text: // Copyright Joyent, Inc. and other Node contributors.
  //
  // Permission is hereby granted, free of charge, to any person obtaining a
  // copy of this software and associated documentation files (the
  // "Software"), to deal in the Software without restriction, including
  // without limitation the rights to use, copy, modify, merge, publish,
  // distribute, sublicense, and/or sell copies of the Software, and to permit
  // persons to whom the Software is furnished to do so, subject to the
  // following conditions:
  //
  // The above copyright notice and this permission notice shall be included
  // in all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  // OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
  // NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
  // DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  // USE OR OTHER DEALINGS IN THE SOFTWARE.
  
  'use strict';
  
  import { Buffer } from '../iso-safe-buffer/safe-buffer.js'
  
  var isEncoding = Buffer.isEncoding || function (encoding) {
    encoding = '' + encoding;
    switch (encoding && encoding.toLowerCase()) {
      case 'hex':case 'utf8':case 'utf-8':case 'ascii':case 'binary':case 'base64':case 'ucs2':case 'ucs-2':case 'utf16le':case 'utf-16le':case 'raw':
        return true;
      default:
        return false;
    }
  };
  
  function _normalizeEncoding(enc) {
    if (!enc) return 'utf8';
    var retried;
    while (true) {
      switch (enc) {
        case 'utf8':
        case 'utf-8':
          return 'utf8';
        case 'ucs2':
        case 'ucs-2':
        case 'utf16le':
        case 'utf-16le':
          return 'utf16le';
        case 'latin1':
        case 'binary':
          return 'latin1';
        case 'base64':
        case 'ascii':
        case 'hex':
          return enc;
        default:
          if (retried) return; // undefined
          enc = ('' + enc).toLowerCase();
          retried = true;
      }
    }
  };
  
  // Do not cache `Buffer.isEncoding` when checking encoding names as some
  // modules monkey-patch it to support additional encodings
  function normalizeEncoding(enc) {
    var nenc = _normalizeEncoding(enc);
    if (typeof nenc !== 'string' && (Buffer.isEncoding === isEncoding || !isEncoding(enc))) throw new Error('Unknown encoding: ' + enc);
    return nenc || enc;
  }
  
  // StringDecoder provides an interface for efficiently splitting a series of
  // buffers into a series of JS strings without breaking apart multi-byte
  // characters.
  export var StringDecoder = function (encoding) {
    this.encoding = normalizeEncoding(encoding);
    var nb;
    switch (this.encoding) {
      case 'utf16le':
        this.text = utf16Text;
        this.end = utf16End;
        nb = 4;
        break;
      case 'utf8':
        this.fillLast = utf8FillLast;
        nb = 4;
        break;
      case 'base64':
        this.text = base64Text;
        this.end = base64End;
        nb = 3;
        break;
      default:
        this.write = simpleWrite;
        this.end = simpleEnd;
        return;
    }
    this.lastNeed = 0;
    this.lastTotal = 0;
    this.lastChar = Buffer.allocUnsafe(nb);
  }
  
  StringDecoder.prototype.write = function (buf) {
    if (buf.length === 0) return '';
    var r;
    var i;
    if (this.lastNeed) {
      r = this.fillLast(buf);
      if (r === undefined) return '';
      i = this.lastNeed;
      this.lastNeed = 0;
    } else {
      i = 0;
    }
    if (i < buf.length) return r ? r + this.text(buf, i) : this.text(buf, i);
    return r || '';
  };
  
  StringDecoder.prototype.end = utf8End;
  
  // Returns only complete characters in a Buffer
  StringDecoder.prototype.text = utf8Text;
  
  // Attempts to complete a partial non-UTF-8 character using bytes from a Buffer
  StringDecoder.prototype.fillLast = function (buf) {
    if (this.lastNeed <= buf.length) {
      buf.copy(this.lastChar, this.lastTotal - this.lastNeed, 0, this.lastNeed);
      return this.lastChar.toString(this.encoding, 0, this.lastTotal);
    }
    buf.copy(this.lastChar, this.lastTotal - this.lastNeed, 0, buf.length);
    this.lastNeed -= buf.length;
  };
  
  // Checks the type of a UTF-8 byte, whether it's ASCII, a leading byte, or a
  // continuation byte. If an invalid byte is detected, -2 is returned.
  function utf8CheckByte(byte) {
    if (byte <= 0x7F) return 0;else if (byte >> 5 === 0x06) return 2;else if (byte >> 4 === 0x0E) return 3;else if (byte >> 3 === 0x1E) return 4;
    return byte >> 6 === 0x02 ? -1 : -2;
  }
  
  // Checks at most 3 bytes at the end of a Buffer in order to detect an
  // incomplete multi-byte UTF-8 character. The total number of bytes (2, 3, or 4)
  // needed to complete the UTF-8 character (if applicable) are returned.
  function utf8CheckIncomplete(self, buf, i) {
    var j = buf.length - 1;
    if (j < i) return 0;
    var nb = utf8CheckByte(buf[j]);
    if (nb >= 0) {
      if (nb > 0) self.lastNeed = nb - 1;
      return nb;
    }
    if (--j < i || nb === -2) return 0;
    nb = utf8CheckByte(buf[j]);
    if (nb >= 0) {
      if (nb > 0) self.lastNeed = nb - 2;
      return nb;
    }
    if (--j < i || nb === -2) return 0;
    nb = utf8CheckByte(buf[j]);
    if (nb >= 0) {
      if (nb > 0) {
        if (nb === 2) nb = 0;else self.lastNeed = nb - 3;
      }
      return nb;
    }
    return 0;
  }
  
