282 lines
8.6 KiB
JavaScript
282 lines
8.6 KiB
JavaScript
'use strict';
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var Buffer = require('safer-buffer').Buffer;
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// == UTF32-LE/BE codec. ==========================================================
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exports._utf32 = Utf32Codec;
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function Utf32Codec(codecOptions, iconv) {
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this.iconv = iconv;
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this.bomAware = true;
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this.isLE = codecOptions.isLE;
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}
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exports.utf32le = { type: '_utf32', isLE: true };
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exports.utf32be = { type: '_utf32', isLE: false };
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// Aliases
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exports.ucs4le = 'utf32le';
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exports.ucs4be = 'utf32be';
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Utf32Codec.prototype.encoder = Utf32Encoder;
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Utf32Codec.prototype.decoder = Utf32Decoder;
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// -- Encoding
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function Utf32Encoder(options, codec) {
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this.isLE = codec.isLE;
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this.highSurrogate = 0;
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}
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Utf32Encoder.prototype.write = function(str) {
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var src = Buffer.from(str, 'ucs2');
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var dst = Buffer.alloc(src.length * 2);
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var write32 = this.isLE ? dst.writeUInt32LE : dst.writeUInt32BE;
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var offset = 0;
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for (var i = 0; i < src.length; i += 2) {
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var code = src.readUInt16LE(i);
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var isHighSurrogate = (0xD800 <= code && code < 0xDC00);
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var isLowSurrogate = (0xDC00 <= code && code < 0xE000);
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if (this.highSurrogate) {
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if (isHighSurrogate || !isLowSurrogate) {
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// There shouldn't be two high surrogates in a row, nor a high surrogate which isn't followed by a low
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// surrogate. If this happens, keep the pending high surrogate as a stand-alone semi-invalid character
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// (technically wrong, but expected by some applications, like Windows file names).
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write32.call(dst, this.highSurrogate, offset);
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offset += 4;
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}
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else {
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// Create 32-bit value from high and low surrogates;
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var codepoint = (((this.highSurrogate - 0xD800) << 10) | (code - 0xDC00)) + 0x10000;
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write32.call(dst, codepoint, offset);
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offset += 4;
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this.highSurrogate = 0;
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continue;
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}
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}
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if (isHighSurrogate)
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this.highSurrogate = code;
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else {
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// Even if the current character is a low surrogate, with no previous high surrogate, we'll
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// encode it as a semi-invalid stand-alone character for the same reasons expressed above for
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// unpaired high surrogates.
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write32.call(dst, code, offset);
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offset += 4;
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this.highSurrogate = 0;
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}
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}
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if (offset < dst.length)
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dst = dst.slice(0, offset);
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return dst;
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};
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Utf32Encoder.prototype.end = function() {
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// Treat any leftover high surrogate as a semi-valid independent character.
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if (!this.highSurrogate)
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return;
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var buf = Buffer.alloc(4);
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if (this.isLE)
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buf.writeUInt32LE(this.highSurrogate, 0);
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else
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buf.writeUInt32BE(this.highSurrogate, 0);
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this.highSurrogate = 0;
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return buf;
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};
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// -- Decoding
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function Utf32Decoder(options, codec) {
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this.isLE = codec.isLE;
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this.badChar = codec.iconv.defaultCharUnicode.charCodeAt(0);
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this.overflow = null;
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}
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Utf32Decoder.prototype.write = function(src) {
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if (src.length === 0)
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return '';
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if (this.overflow)
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src = Buffer.concat([this.overflow, src]);
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var goodLength = src.length - src.length % 4;
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if (src.length !== goodLength) {
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this.overflow = src.slice(goodLength);
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src = src.slice(0, goodLength);
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}
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else
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this.overflow = null;
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var dst = Buffer.alloc(goodLength);
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var offset = 0;
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for (var i = 0; i < goodLength; i += 4) {
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var codepoint = this.isLE ? src.readUInt32LE(i) : src.readUInt32BE(i);
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if (codepoint < 0x10000) {
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// Simple 16-bit character
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dst.writeUInt16LE(codepoint, offset);
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offset += 2;
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}
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else {
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if (codepoint > 0x10FFFF) {
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// Not a valid Unicode codepoint
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dst.writeUInt16LE(this.badChar, offset);
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offset += 2;
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}
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else {
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// Create high and low surrogates.
