Trying to re-land http://codereview.chromium.org/6901141.

src/extensions/experimental/language-matcher.h

+// Copyright 2011 the V8 project authors. 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
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// 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.
+
+#ifndef V8_EXTENSIONS_EXPERIMENTAL_LANGUAGE_MATCHER_H_
+#define V8_EXTENSIONS_EXPERIMENTAL_LANGUAGE_MATCHER_H_
+
+#include <v8.h>
+
+#include "unicode/uloc.h"
+
+namespace v8 {
+namespace internal {
+
+struct LocaleIDMatch {
+  LocaleIDMatch();
+
+  LocaleIDMatch& operator=(const LocaleIDMatch& rhs);
+
+  // Bcp47 locale id - "de-Latn-DE-u-co-phonebk".
+  char bcp47_id[ULOC_FULLNAME_CAPACITY];
+
+  // ICU locale id - "de_Latn_DE@collation=phonebk".
+  char icu_id[ULOC_FULLNAME_CAPACITY];
+
+  // Score for this locale.
+  int score;
+};
+
+class LanguageMatcher {
+ public:
+  // Default locale.
+  static const char* const kDefaultLocale;
+
+  // Finds best supported locale for a given a list of locale identifiers.
+  // It preserves the extension for the locale id.
+  static void GetBestMatchForPriorityList(
+      v8::Handle<v8::Array> locale_list, LocaleIDMatch* result);
+
+  // Finds best supported locale for a single locale identifier.
+  // It preserves the extension for the locale id.
+  static void GetBestMatchForString(
+      v8::Handle<v8::String> locale_id, LocaleIDMatch* result);
+
+ private:
+  // If langauge subtags match add this amount to the score.
+  static const unsigned int kLanguageWeight;
+
+  // If script subtags match add this amount to the score.
+  static const unsigned int kScriptWeight;
+
+  // If region subtags match add this amount to the score.
+  static const unsigned int kRegionWeight;
+
+  // LocaleID match score has to be over this number to accept the match.
+  static const unsigned int kThreshold;
+
+  // For breaking ties in priority queue.
+  static const unsigned int kPositionBonus;
+
+  LanguageMatcher();
+
+  // Compares locale_id to the supported list of locales and returns best
+  // match.
+  // Returns false if it fails to convert locale id from ICU to BCP47 format.
+  static bool CompareToSupportedLocaleIDList(v8::Handle<v8::String> locale_id,
+                                             LocaleIDMatch* result);
+};
+
+} }  // namespace v8::internal
+
+#endif  // V8_EXTENSIONS_EXPERIMENTAL_LANGUAGE_MATCHER_H_