lapo.it
1// Hex JavaScript decoder
2// Copyright (c) 2008-2022 Lapo Luchini <lapo@lapo.it>
3
4// Permission to use, copy, modify, and/or distribute this software for any
5// purpose with or without fee is hereby granted, provided that the above
6// copyright notice and this permission notice appear in all copies.
7//
8// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15
16(typeof define != 'undefined' ? define : function (factory) { 'use strict';
17 if (typeof module == 'object') module.exports = factory();
18 else window.hex = factory();
19})(function () {
20"use strict";
21
22var Hex = {},
23 decoder, // populated on first usage
24 haveU8 = (typeof Uint8Array == 'function');
25
26/**
27 * Decodes an hexadecimal value.
28 * @param {string|Array|Uint8Array} a - a string representing hexadecimal data, or an array representation of its charcodes
29 */
30Hex.decode = function(a) {
31 var isString = (typeof a == 'string');
32 var i;
33 if (decoder === undefined) {
34 var hex = "0123456789ABCDEF",
35 ignore = " \f\n\r\t\u00A0\u2028\u2029";
36 decoder = [];
37 for (i = 0; i < 16; ++i)
38 decoder[hex.charCodeAt(i)] = i;
39 hex = hex.toLowerCase();
40 for (i = 10; i < 16; ++i)
41 decoder[hex.charCodeAt(i)] = i;
42 for (i = 0; i < ignore.length; ++i)
43 decoder[ignore.charCodeAt(i)] = -1;
44 }
45 var out = haveU8 ? new Uint8Array(a.length >> 1) : [],
46 bits = 0,
47 char_count = 0,
48 len = 0;
49 for (i = 0; i < a.length; ++i) {
50 var c = isString ? a.charCodeAt(i) : a[i];
51 c = decoder[c];
52 if (c == -1)
53 continue;
54 if (c === undefined)
55 throw 'Illegal character at offset ' + i;
56 bits |= c;
57 if (++char_count >= 2) {
58 out[len++] = bits;
59 bits = 0;
60 char_count = 0;
61 } else {
62 bits <<= 4;
63 }
64 }
65 if (char_count)
66 throw "Hex encoding incomplete: 4 bits missing";
67 if (haveU8 && out.length > len) // in case it was originally longer because of ignored characters
68 out = out.subarray(0, len);
69 return out;
70};
71
72return Hex;
73
74});