1 /* 2 * Copyright (C) 2013 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 //#define LOG_NDEBUG 0 18 #define LOG_TAG "CharacterEncodingDector" 19 #include <utils/Log.h> 20 21 #include <CharacterEncodingDetector.h> 22 #include "CharacterEncodingDetectorTables.h" 23 24 #include "utils/Vector.h" 25 #include "StringArray.h" 26 27 #include "unicode/ucnv.h" 28 #include "unicode/ucsdet.h" 29 #include "unicode/ustring.h" 30 31 namespace android { 32 33 CharacterEncodingDetector::CharacterEncodingDetector() { 34 35 UErrorCode status = U_ZERO_ERROR; 36 mUtf8Conv = ucnv_open("UTF-8", &status); 37 if (U_FAILURE(status)) { 38 ALOGE("could not create UConverter for UTF-8"); 39 mUtf8Conv = NULL; 40 } 41 } 42 43 CharacterEncodingDetector::~CharacterEncodingDetector() { 44 ucnv_close(mUtf8Conv); 45 } 46 47 void CharacterEncodingDetector::addTag(const char *name, const char *value) { 48 mNames.push_back(name); 49 mValues.push_back(value); 50 } 51 52 size_t CharacterEncodingDetector::size() { 53 return mNames.size(); 54 } 55 56 status_t CharacterEncodingDetector::getTag(int index, const char **name, const char**value) { 57 if (index >= mNames.size()) { 58 return BAD_VALUE; 59 } 60 61 *name = mNames.getEntry(index); 62 *value = mValues.getEntry(index); 63 return OK; 64 } 65 66 static bool isPrintableAscii(const char *value, size_t len) { 67 for (size_t i = 0; i < len; i++) { 68 if ((value[i] & 0x80) || value[i] < 0x20 || value[i] == 0x7f) { 69 return false; 70 } 71 } 72 return true; 73 } 74 75 void CharacterEncodingDetector::detectAndConvert() { 76 77 int size = mNames.size(); 78 ALOGV("%d tags before conversion", size); 79 for (int i = 0; i < size; i++) { 80 ALOGV("%s: %s", mNames.getEntry(i), mValues.getEntry(i)); 81 } 82 83 if (size && mUtf8Conv) { 84 85 UErrorCode status = U_ZERO_ERROR; 86 UCharsetDetector *csd = ucsdet_open(&status); 87 const UCharsetMatch *ucm; 88 89 // try combined detection of artist/album/title etc. 90 char buf[1024]; 91 buf[0] = 0; 92 bool allprintable = true; 93 for (int i = 0; i < size; i++) { 94 const char *name = mNames.getEntry(i); 95 const char *value = mValues.getEntry(i); 96 if (!isPrintableAscii(value, strlen(value)) && ( 97 !strcmp(name, "artist") || 98 !strcmp(name, "albumartist") || 99 !strcmp(name, "composer") || 100 !strcmp(name, "genre") || 101 !strcmp(name, "album") || 102 !strcmp(name, "title"))) { 103 strlcat(buf, value, sizeof(buf)); 104 // separate tags by space so ICU's ngram detector can do its job 105 strlcat(buf, " ", sizeof(buf)); 106 allprintable = false; 107 } 108 } 109 110 const char *combinedenc = "UTF-8"; 111 if (allprintable) { 112 // since 'buf' is empty, ICU would return a UTF-8 matcher with low confidence, so 113 // no need to even call it 114 ALOGV("all tags are printable, assuming ascii (%zu)", strlen(buf)); 115 } else { 116 ucsdet_setText(csd, buf, strlen(buf), &status); 117 int32_t matches; 118 const UCharsetMatch** ucma = ucsdet_detectAll(csd, &matches, &status); 119 bool goodmatch = true; 120 int highest = 0; 121 const UCharsetMatch* bestCombinedMatch = getPreferred(buf, strlen(buf), 122 ucma, matches, &goodmatch, &highest); 123 124 ALOGV("goodmatch: %s, highest: %d", goodmatch ? "true" : "false", highest); 125 if (!goodmatch && (highest < 15 || strlen(buf) < 20)) { 126 ALOGV("not a good match, trying with more data"); 127 // This string might be too short for ICU to do anything useful with. 128 // (real world example: "Bjrk" in ISO-8859-1 might be detected as GB18030, because 129 // the ISO detector reports a confidence of 0, while the GB18030 detector reports 130 // a confidence of 10 with no invalid characters) 131 // Append artist, album and title if they were previously omitted because they 132 // were printable ascii. 