这篇文章主要介绍了c#检测文本文件编码的方法
这篇文章主要介绍了c#检测文本文件编码的方法
正文
c#检测文本文件编码的方法
C#如何检测文本文件的编码，本文为大家分享了示例代码，具体内容如下
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 | using System;using System.Text;using System.Text.RegularExpressions;using System.IO; namespace KlerksSoft{ public static class TextFileEncodingDetector { /** Simple class to handle text file encoding woes (in a primarily English-speaking tech* world).** - This code is fully managed, no shady calls to MLang (the unmanaged codepage* detection library originally developed for Internet Explorer).** - This class does NOT try to detect arbitrary codepages/charsets, it really only* aims to differentiate between some of the most common variants of Unicode* encoding, and a "default" (western / ascii-based) encoding alternative provided* by the caller.** - As there is no "Reliable" way to distinguish between UTF-8 (without BOM) and* Windows-1252 (in .Net, also incorrectly called "ASCII") encodings, we use a* heuristic - so the more of the file we can sample the better the guess. If you* are going to read the whole file into memory at some point, then best to pass* in the whole byte byte array directly. Otherwise, decide how to trade off* reliability against performance / memory usage.** - The UTF-8 detection heuristic only works for western text, as it relies on* the presence of UTF-8 encoded accented and other characters found in the upper* ranges of the Latin-1 and (particularly) Windows-1252 codepages.** - For more general detection routines, see existing projects / resources:* - MLang - Microsoft library originally for IE6, available in Windows XP and later APIs now (I think?)* - MLang .Net bindings: http://www.codeproject.com/KB/recipes/DetectEncoding.aspx* - CharDet - Mozilla browser's detection routines* - Ported to Java then .Net: http://www.conceptdevelopment.net/Localization/NCharDet/* - Ported straight to .Net: http://code.google.com/p/chardetsharp/source/browse** Copyright Tao Klerks, Jan 2010, tao@klerks.biz* Licensed under the modified BSD license:* Redistribution and use in source and binary forms, with or without modification, arepermitted provided that the following conditions are met: - Redistributions of source code must retain the above copyright notice, this list ofconditions and the following disclaimer.- Redistributions in binary form must reproduce the above copyright notice, this listof conditions and the following disclaimer in the documentation and/or other materialsprovided with the distribution.- The name of the author may not be used to endorse or promote products derived fromthis software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FORA PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANYDIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, ORPROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITYOF SUCH DAMAGE. **/ const long _defaultHeuristicSampleSize = 0x10000; //completely arbitrary - inappropriate for high numbers of files / high speed requirements public static Encoding DetectTextFileEncoding(string InputFilename, Encoding DefaultEncoding) { using (FileStream textfileStream = File.OpenRead(InputFilename)) { return DetectTextFileEncoding(textfileStream, DefaultEncoding, _defaultHeuristicSampleSize); } } public static Encoding DetectTextFileEncoding(FileStream InputFileStream, Encoding DefaultEncoding, long HeuristicSampleSize) { if (InputFileStream == null) throw new ArgumentNullException("Must provide a valid Filestream!", "InputFileStream"); if (!InputFileStream.CanRead) throw new ArgumentException("Provided file stream is not readable!", "InputFileStream"); if (!InputFileStream.CanSeek) throw new ArgumentException("Provided file stream cannot seek!", "InputFileStream"); Encoding encodingFound = null; long originalPos = InputFileStream.Position; InputFileStream.Position = 0; //First read only what we need for BOM detection byte[] bomBytes = new byte[InputFileStream.Length > 4 ? 