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codepoint -= 0x10000;
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var high = 0xD800 | (codepoint >> 10);
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var low = 0xDC00 + (codepoint & 0x3FF);
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dst.writeUInt16LE(high, offset);
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offset += 2;
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dst.writeUInt16LE(low, offset);
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offset += 2;
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}
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}
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}
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return dst.slice(0, offset).toString('ucs2');
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};
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Utf32Decoder.prototype.end = function() {
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this.overflow = null;
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};
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// == UTF-32 Auto codec =============================================================
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// Decoder chooses automatically from UTF-32LE and UTF-32BE using BOM and space-based heuristic.
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// Defaults to UTF-32LE. http://en.wikipedia.org/wiki/UTF-32
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// Encoder/decoder default can be changed: iconv.decode(buf, 'utf32', {defaultEncoding: 'utf-32be'});
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// Encoder prepends BOM (which can be overridden with (addBOM: false}).
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exports.utf32 = Utf32AutoCodec;
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exports.ucs4 = Utf32AutoCodec;
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function Utf32AutoCodec(options, iconv) {
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this.iconv = iconv;
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}
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Utf32AutoCodec.prototype.encoder = Utf32AutoEncoder;
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Utf32AutoCodec.prototype.decoder = Utf32AutoDecoder;
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// -- Encoding
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function Utf32AutoEncoder(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(options.defaultEncoding || 'utf-32le', options);
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}
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Utf32AutoEncoder.prototype.write = function(str) {
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return this.encoder.write(str);
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};
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Utf32AutoEncoder.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 Utf32AutoDecoder(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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Utf32AutoDecoder.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 < 32) // 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 buf2 = Buffer.concat(this.initialBytes),
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encoding = detectEncoding(buf2, 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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Utf32AutoDecoder.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-32le';
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if (buf.length >= 4) {
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// Check BOM.
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if (buf.readUInt32BE(0) === 0xFEFF) // UTF-32LE BOM
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enc = 'utf-32be';
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else if (buf.readUInt32LE(0) === 0xFEFF) // UTF-32LE BOM
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enc = 'utf-32le';
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else {
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// No BOM found. Try to deduce encoding from initial content.
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// Using the wrong endian-ism for UTF-32 will very often result in codepoints that are beyond
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// the valid Unicode limit of 0x10FFFF. That will be used as the primary determinant.
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//
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// Further, we can suppose the content is mostly plain ASCII chars (U+00**).
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// So, we count ASCII as if it was LE or BE, and decide from that.
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var invalidLE = 0, invalidBE = 0;
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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 % 4), 128); // Len is always even.
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for (var i = 0; i < _len; i += 4) {
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var b0 = buf[i], b1 = buf[i + 1], b2 = buf[i + 2], b3 = buf[i + 3];
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if (b0 !== 0 || b1 > 0x10) ++invalidBE;
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if (b3 !== 0 || b2 > 0x10) ++invalidLE;
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if (b0 === 0 && b1 === 0 && b2 === 0 && b3 !== 0) asciiCharsBE++;
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if (b0 !== 0 && b1 === 0 && b2 === 0 && b3 === 0) asciiCharsLE++;
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}
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if (invalidBE < invalidLE)
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enc = 'utf-32be';
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else if (invalidLE < invalidBE)
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enc = 'utf-32le';
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if (asciiCharsBE > asciiCharsLE)
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enc = 'utf-32be';
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else if (asciiCharsBE < asciiCharsLE)
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enc = 'utf-32le';
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}
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}
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return enc;
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}
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