Rework finding of locale data to be index-based

Instead of returning a pointer (from which we then have to infer an
index for use in calendar data access), compute the index as primary
and infer the data pointer from it. Also refer to the index as such,
rather than as an offset.

Comments advocating this wanted to dispense with the pointer entirely;
that's not an option, however, due to the system locale having its
data in a separate object, outside the array that contains all the
other locales' data.

Change-Id: I1c60e688229394003e61372dbfc6cfb11086eafa
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

2 files changed, 52 insertions, 84 deletions

diff --git a/src/corelib/text/qlocale.cpp b/src/corelib/text/qlocale.cpp
index 7438ed2e61..5375f71153 100644
--- a/src/corelib/text/qlocale.cpp
+++ b/src/corelib/text/qlocale.cpp
@@ -350,64 +350,60 @@ QByteArray QLocalePrivate::rawName(char separator) const
     return parts.join(separator);
 }
 
-static const QLocaleData *findLocaleDataById(const QLocaleId &localeId)
+static int findLocaleIndexById(const QLocaleId &localeId)
 {
-    const uint idx = locale_index[localeId.language_id];
+    uint idx = locale_index[localeId.language_id];
     // If there are no locales for specified language (so we we've got the
     // default language, which has no associated script or country), give up:
     if (localeId.language_id && idx == 0)
-        return locale_data;
+        return idx;
 
-    const QLocaleData *data = locale_data + idx;
-    Q_ASSERT(localeId.acceptLanguage(data->m_language_id));
+    Q_ASSERT(localeId.acceptLanguage(locale_data[idx].m_language_id));
 
     do {
-        if (localeId.acceptScriptCountry(data->id()))
-            return data;
-        ++data;
-    } while (localeId.acceptLanguage(data->m_language_id));
+        if (localeId.acceptScriptCountry(locale_data[idx].id()))
+            return idx;
+        ++idx;
+    } while (localeId.acceptLanguage(locale_data[idx].m_language_id));
 
-    return nullptr;
+    return -1;
 }
 
-const QLocaleData *QLocaleData::findLocaleData(QLocale::Language language, QLocale::Script script,
-                                               QLocale::Country country)
+uint QLocaleData::findLocaleIndex(QLocale::Language language, QLocale::Script script,
+                                  QLocale::Country country)
 {
     QLocaleId localeId { language, script, country };
     QLocaleId likelyId = localeId.withLikelySubtagsAdded();
-
-    const uint idx = locale_index[likelyId.language_id];
+    const ushort fallback = likelyId.language_id;
 
     // Try a straight match with the likely data:
-    if (const QLocaleData *const data = findLocaleDataById(likelyId))
-        return data;
+    int index = findLocaleIndexById(likelyId);
+    if (index >= 0)
+        return index;
     QList<QLocaleId> tried;
     tried.push_back(likelyId);
 
+#define CheckCandidate(id) do { \
+        if (!tried.contains(id)) { \
+            index = findLocaleIndexById(id); \
+            if (index >= 0) \
+                return index; \
+            tried.push_back(id); \
+        } \
+    } while (false) // end CheckCandidate
+
     // No match; try again with raw data:
-    if (!tried.contains(localeId)) {
-        if (const QLocaleData *const data = findLocaleDataById(localeId))
-            return data;
-        tried.push_back(localeId);
-    }
+    CheckCandidate(localeId);
 
     // No match; try again with likely country for language_script
     if (country != QLocale::AnyCountry
         && (language != QLocale::AnyLanguage || script != QLocale::AnyScript)) {
         localeId = QLocaleId { language, script, QLocale::AnyCountry };
         likelyId = localeId.withLikelySubtagsAdded();
-        if (!tried.contains(likelyId)) {
-            if (const QLocaleData *const data = findLocaleDataById(likelyId))
-                return data;
-            tried.push_back(likelyId);
-        }
+        CheckCandidate(likelyId);
 
         // No match; try again with any country
-        if (!tried.contains(localeId)) {
-            if (const QLocaleData *const data = findLocaleDataById(localeId))
-                return data;
-            tried.push_back(localeId);
-        }
+        CheckCandidate(localeId);
     }
 
     // No match; try again with likely script for language_region
@@ -415,28 +411,15 @@ const QLocaleData *QLocaleData::findLocaleData(QLocale::Language language, QLoca
         && (language != QLocale::AnyLanguage || country != QLocale::AnyCountry)) {
         localeId = QLocaleId { language, QLocale::AnyScript, country };
         likelyId = localeId.withLikelySubtagsAdded();
-        if (!tried.contains(likelyId)) {
-            if (const QLocaleData *const data = findLocaleDataById(likelyId))
-                return data;
-            tried.push_back(likelyId);
-        }
+        CheckCandidate(likelyId);
 
         // No match; try again with any script
-        if (!tried.contains(localeId)) {
-            if (const QLocaleData *const data = findLocaleDataById(localeId))
-                return data;
-            tried.push_back(localeId);
-        }
+        CheckCandidate(localeId);
     }
+#undef CheckCandidate
 
