QLocale: port findTag to std::string_view

QStringView lacks the equivalent of find_first_of, so use string_view
for now.

Fixes an unnecessary QString ctor/dtor call, as well as the
int/qsizetype mismatch, looking for which I found this code.

The function can now be properly noexcept.

Task-number: QTBUG-103531
Pick-to: 6.4 6.3
Change-Id: I1198c082a2ee0addbe7c0d2192073b017d9f8dd7
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 6 insertions, 6 deletions

diff --git a/src/corelib/text/qlocale.cpp b/src/corelib/text/qlocale.cpp
index 0bfcba2f97..82e15186cb 100644
--- a/src/corelib/text/qlocale.cpp
+++ b/src/corelib/text/qlocale.cpp
@@ -530,13 +530,13 @@ int QLocaleData::findLocaleIndex(QLocaleId lid)
     return locale_index[fallback];
 }
 
-static QStringView findTag(QStringView name)
+static QStringView findTag(QStringView name) noexcept
 {
-    const QString separators = QStringLiteral("_-.@");
-    int i = 0;
-    while (i < name.size() && !separators.contains(name[i]))
-        i++;
-    return name.first(i);
+    const std::u16string_view v(name.utf16(), size_t(name.size()));
+    const auto i = v.find_first_of(u"_-.@");
+    if (i == std::string_view::npos)
+        return name;
+    return name.first(qsizetype(i));
 }
 
 static bool validTag(QStringView tag)