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 int idx; 93 bool allprintable = true; 94 for (int i = 0; i < size; i++) { 95 const char *name = mNames.getEntry(i); 96 const char *value = mValues.getEntry(i); 97 if (!isPrintableAscii(value, strlen(value)) && ( 98 !strcmp(name, "artist") || 99 !strcmp(name, "albumartist") || 100 !strcmp(name, "composer") || 101 !strcmp(name, "genre") || 102 !strcmp(name, "album") || 103 !strcmp(name, "title"))) { 104 strlcat(buf, value, sizeof(buf)); 105 // separate tags by space so ICU's ngram detector can do its job 106 strlcat(buf, " ", sizeof(buf)); 107 allprintable = false; 108 } 109 } 110 111 const char *combinedenc = "UTF-8"; 112 if (allprintable) { 113 // since 'buf' is empty, ICU would return a UTF-8 matcher with low confidence, so 114 // no need to even call it 115 ALOGV("all tags are printable, assuming ascii (%zu)", strlen(buf)); 116 } else { 117 ucsdet_setText(csd, buf, strlen(buf), &status); 118 int32_t matches; 119 const UCharsetMatch** ucma = ucsdet_detectAll(csd, &matches, &status); 120 bool goodmatch = true; 121 int highest = 0; 122 const UCharsetMatch* bestCombinedMatch = getPreferred(buf, strlen(buf), 123 ucma, matches, &goodmatch, &highest); 124 125 ALOGV("goodmatch: %s, highest: %d", goodmatch ? "true" : "false", highest); 126 if (!goodmatch && (highest < 15 || strlen(buf) < 20)) { 127 ALOGV("not a good match, trying with more data"); 128 // This string might be too short for ICU to do anything useful with. 129 // (real world example: "Bjrk" in ISO-8859-1 might be detected as GB18030, because 130 // the ISO detector reports a confidence of 0, while the GB18030 detector reports 131 // a confidence of 10 with no invalid characters) 132 // Append artist, album and title if they were previously omitted because they 133 // were printable ascii. 134 bool added = false; 135 for (int i = 0; i < size; i++) { 136 const char *name = mNames.getEntry(i); 137 const char *value = mValues.getEntry(i); 138 if (isPrintableAscii(value, strlen(value)) && ( 139 !strcmp(name, "artist") || 140 !strcmp(name, "album") || 141 !strcmp(name, "title"))) { 142 strlcat(buf, value, sizeof(buf)); 143 strlcat(buf, " ", sizeof(buf)); 144 added = true; 145 } 146 } 147 if (added) { 148 ucsdet_setText(csd, buf, strlen(buf), &status); 149 ucma = ucsdet_detectAll(csd, &matches, &status); 150 bestCombinedMatch = getPreferred(buf, strlen(buf), 151 ucma, matches, &goodmatch, &highest); 152 if (!goodmatch && highest <= 15) { 153 ALOGV("still not a good match after adding printable tags"); 154 bestCombinedMatch = NULL; 155 } 156 } else { 157 ALOGV("no printable tags to add"); 158 } 159 } 160 161 if (bestCombinedMatch != NULL) { 162 combinedenc = ucsdet_getName(bestCombinedMatch, &status); 163 } else { 164 combinedenc = "ISO-8859-1"; 165 } 166 } 167 168 for (int i = 0; i < size; i++) { 169 const char *name = mNames.getEntry(i); 170 uint8_t* src = (uint8_t *)mValues.getEntry(i); 171 int len = strlen((char *)src); 172 uint8_t* dest = src; 173 174 ALOGV("@@@ checking %s", name); 175 const char *s = mValues.getEntry(i); 176 int32_t inputLength = strlen(s); 177 const char *enc; 178 179 if (!allprintable && (!strcmp(name, "artist") || 180 !strcmp(name, "albumartist") || 181 !strcmp(name, "composer") || 182 !strcmp(name, "genre") || 183 !strcmp(name, "album") || 184 !strcmp(name, "title"))) { 185 // use encoding determined from the combination of artist/album/title etc. 186 enc = combinedenc; 187 } else { 188 if (isPrintableAscii(s, inputLength)) { 189 enc = "UTF-8"; 190 ALOGV("@@@@ %s is ascii", mNames.getEntry(i)); 191 } else { 192 ucsdet_setText(csd, s, inputLength, &status); 193 ucm = ucsdet_detect(csd, &status); 194 if (!ucm) { 195 mValues.setEntry(i, "???"); 196 continue; 197 } 198 enc = ucsdet_getName(ucm, &status); 199 ALOGV("@@@@ recognized charset: %s for %s confidence %d", 200 enc, mNames.getEntry(i), ucsdet_getConfidence(ucm, &status)); 201 } 202 } 203 204 if (strcmp(enc,"UTF-8") != 0) { 205 // only convert if the source encoding isn't already UTF-8 206 ALOGV("@@@ using converter %s for %s", enc, mNames.getEntry(i)); 207 status = U_ZERO_ERROR; 208 UConverter *conv = ucnv_open(enc, &status); 209 if (U_FAILURE(status)) { 210 ALOGW("could not create UConverter for %s (%d), falling back to ISO-8859-1", 211 enc, status); 212 status = U_ZERO_ERROR; 213 conv = ucnv_open("ISO-8859-1", &status); 214 if (U_FAILURE(status)) { 215 ALOGW("could not create UConverter for ISO-8859-1 either"); 216 continue; 217 } 218 } 219 220 // convert from native encoding to UTF-8 221 const char* source = mValues.getEntry(i); 222 int targetLength = len * 3 + 1; 223 char* buffer = new char[targetLength]; 224 // don't normally check for NULL, but in this case targetLength may be large 225 if (!buffer) 226 break; 227 char* target = buffer; 228 229 ucnv_convertEx(mUtf8Conv, conv, &target, target + targetLength, 230 &source, source + strlen(source), 231 NULL, NULL, NULL, NULL, TRUE, TRUE, &status); 232 233 if (U_FAILURE(status)) { 234 ALOGE("ucnv_convertEx failed: %d", status); 235 mValues.setEntry(i, "???"); 236 } else { 237 // zero terminate 238 *target = 0; 239 // strip trailing spaces 240 while (--target > buffer && *target == ' ') { 241 *target = 0; 242 } 243 // skip leading spaces 244 char *start = buffer; 245 while (*start == ' ') { 246 start++; 247 } 248 mValues.setEntry(i, start); 249 } 250 251 delete[] buffer; 252 253 ucnv_close(conv); 254 } 255 } 256 257 for (int i = size - 1; i >= 0; --i) { 258 if (strlen(mValues.getEntry(i)) == 0) { 259 ALOGV("erasing %s because entry is empty", mNames.getEntry(i)); 260 mNames.erase(i); 261 mValues.erase(i); 262 } 263 } 264 265 ucsdet_close(csd); 266 } 267 } 268 269 /* 270 * When ICU detects multiple encoding matches, apply additional heuristics to determine 271 * which one is the best match, since ICU can't always be trusted to make the right choice. 272 * 273 * What this method does is: 274 * - decode the input using each of the matches found 275 * - recalculate the starting confidence level for multibyte encodings using a different 276 * algorithm and larger frequent character lists than ICU 277 * - devalue encoding where the conversion contains unlikely characters (symbols, reserved, etc) 278 * - pick the highest match 279 * - signal to the caller whether this match is considered good: confidence > 15, and confidence 280 * delta with the next runner up > 15 281 */ 282 const UCharsetMatch *CharacterEncodingDetector::getPreferred( 283 const char *input, size_t len, 284 const UCharsetMatch** ucma, size_t nummatches, 285 bool *goodmatch, int *highestmatch) { 286 287 *goodmatch = false; 288 Vector<const UCharsetMatch*> matches; 289 UErrorCode status = U_ZERO_ERROR; 290 291 ALOGV("%zu matches", nummatches); 292 for (size_t i = 0; i < nummatches; i++) { 293 const char *encname = ucsdet_getName(ucma[i], &status); 294 int confidence = ucsdet_getConfidence(ucma[i], &status); 295 ALOGV("%zu: %s %d", i, encname, confidence); 296 matches.push_back(ucma[i]); 297 } 298 299 size_t num = matches.size(); 300 if (num == 0) { 301 return NULL; 302 } 303 if (num == 1) { 304 int confidence = ucsdet_getConfidence(matches[0], &status); 305 if (confidence > 15) { 306 *goodmatch = true; 307 } 308 return matches[0]; 309 } 310 311 ALOGV("considering %zu matches", num); 312 313 // keep track of how many "special" characters result when converting the input using each 314 // encoding 315 Vector<int> newconfidence; 316 for (size_t i = 0; i < num; i++) { 317 const uint16_t *freqdata = NULL; 318 float freqcoverage = 0; 319 status = U_ZERO_ERROR; 320 const char *encname = ucsdet_getName(matches[i], &status); 321 int confidence = ucsdet_getConfidence(matches[i], &status); 322 if (!strcmp("GB18030", encname)) { 323 freqdata = frequent_zhCN; 324 freqcoverage = frequent_zhCN_coverage; 325 } else if (!strcmp("Big5", encname)) { 326 freqdata = frequent_zhTW; 327 freqcoverage = frequent_zhTW_coverage; 328 } else if (!strcmp("EUC-KR", encname)) { 329 freqdata = frequent_ko; 330 freqcoverage = frequent_ko_coverage; 331 } else if (!strcmp("EUC-JP", encname)) { 332 freqdata = frequent_ja; 333 freqcoverage = frequent_ja_coverage; 334 } else if (!strcmp("Shift_JIS", encname)) { 335 freqdata = frequent_ja; 336 freqcoverage = frequent_ja_coverage; 337 } 338 339 ALOGV("%zu: %s %d", i, encname, confidence); 340 status = U_ZERO_ERROR; 341 UConverter *conv = ucnv_open(encname, &status); 342 int demerit = 0; 343 if (U_FAILURE(status)) { 344 ALOGV("failed to open %s: %d", encname, status); 345 confidence = 0; 346 demerit += 1000; 347 } 348 const char *source = input; 349 const char *sourceLimit = input + len; 350 status = U_ZERO_ERROR; 351 int frequentchars = 0; 352 int totalchars = 0; 353 while (true) { 354 // demerit the current encoding for each "special" character found after conversion. 