-    // No match; return data at original index
-    return locale_data + idx;
-}
-
-uint QLocaleData::findLocaleOffset(QLocale::Language language, QLocale::Script script,
-                                   QLocale::Country country)
-{
-    return findLocaleData(language, script, country) - locale_data;
+    // No match; return base index for initial likely language:
+    return locale_index[fallback];
 }
 
 static bool parse_locale_tag(const QString &input, int &i, QString *result,
@@ -536,24 +519,14 @@ void QLocalePrivate::getLangAndCountry(const QString &name, QLocale::Language &l
     cntry = QLocalePrivate::codeToCountry(cntry_code);
 }
 
-static const QLocaleData *findLocaleData(const QString &name)
+static uint findLocaleIndex(const QString &name)
 {
     QLocale::Language lang;
     QLocale::Script script;
     QLocale::Country cntry;
     QLocalePrivate::getLangAndCountry(name, lang, script, cntry);
 
-    return QLocaleData::findLocaleData(lang, script, cntry);
-}
-
-static uint findLocaleOffset(const QString &name)
-{
-    QLocale::Language lang;
-    QLocale::Script script;
-    QLocale::Country cntry;
-    QLocalePrivate::getLangAndCountry(name, lang, script, cntry);
-
-    return QLocaleData::findLocaleOffset(lang, script, cntry);
+    return QLocaleData::findLocaleIndex(lang, script, cntry);
 }
 
 QString qt_readEscapedFormatString(QStringView format, int *idx)
@@ -771,10 +744,9 @@ static QLocalePrivate *localePrivateByName(const QString &name)
 {
     if (name == QLatin1String("C"))
         return c_private();
-    // TODO: Remove this version, and use offset everywhere
-    const QLocaleData *data = findLocaleData(name);
-    return QLocalePrivate::create(data, findLocaleOffset(name),
-                                  data->m_language_id == QLocale::C
+    const uint index = findLocaleIndex(name);
+    return QLocalePrivate::create(locale_data + index, index,
+                                  locale_data[index].m_language_id == QLocale::C
                                   ? QLocale::OmitGroupSeparator : QLocale::DefaultNumberOptions);
 }
 
@@ -784,9 +756,8 @@ static QLocalePrivate *findLocalePrivate(QLocale::Language language, QLocale::Sc
     if (language == QLocale::C)
         return c_private();
 
-    // TODO: Remove pointer, use index instead
-    const QLocaleData *data = QLocaleData::findLocaleData(language, script, country);
-    const uint offset = QLocaleData::findLocaleOffset(language, script, country);
+    uint index = QLocaleData::findLocaleIndex(language, script, country);
+    const QLocaleData *data = locale_data + index;
 
     QLocale::NumberOptions numberOptions = QLocale::DefaultNumberOptions;
 
@@ -796,7 +767,7 @@ static QLocalePrivate *findLocalePrivate(QLocale::Language language, QLocale::Sc
             numberOptions = defaultLocalePrivate->data()->m_numberOptions;
         data = defaultData();
     }
-    return QLocalePrivate::create(data, offset, numberOptions);
+    return QLocalePrivate::create(data, index, numberOptions);
 }
 
 QString QLocaleData::decimalPoint() const
@@ -2499,17 +2470,17 @@ QList<QLocale> QLocale::matchingLocales(QLocale::Language language,
     if (filter.matchesAll())
         result.reserve(locale_data_size);
 
-    const QLocaleData *data = locale_data + locale_index[language];
-    Q_ASSERT(filter.acceptLanguage(data->m_language_id));
+    uint index = locale_index[language];
+    Q_ASSERT(filter.acceptLanguage(locale_data[index].m_language_id));
     do {
-        const QLocaleId id = data->id();
+        const QLocaleId id = locale_data[index].id();
         if (filter.acceptScriptCountry(id)) {
             result.append(QLocale(*(id.language_id == C ? c_private()
-                                    : QLocalePrivate::create(data))));
+                                    : QLocalePrivate::create(locale_data + index, index))));
         }
-        ++data;
-        // Only the terminating entry in locale_data has 0 as language_id:
-    } while (filter.acceptLanguage(data->m_language_id));
+        ++index;
+    } while (filter.acceptLanguage(locale_data[index].m_language_id));
+
     return result;
 }
 
diff --git a/src/corelib/text/qlocale_p.h b/src/corelib/text/qlocale_p.h
index 8943edddb8..756e1afc93 100644
--- a/src/corelib/text/qlocale_p.h
+++ b/src/corelib/text/qlocale_p.h
@@ -186,14 +186,11 @@ Q_DECLARE_TYPEINFO(QLocaleId, Q_PRIMITIVE_TYPE);
 struct QLocaleData
 {
 public:
-    // TODO: Remove this?
-    static const QLocaleData *findLocaleData(QLocale::Language language,
-                                             QLocale::Script script,
-                                             QLocale::Country country);
-    // Having an offset of current locale, enables us to have multiple sources of data, i.e. user-provided calendar locales
-    static uint findLocaleOffset(QLocale::Language language,
-                                 QLocale::Script script,
-                                 QLocale::Country country);
+    // Having an index for each locale enables us to have diverse sources of
+    // data, e.g. calendar locales, as well as the main CLDR-derived data.
+    static uint findLocaleIndex(QLocale::Language language,
+                                QLocale::Script script,
+                                QLocale::Country country);
     static const QLocaleData *c();
 
     enum DoubleForm {