Reland "Replace ICU with CED for auto encoding detection"

third_party/WebKit/Source/platform/text/TextEncodingDetector.cpp

 /*
  * Copyright (C) 2008, 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 12 matching lines @@
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "platform/text/TextEncodingDetector.h"
 
+#include "third_party/ced/src/compact_enc_det/compact_enc_det.h"
 #include "wtf/text/TextEncoding.h"
-#include <unicode/ucnv.h>
-#include <unicode/ucsdet.h>
 
 namespace blink {
 
 bool detectTextEncoding(const char* data, size_t length,
     const char* hintEncodingName, WTF::TextEncoding* detectedEncoding)
 {
     *detectedEncoding = WTF::TextEncoding();
-    int matchesCount = 0;
-    UErrorCode status = U_ZERO_ERROR;
-    UCharsetDetector* detector = ucsdet_open(&status);
-    if (U_FAILURE(status))
-        return false;
-    ucsdet_enableInputFilter(detector, true);
-    ucsdet_setText(detector, data, static_cast<int32_t>(length), &status);
-    if (U_FAILURE(status))
-        return false;
-
-    // FIXME: A few things we can do other than improving
-    // the ICU detector itself.
-    // 1. Use ucsdet_detectAll and pick the most likely one given
-    // "the context" (parent-encoding, referrer encoding, etc).
-    // 2. 'Emulate' Firefox/IE's non-Universal detectors (e.g.
-    // Chinese, Japanese, Russian, Korean and Hebrew) by picking the
-    // encoding with a highest confidence among the detector-specific
-    // limited set of candidate encodings.
-    // Below is a partial implementation of the first part of what's outlined
-    // above.
-    const UCharsetMatch** matches = ucsdet_detectAll(detector, &matchesCount, &status);
-    if (U_FAILURE(status)) {
-        ucsdet_close(detector);
-        return false;
-    }
-
-    const char* encoding = 0;
-    if (hintEncodingName) {
-        WTF::TextEncoding hintEncoding(hintEncodingName);
-        // 10 is the minimum confidence value consistent with the codepoint
-        // allocation in a given encoding. The size of a chunk passed to
-        // us varies even for the same html file (apparently depending on
-        // the network load). When we're given a rather short chunk, we
-        // don't have a sufficiently reliable signal other than the fact that
-        // the chunk is consistent with a set of encodings. So, instead of
-        // setting an arbitrary threshold, we have to scan all the encodings
-        // consistent with the data.
-        const int32_t kThresold = 10;
-        for (int i = 0; i < matchesCount; ++i) {
-            int32_t confidence = ucsdet_getConfidence(matches[i], &status);
-            if (U_FAILURE(status)) {
-                status = U_ZERO_ERROR;
-                continue;
-            }
-            if (confidence < kThresold)
-                break;
-            const char* matchEncoding = ucsdet_getName(matches[i], &status);
-            if (U_FAILURE(status)) {
-                status = U_ZERO_ERROR;
-                continue;
-            }
-            if (WTF::TextEncoding(matchEncoding) == hintEncoding) {
-                encoding = hintEncodingName;
-                break;
-            }
-        }
-    }
-    // If no match is found so far, just pick the top match.
-    // This can happen, say, when a parent frame in EUC-JP refers to
-    // a child frame in Shift_JIS and both frames do NOT specify the encoding
-    // making us resort to auto-detection (when it IS turned on).
-    if (!encoding && matchesCount > 0)
-        encoding = ucsdet_getName(matches[0], &status);
-    if (U_SUCCESS(status)) {
-        *detectedEncoding = WTF::TextEncoding(encoding);
-        ucsdet_close(detector);
+    int consumedBytes;
+    bool isReliable;
+    Encoding encoding = CompactEncDet::DetectEncoding(
+        data, length, nullptr, nullptr, nullptr,
+        EncodingNameAliasToEncoding(hintEncodingName),
+        UNKNOWN_LANGUAGE,
+        CompactEncDet::WEB_CORPUS,
+        false, // Include 7-bit encodings
+        &consumedBytes,
+        &isReliable);
+    if (encoding != UNKNOWN_ENCODING) {
+        *detectedEncoding = WTF::TextEncoding(MimeEncodingName(encoding));
         return true;
     }
-    ucsdet_close(detector);
     return false;
 }
 
 } // namespace blink