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Tree: d2f2697f296dd39aed6a8b63c6d04a736a7db5b3

Files: d2f2697f296dd39aed6a8b63c6d04a736a7db5b3 / node_modules / string_decoder / lib / string_decoder.js

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1// Copyright Joyent, Inc. and other Node contributors.
2//
3// Permission is hereby granted, free of charge, to any person obtaining a
4// copy of this software and associated documentation files (the
5// "Software"), to deal in the Software without restriction, including
6// without limitation the rights to use, copy, modify, merge, publish,
7// distribute, sublicense, and/or sell copies of the Software, and to permit
8// persons to whom the Software is furnished to do so, subject to the
9// following conditions:
10//
11// The above copyright notice and this permission notice shall be included
12// in all copies or substantial portions of the Software.
13//
14// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
15// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
16// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
17// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
18// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
19// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
20// USE OR OTHER DEALINGS IN THE SOFTWARE.
21
22'use strict';
23
24/*<replacement>*/
25
26var Buffer = require('safe-buffer').Buffer;
27/*</replacement>*/
28
29var isEncoding = Buffer.isEncoding || function (encoding) {
30  encoding = '' + encoding;
31  switch (encoding && encoding.toLowerCase()) {
32    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':
33      return true;
34    default:
35      return false;
36  }
37};
38
39function _normalizeEncoding(enc) {
40  if (!enc) return 'utf8';
41  var retried;
42  while (true) {
43    switch (enc) {
44      case 'utf8':
45      case 'utf-8':
46        return 'utf8';
47      case 'ucs2':
48      case 'ucs-2':
49      case 'utf16le':
50      case 'utf-16le':
51        return 'utf16le';
52      case 'latin1':
53      case 'binary':
54        return 'latin1';
55      case 'base64':
56      case 'ascii':
57      case 'hex':
58        return enc;
59      default:
60        if (retried) return; // undefined
61        enc = ('' + enc).toLowerCase();
62        retried = true;
63    }
64  }
65};
66
67// Do not cache `Buffer.isEncoding` when checking encoding names as some
68// modules monkey-patch it to support additional encodings
69function normalizeEncoding(enc) {
70  var nenc = _normalizeEncoding(enc);
71  if (typeof nenc !== 'string' && (Buffer.isEncoding === isEncoding || !isEncoding(enc))) throw new Error('Unknown encoding: ' + enc);
72  return nenc || enc;
73}
74
75// StringDecoder provides an interface for efficiently splitting a series of
76// buffers into a series of JS strings without breaking apart multi-byte
77// characters.
78exports.StringDecoder = StringDecoder;
79function StringDecoder(encoding) {
80  this.encoding = normalizeEncoding(encoding);
81  var nb;
82  switch (this.encoding) {
83    case 'utf16le':
84      this.text = utf16Text;
85      this.end = utf16End;
86      nb = 4;
87      break;
88    case 'utf8':
89      this.fillLast = utf8FillLast;
90      nb = 4;
91      break;
92    case 'base64':
93      this.text = base64Text;
94      this.end = base64End;
95      nb = 3;
96      break;
97    default:
98      this.write = simpleWrite;
99      this.end = simpleEnd;
100      return;
101  }
102  this.lastNeed = 0;
103  this.lastTotal = 0;
104  this.lastChar = Buffer.allocUnsafe(nb);
105}
106
107StringDecoder.prototype.write = function (buf) {
108  if (buf.length === 0) return '';
109  var r;
110  var i;
111  if (this.lastNeed) {
112    r = this.fillLast(buf);
113    if (r === undefined) return '';
114    i = this.lastNeed;
115    this.lastNeed = 0;
116  } else {
117    i = 0;
118  }
119  if (i < buf.length) return r ? r + this.text(buf, i) : this.text(buf, i);
120  return r || '';
121};
122
123StringDecoder.prototype.end = utf8End;
124
125// Returns only complete characters in a Buffer
126StringDecoder.prototype.text = utf8Text;
127
128// Attempts to complete a partial non-UTF-8 character using bytes from a Buffer
129StringDecoder.prototype.fillLast = function (buf) {
130  if (this.lastNeed <= buf.length) {
131    buf.copy(this.lastChar, this.lastTotal - this.lastNeed, 0, this.lastNeed);
132    return this.lastChar.toString(this.encoding, 0, this.lastTotal);
133  }
134  buf.copy(this.lastChar, this.lastTotal - this.lastNeed, 0, buf.length);
135  this.lastNeed -= buf.length;
136};
137
138// Checks the type of a UTF-8 byte, whether it's ASCII, a leading byte, or a
139// continuation byte. If an invalid byte is detected, -2 is returned.
140function utf8CheckByte(byte) {
141  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;
142  return byte >> 6 === 0x02 ? -1 : -2;
143}
144
145// Checks at most 3 bytes at the end of a Buffer in order to detect an
146// incomplete multi-byte UTF-8 character. The total number of bytes (2, 3, or 4)
147// needed to complete the UTF-8 character (if applicable) are returned.
