68 lines
1.5 KiB
JavaScript
68 lines
1.5 KiB
JavaScript
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/* -*- Mode: js; js-indent-level: 2; -*- */
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/*
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* Copyright 2011 Mozilla Foundation and contributors
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* Licensed under the New BSD license. See LICENSE or:
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* http://opensource.org/licenses/BSD-3-Clause
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*/
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var intToCharMap = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'.split('');
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/**
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* Encode an integer in the range of 0 to 63 to a single base 64 digit.
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*/
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exports.encode = function (number) {
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if (0 <= number && number < intToCharMap.length) {
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return intToCharMap[number];
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}
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throw new TypeError("Must be between 0 and 63: " + number);
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};
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/**
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* Decode a single base 64 character code digit to an integer. Returns -1 on
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* failure.
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*/
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exports.decode = function (charCode) {
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var bigA = 65; // 'A'
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var bigZ = 90; // 'Z'
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var littleA = 97; // 'a'
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var littleZ = 122; // 'z'
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var zero = 48; // '0'
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var nine = 57; // '9'
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var plus = 43; // '+'
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var slash = 47; // '/'
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var littleOffset = 26;
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var numberOffset = 52;
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// 0 - 25: ABCDEFGHIJKLMNOPQRSTUVWXYZ
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if (bigA <= charCode && charCode <= bigZ) {
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return (charCode - bigA);
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}
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// 26 - 51: abcdefghijklmnopqrstuvwxyz
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if (littleA <= charCode && charCode <= littleZ) {
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return (charCode - littleA + littleOffset);
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}
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// 52 - 61: 0123456789
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if (zero <= charCode && charCode <= nine) {
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return (charCode - zero + numberOffset);
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}
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// 62: +
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if (charCode == plus) {
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return 62;
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}
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// 63: /
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if (charCode == slash) {
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return 63;
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}
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// Invalid base64 digit.
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return -1;
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};
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