4 : InputFileStream.Length]; InputFileStream.Read(bomBytes, 0, bomBytes.Length); encodingFound = DetectBOMBytes(bomBytes); if (encodingFound != null) { InputFileStream.Position = originalPos; return encodingFound; } //BOM Detection failed, going for heuristics now. // create sample byte array and populate it byte[] sampleBytes = new byte[HeuristicSampleSize > InputFileStream.Length ? InputFileStream.Length : HeuristicSampleSize]; Array.Copy(bomBytes, sampleBytes, bomBytes.Length); if (InputFileStream.Length > bomBytes.Length) InputFileStream.Read(sampleBytes, bomBytes.Length, sampleBytes.Length - bomBytes.Length); InputFileStream.Position = originalPos; //test byte array content encodingFound = DetectUnicodeInByteSampleByHeuristics(sampleBytes); if (encodingFound != null) return encodingFound; else return DefaultEncoding; } public static Encoding DetectTextByteArrayEncoding(byte[] TextData, Encoding DefaultEncoding) { if (TextData == null) throw new ArgumentNullException("Must provide a valid text data byte array!", "TextData"); Encoding encodingFound = null; encodingFound = DetectBOMBytes(TextData); if (encodingFound != null) { return encodingFound; } else { //test byte array content encodingFound = DetectUnicodeInByteSampleByHeuristics(TextData); if (encodingFound != null) return encodingFound; else return DefaultEncoding; } } public static Encoding DetectBOMBytes(byte[] BOMBytes) { if (BOMBytes == null) throw new ArgumentNullException("Must provide a valid BOM byte array!", "BOMBytes"); if (BOMBytes.Length < 2) return null; if (BOMBytes[0] == 0xff && BOMBytes[1] == 0xfe && (BOMBytes.Length < 4 || BOMBytes[2] != 0 || BOMBytes[3] != 0 ) ) return Encoding.Unicode; if (BOMBytes[0] == 0xfe && BOMBytes[1] == 0xff ) return Encoding.BigEndianUnicode; if (BOMBytes.Length < 3) return null; if (BOMBytes[0] == 0xef && BOMBytes[1] == 0xbb && BOMBytes[2] == 0xbf) return Encoding.UTF8; if (BOMBytes[0] == 0x2b && BOMBytes[1] == 0x2f && BOMBytes[2] == 0x76) return Encoding.UTF7; if (BOMBytes.Length < 4) return null; if (BOMBytes[0] == 0xff && BOMBytes[1] == 0xfe && BOMBytes[2] == 0 && BOMBytes[3] == 0) return Encoding.UTF32; if (BOMBytes[0] == 0 && BOMBytes[1] == 0 && BOMBytes[2] == 0xfe && BOMBytes[3] == 0xff) return Encoding.GetEncoding(12001); return null; } public static Encoding DetectUnicodeInByteSampleByHeuristics(byte[] SampleBytes) { long oddBinaryNullsInSample = 0; long evenBinaryNullsInSample = 0; long suspiciousUTF8SequenceCount = 0; long suspiciousUTF8BytesTotal = 0; long likelyUSASCIIBytesInSample = 0; //Cycle through, keeping count of binary null positions, possible UTF-8 // sequences from upper ranges of Windows-1252, and probable US-ASCII // character counts. long currentPos = 0; int skipUTF8Bytes = 0; while (currentPos < SampleBytes.Length) { //binary null distribution if (SampleBytes[currentPos] == 0) { if (currentPos % 2 == 0) evenBinaryNullsInSample++; else oddBinaryNullsInSample++; } //likely US-ASCII characters if (IsCommonUSASCIIByte(SampleBytes[currentPos])) likelyUSASCIIBytesInSample++; //suspicious