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"use strict";
var Buffer = require("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 = new Buffer(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 = new Buffer(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;
}
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