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 #include <cutils/properties.h>
32
33 namespace android {
34
CharacterEncodingDetector()35 CharacterEncodingDetector::CharacterEncodingDetector() {
36
37 UErrorCode status = U_ZERO_ERROR;
38 mUtf8Conv = ucnv_open("UTF-8", &status);
39 if (U_FAILURE(status)) {
40 ALOGE("could not create UConverter for UTF-8");
41 mUtf8Conv = NULL;
42 }
43
44 // Read system locale setting from system property and map to ICU encoding names.
45 mLocaleEnc = NULL;
46 char locale_value[PROPERTY_VALUE_MAX] = "";
47 if (property_get("persist.sys.locale", locale_value, NULL) > 0) {
48 const size_t len = strnlen(locale_value, sizeof(locale_value));
49
50 if (len == 3 && !strncmp(locale_value, "und", 3)) {
51 // Undetermined
52 } else if (!strncmp(locale_value, "th", 2)) { // Thai
53 mLocaleEnc = "windows-874-2000";
54 }
55 if (mLocaleEnc != NULL) {
56 ALOGV("System locale encoding = %s", mLocaleEnc);
57 } else {
58 ALOGV("Didn't recognize system locale setting, defaulting to en_US");
59 }
60 } else {
61 ALOGV("Couldn't read system locale setting, assuming en_US");
62 }
63 }
64
~CharacterEncodingDetector()65 CharacterEncodingDetector::~CharacterEncodingDetector() {
66 ucnv_close(mUtf8Conv);
67 }
68
addTag(const char * name,const char * value)69 void CharacterEncodingDetector::addTag(const char *name, const char *value) {
70 mNames.push_back(name);
71 mValues.push_back(value);
72 }
73
size()74 size_t CharacterEncodingDetector::size() {
75 return mNames.size();
76 }
77
getTag(int index,const char ** name,const char ** value)78 status_t CharacterEncodingDetector::getTag(int index, const char **name, const char**value) {
79 if (index >= mNames.size()) {
80 return BAD_VALUE;
81 }
82
83 *name = mNames.getEntry(index);
84 *value = mValues.getEntry(index);
85 return OK;
86 }
87
isPrintableAscii(const char * value,size_t len)88 static bool isPrintableAscii(const char *value, size_t len) {
89 for (size_t i = 0; i < len; i++) {
90 if ((value[i] & 0x80) || value[i] < 0x20 || value[i] == 0x7f) {
91 return false;
92 }
93 }
94 return true;
95 }
96
detectAndConvert()97 void CharacterEncodingDetector::detectAndConvert() {
98
99 int size = mNames.size();
100 ALOGV("%d tags before conversion", size);
101 for (int i = 0; i < size; i++) {
102 ALOGV("%s: %s", mNames.getEntry(i), mValues.getEntry(i));
103 }
104
105 if (size && mUtf8Conv) {
106
107 UErrorCode status = U_ZERO_ERROR;
108 UCharsetDetector *csd = ucsdet_open(&status);
109 const UCharsetMatch *ucm;
110 bool goodmatch = true;
111 int highest = 0;
112
113 // try combined detection of artist/album/title etc.
114 char buf[1024];
115 buf[0] = 0;
116 bool allprintable = true;
117 for (int i = 0; i < size; i++) {
118 const char *name = mNames.getEntry(i);
119 const char *value = mValues.getEntry(i);
120 if (!isPrintableAscii(value, strlen(value)) && (
121 !strcmp(name, "artist") ||
122 !strcmp(name, "albumartist") ||
123 !strcmp(name, "composer") ||
124 !strcmp(name, "genre") ||
125 !strcmp(name, "album") ||
126 !strcmp(name, "title"))) {
127 strlcat(buf, value, sizeof(buf));
128 // separate tags by space so ICU's ngram detector can do its job
129 strlcat(buf, " ", sizeof(buf));
130 allprintable = false;
131 }
132 }
133
134 const char *combinedenc = "UTF-8";
135 if (allprintable) {
136 // since 'buf' is empty, ICU would return a UTF-8 matcher with low confidence, so
137 // no need to even call it
138 ALOGV("all tags are printable, assuming ascii (%zu)", strlen(buf));
139 } else {
140 ucsdet_setText(csd, buf, strlen(buf), &status);
141 int32_t matches;
142 const UCharsetMatch** ucma = ucsdet_detectAll(csd, &matches, &status);
143 const UCharsetMatch* bestCombinedMatch = getPreferred(buf, strlen(buf),
144 ucma, matches, &goodmatch, &highest);
145
146 ALOGV("goodmatch: %s, highest: %d", goodmatch ? "true" : "false", highest);
147 if (!goodmatch && (highest < 15 || strlen(buf) < 20)) {
148 ALOGV("not a good match, trying with more data");
149 // This string might be too short for ICU to do anything useful with.
