83 lines
1.7 KiB
Go
83 lines
1.7 KiB
Go
package rle
|
|
|
|
import (
|
|
"bytes"
|
|
"errors"
|
|
|
|
"github.com/ethereum/go-ethereum/crypto"
|
|
)
|
|
|
|
const (
|
|
token byte = 0xfe
|
|
emptyShaToken = 0xfd
|
|
emptyListShaToken = 0xfe
|
|
tokenToken = 0xff
|
|
)
|
|
|
|
var empty = crypto.Sha3([]byte(""))
|
|
var emptyList = crypto.Sha3([]byte{0x80})
|
|
|
|
func Decompress(dat []byte) ([]byte, error) {
|
|
buf := new(bytes.Buffer)
|
|
|
|
for i := 0; i < len(dat); i++ {
|
|
if dat[i] == token {
|
|
if i+1 < len(dat) {
|
|
switch dat[i+1] {
|
|
case emptyShaToken:
|
|
buf.Write(empty)
|
|
case emptyListShaToken:
|
|
buf.Write(emptyList)
|
|
case tokenToken:
|
|
buf.WriteByte(token)
|
|
default:
|
|
buf.Write(make([]byte, int(dat[i+1]-2)))
|
|
}
|
|
i++
|
|
} else {
|
|
return nil, errors.New("error reading bytes. token encountered without proceeding bytes")
|
|
}
|
|
}
|
|
}
|
|
|
|
return buf.Bytes(), nil
|
|
}
|
|
|
|
func Compress(dat []byte) []byte {
|
|
buf := new(bytes.Buffer)
|
|
|
|
for i := 0; i < len(dat); i++ {
|
|
if dat[i] == token {
|
|
buf.Write([]byte{token, tokenToken})
|
|
} else if i+1 < len(dat) {
|
|
if dat[i] == 0x0 && dat[i+1] == 0x0 {
|
|
j := 0
|
|
for j <= 254 && i+j < len(dat) {
|
|
if dat[i+j] != 0 {
|
|
break
|
|
}
|
|
j++
|
|
}
|
|
buf.Write([]byte{token, byte(j + 2)})
|
|
i += (j - 1)
|
|
} else if len(dat[i:]) >= 32 {
|
|
if dat[i] == empty[0] && bytes.Compare(dat[i:i+32], empty) == 0 {
|
|
buf.Write([]byte{token, emptyShaToken})
|
|
i += 31
|
|
} else if dat[i] == emptyList[0] && bytes.Compare(dat[i:i+32], emptyList) == 0 {
|
|
buf.Write([]byte{token, emptyListShaToken})
|
|
i += 31
|
|
} else {
|
|
buf.WriteByte(dat[i])
|
|
}
|
|
} else {
|
|
buf.WriteByte(dat[i])
|
|
}
|
|
} else {
|
|
buf.WriteByte(dat[i])
|
|
}
|
|
}
|
|
|
|
return buf.Bytes()
|
|
}
|