133 bool added = false; 134 for (int i = 0; i < size; i++) { 135 const char *name = mNames.getEntry(i); 136 const char *value = mValues.getEntry(i); 137 if (isPrintableAscii(value, strlen(value)) && ( 138 !strcmp(name, "artist") || 139 !strcmp(name, "album") || 140 !strcmp(name, "title"))) { 141 strlcat(buf, value, sizeof(buf)); 142 strlcat(buf, " ", sizeof(buf)); 143 added = true; 144 } 145 } 146 if (added) { 147 ucsdet_setText(csd, buf, strlen(buf), &status); 148 ucma = ucsdet_detectAll(csd, &matches, &status); 149 bestCombinedMatch = getPreferred(buf, strlen(buf), 150 ucma, matches, &goodmatch, &highest); 151 if (!goodmatch && highest <= 15) { 152 ALOGV("still not a good match after adding printable tags"); 153 bestCombinedMatch = NULL; 154 } 155 } else { 156 ALOGV("no printable tags to add"); 157 } 158 } 159 160 if (bestCombinedMatch != NULL) { 161 combinedenc = ucsdet_getName(bestCombinedMatch, &status); 162 } else { 163 combinedenc = "ISO-8859-1"; 164 } 165 } 166 167 for (int i = 0; i < size; i++) { 168 const char *name = mNames.getEntry(i); 169 uint8_t* src = (uint8_t *)mValues.getEntry(i); 170 int len = strlen((char *)src); 171 172 ALOGV("@@@ checking %s", name); 173 const char *s = mValues.getEntry(i); 174 int32_t inputLength = strlen(s); 175 const char *enc; 176 177 if (!allprintable && (!strcmp(name, "artist") || 178 !strcmp(name, "albumartist") || 179 !strcmp(name, "composer") || 180 !strcmp(name, "genre") || 181 !strcmp(name, "album") || 182 !strcmp(name, "title"))) { 183 // use encoding determined from the combination of artist/album/title etc. 184 enc = combinedenc; 185 } else { 186 if (isPrintableAscii(s, inputLength)) { 187 enc = "UTF-8"; 188 ALOGV("@@@@ %s is ascii", mNames.getEntry(i)); 189 } else { 190 ucsdet_setText(csd, s, inputLength, &status); 191 ucm = ucsdet_detect(csd, &status); 192 if (!ucm) { 193 mValues.setEntry(i, "???"); 194 continue; 195 } 196 enc = ucsdet_getName(ucm, &status); 197 ALOGV("@@@@ recognized charset: %s for %s confidence %d", 198 enc, mNames.getEntry(i), ucsdet_getConfidence(ucm, &status)); 199 } 200 } 201 202 if (strcmp(enc,"UTF-8") != 0) { 203 // only convert if the source encoding isn't already UTF-8 204 ALOGV("@@@ using converter %s for %s", enc, mNames.getEntry(i)); 205 status = U_ZERO_ERROR; 206 UConverter *conv = ucnv_open(enc, &status); 207 if (U_FAILURE(status)) { 208 ALOGW("could not create UConverter for %s (%d), falling back to ISO-8859-1", 209 enc, status); 210 status = U_ZERO_ERROR; 211 conv = ucnv_open("ISO-8859-1", &status); 212 if (U_FAILURE(status)) { 213 ALOGW("could not create UConverter for ISO-8859-1 either"); 214 continue; 215 } 216 } 217 218 // convert from native encoding to UTF-8 219 const char* source = mValues.getEntry(i); 220 int targetLength = len * 3 + 1; 221 char* buffer = new char[targetLength]; 222 // don't normally check for NULL, but in this case targetLength may be large 223 if (!buffer) 224 break; 225 char* target = buffer; 226 227 ucnv_convertEx(mUtf8Conv, conv, &target, target + targetLength, 228 &source, source + strlen(source), 229 NULL, NULL, NULL, NULL, TRUE, TRUE, &status); 230 231 if (U_FAILURE(status)) { 232 ALOGE("ucnv_convertEx failed: %d", status); 233 mValues.setEntry(i, "???"); 234 } else { 235 // zero terminate 236 *target = 0; 237 // strip trailing spaces 238 while (--target > buffer && *target == ' ') { 239 *target = 