150 // (real world example: "Björk" in ISO-8859-1 might be detected as GB18030, because
151 // the ISO detector reports a confidence of 0, while the GB18030 detector reports
152 // a confidence of 10 with no invalid characters)
153 // Append artist, album and title if they were previously omitted because they
154 // were printable ascii.
155 bool added = false;
156 for (int i = 0; i < size; i++) {
157 const char *name = mNames.getEntry(i);
158 const char *value = mValues.getEntry(i);
159 if (isPrintableAscii(value, strlen(value)) && (
160 !strcmp(name, "artist") ||
161 !strcmp(name, "album") ||
162 !strcmp(name, "title"))) {
163 strlcat(buf, value, sizeof(buf));
164 strlcat(buf, " ", sizeof(buf));
165 added = true;
166 }
167 }
168 if (added) {
169 ucsdet_setText(csd, buf, strlen(buf), &status);
170 ucma = ucsdet_detectAll(csd, &matches, &status);
171 bestCombinedMatch = getPreferred(buf, strlen(buf),
172 ucma, matches, &goodmatch, &highest);
173 if (!goodmatch && highest <= 15) {
174 ALOGV("still not a good match after adding printable tags");
175 bestCombinedMatch = NULL;
176 }
177 } else {
178 ALOGV("no printable tags to add");
179 }
180 }
181
182 if (mLocaleEnc != NULL && !goodmatch && highest < 50) {
183 combinedenc = mLocaleEnc;
184 ALOGV("confidence is low but we have recognized predefined encoding, "
185 "so try this (%s) instead", mLocaleEnc);
186 } else if (bestCombinedMatch != NULL) {
187 combinedenc = ucsdet_getName(bestCombinedMatch, &status);
188 } else {
189 combinedenc = "ISO-8859-1";
190 }
191 }
192
193 for (int i = 0; i < size; i++) {
194 const char *name = mNames.getEntry(i);
195 uint8_t* src = (uint8_t *)mValues.getEntry(i);
196 int len = strlen((char *)src);
197
198 ALOGV("@@@ checking %s", name);
199 const char *s = mValues.getEntry(i);
200 int32_t inputLength = strlen(s);
201 // Use encoding determined from the combination of artist/album/title etc.
202 // as default if there is no better match found.
203 const char *enc = combinedenc;
204
205 if (!allprintable && (!strcmp(name, "artist") ||
206 !strcmp(name, "albumartist") ||
207 !strcmp(name, "composer") ||
208 !strcmp(name, "genre") ||
209 !strcmp(name, "album") ||
210 !strcmp(name, "title"))) {
211 if (!goodmatch && highest < 0) {
212 // Give it one more chance if there is no good match.
213 ALOGV("Trying to detect %s separately", name);
214 int32_t matches;
215 bool goodmatchSingle = true;
216 int highestSingle = 0;
217 ucsdet_setText(csd, s, inputLength, &status);
218 const UCharsetMatch** ucma = ucsdet_detectAll(csd, &matches, &status);
219 const UCharsetMatch* bestSingleMatch = getPreferred(s, inputLength,
220 ucma, matches, &goodmatchSingle, &highestSingle);
221 // getPreferred could return a null. Check for null before calling
222 // ucsdet_getName.
223 if (bestSingleMatch != NULL) {
224 if (goodmatchSingle || highestSingle > highest)
225 enc = ucsdet_getName(bestSingleMatch, &status);
226 }
227 }
228 } else {
229 if (isPrintableAscii(s, inputLength)) {
230 enc = "UTF-8";
231 ALOGV("@@@@ %s is ascii", mNames.getEntry(i));
232 } else {
233 ucsdet_setText(csd, s, inputLength, &status);
234 ucm = ucsdet_detect(csd, &status);
235 if (!ucm) {
236 mValues.setEntry(i, "???");
237 continue;
238 }
239 enc = ucsdet_getName(ucm, &status);
240 ALOGV("@@@@ recognized charset: %s for %s confidence %d",
241 enc, mNames.getEntry(i), ucsdet_getConfidence(ucm, &status));
242 }
243 }
244
245 if (strcmp(enc,"UTF-8") != 0) {
246 // only convert if the source encoding isn't already UTF-8
247 ALOGV("@@@ using converter %s for %s", enc, mNames.getEntry(i));
248 status = U_ZERO_ERROR;
249 UConverter *conv = ucnv_open(enc, &status);
250 if (U_FAILURE(status)) {
251 ALOGW("could not create UConverter for %s (%d), falling back to ISO-8859-1",
252 enc, status);
253 status = U_ZERO_ERROR;
254 conv = ucnv_open("ISO-8859-1", &status);
255 if (U_FAILURE(status)) {
256 ALOGW("could not create UConverter for ISO-8859-1 either");
257 continue;
258 }
259 }
260
261 // convert from native encoding to UTF-8
262 const char* source = mValues.getEntry(i);
263 int targetLength = len * 3 + 1;
264 char* buffer = new char[targetLength];
265 // don't normally check for NULL, but in this case targetLength may be large