  // Validates as many continuation bytes for a multi-byte UTF-8 character as
  // needed or are available. If we see a non-continuation byte where we expect
  // one, we "replace" the validated continuation bytes we've seen so far with
  // a single UTF-8 replacement character ('\ufffd'), to match v8's UTF-8 decoding
  // behavior. The continuation byte check is included three times in the case
  // where all of the continuation bytes for a character exist in the same buffer.
  // It is also done this way as a slight performance increase instead of using a
  // loop.
  function utf8CheckExtraBytes(self, buf, p) {
    if ((buf[0] & 0xC0) !== 0x80) {
      self.lastNeed = 0;
      return '\ufffd';
    }
    if (self.lastNeed > 1 && buf.length > 1) {
      if ((buf[1] & 0xC0) !== 0x80) {
        self.lastNeed = 1;
        return '\ufffd';
      }
      if (self.lastNeed > 2 && buf.length > 2) {
        if ((buf[2] & 0xC0) !== 0x80) {
          self.lastNeed = 2;
          return '\ufffd';
        }
      }
    }
  }
  
  // Attempts to complete a multi-byte UTF-8 character using bytes from a Buffer.
  function utf8FillLast(buf) {
    var p = this.lastTotal - this.lastNeed;
    var r = utf8CheckExtraBytes(this, buf, p);
    if (r !== undefined) return r;
    if (this.lastNeed <= buf.length) {
      buf.copy(this.lastChar, p, 0, this.lastNeed);
      return this.lastChar.toString(this.encoding, 0, this.lastTotal);
    }
    buf.copy(this.lastChar, p, 0, buf.length);
    this.lastNeed -= buf.length;
  }
  
  // Returns all complete UTF-8 characters in a Buffer. If the Buffer ended on a
  // partial character, the character's bytes are buffered until the required
  // number of bytes are available.
  function utf8Text(buf, i) {
    var total = utf8CheckIncomplete(this, buf, i);
    if (!this.lastNeed) return buf.toString('utf8', i);
    this.lastTotal = total;
    var end = buf.length - (total - this.lastNeed);
    buf.copy(this.lastChar, 0, end);
    return buf.toString('utf8', i, end);
  }
  
  // For UTF-8, a replacement character is added when ending on a partial
  // character.
  function utf8End(buf) {
    var r = buf && buf.length ? this.write(buf) : '';
    if (this.lastNeed) return r + '\ufffd';
    return r;
  }
  
  // UTF-16LE typically needs two bytes per character, but even if we have an even
  // number of bytes available, we need to check if we end on a leading/high
  // surrogate. In that case, we need to wait for the next two bytes in order to
  // decode the last character properly.
  function utf16Text(buf, i) {
    if ((buf.length - i) % 2 === 0) {
      var r = buf.toString('utf16le', i);
      if (r) {
        var c = r.charCodeAt(r.length - 1);
        if (c >= 0xD800 && c <= 0xDBFF) {
          this.lastNeed = 2;
          this.lastTotal = 4;
          this.lastChar[0] = buf[buf.length - 2];
          this.lastChar[1] = buf[buf.length - 1];
          return r.slice(0, -1);
        }
      }
      return r;
    }
    this.lastNeed = 1;
    this.lastTotal = 2;
    this.lastChar[0] = buf[buf.length - 1];
    return buf.toString('utf16le', i, buf.length - 1);
  }
  
  // For UTF-16LE we do not explicitly append special replacement characters if we
  // end on a partial character, we simply let v8 handle that.
  function utf16End(buf) {
    var r = buf && buf.length ? this.write(buf) : '';
    if (this.lastNeed) {
      var end = this.lastTotal - this.lastNeed;
      return r + this.lastChar.toString('utf16le', 0, end);
    }
    return r;
  }
  
  function base64Text(buf, i) {
    var n = (buf.length - i) % 3;
    if (n === 0) return buf.toString('base64', i);
    this.lastNeed = 3 - n;
    this.lastTotal = 3;
    if (n === 1) {
      this.lastChar[0] = buf[buf.length - 1];
    } else {
      this.lastChar[0] = buf[buf.length - 2];
      this.lastChar[1] = buf[buf.length - 1];
    }
    return buf.toString('base64', i, buf.length - n);
  }
  
  function base64End(buf) {
    var r = buf && buf.length ? this.write(buf) : '';
    if (this.lastNeed) return r + this.lastChar.toString('base64', 0, 3 - this.lastNeed);
    return r;
  }
  
  // Pass bytes on through for single-byte encodings (e.g. ascii, latin1, hex)
  function simpleWrite(buf) {
    return buf.toString(this.encoding);
  }
  
  function simpleEnd(buf) {
    return buf && buf.length ? this.write(buf) : '';
  }
  
  var string_decoder = {
    StringDecoder: StringDecoder
  }
  if (typeof(process) !== 'undefined' && process.release && process.release.name === 'node' && typeof (require) !== 'undefined') {
    string_decoder = require('string_decoder')
    StringDecoder = string_decoder.StringDecoder || StringDecoder
  }
  
  export default StringDecoder
  
  