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