sequences (look like UTF-8) if (skipUTF8Bytes == 0) { int lengthFound = DetectSuspiciousUTF8SequenceLength(SampleBytes, currentPos); if (lengthFound > 0) { suspiciousUTF8SequenceCount++; suspiciousUTF8BytesTotal += lengthFound; skipUTF8Bytes = lengthFound - 1; } } else { skipUTF8Bytes--; } currentPos++; } //1: UTF-16 LE - in english / european environments, this is usually characterized by a // high proportion of odd binary nulls (starting at 0), with (as this is text) a low // proportion of even binary nulls. // The thresholds here used (less than 20% nulls where you expect non-nulls, and more than // 60% nulls where you do expect nulls) are completely arbitrary. if (((evenBinaryNullsInSample * 2.0) / SampleBytes.Length) < 0.2 && ((oddBinaryNullsInSample * 2.0) / SampleBytes.Length) > 0.6 ) return Encoding.Unicode; //2: UTF-16 BE - in english / european environments, this is usually characterized by a // high proportion of even binary nulls (starting at 0), with (as this is text) a low // proportion of odd binary nulls. // The thresholds here used (less than 20% nulls where you expect non-nulls, and more than // 60% nulls where you do expect nulls) are completely arbitrary. if (((oddBinaryNullsInSample * 2.0) / SampleBytes.Length) < 0.2 && ((evenBinaryNullsInSample * 2.0) / SampleBytes.Length) > 0.6 ) return Encoding.BigEndianUnicode; //3: UTF-8 - Martin Dürst outlines a method for detecting whether something CAN be UTF-8 content // using regexp, in his w3c.org unicode FAQ entry: // http://www.w3.org/International/questions/qa-forms-utf-8 // adapted here for C#. string potentiallyMangledString = Encoding.ASCII.GetString(SampleBytes); Regex UTF8Validator = new Regex(@"\A(" + @"[\x09\x0A\x0D\x20-\x7E]" + @"|[\xC2-\xDF][\x80-\xBF]" + @"|\xE0[\xA0-\xBF][\x80-\xBF]" + @"|[\xE1-\xEC\xEE\xEF][\x80-\xBF]{2}" + @"|\xED[\x80-\x9F][\x80-\xBF]" + @"|\xF0[\x90-\xBF][\x80-\xBF]{2}" + @"|[\xF1-\xF3][\x80-\xBF]{3}" + @"|\xF4[\x80-\x8F][\x80-\xBF]{2}" + @")*\z"); if (UTF8Validator.IsMatch(potentiallyMangledString)) { //Unfortunately, just the fact that it CAN be UTF-8 doesn't tell you much about probabilities. //If all the characters are in the 0-127 range, no harm done, most western charsets are same as UTF-8 in these ranges. //If some of the characters were in the upper range (western accented characters), however, they would likely be mangled to 2-byte by the UTF-8 encoding process. // So, we need to play stats. // The "Random" likelihood of any pair of randomly generated characters being one // of these "suspicious" character sequences is: // 128 / (256 * 256) = 0.2%. // // In western text data, that is SIGNIFICANTLY reduced - most text data stays in the <127 // character range, so we assume that more than 1 in 500,000 of these character // sequences indicates UTF-8. The number 500,000 is completely arbitrary - so sue me. // // We can only assume these character sequences will be rare if we ALSO assume that this // IS in fact western text - in which case the bulk of the UTF-8 encoded data (that is // not already suspicious sequences) should be plain US-ASCII bytes. This, I // arbitrarily decided, should be 80% (a random distribution, eg binary data, would yield // approx 40%, so the chances of hitting this threshold by accident in random data are // VERY low). if ((suspiciousUTF8SequenceCount * 500000.0 / SampleBytes.Length >= 1) //suspicious sequences && ( //all suspicious, so cannot evaluate proportion of US-Ascii SampleBytes.Length - suspiciousUTF8BytesTotal == 0 || likelyUSASCIIBytesInSample * 1.0 / (SampleBytes.Length - suspiciousUTF8BytesTotal) >= 0.8 ) ) return Encoding.UTF8; } return null; } private static bool IsCommonUSASCIIByte(byte testByte) { if (testByte == 0x0A //lf || testByte == 0x0D //cr || testByte == 0x09 //tab || (testByte >= 0x20 && testByte <= 0x2F) //common punctuation || (testByte >= 0x30 && testByte <= 0x39) //digits || (testByte >= 0x3A && testByte <= 0x40) //common punctuation || (testByte >= 0x41 && testByte <= 0x5A) //capital letters || (testByte >= 0x5B && testByte <= 0x60) //common punctuation || (testByte >= 0x61 && testByte <= 0x7A) //lowercase letters || (testByte >= 0x7B && testByte <= 0x7E) //common punctuation ) return true; else return false; } private static int DetectSuspiciousUTF8SequenceLength(byte[] SampleBytes, long currentPos) { int lengthFound = 0; if (SampleBytes.Length >= currentPos + 1 && SampleBytes[currentPos] == 0xC2 ) { if (SampleBytes[currentPos + 1] == 0x81 || SampleBytes[currentPos + 1] == 0x8D || SampleBytes[currentPos + 1] == 0x8F ) lengthFound = 2; else if (SampleBytes[currentPos + 1] == 0x90 || SampleBytes[currentPos + 1] == 0x9D ) lengthFound = 2; else if (SampleBytes[currentPos + 1] >= 0xA0 && SampleBytes[currentPos + 1] <= 0xBF ) lengthFound = 2; } else if (SampleBytes.Length >= currentPos + 1 && SampleBytes[currentPos] == 0xC3 ) { if (SampleBytes[currentPos + 1] >= 0x80 && SampleBytes[currentPos + 1] <= 0xBF ) lengthFound = 2; } else if (SampleBytes.Length >= currentPos + 1 && SampleBytes[currentPos] == 0xC5 ) { if (SampleBytes[currentPos + 1] == 0x92 || SampleBytes[currentPos + 1] == 0x93 ) lengthFound = 2; else if (SampleBytes[currentPos + 1] == 0xA0 || SampleBytes[currentPos + 1] == 0xA1 ) lengthFound = 2; else if (SampleBytes[currentPos + 1] == 0xB8 || SampleBytes[currentPos + 1] == 0xBD || SampleBytes[currentPos + 1] == 0xBE ) lengthFound = 2; } else if (SampleBytes.Length >= currentPos + 1 && SampleBytes[currentPos] == 0xC6 ) { if (SampleBytes[currentPos + 1] == 0x92) lengthFound = 2; } else if (SampleBytes.Length >= currentPos + 1 && SampleBytes[currentPos] == 0xCB ) { if (SampleBytes[currentPos + 1] == 0x86 || SampleBytes[currentPos + 1] == 0x9C ) lengthFound = 2; } else if (SampleBytes.Length >= currentPos + 2 && SampleBytes[currentPos] == 0xE2 ) { if (SampleBytes[currentPos + 1] == 0x80) { if (SampleBytes[currentPos + 2] == 0x93 || SampleBytes[currentPos + 2] == 0x94 ) lengthFound = 3; if (SampleBytes[currentPos + 2] == 0x98 || SampleBytes[currentPos + 2] == 0x99 || SampleBytes[currentPos + 2] == 0x9A ) lengthFound = 3; if (SampleBytes[currentPos + 2] == 0x9C || SampleBytes[currentPos + 2] == 0x9D || SampleBytes[currentPos + 2] == 0x9E ) lengthFound = 3; if (SampleBytes[currentPos + 2] == 0xA0 || SampleBytes[currentPos + 2] == 0xA1 || SampleBytes[currentPos + 2] == 0xA2 ) lengthFound = 3; if (SampleBytes[currentPos + 2] == 0xA6) lengthFound = 3; if (SampleBytes[currentPos + 2] == 0xB0) lengthFound = 3; if (SampleBytes[currentPos + 2] == 0xB9 || SampleBytes[currentPos + 2] == 0xBA ) lengthFound = 3; } else if (SampleBytes[currentPos + 1] == 0x82 && SampleBytes[currentPos + 2] == 0xAC ) lengthFound = 3; else if (SampleBytes[currentPos + 1] == 0x84 && SampleBytes[currentPos + 2] == 0xA2 ) lengthFound = 3; } return lengthFound; } }} |
使用方法：
1 | Encoding fileEncoding = TextFileEncodingDetector.DetectTextFileEncoding("you file path",Encoding.Default); |
以上就是本文的全部内容，希望对大家学习C#程序设计有所帮助。
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