0; 240 } 241 // skip leading spaces 242 char *start = buffer; 243 while (*start == ' ') { 244 start++; 245 } 246 mValues.setEntry(i, start); 247 } 248 249 delete[] buffer; 250 251 ucnv_close(conv); 252 } 253 } 254 255 for (int i = size - 1; i >= 0; --i) { 256 if (strlen(mValues.getEntry(i)) == 0) { 257 ALOGV("erasing %s because entry is empty", mNames.getEntry(i)); 258 mNames.erase(i); 259 mValues.erase(i); 260 } 261 } 262 263 ucsdet_close(csd); 264 } 265 } 266 267 /* 268 * When ICU detects multiple encoding matches, apply additional heuristics to determine 269 * which one is the best match, since ICU can't always be trusted to make the right choice. 270 * 271 * What this method does is: 272 * - decode the input using each of the matches found 273 * - recalculate the starting confidence level for multibyte encodings using a different 274 * algorithm and larger frequent character lists than ICU 275 * - devalue encoding where the conversion contains unlikely characters (symbols, reserved, etc) 276 * - pick the highest match 277 * - signal to the caller whether this match is considered good: confidence > 15, and confidence 278 * delta with the next runner up > 15 279 */ 280 const UCharsetMatch *CharacterEncodingDetector::getPreferred( 281 const char *input, size_t len, 282 const UCharsetMatch** ucma, size_t nummatches, 283 bool *goodmatch, int *highestmatch) { 284 285 *goodmatch = false; 286 Vector<const UCharsetMatch*> matches; 287 UErrorCode status = U_ZERO_ERROR; 288 289 ALOGV("%zu matches", nummatches); 290 for (size_t i = 0; i < nummatches; i++) { 291 const char *encname = ucsdet_getName(ucma[i], &status); 292 int confidence = ucsdet_getConfidence(ucma[i], &status); 293 ALOGV("%zu: %s %d", i, encname, confidence); 294 matches.push_back(ucma[i]); 295 } 296 297 size_t num = matches.size(); 298 if (num == 0) { 299 return NULL; 300 } 301 if (num == 1) { 302 int confidence = ucsdet_getConfidence(matches[0], &status); 303 if (confidence > 15) { 304 *goodmatch = true; 305 } 306 return matches[0]; 307 } 308 309 ALOGV("considering %zu matches", num); 310 311 // keep track of how many "special" characters result when converting the input using each 312 // encoding 313 Vector<int> newconfidence; 314 for (size_t i = 0; i < num; i++) { 315 const uint16_t *freqdata = NULL; 316 float freqcoverage = 0; 317 status = U_ZERO_ERROR; 318 const char *encname = ucsdet_getName(matches[i], &status); 319 int confidence = ucsdet_getConfidence(matches[i], &status); 320 if (!strcmp("GB18030", encname)) { 321 freqdata = frequent_zhCN; 322 freqcoverage = frequent_zhCN_coverage; 323 } else if (!strcmp("Big5", encname)) { 324 freqdata = frequent_zhTW; 325 freqcoverage = frequent_zhTW_coverage; 326 } else if (!strcmp("EUC-KR", encname)) { 327 freqdata = frequent_ko; 328 freqcoverage = frequent_ko_coverage; 329 } else if (!strcmp("EUC-JP", encname)) { 330 freqdata = frequent_ja; 331 freqcoverage = frequent_ja_coverage; 332 } else if (!strcmp("Shift_JIS", encname)) { 333 freqdata = frequent_ja; 334 freqcoverage = frequent_ja_coverage; 335 } 336 337 ALOGV("%zu: %s %d", i, encname, confidence); 338 status = U_ZERO_ERROR; 339 UConverter *conv = ucnv_open(encname, &status); 340 int demerit = 0; 341 if (U_FAILURE(status)) { 342 ALOGV("failed to open %s: %d", encname, status); 343 confidence = 0; 344 demerit += 1000; 345 } 346 const char *source = input; 347 const char *sourceLimit = input + len; 348 status = U_ZERO_ERROR; 349 int frequentchars = 0; 350 int totalchars = 0; 351 while (true) { 352 // demerit the current encoding for each "special" character found after conversion. 