encoding.js

var END_OF_INPUT = -1;

var base64Chars = new Array(
    'A','B','C','D','E','F','G','H',
    'I','J','K','L','M','N','O','P',
    'Q','R','S','T','U','V','W','X',
    'Y','Z','a','b','c','d','e','f',
    'g','h','i','j','k','l','m','n',
    'o','p','q','r','s','t','u','v',
    'w','x','y','z','0','1','2','3',
    '4','5','6','7','8','9','+','/'
);

var reverseBase64Chars = new Array();
for (var i=0; i < base64Chars.length; i++){
    reverseBase64Chars[base64Chars[i]] = i;
}

var base64Str;
var base64Count;
function setBase64Str(str){
    base64Str = str;
    base64Count = 0;
}
function readBase64(){
    if (!base64Str) return END_OF_INPUT;
    if (base64Count >= base64Str.length) return END_OF_INPUT;
    var c = base64Str.charCodeAt(base64Count) & 0xff;
    base64Count++;
    return c;
}
function encodeBase64(str){
    setBase64Str(str);
    var result = '';
    var inBuffer = new Array(3);
    var lineCount = 0;
    var done = false;
    while (!done && (inBuffer[0] = readBase64()) != END_OF_INPUT){
        inBuffer[1] = readBase64();
        inBuffer[2] = readBase64();
        result += (base64Chars[ inBuffer[0] >> 2 ]);
        if (inBuffer[1] != END_OF_INPUT){
            result += (base64Chars [(( inBuffer[0] << 4 ) & 0x30) | (inBuffer[1] >> 4) ]);
            if (inBuffer[2] != END_OF_INPUT){
                result += (base64Chars [((inBuffer[1] << 2) & 0x3c) | (inBuffer[2] >> 6) ]);
                result += (base64Chars [inBuffer[2] & 0x3F]);
            } else {
                result += (base64Chars [((inBuffer[1] << 2) & 0x3c)]);
                result += ('=');
                done = true;
            }
        } else {
            result += (base64Chars [(( inBuffer[0] << 4 ) & 0x30)]);
            result += ('=');
            result += ('=');
            done = true;
        }
        lineCount += 4;
        if (lineCount >= 76){
            result += ('\n');
            lineCount = 0;
        }
    }
    return result;
}
function readReverseBase64(){
    if (!base64Str) return END_OF_INPUT;
    while (true){
        if (base64Count >= base64Str.length) return END_OF_INPUT;
        var nextCharacter = base64Str.charAt(base64Count);
        base64Count++;
        if (reverseBase64Chars[nextCharacter]){
            return reverseBase64Chars[nextCharacter];
        }
        if (nextCharacter == 'A') return 0;
    }
    return END_OF_INPUT;
}

function ntos(n){
    n=n.toString(16);
    if (n.length == 1) n="0"+n;
    n="%"+n;
    return unescape(n);
}

function decodeBase64(str){
    setBase64Str(str);
    var result = "";
    var inBuffer = new Array(4);
    var done = false;
    while (!done && (inBuffer[0] = readReverseBase64()) != END_OF_INPUT
        && (inBuffer[1] = readReverseBase64()) != END_OF_INPUT){
        inBuffer[2] = readReverseBase64();
        inBuffer[3] = readReverseBase64();
        result += ntos((((inBuffer[0] << 2) & 0xff)| inBuffer[1] >> 4));
        if (inBuffer[2] != END_OF_INPUT){
            result +=  ntos((((inBuffer[1] << 4) & 0xff)| inBuffer[2] >> 2));
            if (inBuffer[3] != END_OF_INPUT){
                result +=  ntos((((inBuffer[2] << 6)  & 0xff) | inBuffer[3]));
            } else {
                done = true;
            }
        } else {
            done = true;
        }
    }
    return result;
}

exports.base64 = encodeBase64;