This adds a formatter for plurals that works for all locales.

chrome/common/plural_formatter.cc

Index: chrome/common/plural_formatter.cc
diff --git a/chrome/common/plural_formatter.cc b/chrome/common/plural_formatter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..dc996b66002014afea694be2afecbb597d8618f8
--- /dev/null
+++ b/chrome/common/plural_formatter.cc
@@ -0,0 +1,131 @@
+// 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 "chrome/common/plural_formatter.h"
+
+#include <vector>
+
+#include "base/scoped_ptr.h"
+#include "base/stl_util-inl.h"
+#include "base/string16.h"
+#include "base/utf_string_conversions.h"
+#include "grit/generated_resources.h"
+#include "ui/base/l10n/l10n_util.h"
+#include "unicode/locid.h"
+#include "unicode/plurfmt.h"
+#include "unicode/plurrule.h"
+
+namespace {
+
+// This is the functor for mapping message IDs to strings.  We reset
+// it for tests so that we can avoid grit for the tests.
+static PluralFormatter::StringSourceFunction g_string_source =
+    l10n_util::GetStringUTF8;
+
+static const char* g_override_locale = NULL;
+}  // anonymous namespace

[Paweł Hajdan Jr., 2011/03/25 09:32:19]

nit: Add empty line above.

[Greg Spencer (Chromium), 2011/03/25 23:05:31]

Done.

+
+class PluralFormatterImpl {

[Paweł Hajdan Jr., 2011/03/25 09:32:19]

Is it worth to have an Impl class here? How about just forward-declaring
icu::PluralFormat (if possible) and using the scoped_ptr directly in
PluralFormatter?

[Greg Spencer (Chromium), 2011/03/25 23:05:31]

This is a good point, and I considered it, but an implementation class
is necessary here because icu does some funky things with namespaces:
it declares its stuff under a macro-constructed namespace name and
then aliases it to 'icu', which means you have to include the icu
header before any forward declaration (which defeats the purpose of
forward declarations) in order to use the namespace "icu" or the
macro.

[Paweł Hajdan Jr., 2011/03/28 18:52:28]

Makes sense.

+ public:
+  explicit PluralFormatterImpl(const int message_ids[]);
+  string16 GetPluralString(int number);
+ private:
+  scoped_ptr<icu::PluralFormat> formatter_;
+};
+
+PluralFormatterImpl::PluralFormatterImpl(const int message_ids[]) {
+  static const icu::UnicodeString kKeywords[] = {
+    UNICODE_STRING_SIMPLE("zero"), UNICODE_STRING_SIMPLE("one"),
+    UNICODE_STRING_SIMPLE("two"),  UNICODE_STRING_SIMPLE("few"),
+    UNICODE_STRING_SIMPLE("many"), UNICODE_STRING_SIMPLE("other"),
+  };
+
+  UErrorCode err = U_ZERO_ERROR;
+  scoped_ptr<icu::PluralRules> rules;
+  if (g_override_locale) {
+    icu::Locale overridden_locale(g_override_locale);
+    rules.reset(icu::PluralRules::forLocale(overridden_locale, err));
+  } else {
+    rules.reset(icu::PluralRules::forLocale(icu::Locale::getDefault(), err));
+  }
+  if (U_FAILURE(err)) {
+    err = U_ZERO_ERROR;
+    icu::UnicodeString fallback_rules("one: n is 1", -1, US_INV);
+    rules.reset(icu::PluralRules::createRules(fallback_rules, err));
+    DCHECK(U_SUCCESS(err));

[Paweł Hajdan Jr., 2011/03/25 09:32:19]

DCHECKs are only for Debug builds. Don't you want to check the return value also
for Release builds?

[Greg Spencer (Chromium), 2011/03/25 23:05:31]

In this case, we want to fall back to a simple rule if we can't load the rule
from the locale.  It's still probably a programming error, though, so a DCHECK
is warranted.

[Paweł Hajdan Jr., 2011/03/28 18:52:28]

My understanding of this code is that this DCHECK will fire if we fail to load
the _fallback_ rules. If that's still intended, please add a short comment, the
intention of this DCHECK might be non-obvious.

+  }
+
+  icu::UnicodeString pattern;
+  for (size_t j = 0; j < arraysize(kKeywords); ++j) {
+    int msg_id = message_ids[j];
+    std::string sub_pattern = (*g_string_source)(msg_id);
+    // NA means this keyword is not used in the current locale.  Even
+    // if a translator translated for this keyword, we do not use it
+    // unless it's 'other' or it's defined in the rules for the
+    // current locale. Special-casing of 'other' (j = 5) will be
+    // removed once ICU's isKeyword is fixed to return true for
+    // isKeyword('other').
+    if (sub_pattern.compare("NA") != 0 &&
+        (j == 5 || rules->isKeyword(kKeywords[j]))) {
+      pattern += kKeywords[j];
+      pattern += UNICODE_STRING_SIMPLE("{");
+      pattern += icu::UnicodeString(sub_pattern.c_str(), "UTF-8");
+      pattern += UNICODE_STRING_SIMPLE("}");
+    }
+  }
+
+  scoped_ptr<icu::PluralFormat> format(
+      new icu::PluralFormat(*rules, pattern, err));
+  DCHECK(U_SUCCESS(err));

[Paweł Hajdan Jr., 2011/03/25 09:32:19]

Similarly here, I think you want to always check the return value. Maybe it
would be better to have a bool Init method?

[Greg Spencer (Chromium), 2011/03/25 23:05:31]

I had that at first, and went back to DCHECK to be consistent with what the
TimeFormat code (which a lot of this code is based on) already does, and because
I was thinking that any error here really indicates either a programming or
translator error, not an expected failure condition.

I think you're probably right though: a translator error is really a bad input,
not a programming error, so I'll switch this to an Init.

+  formatter_.swap(format);
+}
+
+string16 PluralFormatterImpl::GetPluralString(int number) {
+  icu::UnicodeString plural_string;
+  UErrorCode error = U_ZERO_ERROR;
+  plural_string = formatter_->format(number, error);
+  DCHECK(U_SUCCESS(error));
+  string16 result;
+  int capacity = plural_string.length() + 1;
+  plural_string.extract(static_cast<UChar*>(WriteInto(&result, capacity)),
+                        capacity, error);
+  DCHECK(U_SUCCESS(error));
+  return result;
+}
+
+PluralFormatter::PluralFormatter(int zero_message_id,
+                                 int one_message_id,
+                                 int two_message_id,
+                                 int few_message_id,
+                                 int many_message_id,
+                                 int default_message_id) {
+  int message_ids[6];
+  message_ids[0] = zero_message_id;
+  message_ids[1] = one_message_id;
+  message_ids[2] = two_message_id;
+  message_ids[3] = few_message_id;
+  message_ids[4] = many_message_id;
+  message_ids[5] = default_message_id;
+  impl_ = new PluralFormatterImpl(message_ids);
+}
+
+PluralFormatter::PluralFormatter(const int message_ids[])
+    : impl_(new PluralFormatterImpl(message_ids)) {
+}
+
+PluralFormatter::~PluralFormatter() {
+  delete impl_;
+}
+
+string16 PluralFormatter::GetPluralString(int number) {
+  return impl_->GetPluralString(number);
+}
+
+void PluralFormatter::SetStringSource(StringSourceFunction string_source) {
+  g_string_source = string_source;
+}
+
+void PluralFormatter::SetOverrideLocale(const char* overrride_locale) {
+  g_override_locale = overrride_locale;
+}