blob: 2081c7a8c1c7f1ed64420de55ebad2815647ecb0 [file] [log] [blame]
// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/i18n/icu_encoding_detection.h"
#include <set>
#include "base/string_util.h"
#include "unicode/ucsdet.h"
namespace base {
bool DetectEncoding(const std::string& text, std::string* encoding) {
if (IsStringASCII(text)) {
*encoding = std::string();
return true;
}
UErrorCode status = U_ZERO_ERROR;
UCharsetDetector* detector = ucsdet_open(&status);
ucsdet_setText(detector, text.data(), static_cast<int32_t>(text.length()),
&status);
const UCharsetMatch* match = ucsdet_detect(detector, &status);
if (match == NULL)
return false;
const char* detected_encoding = ucsdet_getName(match, &status);
ucsdet_close(detector);
if (U_FAILURE(status))
return false;
*encoding = detected_encoding;
return true;
}
bool DetectAllEncodings(const std::string& text,
std::vector<std::string>* encodings) {
UErrorCode status = U_ZERO_ERROR;
UCharsetDetector* detector = ucsdet_open(&status);
ucsdet_setText(detector, text.data(), static_cast<int32_t>(text.length()),
&status);
int matches_count = 0;
const UCharsetMatch** matches = ucsdet_detectAll(detector,
&matches_count,
&status);
if (U_FAILURE(status)) {
ucsdet_close(detector);
return false;
}
// ICU has some heuristics for encoding detection, such that the more likely
// encodings should be returned first. However, it doesn't always return
// all encodings that properly decode |text|, so we'll append more encodings
// later. To make that efficient, keep track of encodings sniffed in this
// first phase.
std::set<std::string> sniffed_encodings;
encodings->clear();
for (int i = 0; i < matches_count; i++) {
UErrorCode get_name_status = U_ZERO_ERROR;
const char* encoding_name = ucsdet_getName(matches[i], &get_name_status);
// If we failed to get the encoding's name, ignore the error.
if (U_FAILURE(get_name_status))
continue;
int32_t confidence = ucsdet_getConfidence(matches[i], &get_name_status);
// We also treat this error as non-fatal.
if (U_FAILURE(get_name_status))
continue;
// A confidence level >= 10 means that the encoding is expected to properly
// decode the text. Drop all encodings with lower confidence level.
if (confidence < 10)
continue;
encodings->push_back(encoding_name);
sniffed_encodings.insert(encoding_name);
}
// Append all encodings not included earlier, in arbitrary order.
// TODO(jshin): This shouldn't be necessary, possible ICU bug.
// See also http://crbug.com/65917.
UEnumeration* detectable_encodings = ucsdet_getAllDetectableCharsets(detector,
&status);
int detectable_count = uenum_count(detectable_encodings, &status);
for (int i = 0; i < detectable_count; i++) {
int name_length;
const char* name_raw = uenum_next(detectable_encodings,
&name_length,
&status);
std::string name(name_raw, name_length);
if (sniffed_encodings.find(name) == sniffed_encodings.end())
encodings->push_back(name);
}
uenum_close(detectable_encodings);
ucsdet_close(detector);
return !encodings->empty();
}
} // namespace base