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// Copyright 2014 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package trie
import (
"bytes"
)
func CompactEncode(hexSlice []byte) []byte {
terminator := 0
if hexSlice[len(hexSlice)-1] == 16 {
terminator = 1
}
if terminator == 1 {
hexSlice = hexSlice[:len(hexSlice)-1]
}
oddlen := len(hexSlice) % 2
flags := byte(2*terminator + oddlen)
if oddlen != 0 {
hexSlice = append([]byte{flags}, hexSlice...)
} else {
hexSlice = append([]byte{flags, 0}, hexSlice...)
}
var buff bytes.Buffer
for i := 0; i < len(hexSlice); i += 2 {
buff.WriteByte(byte(16*hexSlice[i] + hexSlice[i+1]))
}
return buff.Bytes()
}
func CompactDecode(str []byte) []byte {
base := CompactHexDecode(str)
base = base[:len(base)-1]
if base[0] >= 2 {
base = append(base, 16)
}
if base[0]%2 == 1 {
base = base[1:]
} else {
base = base[2:]
}
return base
}
func CompactHexDecode(str []byte) []byte {
var nibbles []byte
for _, b := range str {
nibbles = append(nibbles, b/16)
nibbles = append(nibbles, b%16)
}
nibbles = append(nibbles, 16)
return nibbles
}
// assumes key is odd length
func DecodeCompact(key []byte) []byte {
var res []byte
for i := 0; i < len(key)-1; i += 2 {
v1, v0 := key[i], key[i+1]
res = append(res, v1*16+v0)
}
return res
}
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