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JavaScript generic ASN.1 parser (mirror)
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asn1js hex.js
2.6 kB · 69 lines
JavaScript
at github-104
12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970// Hex JavaScript decoder// Copyright (c) 2008 Lapo Luchini <lapo@lapo.it>
// Permission to use, copy, modify, and/or distribute this software for any// purpose with or without fee is hereby granted, provided that the above// copyright notice and this permission notice appear in all copies.//// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
const haveU8 = (typeof Uint8Array == 'function');
let decoder; // populated on first usage
export class Hex {
/** * Decodes an hexadecimal value. * @param {string|Array|Uint8Array} a - a string representing hexadecimal data, or an array representation of its charcodes */ static decode(a) { let isString = (typeof a == 'string'); let i; if (decoder === undefined) { let hex = '0123456789ABCDEF', ignore = ' \f\n\r\t\u00A0\u2028\u2029'; decoder = []; for (i = 0; i < 16; ++i) decoder[hex.charCodeAt(i)] = i; hex = hex.toLowerCase(); for (i = 10; i < 16; ++i) decoder[hex.charCodeAt(i)] = i; for (i = 0; i < ignore.length; ++i) decoder[ignore.charCodeAt(i)] = -1; } let out = haveU8 ? new Uint8Array(a.length >> 1) : [], bits = 0, char_count = 0, len = 0; for (i = 0; i < a.length; ++i) { let c = isString ? a.charCodeAt(i) : a[i]; c = decoder[c]; if (c == -1) continue; if (c === undefined) throw 'Illegal character at offset ' + i; bits |= c; if (++char_count >= 2) { out[len++] = bits; bits = 0; char_count = 0; } else { bits <<= 4; } } if (char_count) throw 'Hex encoding incomplete: 4 bits missing'; if (haveU8 && out.length > len) // in case it was originally longer because of ignored characters out = out.subarray(0, len); return out; }
}