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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
func compactEncode(hexSlice []byte) []byte {
terminator := byte(0)
if hexSlice[len(hexSlice)-1] == 16 {
terminator = 1
hexSlice = hexSlice[:len(hexSlice)-1]
}
var (
odd = byte(len(hexSlice) % 2)
buflen = len(hexSlice)/2 + 1
bi, hi = 0, 0 // indices
hs = byte(0) // shift: flips between 0 and 4
)
if odd == 0 {
bi = 1
hs = 4
}
buf := make([]byte, buflen)
buf[0] = terminator<<5 | byte(odd)<<4
for bi < len(buf) && hi < len(hexSlice) {
buf[bi] |= hexSlice[hi] << hs
if hs == 0 {
bi++
}
hi, hs = hi+1, hs^(1<<2)
}
return buf
}
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 {
l := len(str)*2 + 1
var nibbles = make([]byte, l)
for i, b := range str {
nibbles[i*2] = b / 16
nibbles[i*2+1] = b % 16
}
nibbles[l-1] = 16
return nibbles
}
// compactHexEncode encodes a series of nibbles into a byte array
func compactHexEncode(nibbles []byte) []byte {
nl := len(nibbles)
if nl == 0 {
return nil
}
if nibbles[nl-1] == 16 {
nl--
}
l := (nl + 1) / 2
var str = make([]byte, l)
for i, _ := range str {
b := nibbles[i*2] * 16
if nl > i*2 {
b += nibbles[i*2+1]
}
str[i] = b
}
return str
}
func decodeCompact(key []byte) []byte {
l := len(key) / 2
var res = make([]byte, l)
for i := 0; i < l; i++ {
v1, v0 := key[2*i], key[2*i+1]
res[i] = v1*16 + v0
}
return res
}
// prefixLen returns the length of the common prefix of a and b.
func prefixLen(a, b []byte) int {
var i, length = 0, len(a)
if len(b) < length {
length = len(b)
}
for ; i < length; i++ {
if a[i] != b[i] {
break
}
}
return i
}
func hasTerm(s []byte) bool {
return s[len(s)-1] == 16
}
func remTerm(s []byte) []byte {
if hasTerm(s) {
b := make([]byte, len(s)-1)
copy(b, s)
return b
}
return s
}
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