129 lines
2.7 KiB
Go
129 lines
2.7 KiB
Go
// Copyright 2014 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package trie
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func compactEncode(hexSlice []byte) []byte {
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terminator := byte(0)
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if hexSlice[len(hexSlice)-1] == 16 {
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terminator = 1
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hexSlice = hexSlice[:len(hexSlice)-1]
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}
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var (
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odd = byte(len(hexSlice) % 2)
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buflen = len(hexSlice)/2 + 1
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bi, hi = 0, 0 // indices
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hs = byte(0) // shift: flips between 0 and 4
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)
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if odd == 0 {
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bi = 1
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hs = 4
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}
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buf := make([]byte, buflen)
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buf[0] = terminator<<5 | byte(odd)<<4
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for bi < len(buf) && hi < len(hexSlice) {
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buf[bi] |= hexSlice[hi] << hs
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if hs == 0 {
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bi++
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}
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hi, hs = hi+1, hs^(1<<2)
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}
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return buf
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}
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func compactDecode(str []byte) []byte {
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base := compactHexDecode(str)
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base = base[:len(base)-1]
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if base[0] >= 2 {
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base = append(base, 16)
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}
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if base[0]%2 == 1 {
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base = base[1:]
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} else {
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base = base[2:]
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}
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return base
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}
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func compactHexDecode(str []byte) []byte {
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l := len(str)*2 + 1
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var nibbles = make([]byte, l)
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for i, b := range str {
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nibbles[i*2] = b / 16
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nibbles[i*2+1] = b % 16
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}
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nibbles[l-1] = 16
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return nibbles
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}
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// compactHexEncode encodes a series of nibbles into a byte array
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func compactHexEncode(nibbles []byte) []byte {
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nl := len(nibbles)
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if nl == 0 {
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return nil
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}
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if nibbles[nl-1] == 16 {
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nl--
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}
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l := (nl + 1) / 2
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var str = make([]byte, l)
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for i := range str {
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b := nibbles[i*2] * 16
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if nl > i*2 {
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b += nibbles[i*2+1]
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}
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str[i] = b
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}
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return str
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}
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func decodeCompact(key []byte) []byte {
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l := len(key) / 2
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var res = make([]byte, l)
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for i := 0; i < l; i++ {
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v1, v0 := key[2*i], key[2*i+1]
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res[i] = v1*16 + v0
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}
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return res
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}
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// prefixLen returns the length of the common prefix of a and b.
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func prefixLen(a, b []byte) int {
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var i, length = 0, len(a)
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if len(b) < length {
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length = len(b)
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}
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for ; i < length; i++ {
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if a[i] != b[i] {
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break
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}
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}
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return i
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}
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func hasTerm(s []byte) bool {
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return s[len(s)-1] == 16
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}
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func remTerm(s []byte) []byte {
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if hasTerm(s) {
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b := make([]byte, len(s)-1)
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copy(b, s)
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return b
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}
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return s
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}
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