355 // The amount of demerit is somewhat arbitrarily chosen. 356 int inchar; 357 if (source != sourceLimit) { 358 inchar = (source[0] << 8) + source[1]; 359 } 360 UChar32 c = ucnv_getNextUChar(conv, &source, sourceLimit, &status); 361 if (!U_SUCCESS(status)) { 362 break; 363 } 364 if (c < 0x20 || (c >= 0x7f && c <= 0x009f)) { 365 ALOGV("control character %x", c); 366 demerit += 100; 367 } else if ((c == 0xa0) // no-break space 368 || (c >= 0xa2 && c <= 0xbe) // symbols, superscripts 369 || (c == 0xd7) || (c == 0xf7) // multiplication and division signs 370 || (c >= 0x2000 && c <= 0x209f)) { // punctuation, superscripts 371 ALOGV("unlikely character %x", c); 372 demerit += 10; 373 } else if (c >= 0xe000 && c <= 0xf8ff) { 374 ALOGV("private use character %x", c); 375 demerit += 30; 376 } else if (c >= 0x2190 && c <= 0x2bff) { 377 // this range comprises various symbol ranges that are unlikely to appear in 378 // music file metadata. 379 ALOGV("symbol %x", c); 380 demerit += 10; 381 } else if (c == 0xfffd) { 382 ALOGV("replacement character"); 383 demerit += 50; 384 } else if (c >= 0xfff0 && c <= 0xfffc) { 385 ALOGV("unicode special %x", c); 386 demerit += 50; 387 } else if (freqdata != NULL) { 388 totalchars++; 389 if (isFrequent(freqdata, c)) { 390 frequentchars++; 391 } 392 } 393 } 394 if (freqdata != NULL && totalchars != 0) { 395 int myconfidence = 10 + float((100 * frequentchars) / totalchars) / freqcoverage; 396 ALOGV("ICU confidence: %d, my confidence: %d (%d %d)", confidence, myconfidence, 397 totalchars, frequentchars); 398 if (myconfidence > 100) myconfidence = 100; 399 if (myconfidence < 0) myconfidence = 0; 400 confidence = myconfidence; 401 } 402 ALOGV("%d-%d=%d", confidence, demerit, confidence - demerit); 403 newconfidence.push_back(confidence - demerit); 404 ucnv_close(conv); 405 if (i == 0 && (confidence - demerit) == 100) { 406 // no need to check any further, we'll end up using this match anyway 407 break; 408 } 409 } 410 411 // find match with highest confidence after adjusting for unlikely characters 412 int highest = newconfidence[0]; 413 size_t highestidx = 0; 414 int runnerup = -10000; 415 int runnerupidx = -10000; 416 num = newconfidence.size(); 417 for (size_t i = 1; i < num; i++) { 418 if (newconfidence[i] > highest) { 419 runnerup = highest; 420 runnerupidx = highestidx; 421 highest = newconfidence[i]; 422 highestidx = i; 423 } else if (newconfidence[i] > runnerup){ 424 runnerup = newconfidence[i]; 425 runnerupidx = i; 426 } 427 } 428 status = U_ZERO_ERROR; 429 ALOGV("selecting: '%s' w/ %d confidence", 430 ucsdet_getName(matches[highestidx], &status), highest); 431 if (runnerupidx < 0) { 432 ALOGV("no runner up"); 433 if (highest > 15) { 434 *goodmatch = true; 435 } 436 } else { 437 ALOGV("runner up: '%s' w/ %d confidence", 438 ucsdet_getName(matches[runnerupidx], &status), runnerup); 439 if (runnerup < 0) { 440 runnerup = 0; 441 } 442 if ((highest - runnerup) > 15) { 443 *goodmatch = true; 444 } 445 } 446 *highestmatch = highest; 447 return matches[highestidx]; 448 } 449 450 451 bool CharacterEncodingDetector::isFrequent(const uint16_t *values, uint32_t c) { 452 453 int start = 0; 454 int end = 511; // All the tables have 512 entries 455 int mid = (start+end)/2; 456 457 while(start <= end) { 458 if(c == values[mid]) { 459 return true; 460 } else if (c > values[mid]) { 461 start = mid + 1; 462 } else { 463 end = mid - 1; 464 } 465 466 mid = (start + end) / 2; 467 } 468 469 return false; 470 } 471 472 473 } // namespace android 474
