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 <media/CharacterEncodingDetector.h> 22 #include "CharacterEncodingDetectorTables.h" 23 24 #include <utils/Vector.h> 25 #include <media/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 bool goodmatch = true; 89 int highest = 0; 90 91 // try combined detection of artist/album/title etc. 92 char buf[1024]; 93 buf[0] = 0; 94 bool allprintable = true; 95 for (int i = 0; i < size; i++) { 96 const char *name = mNames.getEntry(i); 97 const char *value = mValues.getEntry(i); 98 if (!isPrintableAscii(value, strlen(value)) && ( 99 !strcmp(name, "artist") || 100 !strcmp(name, "albumartist") || 101 !strcmp(name, "composer") || 102 !strcmp(name, "genre") || 103 !strcmp(name, "album") || 104 !strcmp(name, "title"))) { 105 strlcat(buf, value, sizeof(buf)); 106 // separate tags by space so ICU's ngram detector can do its job 107 strlcat(buf, " ", sizeof(buf)); 108 allprintable = false; 109 } 110 } 111 112 const char *combinedenc = "UTF-8"; 113 if (allprintable) { 114 // since 'buf' is empty, ICU would return a UTF-8 matcher with low confidence, so 115 // no need to even call it 116 ALOGV("all tags are printable, assuming ascii (%zu)", strlen(buf)); 117 } else { 118 ucsdet_setText(csd, buf, strlen(buf), &status); 119 int32_t matches; 120 const UCharsetMatch** ucma = ucsdet_detectAll(csd, &matches, &status); 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 if (!goodmatch && highest < 0) { 184 // Give it one more chance if there is no good match. 185 ALOGV("Trying to detect %s separately", name); 186 int32_t matches; 187 bool goodmatchSingle = true; 188 int highestSingle = 0; 189 ucsdet_setText(csd, s, inputLength, &status); 190 const UCharsetMatch** ucma = ucsdet_detectAll(csd, &matches, &status); 191 const UCharsetMatch* bestSingleMatch = getPreferred(s, inputLength, 192 ucma, matches, &goodmatchSingle, &highestSingle); 193 if (goodmatchSingle || highestSingle > highest) 194 enc = ucsdet_getName(bestSingleMatch, &status); 195 else 196 enc = combinedenc; 197 } else { 198 // use encoding determined from the combination of artist/album/title etc. 199 enc = combinedenc; 200 } 201 } else { 202 if (isPrintableAscii(s, inputLength)) { 203 enc = "UTF-8"; 204 ALOGV("@@@@ %s is ascii", mNames.getEntry(i)); 205 } else { 206 ucsdet_setText(csd, s, inputLength, &status); 207 ucm = ucsdet_detect(csd, &status); 208 if (!ucm) { 209 mValues.setEntry(i, "???"); 210 continue; 211 } 212 enc = ucsdet_getName(ucm, &status); 213 ALOGV("@@@@ recognized charset: %s for %s confidence %d", 214 enc, mNames.getEntry(i), ucsdet_getConfidence(ucm, &status)); 215 } 216 } 217 218 if (strcmp(enc,"UTF-8") != 0) { 219 // only convert if the source encoding isn't already UTF-8 220 ALOGV("@@@ using converter %s for %s", enc, mNames.getEntry(i)); 221 status = U_ZERO_ERROR; 222 UConverter *conv = ucnv_open(enc, &status); 223 if (U_FAILURE(status)) { 224 ALOGW("could not create UConverter for %s (%d), falling back to ISO-8859-1", 225 enc, status); 226 status = U_ZERO_ERROR; 227 conv = ucnv_open("ISO-8859-1", &status); 228 if (U_FAILURE(status)) { 229 ALOGW("could not create UConverter for ISO-8859-1 either"); 230 continue; 231 } 232 } 233 234 // convert from native encoding to UTF-8 235 const char* source = mValues.getEntry(i); 236 int targetLength = len * 3 + 1; 237 char* buffer = new char[targetLength]; 238 // don't normally check for NULL, but in this case targetLength may be large 239 if (!buffer) 240 break; 241 char* target = buffer; 242 243 ucnv_convertEx(mUtf8Conv, conv, &target, target + targetLength, 244 &source, source + strlen(source), 245 NULL, NULL, NULL, NULL, TRUE, TRUE, &status); 246 247 if (U_FAILURE(status)) { 248 ALOGE("ucnv_convertEx failed: %d", status); 249 mValues.setEntry(i, "???"); 250 } else { 251 // zero terminate 252 *target = 0; 253 // strip trailing spaces 254 while (--target > buffer && *target == ' ') { 255 *target = 0; 256 } 257 // skip leading spaces 258 char *start = buffer; 259 while (*start == ' ') { 260 start++; 261 } 262 mValues.setEntry(i, start); 263 } 264 265 delete[] buffer; 266 267 ucnv_close(conv); 268 } 269 } 270 271 for (int i = size - 1; i >= 0; --i) { 272 if (strlen(mValues.getEntry(i)) == 0) { 273 ALOGV("erasing %s because entry is empty", mNames.getEntry(i)); 274 mNames.erase(i); 275 mValues.erase(i); 276 } 277 } 278 279 ucsdet_close(csd); 280 } 281 } 282 283 /* 284 * When ICU detects multiple encoding matches, apply additional heuristics to determine 285 * which one is the best match, since ICU can't always be trusted to make the right choice. 286 * 287 * What this method does is: 288 * - decode the input using each of the matches found 289 * - recalculate the starting confidence level for multibyte encodings using a different 290 * algorithm and larger frequent character lists than ICU 291 * - devalue encoding where the conversion contains unlikely characters (symbols, reserved, etc) 292 * - pick the highest match 293 * - signal to the caller whether this match is considered good: confidence > 15, and confidence 294 * delta with the next runner up > 15 295 */ 296 const UCharsetMatch *CharacterEncodingDetector::getPreferred( 297 const char *input, size_t len, 298 const UCharsetMatch** ucma, size_t nummatches, 299 bool *goodmatch, int *highestmatch) { 300 301 *goodmatch = false; 302 Vector<const UCharsetMatch*> matches; 303 UErrorCode status = U_ZERO_ERROR; 304 305 ALOGV("%zu matches", nummatches); 306 for (size_t i = 0; i < nummatches; i++) { 307 const char *encname = ucsdet_getName(ucma[i], &status); 308 int confidence = ucsdet_getConfidence(ucma[i], &status); 309 ALOGV("%zu: %s %d", i, encname, confidence); 310 matches.push_back(ucma[i]); 311 } 312 313 size_t num = matches.size(); 314 if (num == 0) { 315 return NULL; 316 } 317 if (num == 1) { 318 int confidence = ucsdet_getConfidence(matches[0], &status); 319 if (confidence > 15) { 320 *goodmatch = true; 321 } 322 return matches[0]; 323 } 324 325 ALOGV("considering %zu matches", num); 326 327 // keep track of how many "special" characters result when converting the input using each 328 // encoding 329 Vector<int> newconfidence; 330 for (size_t i = 0; i < num; i++) { 331 const uint16_t *freqdata = NULL; 332 float freqcoverage = 0; 333 status = U_ZERO_ERROR; 334 const char *encname = ucsdet_getName(matches[i], &status); 335 int confidence = ucsdet_getConfidence(matches[i], &status); 336 if (!strcmp("GB18030", encname)) { 337 freqdata = frequent_zhCN; 338 freqcoverage = frequent_zhCN_coverage; 339 } else if (!strcmp("Big5", encname)) { 340 freqdata = frequent_zhTW; 341 freqcoverage = frequent_zhTW_coverage; 342 } else if (!strcmp("EUC-KR", encname)) { 343 freqdata = frequent_ko; 344 freqcoverage = frequent_ko_coverage; 345 } else if (!strcmp("EUC-JP", encname)) { 346 freqdata = frequent_ja; 347 freqcoverage = frequent_ja_coverage; 348 } else if (!strcmp("Shift_JIS", encname)) { 349 freqdata = frequent_ja; 350 freqcoverage = frequent_ja_coverage; 351 } 352 353 ALOGV("%zu: %s %d", i, encname, confidence); 354 status = U_ZERO_ERROR; 355 UConverter *conv = ucnv_open(encname, &status); 356 int demerit = 0; 357 if (U_FAILURE(status)) { 358 ALOGV("failed to open %s: %d", encname, status); 359 confidence = 0; 360 demerit += 1000; 361 } 362 const char *source = input; 363 const char *sourceLimit = input + len; 364 status = U_ZERO_ERROR; 365 int frequentchars = 0; 366 int totalchars = 0; 367 while (true) { 368 // demerit the current encoding for each "special" character found after conversion. 