266 if (!buffer)
267 break;
268 char* target = buffer;
269
270 ucnv_convertEx(mUtf8Conv, conv, &target, target + targetLength,
271 &source, source + strlen(source),
272 NULL, NULL, NULL, NULL, true, true, &status);
273
274 if (U_FAILURE(status)) {
275 ALOGE("ucnv_convertEx failed: %d", status);
276 mValues.setEntry(i, "???");
277 } else {
278 // zero terminate
279 *target = 0;
280 // strip trailing spaces
281 while (--target > buffer && *target == ' ') {
282 *target = 0;
283 }
284 // skip leading spaces
285 char *start = buffer;
286 while (*start == ' ') {
287 start++;
288 }
289 mValues.setEntry(i, start);
290 }
291
292 delete[] buffer;
293
294 ucnv_close(conv);
295 }
296 }
297
298 for (int i = size - 1; i >= 0; --i) {
299 if (strlen(mValues.getEntry(i)) == 0) {
300 ALOGV("erasing %s because entry is empty", mNames.getEntry(i));
301 mNames.erase(i);
302 mValues.erase(i);
303 }
304 }
305
306 ucsdet_close(csd);
307 }
308 }
309
310 /*
311 * When ICU detects multiple encoding matches, apply additional heuristics to determine
312 * which one is the best match, since ICU can't always be trusted to make the right choice.
313 *
314 * What this method does is:
315 * - decode the input using each of the matches found
316 * - recalculate the starting confidence level for multibyte encodings using a different
317 * algorithm and larger frequent character lists than ICU
318 * - devalue encoding where the conversion contains unlikely characters (symbols, reserved, etc)
319 * - pick the highest match
320 * - signal to the caller whether this match is considered good: confidence > 15, and confidence
321 * delta with the next runner up > 15
322 */
getPreferred(const char * input,size_t len,const UCharsetMatch ** ucma,size_t nummatches,bool * goodmatch,int * highestmatch)323 const UCharsetMatch *CharacterEncodingDetector::getPreferred(
324 const char *input, size_t len,
325 const UCharsetMatch** ucma, size_t nummatches,
326 bool *goodmatch, int *highestmatch) {
327
328 *goodmatch = false;
329 Vector<const UCharsetMatch*> matches;
330 UErrorCode status = U_ZERO_ERROR;
331
332 ALOGV("%zu matches", nummatches);
333 for (size_t i = 0; i < nummatches; i++) {
334 const char *encname = ucsdet_getName(ucma[i], &status);
335 int confidence = ucsdet_getConfidence(ucma[i], &status);
336 ALOGV("%zu: %s %d", i, encname, confidence);
337 matches.push_back(ucma[i]);
338 }
339
340 size_t num = matches.size();
341 if (num == 0) {
342 return NULL;
343 }
344 if (num == 1) {
345 int confidence = ucsdet_getConfidence(matches[0], &status);
346 if (confidence > 15) {
347 *goodmatch = true;
348 }
349 return matches[0];
350 }
351
352 ALOGV("considering %zu matches", num);
353
354 // keep track of how many "special" characters result when converting the input using each
355 // encoding
356 Vector<int> newconfidence;
357 for (size_t i = 0; i < num; i++) {
358 const uint16_t *freqdata = NULL;
359 float freqcoverage = 0;
360 status = U_ZERO_ERROR;
361 const char *encname = ucsdet_getName(matches[i], &status);
362 int confidence = ucsdet_getConfidence(matches[i], &status);
363 if (!strcmp("GB18030", encname)) {
364 freqdata = frequent_zhCN;
365 freqcoverage = frequent_zhCN_coverage;
366 } else if (!strcmp("Big5", encname)) {
367 freqdata = frequent_zhTW;
368 freqcoverage = frequent_zhTW_coverage;
369 } else if (!strcmp("EUC-KR", encname)) {
370 freqdata = frequent_ko;
371 freqcoverage = frequent_ko_coverage;
372 } else if (!strcmp("EUC-JP", encname)) {
373 freqdata = frequent_ja;
374 freqcoverage = frequent_ja_coverage;
375 } else if (!strcmp("Shift_JIS", encname)) {
376 freqdata = frequent_ja;
377 freqcoverage = frequent_ja_coverage;
378 }
379
380 ALOGV("%zu: %s %d", i, encname, confidence);
381 status = U_ZERO_ERROR;
382 UConverter *conv = ucnv_open(encname, &status);
383 int demerit = 0;
384 if (U_FAILURE(status)) {
385 ALOGV("failed to open %s: %d", encname, status);
386 confidence = 0;
387 demerit += 1000;
388 }
389 const char *source = input;
390 const char *sourceLimit = input + len;
391 status = U_ZERO_ERROR;
392 int frequentchars = 0;
393 int totalchars = 0;
394 while (true) {
395 // demerit the current encoding for each "special" character found after conversion.
