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utf16.js
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"use strict"; var Buffer = require("safer-buffer").Buffer; // Note: UTF16-LE (or UCS2) codec is Node.js native. See encodings/internal.js // == UTF16-BE codec. ========================================================== exports.utf16be = Utf16BECodec; function Utf16BECodec() { } Utf16BECodec.prototype.encoder = Utf16BEEncoder; Utf16BECodec.prototype.decoder = Utf16BEDecoder; Utf16BECodec.prototype.bomAware = true; // -- Encoding function Utf16BEEncoder() { } Utf16BEEncoder.prototype.write = function(str) { var buf = Buffer.from(str, 'ucs2'); for (var i = 0; i < buf.length; i += 2) { var tmp = buf[i]; buf[i] = buf[i+1]; buf[i+1] = tmp; } return buf; } Utf16BEEncoder.prototype.end = function() { } // -- Decoding function Utf16BEDecoder() { this.overflowByte = -1; } Utf16BEDecoder.prototype.write = function(buf) { if (buf.length == 0) return ''; var buf2 = Buffer.alloc(buf.length + 1), i = 0, j = 0; if (this.overflowByte !== -1) { buf2[0] = buf[0]; buf2[1] = this.overflowByte; i = 1; j = 2; } for (; i < buf.length-1; i += 2, j+= 2) { buf2[j] = buf[i+1]; buf2[j+1] = buf[i]; } this.overflowByte = (i == buf.length-1) ? buf[buf.length-1] : -1; return buf2.slice(0, j).toString('ucs2'); } Utf16BEDecoder.prototype.end = function() { } // == UTF-16 codec ============================================================= // Decoder chooses automatically from UTF-16LE and UTF-16BE using BOM and space-based heuristic. // Defaults to UTF-16LE, as it's prevalent and default in Node. // http://en.wikipedia.org/wiki/UTF-16 and http://encoding.spec.whatwg.org/#utf-16le // Decoder default can be changed: iconv.decode(buf, 'utf16', {defaultEncoding: 'utf-16be'}); // Encoder uses UTF-16LE and prepends BOM (which can be overridden with addBOM: false). exports.utf16 = Utf16Codec; function Utf16Codec(codecOptions, iconv) { this.iconv = iconv; } Utf16Codec.prototype.encoder = Utf16Encoder; Utf16Codec.prototype.decoder = Utf16Decoder; // -- Encoding (pass-through) function Utf16Encoder(options, codec) { options = options || {}; if (options.addBOM === undefined) options.addBOM = true; this.encoder = codec.iconv.getEncoder('utf-16le', options); } Utf16Encoder.prototype.write = function(str) { return this.encoder.write(str); } Utf16Encoder.prototype.end = function() { return this.encoder.end(); } // -- Decoding function Utf16Decoder(options, codec) { this.decoder = null; this.initialBytes = []; this.initialBytesLen = 0; this.options = options || {}; this.iconv = codec.iconv; } Utf16Decoder.prototype.write = function(buf) { if (!this.decoder) { // Codec is not chosen yet. Accumulate initial bytes. this.initialBytes.push(buf); this.initialBytesLen += buf.length; if (this.initialBytesLen < 16) // We need more bytes to use space heuristic (see below) return ''; // We have enough bytes -> detect endianness. var buf = Buffer.concat(this.initialBytes), encoding = detectEncoding(buf, this.options.defaultEncoding); this.decoder = this.iconv.getDecoder(encoding, this.options); this.initialBytes.length = this.initialBytesLen = 0; } return this.decoder.write(buf); } Utf16Decoder.prototype.end = function() { if (!this.decoder) { var buf = Buffer.concat(this.initialBytes), encoding = detectEncoding(buf, this.options.defaultEncoding); this.decoder = this.iconv.getDecoder(encoding, this.options); var res = this.decoder.write(buf), trail = this.decoder.end(); return trail ? (res + trail) : res; } return this.decoder.end(); } function detectEncoding(buf, defaultEncoding) { var enc = defaultEncoding || 'utf-16le'; if (buf.length >= 2) { // Check BOM. if (buf[0] == 0xFE && buf[1] == 0xFF) // UTF-16BE BOM enc = 'utf-16be'; else if (buf[0] == 0xFF && buf[1] == 0xFE) // UTF-16LE BOM enc = 'utf-16le'; else { // No BOM found. Try to deduce encoding from initial content. // Most of the time, the content has ASCII chars (U+00**), but the opposite (U+**00) is uncommon. // So, we count ASCII as if it was LE or BE, and decide from that. var asciiCharsLE = 0, asciiCharsBE = 0, // Counts of chars in both positions _len = Math.min(buf.length - (buf.length % 2), 64); // Len is always even. for (var i = 0; i < _len; i += 2) { if (buf[i] === 0 && buf[i+1] !== 0) asciiCharsBE++; if (buf[i] !== 0 && buf[i+1] === 0) asciiCharsLE++; } if (asciiCharsBE > asciiCharsLE) enc = 'utf-16be'; else if (asciiCharsBE < asciiCharsLE) enc = 'utf-16le'; } } return enc; }