypto"
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)
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const (
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token byte = 0xfe
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emptyShaToken = 0xfd
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emptyListShaToken = 0xfe
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tokenToken = 0xff
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)
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var empty = crypto.Sha3([]byte(""))
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var emptyList = crypto.Sha3([]byte{0x80})
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func Decompress(dat []byte) ([]byte, error) {
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buf := new(bytes.Buffer)
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for i := 0; i < len(dat); i++ {
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if dat[i] == token {
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if i+1 < len(dat) {
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switch dat[i+1] {
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case emptyShaToken:
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buf.Write(empty)
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case emptyListShaToken:
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buf.Write(emptyList)
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case tokenToken:
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buf.WriteByte(token)
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default:
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buf.Write(make([]byte, int(dat[i+1]-2)))
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}
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i++
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} else {
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return nil, errors.New("error reading bytes. token encountered without proceeding bytes")
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}
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} else {
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buf.WriteByte(dat[i])
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}
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}
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return buf.Bytes(), nil
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}
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func compressChunk(dat []byte) (ret []byte, n int) {
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switch {
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case dat[0] == token:
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return []byte{token, tokenToken}, 1
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case len(dat) > 1 && dat[0] == 0x0 && dat[1] == 0x0:
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j := 0
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for j <= 254 && j < len(dat) {
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if dat[j] != 0 {
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break
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}
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j++
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}
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return []byte{token, byte(j + 2)}, j
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case len(dat) >= 32:
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if dat[0] == empty[0] && bytes.Compare(dat[:32], empty) == 0 {
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return []byte{token, emptyShaToken}, 32
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} else if dat[0] == emptyList[0] && bytes.Compare(dat[:32], emptyList) == 0 {
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return []byte{token, emptyListShaToken}, 32
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}
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fallthrough
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default:
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return dat[:1], 1
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}
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}
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func Compress(dat []byte) []byte {
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buf := new(bytes.Buffer)
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i := 0
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for i < len(dat) {
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b, n := compressChunk(dat[i:])
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buf.Write(b)
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i += n
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}
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return buf.Bytes()
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}
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