javascript base64

/*
 * 不支持中文
 * b64 = base64encode(data);
 * data = base64decode(b64);
 */


var base64EncodeChars = [
    "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 base64DecodeChars = [
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
    52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
    -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
    15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
    -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1
];

function base64encode(str) {
    var out, i, j, len;
    var c1, c2, c3;

    len = str.length;
    i = j = 0;
    out = [];
    while (i < len) {
        c1 = str.charCodeAt(i++) & 0xff;
        if (i == len)
        {
            out[j++] = base64EncodeChars[c1 >> 2];
            out[j++] = base64EncodeChars[(c1 & 0x3) << 4];
            out[j++] = "==";
            break;
        }
        c2 = str.charCodeAt(i++) & 0xff;
        if (i == len)
        {
            out[j++] = base64EncodeChars[c1 >> 2];
            out[j++] = base64EncodeChars[((c1 & 0x03) << 4) | ((c2 & 0xf0) >> 4)];
            out[j++] = base64EncodeChars[(c2 & 0x0f) << 2];
            out[j++] = "=";
            break;
        }
        c3 = str.charCodeAt(i++) & 0xff;
        out[j++] = base64EncodeChars[c1 >> 2];
        out[j++] = base64EncodeChars[((c1 & 0x03) << 4) | ((c2 & 0xf0) >> 4)];
        out[j++] = base64EncodeChars[((c2 & 0x0f) << 2) | ((c3 & 0xc0) >> 6)];
        out[j++] = base64EncodeChars[c3 & 0x3f];
    }
    return out.join('');
}

function base64decode(str) {
    var c1, c2, c3, c4;
    var i, j, len, out;

    len = str.length;
    i = j = 0;
    out = [];
    while (i < len) {
        /* c1 */
        do {
            c1 = base64DecodeChars[str.charCodeAt(i++) & 0xff];
        } while (i < len && c1 == -1);
        if (c1 == -1) break;

        /* c2 */
        do {
            c2 = base64DecodeChars[str.charCodeAt(i++) & 0xff];
        } while (i < len && c2 == -1);
        if (c2 == -1) break;

        out[j++] = String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4));

        /* c3 */
        do {
            c3 = str.charCodeAt(i++) & 0xff;
            if (c3 == 61) return out.join('');
            c3 = base64DecodeChars[c3];
        } while (i < len && c3 == -1);
        if (c3 == -1) break;

        out[j++] = String.fromCharCode(((c2 & 0x0f) << 4) | ((c3 & 0x3c) >> 2));

        /* c4 */
        do {
            c4 = str.charCodeAt(i++) & 0xff;
            if (c4 == 61) return out.join('');
            c4 = base64DecodeChars[c4];
        } while (i < len && c4 == -1);
        if (c4 == -1) break;
        out[j++] = String.fromCharCode(((c3 & 0x03) << 6) | c4);
    }
    return out.join('');
}