mirror of
https://github.com/idanoo/GoScrobble.git
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187 lines
4.9 KiB
JavaScript
187 lines
4.9 KiB
JavaScript
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/**
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* Base-N/Base-X encoding/decoding functions.
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*
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* Original implementation from base-x:
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* https://github.com/cryptocoinjs/base-x
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*
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* Which is MIT licensed:
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*
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* The MIT License (MIT)
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*
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* Copyright base-x contributors (c) 2016
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*/
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var api = {};
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module.exports = api;
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// baseN alphabet indexes
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var _reverseAlphabets = {};
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/**
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* BaseN-encodes a Uint8Array using the given alphabet.
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*
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* @param input the Uint8Array to encode.
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* @param maxline the maximum number of encoded characters per line to use,
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* defaults to none.
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*
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* @return the baseN-encoded output string.
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*/
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api.encode = function(input, alphabet, maxline) {
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if(typeof alphabet !== 'string') {
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throw new TypeError('"alphabet" must be a string.');
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}
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if(maxline !== undefined && typeof maxline !== 'number') {
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throw new TypeError('"maxline" must be a number.');
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}
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var output = '';
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if(!(input instanceof Uint8Array)) {
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// assume forge byte buffer
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output = _encodeWithByteBuffer(input, alphabet);
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} else {
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var i = 0;
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var base = alphabet.length;
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var first = alphabet.charAt(0);
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var digits = [0];
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for(i = 0; i < input.length; ++i) {
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for(var j = 0, carry = input[i]; j < digits.length; ++j) {
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carry += digits[j] << 8;
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digits[j] = carry % base;
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carry = (carry / base) | 0;
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}
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while(carry > 0) {
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digits.push(carry % base);
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carry = (carry / base) | 0;
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}
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}
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// deal with leading zeros
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for(i = 0; input[i] === 0 && i < input.length - 1; ++i) {
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output += first;
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}
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// convert digits to a string
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for(i = digits.length - 1; i >= 0; --i) {
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output += alphabet[digits[i]];
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}
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}
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if(maxline) {
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var regex = new RegExp('.{1,' + maxline + '}', 'g');
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output = output.match(regex).join('\r\n');
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}
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return output;
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};
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/**
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* Decodes a baseN-encoded (using the given alphabet) string to a
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* Uint8Array.
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*
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* @param input the baseN-encoded input string.
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*
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* @return the Uint8Array.
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*/
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api.decode = function(input, alphabet) {
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if(typeof input !== 'string') {
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throw new TypeError('"input" must be a string.');
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}
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if(typeof alphabet !== 'string') {
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throw new TypeError('"alphabet" must be a string.');
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}
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var table = _reverseAlphabets[alphabet];
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if(!table) {
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// compute reverse alphabet
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table = _reverseAlphabets[alphabet] = [];
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for(var i = 0; i < alphabet.length; ++i) {
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table[alphabet.charCodeAt(i)] = i;
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}
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}
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// remove whitespace characters
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input = input.replace(/\s/g, '');
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var base = alphabet.length;
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var first = alphabet.charAt(0);
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var bytes = [0];
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for(var i = 0; i < input.length; i++) {
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var value = table[input.charCodeAt(i)];
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if(value === undefined) {
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return;
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}
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for(var j = 0, carry = value; j < bytes.length; ++j) {
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carry += bytes[j] * base;
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bytes[j] = carry & 0xff;
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carry >>= 8;
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}
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while(carry > 0) {
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bytes.push(carry & 0xff);
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carry >>= 8;
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}
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}
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// deal with leading zeros
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for(var k = 0; input[k] === first && k < input.length - 1; ++k) {
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bytes.push(0);
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}
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if(typeof Buffer !== 'undefined') {
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return Buffer.from(bytes.reverse());
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}
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return new Uint8Array(bytes.reverse());
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};
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function _encodeWithByteBuffer(input, alphabet) {
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var i = 0;
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var base = alphabet.length;
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var first = alphabet.charAt(0);
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var digits = [0];
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for(i = 0; i < input.length(); ++i) {
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for(var j = 0, carry = input.at(i); j < digits.length; ++j) {
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carry += digits[j] << 8;
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digits[j] = carry % base;
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carry = (carry / base) | 0;
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}
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while(carry > 0) {
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digits.push(carry % base);
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carry = (carry / base) | 0;
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}
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}
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var output = '';
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// deal with leading zeros
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for(i = 0; input.at(i) === 0 && i < input.length() - 1; ++i) {
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output += first;
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}
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// convert digits to a string
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for(i = digits.length - 1; i >= 0; --i) {
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output += alphabet[digits[i]];
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}
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return output;
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}
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