396 // The amount of demerit is somewhat arbitrarily chosen.
397 UChar32 c = ucnv_getNextUChar(conv, &source, sourceLimit, &status);
398 if (!U_SUCCESS(status)) {
399 break;
400 }
401 if (c < 0x20 || (c >= 0x7f && c <= 0x009f)) {
402 ALOGV("control character %x", c);
403 demerit += 100;
404 } else if ((c == 0xa0) // no-break space
405 || (c >= 0xa2 && c <= 0xbe) // symbols, superscripts
406 || (c == 0xd7) || (c == 0xf7) // multiplication and division signs
407 || (c >= 0x2000 && c <= 0x209f)) { // punctuation, superscripts
408 ALOGV("unlikely character %x", c);
409 demerit += 10;
410 } else if (c >= 0xe000 && c <= 0xf8ff) {
411 ALOGV("private use character %x", c);
412 demerit += 30;
413 } else if (c >= 0x2190 && c <= 0x2bff) {
414 // this range comprises various symbol ranges that are unlikely to appear in
415 // music file metadata.
416 ALOGV("symbol %x", c);
417 demerit += 10;
418 } else if (c == 0xfffd) {
419 ALOGV("replacement character");
420 demerit += 50;
421 } else if (c >= 0xfff0 && c <= 0xfffc) {
422 ALOGV("unicode special %x", c);
423 demerit += 50;
424 } else if (freqdata != NULL) {
425 totalchars++;
426 if (isFrequent(freqdata, c)) {
427 frequentchars++;
428 }
429 }
430 }
431 if (freqdata != NULL && totalchars != 0) {
432 int myconfidence = 10 + float((100 * frequentchars) / totalchars) / freqcoverage;
433 ALOGV("ICU confidence: %d, my confidence: %d (%d %d)", confidence, myconfidence,
434 totalchars, frequentchars);
435 if (myconfidence > 100) myconfidence = 100;
436 if (myconfidence < 0) myconfidence = 0;
437 confidence = myconfidence;
438 }
439 ALOGV("%d-%d=%d", confidence, demerit, confidence - demerit);
440 newconfidence.push_back(confidence - demerit);
441 ucnv_close(conv);
442 if (i == 0 && (confidence - demerit) == 100) {
443 // no need to check any further, we'll end up using this match anyway
444 break;
445 }
446 }
447
448 // find match with highest confidence after adjusting for unlikely characters
449 int highest = newconfidence[0];
450 size_t highestidx = 0;
451 int runnerup = -10000;
452 int runnerupidx = -10000;
453 num = newconfidence.size();
454 for (size_t i = 1; i < num; i++) {
455 if (newconfidence[i] > highest) {
456 runnerup = highest;
457 runnerupidx = highestidx;
458 highest = newconfidence[i];
459 highestidx = i;
460 } else if (newconfidence[i] > runnerup){
461 runnerup = newconfidence[i];
462 runnerupidx = i;
463 }
464 }
465 status = U_ZERO_ERROR;
466 ALOGV("selecting: '%s' w/ %d confidence",
467 ucsdet_getName(matches[highestidx], &status), highest);
468 if (runnerupidx < 0) {
469 ALOGV("no runner up");
470 if (highest > 15) {
471 *goodmatch = true;
472 }
473 } else {
474 ALOGV("runner up: '%s' w/ %d confidence",
475 ucsdet_getName(matches[runnerupidx], &status), runnerup);
476 if (runnerup < 0) {
477 runnerup = 0;
478 }
479 if ((highest - runnerup) > 15) {
480 *goodmatch = true;
481 }
482 }
483 *highestmatch = highest;
484 return matches[highestidx];
485 }
486
487
isFrequent(const uint16_t * values,uint32_t c)488 bool CharacterEncodingDetector::isFrequent(const uint16_t *values, uint32_t c) {
489
490 int start = 0;
491 int end = 511; // All the tables have 512 entries
492 int mid = (start+end)/2;
493
494 while(start <= end) {
495 if(c == values[mid]) {
496 return true;
497 } else if (c > values[mid]) {
498 start = mid + 1;
499 } else {
500 end = mid - 1;
501 }
502
503 mid = (start + end) / 2;
504 }
505
506 return false;
507 }
508
509
510 } // namespace android
511