353 // The amount of demerit is somewhat arbitrarily chosen. 354 int inchar; 355 if (source != sourceLimit) { 356 inchar = (source[0] << 8) + source[1]; 357 } 358 UChar32 c = ucnv_getNextUChar(conv, &source, sourceLimit, &status); 359 if (!U_SUCCESS(status)) { 360 break; 361 } 362 if (c < 0x20 || (c >= 0x7f && c <= 0x009f)) { 363 ALOGV("control character %x", c); 364 demerit += 100; 365 } else if ((c == 0xa0) // no-break space 366 || (c >= 0xa2 && c <= 0xbe) // symbols, superscripts 367 || (c == 0xd7) || (c == 0xf7) // multiplication and division signs 368 || (c >= 0x2000 && c <= 0x209f)) { // punctuation, superscripts 369 ALOGV("unlikely character %x", c); 370 demerit += 10; 371 } else if (c >= 0xe000 && c <= 0xf8ff) { 372 ALOGV("private use character %x", c); 373 demerit += 30; 374 } else if (c >= 0x2190 && c <= 0x2bff) { 375 // this range comprises various symbol ranges that are unlikely to appear in 376 // music file metadata. 377 ALOGV("symbol %x", c); 378 demerit += 10; 379 } else if (c == 0xfffd) { 380 ALOGV("replacement character"); 381 demerit += 50; 382 } else if (c >= 0xfff0 && c <= 0xfffc) { 383 ALOGV("unicode special %x", c); 384 demerit += 50; 385 } else if (freqdata != NULL) { 386 totalchars++; 387 if (isFrequent(freqdata, c)) { 388 frequentchars++; 389 } 390 } 391 } 392 if (freqdata != NULL && totalchars != 0) { 393 int myconfidence = 10 + float((100 * frequentchars) / totalchars) / freqcoverage; 394 ALOGV("ICU confidence: %d, my confidence: %d (%d %d)", confidence, myconfidence, 395 totalchars, frequentchars); 396 if (myconfidence > 100) myconfidence = 100; 397 if (myconfidence < 0) myconfidence = 0; 398 confidence = myconfidence; 399 } 400 ALOGV("%d-%d=%d", confidence, demerit, confidence - demerit); 401 newconfidence.push_back(confidence - demerit); 402 ucnv_close(conv); 403 if (i == 0 && (confidence - demerit) == 100) { 404 // no need to check any further, we'll end up using this match anyway 405 break; 406 } 407 } 408 409 // find match with highest confidence after adjusting for unlikely characters 410 int highest = newconfidence[0]; 411 size_t highestidx = 0; 412 int runnerup = -10000; 413 int runnerupidx = -10000; 414 num = newconfidence.size(); 415 for (size_t i = 1; i < num; i++) { 416 if (newconfidence[i] > highest) { 417 runnerup = highest; 418 runnerupidx = highestidx; 419 highest = newconfidence[i]; 420 highestidx = i; 421 } else if (newconfidence[i] > runnerup){ 422 runnerup = newconfidence[i]; 423 runnerupidx = i; 424 } 425 } 426 status = U_ZERO_ERROR; 427 ALOGV("selecting: '%s' w/ %d confidence", 428 ucsdet_getName(matches[highestidx], &status), highest); 429 if (runnerupidx < 0) { 430 ALOGV("no runner up"); 431 if (highest > 15) { 432 *goodmatch = true; 433 } 434 } else { 435 ALOGV("runner up: '%s' w/ %d confidence", 436 ucsdet_getName(matches[runnerupidx], &status), runnerup); 437 if (runnerup < 0) { 438 runnerup = 0; 439 } 440 if ((highest - runnerup) > 15) { 441 *goodmatch = true; 442 } 443 } 444 *highestmatch = highest; 445 return matches[highestidx]; 446 } 447 448 449 bool CharacterEncodingDetector::isFrequent(const uint16_t *values, uint32_t c) { 450 451 int start = 0; 452 int end = 511; // All the tables have 512 entries 453 int mid = (start+end)/2; 454 455 while(start <= end) { 456 if(c == values[mid]) { 457 return true; 458 } else if (c > values[mid]) { 459 start = mid + 1; 460 } else { 461 end = mid - 1; 462 } 463 464 mid = (start + end) / 2; 465 } 466 467 return false; 468 } 469 470 471 } // namespace android 472