148function utf8CheckIncomplete(self, buf, i) {
149  var j = buf.length - 1;
150  if (j < i) return 0;
151  var nb = utf8CheckByte(buf[j]);
152  if (nb >= 0) {
153    if (nb > 0) self.lastNeed = nb - 1;
154    return nb;
155  }
156  if (--j < i || nb === -2) return 0;
157  nb = utf8CheckByte(buf[j]);
158  if (nb >= 0) {
159    if (nb > 0) self.lastNeed = nb - 2;
160    return nb;
161  }
162  if (--j < i || nb === -2) return 0;
163  nb = utf8CheckByte(buf[j]);
164  if (nb >= 0) {
165    if (nb > 0) {
166      if (nb === 2) nb = 0;else self.lastNeed = nb - 3;
167    }
168    return nb;
169  }
170  return 0;
171}
172
173// Validates as many continuation bytes for a multi-byte UTF-8 character as
174// needed or are available. If we see a non-continuation byte where we expect
175// one, we "replace" the validated continuation bytes we've seen so far with
176// a single UTF-8 replacement character ('\ufffd'), to match v8's UTF-8 decoding
177// behavior. The continuation byte check is included three times in the case
178// where all of the continuation bytes for a character exist in the same buffer.
179// It is also done this way as a slight performance increase instead of using a
180// loop.
181function utf8CheckExtraBytes(self, buf, p) {
182  if ((buf[0] & 0xC0) !== 0x80) {
183    self.lastNeed = 0;
184    return '\ufffd';
185  }
186  if (self.lastNeed > 1 && buf.length > 1) {
187    if ((buf[1] & 0xC0) !== 0x80) {
188      self.lastNeed = 1;
189      return '\ufffd';
190    }
191    if (self.lastNeed > 2 && buf.length > 2) {
192      if ((buf[2] & 0xC0) !== 0x80) {
193        self.lastNeed = 2;
194        return '\ufffd';
195      }
196    }
197  }
198}
199
200// Attempts to complete a multi-byte UTF-8 character using bytes from a Buffer.
201function utf8FillLast(buf) {
202  var p = this.lastTotal - this.lastNeed;
203  var r = utf8CheckExtraBytes(this, buf, p);
204  if (r !== undefined) return r;
205  if (this.lastNeed <= buf.length) {
206    buf.copy(this.lastChar, p, 0, this.lastNeed);
207    return this.lastChar.toString(this.encoding, 0, this.lastTotal);
208  }
209  buf.copy(this.lastChar, p, 0, buf.length);
210  this.lastNeed -= buf.length;
211}
212
213// Returns all complete UTF-8 characters in a Buffer. If the Buffer ended on a
214// partial character, the character's bytes are buffered until the required
215// number of bytes are available.
216function utf8Text(buf, i) {
217  var total = utf8CheckIncomplete(this, buf, i);
218  if (!this.lastNeed) return buf.toString('utf8', i);
219  this.lastTotal = total;
220  var end = buf.length - (total - this.lastNeed);
221  buf.copy(this.lastChar, 0, end);
222  return buf.toString('utf8', i, end);
223}
224
225// For UTF-8, a replacement character is added when ending on a partial
226// character.
227function utf8End(buf) {
228  var r = buf && buf.length ? this.write(buf) : '';
229  if (this.lastNeed) return r + '\ufffd';
230  return r;
231}
232
233// UTF-16LE typically needs two bytes per character, but even if we have an even
234// number of bytes available, we need to check if we end on a leading/high
235// surrogate. In that case, we need to wait for the next two bytes in order to
236// decode the last character properly.
237function utf16Text(buf, i) {
238  if ((buf.length - i) % 2 === 0) {
239    var r = buf.toString('utf16le', i);
240    if (r) {
241      var c = r.charCodeAt(r.length - 1);
242      if (c >= 0xD800 && c <= 0xDBFF) {
243        this.lastNeed = 2;
244        this.lastTotal = 4;
245        this.lastChar[0] = buf[buf.length - 2];
246        this.lastChar[1] = buf[buf.length - 1];
247        return r.slice(0, -1);
248      }
249    }
250    return r;
251  }
252  this.lastNeed = 1;
253  this.lastTotal = 2;
254  this.lastChar[0] = buf[buf.length - 1];
255  return buf.toString('utf16le', i, buf.length - 1);
256}
257
258// For UTF-16LE we do not explicitly append special replacement characters if we
259// end on a partial character, we simply let v8 handle that.
260function utf16End(buf) {
261  var r = buf && buf.length ? this.write(buf) : '';
262  if (this.lastNeed) {
263    var end = this.lastTotal - this.lastNeed;
264    return r + this.lastChar.toString('utf16le', 0, end);
265  }
266  return r;
267}
268
269function base64Text(buf, i) {
270  var n = (buf.length - i) % 3;
271  if (n === 0) return buf.toString('base64', i);
272  this.lastNeed = 3 - n;
273  this.lastTotal = 3;
274  if (n === 1) {
275    this.lastChar[0] = buf[buf.length - 1];
276  } else {
277    this.lastChar[0] = buf[buf.length - 2];
278    this.lastChar[1] = buf[buf.length - 1];
279  }
280  return buf.toString('base64', i, buf.length - n);
281}
282
283function base64End(buf) {
284  var r = buf && buf.length ? this.write(buf) : '';
285  if (this.lastNeed) return r + this.lastChar.toString('base64', 0, 3 - this.lastNeed);
286  return r;
287}
288
289// Pass bytes on through for single-byte encodings (e.g. ascii, latin1, hex)
290function simpleWrite(buf) {
291  return buf.toString(this.encoding);
292}
293
294function simpleEnd(buf) {
295  return buf && buf.length ? this.write(buf) : '';
296}

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