在JS上对二进制数据做base64转码的源代码参考
下面贴一段网上找的js源代码，供大家参考：// bases.js
// Utility for converting numbers to/from different bases/alphabets.
// See README.md for details.
var bases = (typeof exports !== 'undefined' ? exports : (window.Bases = {}));
// Returns a string representation of the given number for the given alphabet:
bases.toAlphabet = function (num, alphabet) {
var base = alphabet.length;
var digits = []; // these will be in reverse order since arrays are stacks
// execute at least once, even if num is 0, since we should return the '0':
do {
digits.push(num % base); // TODO handle negatives properly?
num = Math.floor(num / base);
} while (num > 0);
var chars = [];
while (digits.length) {
chars.push(alphabet);
}
return chars.join('');
};
// Returns an integer representation of the given string for the given alphabet:
bases.fromAlphabet = function (str, alphabet) {
var base = alphabet.length;
var pos = 0;
var num = 0;
var c;
while (str.length) {
c = str;
str = str.substr(0, str.length - 1);
num += Math.pow(base, pos) * alphabet.indexOf(c);
pos++;
}
return num;
};
// Known alphabets:
bases.NUMERALS = '0123456789';
bases.LETTERS_LOWERCASE = 'abcdefghijklmnopqrstuvwxyz';
bases.LETTERS_UPPERCASE = bases.LETTERS_LOWERCASE.toUpperCase();
bases.KNOWN_ALPHABETS = {};
// Each of the number ones, starting from base-2 (base-1 doesn't make sense?):
for (var i = 2; i <= 10; i++) {
bases.KNOWN_ALPHABETS = bases.NUMERALS.substr(0, i);
}
// Node's native hex is 0-9 followed by *lowercase* a-f, so we'll take that
// approach for everything from base-11 to base-16:
for (var i = 11; i <= 16; i++) {
bases.KNOWN_ALPHABETS = bases.NUMERALS + bases.LETTERS_LOWERCASE.substr(0, i - 10);
}
// We also model base-36 off of that, just using the full letter alphabet:
bases.KNOWN_ALPHABETS = bases.NUMERALS + bases.LETTERS_LOWERCASE;
// And base-62 will be the uppercase letters added:
bases.KNOWN_ALPHABETS = bases.NUMERALS + bases.LETTERS_LOWERCASE + bases.LETTERS_UPPERCASE;
// For base-26, we'll assume the user wants just the letter alphabet:
bases.KNOWN_ALPHABETS = bases.LETTERS_LOWERCASE;
// We'll also add a similar base-52, just letters, lowercase then uppercase:
bases.KNOWN_ALPHABETS = bases.LETTERS_LOWERCASE + bases.LETTERS_UPPERCASE;
// Base-64 is a formally-specified alphabet that has a particular order:
// http://en.wikipedia.org/wiki/Base64 (and Node.js follows this too)
// TODO FIXME But our code above doesn't add padding! Don't use this yet...
bases.KNOWN_ALPHABETS = bases.LETTERS_UPPERCASE + bases.LETTERS_LOWERCASE + bases.NUMERALS + '+/';
// Flickr and others also have a base-58 that removes confusing characters, but
// there isn't consensus on the order of lowercase vs. uppercase... =/
// http://www.flickr.com/groups/api/discuss/72157616713786392/
// https://en.bitcoin.it/wiki/Base58Check_encoding#Base58_symbol_chart
// https://github.com/dougal/base58/blob/master/lib/base58.rb
// http://icoloma.blogspot.com/2010/03/create-your-own-bitly-using-base58.html
// We'll arbitrarily stay consistent with the above and using lowercase first:
bases.KNOWN_ALPHABETS = bases.KNOWN_ALPHABETS.replace(//g, '');
// And Douglas Crockford shared a similar base-32 from base-36:
// http://www.crockford.com/wrmg/base32.html
// Unlike our base-36, he explicitly specifies uppercase letters
bases.KNOWN_ALPHABETS = bases.NUMERALS + bases.LETTERS_UPPERCASE.replace(//g, '');
// Closure helper for convenience aliases like bases.toBase36():
function makeAlias (base, alphabet) {
bases['toBase' + base] = function (num) {
return bases.toAlphabet(num, alphabet);
};
bases['fromBase' + base] = function (str) {
return bases.fromAlphabet(str, alphabet);
};
}
// Do this for all known alphabets:
for (var base in bases.KNOWN_ALPHABETS) {
if (bases.KNOWN_ALPHABETS.hasOwnProperty(base)) {
makeAlias(base, bases.KNOWN_ALPHABETS);
}
}
// And a generic alias too:
bases.toBase = function (num, base) {
return bases.toAlphabet(num, bases.KNOWN_ALPHABETS);
};
bases.fromBase = function (str, base) {
return bases.fromAlphabet(str, bases.KNOWN_ALPHABETS);
};
(function ($) {
var hex_more = $('#hex_more');
$('.js-hex').on('click', function (e) {
hex_more.val($(this).val());
});
$('#main_form').on('submit', function (e) {
e.preventDefault();
var num = $('#num').val();
var hex = hex_more.val();
var num = bases.fromBase(num, hex);
$('#base_2').val(bases.toBase(num, 2));
$('#base_8').val(bases.toBase(num, 8));
$('#base_10').val(bases.toBase(num, 10));
$('#base_16').val(bases.toBase(num, 16));
$('#base_32').val(bases.toBase(num, 32));
$('#base_58').val(bases.toBase(num, 58));
$('#base_62').val(bases.toBase(num, 62));
$('#base_64').val(bases.toBase(num, 64));
});
})(jQuery);
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