75 lines
2.5 KiB
JavaScript
75 lines
2.5 KiB
JavaScript
// Hex JavaScript decoder
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// Copyright (c) 2008-2020 Lapo Luchini <lapo@lapo.it>
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// Permission to use, copy, modify, and/or distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice appear in all copies.
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//
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// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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(typeof define != 'undefined' ? define : function (factory) { 'use strict';
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if (typeof module == 'object') module.exports = factory();
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else window.hex = factory();
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})(function () {
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"use strict";
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var Hex = {},
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decoder, // populated on first usage
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haveU8 = (typeof Uint8Array == 'function');
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/**
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* Decodes an hexadecimal value.
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* @param {string|Array|Uint8Array} a - a string representing hexadecimal data, or an array representation of its charcodes
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*/
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Hex.decode = function(a) {
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var isString = (typeof a == 'string');
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var i;
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if (decoder === undefined) {
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var hex = "0123456789ABCDEF",
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ignore = " \f\n\r\t\u00A0\u2028\u2029";
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decoder = [];
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for (i = 0; i < 16; ++i)
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decoder[hex.charCodeAt(i)] = i;
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hex = hex.toLowerCase();
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for (i = 10; i < 16; ++i)
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decoder[hex.charCodeAt(i)] = i;
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for (i = 0; i < ignore.length; ++i)
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decoder[ignore.charCodeAt(i)] = -1;
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}
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var out = haveU8 ? new Uint8Array(a.length >> 1) : [],
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bits = 0,
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char_count = 0,
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len = 0;
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for (i = 0; i < a.length; ++i) {
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var c = isString ? a.charCodeAt(i) : a[i];
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c = decoder[c];
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if (c == -1)
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continue;
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if (c === undefined)
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throw 'Illegal character at offset ' + i;
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bits |= c;
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if (++char_count >= 2) {
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out[len++] = bits;
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bits = 0;
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char_count = 0;
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} else {
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bits <<= 4;
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}
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}
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if (char_count)
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throw "Hex encoding incomplete: 4 bits missing";
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if (haveU8 && out.length > len) // in case it was originally longer because of ignored characters
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out = out.subarray(0, len);
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return out;
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};
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return Hex;
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});
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