lapo.it
1// Hex JavaScript decoder
2// Copyright (c) 2008-2018 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(function (undefined) {
17"use strict";
18
19var Hex = {},
20 decoder, // populated on first usage
21 haveU8 = ('Uint8Array' in (typeof window == 'object' ? window : global));
22
23Hex.decode = function(a) {
24 var i;
25 if (decoder === undefined) {
26 var hex = "0123456789ABCDEF",
27 ignore = " \f\n\r\t\u00A0\u2028\u2029";
28 decoder = [];
29 for (i = 0; i < 16; ++i)
30 decoder[hex.charAt(i)] = i;
31 hex = hex.toLowerCase();
32 for (i = 10; i < 16; ++i)
33 decoder[hex.charAt(i)] = i;
34 for (i = 0; i < ignore.length; ++i)
35 decoder[ignore.charAt(i)] = -1;
36 }
37 var out = haveU8 ? new Uint8Array(a.length >> 1) : [],
38 bits = 0,
39 char_count = 0,
40 len = 0;
41 for (i = 0; i < a.length; ++i) {
42 var c = a.charAt(i);
43 if (c == '=')
44 break;
45 c = decoder[c];
46 if (c == -1)
47 continue;
48 if (c === undefined)
49 throw 'Illegal character at offset ' + i;
50 bits |= c;
51 if (++char_count >= 2) {
52 out[len++] = bits;
53 bits = 0;
54 char_count = 0;
55 } else {
56 bits <<= 4;
57 }
58 }
59 if (char_count)
60 throw "Hex encoding incomplete: 4 bits missing";
61 if (haveU8 && out.length > len) // in case it was originally longer because of ignored characters
62 out = out.subarray(0, len);
63 return out;
64};
65
66// export globals
67if (typeof module !== 'undefined') { module.exports = Hex; } else { window.Hex = Hex; }
68})();