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