/* * Copyright (C) 2013 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ //#define LOG_NDEBUG 0 #define LOG_TAG "CharacterEncodingDector" #include #include #include "CharacterEncodingDetectorTables.h" #include #include #include #include #include #include namespace android { CharacterEncodingDetector::CharacterEncodingDetector() { UErrorCode status = U_ZERO_ERROR; mUtf8Conv = ucnv_open("UTF-8", &status); if (U_FAILURE(status)) { ALOGE("could not create UConverter for UTF-8"); mUtf8Conv = NULL; } // Read system locale setting from system property and map to ICU encoding names. mLocaleEnc = NULL; char locale_value[PROPERTY_VALUE_MAX] = ""; if (property_get("persist.sys.locale", locale_value, NULL) > 0) { const size_t len = strnlen(locale_value, sizeof(locale_value)); if (len == 3 && !strncmp(locale_value, "und", 3)) { // Undetermined } else if (!strncmp(locale_value, "th", 2)) { // Thai mLocaleEnc = "windows-874-2000"; } if (mLocaleEnc != NULL) { ALOGV("System locale encoding = %s", mLocaleEnc); } else { ALOGV("Didn't recognize system locale setting, defaulting to en_US"); } } else { ALOGV("Couldn't read system locale setting, assuming en_US"); } } CharacterEncodingDetector::~CharacterEncodingDetector() { ucnv_close(mUtf8Conv); } void CharacterEncodingDetector::addTag(const char *name, const char *value) { mNames.push_back(name); mValues.push_back(value); } size_t CharacterEncodingDetector::size() { return mNames.size(); } status_t CharacterEncodingDetector::getTag(int index, const char **name, const char**value) { if (index >= mNames.size()) { return BAD_VALUE; } *name = mNames.getEntry(index); *value = mValues.getEntry(index); return OK; } static bool isPrintableAscii(const char *value, size_t len) { for (size_t i = 0; i < len; i++) { if ((value[i] & 0x80) || value[i] < 0x20 || value[i] == 0x7f) { return false; } } return true; } void CharacterEncodingDetector::detectAndConvert() { int size = mNames.size(); ALOGV("%d tags before conversion", size); for (int i = 0; i < size; i++) { ALOGV("%s: %s", mNames.getEntry(i), mValues.getEntry(i)); } if (size && mUtf8Conv) { UErrorCode status = U_ZERO_ERROR; UCharsetDetector *csd = ucsdet_open(&status); const UCharsetMatch *ucm; bool goodmatch = true; int highest = 0; // try combined detection of artist/album/title etc. char buf[1024]; buf[0] = 0; bool allprintable = true; for (int i = 0; i < size; i++) { const char *name = mNames.getEntry(i); const char *value = mValues.getEntry(i); if (!isPrintableAscii(value, strlen(value)) && ( !strcmp(name, "artist") || !strcmp(name, "albumartist") || !strcmp(name, "composer") || !strcmp(name, "genre") || !strcmp(name, "album") || !strcmp(name, "title"))) { strlcat(buf, value, sizeof(buf)); // separate tags by space so ICU's ngram detector can do its job strlcat(buf, " ", sizeof(buf)); allprintable = false; } } const char *combinedenc = "UTF-8"; if (allprintable) { // since 'buf' is empty, ICU would return a UTF-8 matcher with low confidence, so // no need to even call it ALOGV("all tags are printable, assuming ascii (%zu)", strlen(buf)); } else { ucsdet_setText(csd, buf, strlen(buf), &status); int32_t matches; const UCharsetMatch** ucma = ucsdet_detectAll(csd, &matches, &status); const UCharsetMatch* bestCombinedMatch = getPreferred(buf, strlen(buf), ucma, matches, &goodmatch, &highest); ALOGV("goodmatch: %s, highest: %d", goodmatch ? "true" : "false", highest); if (!goodmatch && (highest < 15 || strlen(buf) < 20)) { ALOGV("not a good match, trying with more data"); // This string might be too short for ICU to do anything useful with. // (real world example: "Björk" in ISO-8859-1 might be detected as GB18030, because // the ISO detector reports a confidence of 0, while the GB18030 detector reports // a confidence of 10 with no invalid characters) // Append artist, album and title if they were previously omitted because they // were printable ascii. bool added = false; for (int i = 0; i < size; i++) { const char *name = mNames.getEntry(i); const char *value = mValues.getEntry(i); if (isPrintableAscii(value, strlen(value)) && ( !strcmp(name, "artist") || !strcmp(name, "album") || !strcmp(name, "title"))) { strlcat(buf, value, sizeof(buf)); strlcat(buf, " ", sizeof(buf)); added = true; } } if (added) { ucsdet_setText(csd, buf, strlen(buf), &status); ucma = ucsdet_detectAll(csd, &matches, &status); bestCombinedMatch = getPreferred(buf, strlen(buf), ucma, matches, &goodmatch, &highest); if (!goodmatch && highest <= 15) { ALOGV("still not a good match after adding printable tags"); bestCombinedMatch = NULL; } } else { ALOGV("no printable