369 // The amount of demerit is somewhat arbitrarily chosen. 370 int inchar; 371 if (source != sourceLimit) { 372 inchar = (source[0] << 8) + source[1]; 373 } 374 UChar32 c = ucnv_getNextUChar(conv, &source, sourceLimit, &status); 375 if (!U_SUCCESS(status)) { 376 break; 377 } 378 if (c < 0x20 || (c >= 0x7f && c <= 0x009f)) { 379 ALOGV("control character %x", c); 380 demerit += 100; 381 } else if ((c == 0xa0) // no-break space 382 || (c >= 0xa2 && c <= 0xbe) // symbols, superscripts 383 || (c == 0xd7) || (c == 0xf7) // multiplication and division signs 384 || (c >= 0x2000 && c <= 0x209f)) { // punctuation, superscripts 385 ALOGV("unlikely character %x", c); 386 demerit += 10; 387 } else if (c >= 0xe000 && c <= 0xf8ff) { 388 ALOGV("private use character %x", c); 389 demerit += 30; 390 } else if (c >= 0x2190 && c <= 0x2bff) { 391 // this range comprises various symbol ranges that are unlikely to appear in 392 // music file metadata. 393 ALOGV("symbol %x", c); 394 demerit += 10; 395 } else if (c == 0xfffd) { 396 ALOGV("replacement character"); 397 demerit += 50; 398 } else if (c >= 0xfff0 && c <= 0xfffc) { 399 ALOGV("unicode special %x", c); 400 demerit += 50; 401 } else if (freqdata != NULL) { 402 totalchars++; 403 if (isFrequent(freqdata, c)) { 404 frequentchars++; 405 } 406 } 407 } 408 if (freqdata != NULL && totalchars != 0) { 409 int myconfidence = 10 + float((100 * frequentchars) / totalchars) / freqcoverage; 410 ALOGV("ICU confidence: %d, my confidence: %d (%d %d)", confidence, myconfidence, 411 totalchars, frequentchars); 412 if (myconfidence > 100) myconfidence = 100; 413 if (myconfidence < 0) myconfidence = 0; 414 confidence = myconfidence; 415 } 416 ALOGV("%d-%d=%d", confidence, demerit, confidence - demerit); 417 newconfidence.push_back(confidence - demerit); 418 ucnv_close(conv); 419 if (i == 0 && (confidence - demerit) == 100) { 420 // no need to check any further, we'll end up using this match anyway 421 break; 422 } 423 } 424 425 // find match with highest confidence after adjusting for unlikely characters 426 int highest = newconfidence[0]; 427 size_t highestidx = 0; 428 int runnerup = -10000; 429 int runnerupidx = -10000; 430 num = newconfidence.size(); 431 for (size_t i = 1; i < num; i++) { 432 if (newconfidence[i] > highest) { 433 runnerup = highest; 434 runnerupidx = highestidx; 435 highest = newconfidence[i]; 436 highestidx = i; 437 } else if (newconfidence[i] > runnerup){ 438 runnerup = newconfidence[i]; 439 runnerupidx = i; 440 } 441 } 442 status = U_ZERO_ERROR; 443 ALOGV("selecting: '%s' w/ %d confidence", 444 ucsdet_getName(matches[highestidx], &status), highest); 445 if (runnerupidx < 0) { 446 ALOGV("no runner up"); 447 if (highest > 15) { 448 *goodmatch = true; 449 } 450 } else { 451 ALOGV("runner up: '%s' w/ %d confidence", 452 ucsdet_getName(matches[runnerupidx], &status), runnerup); 453 if (runnerup < 0) { 454 runnerup = 0; 455 } 456 if ((highest - runnerup) > 15) { 457 *goodmatch = true; 458 } 459 } 460 *highestmatch = highest; 461 return matches[highestidx]; 462 } 463 464 465 bool CharacterEncodingDetector::isFrequent(const uint16_t *values, uint32_t c) { 466 467 int start = 0; 468 int end = 511; // All the tables have 512 entries 469 int mid = (start+end)/2; 470 471 while(start <= end) { 472 if(c == values[mid]) { 473 return true; 474 } else if (c > values[mid]) { 475 start = mid + 1; 476 } else { 477 end = mid - 1; 478 } 479 480 mid = (start + end) / 2; 481 } 482 483 return false; 484 } 485 486 487 } // namespace android 488
