
var base64EncodeChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
var base64DecodeChars = new Array(
  -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);
//编码的方法
function base64encode(str) {
  var out, i, len;
  var c1, c2, c3;
  len = str.length;
  i = 0;
  out = "";
  while (i < len) {
    c1 = str.charCodeAt(i++) & 0xff;
    if (i == len) {
      out += base64EncodeChars.charAt(c1 >> 2);
      out += base64EncodeChars.charAt((c1 & 0x3) << 4);
      out += "==";
      break;
    }
    c2 = str.charCodeAt(i++);
    if (i == len) {
      out += base64EncodeChars.charAt(c1 >> 2);
      out += base64EncodeChars.charAt(((c1 & 0x3) << 4) | ((c2 & 0xF0) >> 4));
      out += base64EncodeChars.charAt((c2 & 0xF) << 2);
      out += "=";
      break;
    }
    c3 = str.charCodeAt(i++);
    out += base64EncodeChars.charAt(c1 >> 2);
    out += base64EncodeChars.charAt(((c1 & 0x3) << 4) | ((c2 & 0xF0) >> 4));
    out += base64EncodeChars.charAt(((c2 & 0xF) << 2) | ((c3 & 0xC0) >> 6));
    out += base64EncodeChars.charAt(c3 & 0x3F);
  }
  return out;
}
//解码的方法
function base64decode(str) {
  var c1, c2, c3, c4;
  var i, len, out;
  len = str.length;
  i = 0;
  out = "";
  while (i < len) {
    do {
      c1 = base64DecodeChars[str.charCodeAt(i++) & 0xff];
    } while (i < len && c1 == -1);
    if (c1 == -1)
      break;
    do {
      c2 = base64DecodeChars[str.charCodeAt(i++) & 0xff];
    } while (i < len && c2 == -1);
    if (c2 == -1)
      break;
    out += String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4));
    do {
      c3 = str.charCodeAt(i++) & 0xff;
      if (c3 == 61)
        return out;
      c3 = base64DecodeChars[c3];
    } while (i < len && c3 == -1);
    if (c3 == -1)
      break;
    out += String.fromCharCode(((c2 & 0XF) << 4) | ((c3 & 0x3C) >> 2));
    do {
      c4 = str.charCodeAt(i++) & 0xff;
      if (c4 == 61)
        return out;
      c4 = base64DecodeChars[c4];
    } while (i < len && c4 == -1);
    if (c4 == -1)
      break;
    out += String.fromCharCode(((c3 & 0x03) << 6) | c4);
  }
  return out;
}
function utf16to8(str) {
  var out, i, len, c;
  out = "";
  len = str.length;
  for (i = 0; i < len; i++) {
    c = str.charCodeAt(i);
    if ((c >= 0x0001) && (c <= 0x007F)) {
      out += str.charAt(i);
    } else if (c > 0x07FF) {
      out += String.fromCharCode(0xE0 | ((c >> 12) & 0x0F));
      out += String.fromCharCode(0x80 | ((c >> 6) & 0x3F));
      out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
    } else {
      out += String.fromCharCode(0xC0 | ((c >> 6) & 0x1F));
      out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
    }
  }
  return out;
}
function utf8to16(str) {
  var out, i, len, c;
  var char2, char3;
  out = "";
  len = str.length;
  i = 0;
  while (i < len) {
    c = str.charCodeAt(i++);
    switch (c >> 4) {
      case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
        // 0xxxxxxx
        out += str.charAt(i - 1);
        break;
      case 12: case 13:
        // 110x xxxx   10xx xxxx
        char2 = str.charCodeAt(i++);
        out += String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F));
        break;
      case 14:
        // 1110 xxxx  10xx xxxx  10xx xxxx
        char2 = str.charCodeAt(i++);
        char3 = str.charCodeAt(i++);
        out += String.fromCharCode(((c & 0x0F) << 12) |
          ((char2 & 0x3F) << 6) |
          ((char3 & 0x3F) << 0));
        break;
    }
  }
  return out;
}
// module.exports = {
//   base64encode: base64encode
// }
