ethers.js/src.ts/utils/basex.ts

/**
 * var basex = require('base-x');
 *
 * This implementation is heavily based on base-x. The main reason to
 * deviate was to prevent the dependency of Buffer.
 *
 * Contributors:
 *
 * base-x encoding
 * Forked from https://github.com/cryptocoinjs/bs58
 * Originally written by Mike Hearn for BitcoinJ
 * Copyright (c) 2011 Google Inc
 * Ported to JavaScript by Stefan Thomas
 * Merged Buffer refactorings from base58-native by Stephen Pair
 * Copyright (c) 2013 BitPay Inc
 *
 * The MIT License (MIT)
 *
 * Copyright base-x contributors (c) 2016
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 */

import { arrayify, Arrayish } from "./bytes";
import { defineReadOnly } from "./properties";

export class BaseX {
    readonly alphabet: string;
    readonly base: number;

    private _alphabetMap: { [ character: string ]: number };
    private _leader: string;

    constructor(alphabet: string) {
        defineReadOnly(this, "alphabet", alphabet);
        defineReadOnly(this, "base", alphabet.length);

        defineReadOnly(this, "_alphabetMap", { });
        defineReadOnly(this, "_leader", alphabet.charAt(0));

        // pre-compute lookup table
        for (let i = 0; i < alphabet.length; i++) {
            this._alphabetMap[alphabet.charAt(i)] = i;
        }
    }

    encode(value: Arrayish | string): string {
        let source = arrayify(value);

        if (source.length === 0) { return ''; }

        let digits = [ 0 ]
        for (let i = 0; i < source.length; ++i) {
            let carry = source[i];
            for (let j = 0; j < digits.length; ++j) {
                carry += digits[j] << 8;
                digits[j] = carry % this.base;
                carry = (carry / this.base) | 0;
            }

            while (carry > 0) {
                digits.push(carry % this.base);
                carry = (carry / this.base) | 0;
            }
        }

        let string = ''

        // deal with leading zeros
        for (let k = 0; source[k] === 0 && k < source.length - 1; ++k) {
            string += this._leader;
        }

        // convert digits to a string
        for (let q = digits.length - 1; q >= 0; --q) {
            string += this.alphabet[digits[q]];
        }

        return string;
    }

    decode(value: string): Uint8Array {
        if (typeof(value) !== 'string') {
            throw new TypeError('Expected String');
        }

        let bytes: Array<number> = [];
        if (value.length === 0) { return new Uint8Array(bytes); }

        bytes.push(0);
        for (let i = 0; i < value.length; i++) {
            let byte = this._alphabetMap[value[i]];

            if (byte === undefined) {
                throw new Error('Non-base' + this.base + ' character');
            }

            let carry = byte;
            for (let j = 0; j < bytes.length; ++j) {
                carry += bytes[j] * this.base;
                bytes[j] = carry & 0xff;
                carry >>= 8;
            }

            while (carry > 0) {
                bytes.push(carry & 0xff);
                carry >>= 8;
            }
        }

        // deal with leading zeros
        for (let k = 0; value[k] === this._leader && k < value.length - 1; ++k) {
            bytes.push(0)
        }

        return arrayify(new Uint8Array(bytes.reverse()))
    }
}

const Base32 = new BaseX("abcdefghijklmnopqrstuvwxyz234567");
const Base58 = new BaseX("123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz");

export { Base32, Base58 };

//console.log(Base58.decode("Qmd2V777o5XvJbYMeMb8k2nU5f8d3ciUQ5YpYuWhzv8iDj"))
//console.log(Base58.encode(Base58.decode("Qmd2V777o5XvJbYMeMb8k2nU5f8d3ciUQ5YpYuWhzv8iDj")))