tags to add"); } } if (mLocaleEnc != NULL && !goodmatch && highest < 50) { combinedenc = mLocaleEnc; ALOGV("confidence is low but we have recognized predefined encoding, " "so try this (%s) instead", mLocaleEnc); } else if (bestCombinedMatch != NULL) { combinedenc = ucsdet_getName(bestCombinedMatch, &status); } else { combinedenc = "ISO-8859-1"; } } for (int i = 0; i < size; i++) { const char *name = mNames.getEntry(i); uint8_t* src = (uint8_t *)mValues.getEntry(i); int len = strlen((char *)src); ALOGV("@@@ checking %s", name); const char *s = mValues.getEntry(i); int32_t inputLength = strlen(s); const char *enc; if (!allprintable && (!strcmp(name, "artist") || !strcmp(name, "albumartist") || !strcmp(name, "composer") || !strcmp(name, "genre") || !strcmp(name, "album") || !strcmp(name, "title"))) { if (!goodmatch && highest < 0) { // Give it one more chance if there is no good match. ALOGV("Trying to detect %s separately", name); int32_t matches; bool goodmatchSingle = true; int highestSingle = 0; ucsdet_setText(csd, s, inputLength, &status); const UCharsetMatch** ucma = ucsdet_detectAll(csd, &matches, &status); const UCharsetMatch* bestSingleMatch = getPreferred(s, inputLength, ucma, matches, &goodmatchSingle, &highestSingle); if (goodmatchSingle || highestSingle > highest) enc = ucsdet_getName(bestSingleMatch, &status); else enc = combinedenc; } else { // use encoding determined from the combination of artist/album/title etc. enc = combinedenc; } } else { if (isPrintableAscii(s, inputLength)) { enc = "UTF-8"; ALOGV("@@@@ %s is ascii", mNames.getEntry(i)); } else { ucsdet_setText(csd, s, inputLength, &status); ucm = ucsdet_detect(csd, &status); if (!ucm) { mValues.setEntry(i, "???"); continue; } enc = ucsdet_getName(ucm, &status); ALOGV("@@@@ recognized charset: %s for %s confidence %d", enc, mNames.getEntry(i), ucsdet_getConfidence(ucm, &status)); } } if (strcmp(enc,"UTF-8") != 0) { // only convert if the source encoding isn't already UTF-8 ALOGV("@@@ using converter %s for %s", enc, mNames.getEntry(i)); status = U_ZERO_ERROR; UConverter *conv = ucnv_open(enc, &status); if (U_FAILURE(status)) { ALOGW("could not create UConverter for %s (%d), falling back to ISO-8859-1", enc, status); status = U_ZERO_ERROR; conv = ucnv_open("ISO-8859-1", &status); if (U_FAILURE(status)) { ALOGW("could not create UConverter for ISO-8859-1 either"); continue; } } // convert from native encoding to UTF-8 const char* source = mValues.getEntry(i); int targetLength = len * 3 + 1; char* buffer = new char[targetLength]; // don't normally check for NULL, but in this case targetLength may be large if (!buffer) break; char* target = buffer; ucnv_convertEx(mUtf8Conv, conv, &target, target + targetLength, &source, source + strlen(source), NULL, NULL, NULL, NULL, true, true, &status); if (U_FAILURE(status)) { ALOGE("ucnv_convertEx failed: %d", status); mValues.setEntry(i, "???"); } else { // zero terminate *target = 0; // strip trailing spaces while (--target > buffer && *target == ' ') { *target = 0; } // skip leading spaces char *start = buffer; while (*start == ' ') { start++; } mValues.setEntry(i, start); } delete[] buffer; ucnv_close(conv); } } for (int i = size - 1; i >= 0; --i) { if (strlen(mValues.getEntry(i)) == 0) { ALOGV("erasing %s because entry is empty", mNames.getEntry(i)); mNames.erase(i); mValues.erase(i); } } ucsdet_close(csd); } } /* * When ICU detects multiple encoding matches, apply additional heuristics to determine * which one is the best match, since ICU can't always be trusted to make the right choice. * * What this method does is: * - decode the input using each of the matches found * - recalculate the starting confidence level for multibyte encodings using a different * algorithm and larger frequent character lists than ICU * - devalue encoding where the conversion contains unlikely characters (symbols, reserved, etc) * - pick the highest match * - signal to the caller whether this match is considered good: confidence > 15, and confidence * delta with the next runner up > 15 */ const UCharsetMatch *CharacterEncodingDetector::getPreferred( const char *input, size_t len, const UCharsetMatch** ucma, size_t nummatches, bool *goodmatch, int *highestmatch) { *goodmatch = false; Vector matches; UErrorCode status = U_ZERO_ERROR; ALOGV("%zu matches", nummatches); for (size_t i = 0; i < nummatches; i++) { const char *encname = ucsdet_getName(ucma[i], &status); int confidence = ucsdet_getConfidence(ucma[i], &status); ALOGV("%zu: %s %d", i, encname, confidence); matches.push_back(ucma[i]); } size_t num = matches.size(); if (num == 0) { return NULL; } if (num == 1) { int confidence = ucsdet_getConfidence(matches[0], &status); if (confidence > 15) { *goodmatch = true; } return matches[0]; } ALOGV("considering %zu matches", num); // keep track of how many "special" characters result when converting the input using each // encoding Vector newconfidence; for (size_t i = 0; i < num; i++) { const uint16_t *freqdata = NULL; float freqcoverage = 0; status = U_ZERO_ERROR; const char *encname = ucsdet_getName(matches[i], &status); int confidence = ucsdet_getConfidence(matches[i], &status); if (!strcmp("GB18030", encname)) { freqdata = frequent_zhCN; freqcoverage = frequent_zhCN_coverage; } else if (!strcmp("Big5", encname)) { freqdata = frequent_zhTW; freqcoverage = frequent_zhTW_coverage; } else if (!strcmp("EUC-KR", encname)) { freqdata = frequent_ko; freqcoverage = frequent_ko_coverage; } else if (!strcmp("EUC-JP", encname)) { freqdata = frequent_ja; freqcoverage = frequent_ja_coverage; } else if (!strcmp("Shift_JIS", encname)) { freqdata = frequent_ja; freqcoverage = frequent_ja_coverage; } ALOGV("%zu: %s %d", i, encname, confidence); status = U_ZERO_ERROR; UConverter *conv = ucnv_open(encname, &status); int demerit = 0; if (U_FAILURE(status)) { ALOGV("failed to open %s: %d", encname, status); confidence = 0; demerit += 1000; } const char *source = input; const char *sourceLimit = input + len; status = U_ZERO_ERROR; int frequentchars = 0; int totalchars = 0; while (true) { // demerit the current encoding for each "special" character found after conversion. // The amount of demerit is somewhat arbitrarily chosen. int inchar; if (source != sourceLimit) { inchar = (source[0] << 8) + source[1]; } UChar32 c = ucnv_getNextUChar(conv, &source, sourceLimit, &status); if (!U_SUCCESS(status)) { break; } if (c < 0x20 || (c >= 0x7f && c <= 0x009f)) { ALOGV("control character %x", c); demerit += 100; } else if ((c == 0xa0) // no-break space || (c >= 0xa2 && c <= 0xbe) // symbols, superscripts || (c == 0xd7) || (c == 0xf7) // multiplication and division signs || (c >= 0x2000 && c <= 0x209f)) { // punctuation, superscripts ALOGV("unlikely character %x", c); demerit += 10; } else if (c >= 0xe000 && c <= 0xf8ff) { ALOGV("private use character %x", c); demerit += 30; } else if (c >= 0x2190 && c <= 0x2bff) { // this range comprises various symbol ranges that are unlikely to appear in // music file metadata. ALOGV("symbol %x", c); demerit += 10; } else if (c == 0xfffd) { ALOGV("replacement character"); demerit += 50; } else if (c >= 0xfff0 && c <= 0xfffc) { ALOGV("unicode special %x", c); demerit += 50; } else if (freqdata != NULL) { totalchars++; if (isFrequent(freqdata, c)) { frequentchars++; } } } if (freqdata != NULL && totalchars != 0) { int myconfidence = 10 + float((100 * frequentchars) / totalchars) / freqcoverage; ALOGV("ICU confidence: %d, my confidence: %d (%d %d)", confidence, myconfidence, totalchars, frequentchars); if (myconfidence > 100) myconfidence = 100; if (myconfidence < 0) myconfidence = 0; confidence = myconfidence; } ALOGV("%d-%d=%d", confidence, demerit, confidence - demerit); newconfidence.push_back(confidence - demerit); ucnv_close(conv); if (i == 0 && (confidence - demerit) == 100) { // no need to check any further, we'll end up using this match anyway break; } } // find match with highest confidence after adjusting for unlikely characters int highest = newconfidence[0]; size_t highestidx = 0; int runnerup = -10000; int runnerupidx = -10000; num = newconfidence.size(); for (size_t i = 1; i < num; i++) { if (newconfidence[i] > highest) { runnerup = highest; runnerupidx = highestidx; highest = newconfidence[i]; highestidx = i; } else if (newconfidence[i] > runnerup){ runnerup = newconfidence[i]; runnerupidx = i; } } status = U_ZERO_ERROR; ALOGV("selecting: '%s' w/ %d confidence", ucsdet_getName(matches[highestidx], &status), highest); if (runnerupidx < 0) { ALOGV("no runner up"); if (highest > 15) { *goodmatch = true; } } else { ALOGV("runner up: '%s' w/ %d confidence", ucsdet_getName(matches[runnerupidx], &status), runnerup); if (runnerup < 0) { runnerup = 0; } if ((highest - runnerup) > 15) { *goodmatch = true; } } *highestmatch = highest; return matches[highestidx]; } bool CharacterEncodingDetector::isFrequent(const uint16_t *values, uint32_t c) { int start = 0; int end = 511; // All the tables have 512 entries int mid = (start+end)/2; while(start <= end) { if(c == values[mid]) { return true; } else if (c > values[mid]) { start = mid + 1; } else { end = mid - 1; } mid = (start + end) / 2; } return false; } } // namespace android