// base64加密开始  
	var keystr = "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz0123456789+/=";
	function encode64(input) {
		var output = "";
		var chr1, chr2, chr3 = "";
		var enc1, enc2, enc3, enc4 = "";
		var i = 0;
		do {
			chr1 = input.charcodeat(i++);
			chr2 = input.charcodeat(i++);
			chr3 = input.charcodeat(i++);
			enc1 = chr1 >> 2;
			enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
			enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
			enc4 = chr3 & 63;
			if (isnan(chr2)) {
				enc3 = enc4 = 64;
			} else if (isnan(chr3)) {
				enc4 = 64;
			}
			output = output + keystr.charat(enc1) + keystr.charat(enc2) + keystr.charat(enc3) + keystr.charat(enc4);
			chr1 = chr2 = chr3 = "";
			enc1 = enc2 = enc3 = enc4 = "";
		} while (i < input.length);
			return output;
	}
// base64加密结束