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Editing: string_decoder.js
// 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'; /*<replacement>*/ var Buffer = require('safe-buffer').Buffer; /*</replacement>*/ 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. exports.StringDecoder = StringDecoder; function StringDecoder(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) : ''; }
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