166 lines
4.7 KiB
JavaScript
166 lines
4.7 KiB
JavaScript
/**
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* Base85 operations.
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*
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* @author George J [george@penguingeorge.com]
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* @copyright Crown Copyright 2018
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* @license Apache-2.0
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*
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* @namespace
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*/
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const Base85 = {
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/**
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* @constant
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* @default
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*/
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ALPHABET_OPTIONS: [
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{
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name: "Standard",
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value: "!\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstu",
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},
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{
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name: "Z85 (ZeroMQ)",
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value: "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ.-:+=^!/*?&<>()[]{}@%$#",
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},
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{
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name: "IPv6",
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value: "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|~}",
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},
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],
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/**
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* Includes a '<~' and '~>' at the beginning and end of the Base85 data.
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* @constant
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* @default
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*/
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INCLUDE_DELIMITER: false,
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/**
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* To Base85 operation.
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*
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* @param {byteArray} input
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* @param {Object[]} args
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* @returns {string}
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*/
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runTo: function(input, args) {
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let alphabet = args[0] || Base85.ALPHABET_OPTIONS[0].value,
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encoding = Base85._alphabetName(alphabet),
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result = "";
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if (alphabet.length !== 85 || [].unique.call(alphabet).length !== 85) {
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throw ("Alphabet must be of length 85");
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}
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let block;
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for (let i = 0; i < input.length; i += 4) {
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block = (
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((input[i]) << 24) +
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((input[i + 1] || 0) << 16) +
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((input[i + 2] || 0) << 8) +
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((input[i + 3] || 0))
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) >>> 0;
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if (encoding !== "Standard" || block > 0) {
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let digits = [];
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for (let j = 0; j < 5; j++) {
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digits.push(block % 85);
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block = Math.floor(block / 85);
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}
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digits = digits.reverse();
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if (input.length < i + 4) {
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digits.splice(input.length - (i + 4), 4);
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}
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result += digits.map(digit => alphabet[digit]).join("");
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} else {
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result += (encoding === "Standard") ? "z" : null;
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}
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}
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if (args[1] || Base85.INCLUDE_DELIMITER) result = "<~" + result + "~>";
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return result;
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},
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/**
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* From Base85 operation.
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*
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* @param {string} input
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* @param {Object[]} args
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* @returns {byteArray}
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*/
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runFrom: function(input, args) {
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let alphabet = args[0] || Base85.ALPHABET_OPTIONS[0].value,
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encoding = Base85._alphabetName(alphabet),
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result = [];
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if (alphabet.length !== 85 || [].unique.call(alphabet).length !== 85) {
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throw ("Alphabet must be of length 85");
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}
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let matches = input.match(/<~(.+?)~>/);
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if (matches !== null) input = matches[1];
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let i = 0;
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let block, blockBytes;
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while (i < input.length) {
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if (encoding === "Standard" && input[i] === "z") {
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result.push(0, 0, 0, 0);
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i++;
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} else {
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let digits = [];
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digits = input
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.substr(i, 5)
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.split("")
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.map((chr, idx) => {
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let digit = alphabet.indexOf(chr);
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if (digit < 0 || digit > 84) {
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throw "Invalid character '" + chr + "' at index " + idx;
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}
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return digit;
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});
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block =
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digits[0] * 52200625 +
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digits[1] * 614125 +
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(i + 2 < input.length ? digits[2] : 84) * 7225 +
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(i + 3 < input.length ? digits[3] : 84) * 85 +
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(i + 4 < input.length ? digits[4] : 84);
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blockBytes = [
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(block >> 24) & 0xff,
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(block >> 16) & 0xff,
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(block >> 8) & 0xff,
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block & 0xff
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];
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if (input.length < i + 5) {
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blockBytes.splice(input.length - (i + 5), 5);
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}
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result.push.apply(result, blockBytes);
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i += 5;
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}
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}
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return result;
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},
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/**
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* Returns the name of the alphabet, when given the alphabet.
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*/
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_alphabetName: function(alphabet) {
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alphabet = alphabet.replace("'", "'");
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let name;
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Base85.ALPHABET_OPTIONS.forEach(function(a) {
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if (escape(alphabet) === escape(a.value)) name = a.name;
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});
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return name;
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}
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};
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export default Base85;
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