Utils: Improve string conversion for Qt6

Skip the creation auf a QByteArray. Use QStringEncoder instead.

Change-Id: I3d2297b1fef27acb2136a64587c5af9099d92aa6
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/libs/utils/smallstring.h

@@ -34,6 +34,9 @@
 
 #include <QByteArray>
 #include <QString>
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+#include <QStringEncoder>
+#endif
 
 #include <algorithm>
 #include <cmath>
@@ -135,6 +138,10 @@ public:
         : BasicSmallString(BasicSmallString::fromQString(qString))
     {}
 
+    BasicSmallString(const QStringView qStringView)
+        : BasicSmallString(BasicSmallString::fromQStringView(qStringView))
+    {}
+
     BasicSmallString(const QByteArray &qByteArray)
         : BasicSmallString(qByteArray.constData(), qByteArray.size())
     {}
@@ -353,16 +360,23 @@ public:
         return end();
     }
 
-    static
-    BasicSmallString fromQString(const QString &qString)
+    static BasicSmallString fromQString(const QString &qString)
     {
-        const QByteArray &utf8ByteArray = qString.toUtf8();
+        BasicSmallString string;
+        string.append(qString);
 
-        return BasicSmallString(utf8ByteArray.constData(), uint(utf8ByteArray.size()));
+        return string;
     }
 
-    static
-    BasicSmallString fromQByteArray(const QByteArray &utf8ByteArray)
+    static BasicSmallString fromQStringView(QStringView qStringView)
+    {
+        BasicSmallString string;
+        string.append(qStringView);
+
+        return string;
+    }
+
+    static BasicSmallString fromQByteArray(const QByteArray &utf8ByteArray)
     {
         return BasicSmallString(utf8ByteArray.constData(), uint(utf8ByteArray.size()));
     }
@@ -467,6 +481,24 @@ public:
         setSize(newSize);
     }
 
+    void append(QStringView string)
+    {
+#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+        QStringEncoder encoder{QStringEncoder::Utf8};
+
+        size_type oldSize = size();
+        size_type newSize = oldSize + static_cast<size_type>(encoder.requiredSpace(string.size()));
+
+        reserve(optimalCapacity(newSize));
+        auto newEnd = encoder.appendToBuffer(data() + size(), string);
+        *newEnd = 0;
+        setSize(newEnd - data());
+#else
+        QByteArray array = string.toUtf8();
+        append(SmallStringView{array.data(), static_cast<size_type>(array.size())});
+#endif
+    }
+
     BasicSmallString &operator+=(SmallStringView string)
     {
         append(string);
@@ -474,6 +506,13 @@ public:
         return *this;
     }
 
+    BasicSmallString &operator+=(QStringView string)
+    {
+        append(string);
+
+        return *this;
+    }
+
     BasicSmallString &operator+=(std::initializer_list<SmallStringView> list)
     {
         appendInitializerList(list, size());

tests/unit/unittest/smallstring-test.cpp

@@ -825,6 +825,15 @@ TEST(SmallString, AppendNullSmallString)
     ASSERT_THAT(text, SmallString("text"));
 }
 
+TEST(SmallString, AppendNullQString)
+{
+    SmallString text("text");
+
+    text += QString();
+
+    ASSERT_THAT(text, SmallString("text"));
+}
+
 TEST(SmallString, AppendEmptySmallString)
 {
     SmallString text("text");
@@ -834,6 +843,15 @@ TEST(SmallString, AppendEmptySmallString)
     ASSERT_THAT(text, SmallString("text"));
 }
 
+TEST(SmallString, AppendEmptyQString)
+{
+    SmallString text("text");
+
+    text += QString("");
+
+    ASSERT_THAT(text, SmallString("text"));
+}
+
 TEST(SmallString, AppendShortSmallString)
 {
     SmallString text("some ");
@@ -843,6 +861,15 @@ TEST(SmallString, AppendShortSmallString)
     ASSERT_THAT(text, SmallString("some text"));
 }
 
+TEST(SmallString, AppendShortQString)
+{
+    SmallString text("some ");
+
+    text += QString("text");
+
+    ASSERT_THAT(text, SmallString("some text"));
+}
+
 TEST(SmallString, AppendLongSmallStringToShortSmallString)
 {
     SmallString text("some ");
@@ -852,14 +879,36 @@ TEST(SmallString, AppendLongSmallStringToShortSmallString)
     ASSERT_THAT(text, SmallString("some very very very very very long string"));
 }
 
+TEST(SmallString, AppendLongQStringToShortSmallString)
+{
+    SmallString text("some ");
+
+    text += QString("very very very very very long string");
+
+    ASSERT_THAT(text, SmallString("some very very very very very long string"));
+}
+
 TEST(SmallString, AppendLongSmallString)
 {
     SmallString longText("some very very very very very very very very very very very long string");
-    longText+= SmallString(" text");
+
+    longText += SmallString(" text");
 
     ASSERT_THAT(longText, SmallString("some very very very very very very very very very very very long string text"));
 }
 
+TEST(SmallString, AppendLongQString)
+{
+    SmallString longText("some very very very very very very very very very very very long string");
+
+    longText += QString(" text");
+
+    ASSERT_THAT(
+        longText,
+        SmallString(
+            "some very very very very very very very very very very very long string text"));
+}
+
 TEST(SmallString, AppendInitializerList)
 {
     SmallString text("some text");