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// base-x encoding / decoding
// Copyright (c) 2018 base-x contributors
// Copyright (c) 2014-2018 The Bitcoin Core developers (base58.cpp)
// Distributed under the MIT software license, see the accompanying
// file LICENSE or http://www.opensource.org/licenses/mit-license.php.
// @ts-ignore
const _Buffer = require('safe-buffer').Buffer;
function base (ALPHABET: string): base.BaseConverter {
if (ALPHABET.length >= 255) throw new TypeError('Alphabet too long')
const BASE_MAP = new Uint8Array(256)
BASE_MAP.fill(255)
for (let i = 0; i < ALPHABET.length; i++) {
const x = ALPHABET.charAt(i)
const xc = x.charCodeAt(0)
if (BASE_MAP[xc] !== 255) throw new TypeError(x + ' is ambiguous')
BASE_MAP[xc] = i
}
const BASE = ALPHABET.length
const LEADER = ALPHABET.charAt(0)
const FACTOR = Math.log(BASE) / Math.log(256) // log(BASE) / log(256), rounded up
const iFACTOR = Math.log(256) / Math.log(BASE) // log(256) / log(BASE), rounded up
function encode (source: Buffer): string {
if (!_Buffer.isBuffer(source)) throw new TypeError('Expected Buffer')
if (source.length === 0) return ''
// Skip & count leading zeroes.
let zeroes = 0
let length = 0
let pbegin = 0
const pend = source.length
while (pbegin !== pend && source[pbegin] === 0) {
pbegin++
zeroes++
}
// Allocate enough space in big-endian base58 representation.
const size = ((pend - pbegin) * iFACTOR + 1) >>> 0
const b58 = new Uint8Array(size)
// Process the bytes.
while (pbegin !== pend) {
let carry = source[pbegin]
// Apply "b58 = b58 * 256 + ch".
let i = 0
for (let it1 = size - 1; (carry !== 0 || i < length) && (it1 !== -1); it1--, i++) {
carry += (256 * b58[it1]) >>> 0
b58[it1] = (carry % BASE) >>> 0
carry = (carry / BASE) >>> 0
}
if (carry !== 0) throw new Error('Non-zero carry')
length = i
pbegin++
}
// Skip leading zeroes in base58 result.
let it2 = size - length
while (it2 !== size && b58[it2] === 0) {
it2++
}
// Translate the result into a string.
let str = LEADER.repeat(zeroes)
for (; it2 < size; ++it2) str += ALPHABET.charAt(b58[it2])
return str
}
function decodeUnsafe (source: string): Buffer | undefined {
if (typeof source !== 'string') throw new TypeError('Expected String')
if (source.length === 0) return _Buffer.alloc(0)
let psz = 0
// Skip leading spaces.
if (source[psz] === ' ') return
// Skip and count leading '1's.
let zeroes = 0
let length = 0
while (source[psz] === LEADER) {
zeroes++
psz++
}
// Allocate enough space in big-endian base256 representation.
const size = (((source.length - psz) * FACTOR) + 1) >>> 0 // log(58) / log(256), rounded up.
const b256 = new Uint8Array(size)
// Process the characters.
while (source[psz]) {
// Decode character
let carry = BASE_MAP[source.charCodeAt(psz)]
// Invalid character
if (carry === 255) return
let i = 0
for (let it3 = size - 1; (carry !== 0 || i < length) && (it3 !== -1); it3--, i++) {
carry += (BASE * b256[it3]) >>> 0
b256[it3] = (carry % 256) >>> 0
carry = (carry / 256) >>> 0
}
if (carry !== 0) throw new Error('Non-zero carry')
length = i
psz++
}
// Skip trailing spaces.
if (source[psz] === ' ') return
// Skip leading zeroes in b256.
let it4 = size - length
while (it4 !== size && b256[it4] === 0) {
it4++
}
const vch = _Buffer.allocUnsafe(zeroes + (size - it4))
vch.fill(0x00, 0, zeroes)
let j = zeroes
while (it4 !== size) {
vch[j++] = b256[it4++]
}
return vch
}
function decode (string: string): Buffer {
const buffer = decodeUnsafe(string)
if (buffer) return buffer
throw new Error('Non-base' + BASE + ' character')
}
return {
encode: encode,
decodeUnsafe: decodeUnsafe,
decode: decode
}
}
export = base;
declare namespace base {
interface BaseConverter {
encode(buffer: Buffer): string;
decodeUnsafe(string: string): Buffer | undefined;
decode(string: string): Buffer;
}
}
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