Introduce QString(View)::isValidUtf16

QString(View)s can be built or manipulated in ways that make them
contain/refer to improperly encoded UTF-16 data. Problem is,
we don't have public APIs to check whether a string contains
valid UTF-16. This knowledge is precious if the string is to be fed in
algorithms, regular expressions, etc. that expect validated input
(e.g. QRegularExpression can be faster if it can assume valid UTF-16,
otherwise it has to employ extra checks).

Add a function that does the validation.

[ChangeLog][QtCore][QStringView] Added QStringView::isValidUtf16.

[ChangeLog][QtCore][QString] Added QString::isValidUtf16.

Change-Id: Idd699183f6ec08013046c76c6a5a7c524b6c6fbc
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 48 insertions, 0 deletions

diff --git a/tests/auto/corelib/text/qstring/tst_qstring.cpp b/tests/auto/corelib/text/qstring/tst_qstring.cpp
index 2108e99f20..f86fbc5988 100644
--- a/tests/auto/corelib/text/qstring/tst_qstring.cpp
+++ b/tests/auto/corelib/text/qstring/tst_qstring.cpp
@@ -596,6 +596,8 @@ private slots:
     void assignQChar();
     void isRightToLeft_data();
     void isRightToLeft();
+    void isValidUtf16_data();
+    void isValidUtf16();
     void unicodeStrings();
 };
 
@@ -7025,6 +7027,52 @@ void tst_QString::isRightToLeft()
     QCOMPARE(unicode.isRightToLeft(), rtl);
 }
 
+void tst_QString::isValidUtf16_data()
+{
+    QTest::addColumn<QString>("string");
+    QTest::addColumn<bool>("valid");
+
+    int row = 0;
+    QTest::addRow("valid-%02d", row++) << QString() << true;
+    QTest::addRow("valid-%02d", row++) << QString("") << true;
+    QTest::addRow("valid-%02d", row++) << QString("abc def") << true;
+    QTest::addRow("valid-%02d", row++) << QString("àbç") << true;
+    QTest::addRow("valid-%02d", row++) << QString("ßẞ") << true;
+    QTest::addRow("valid-%02d", row++) << QString("𝐀𝐁𝐂abc𝐃𝐄𝐅def") << true;
+    QTest::addRow("valid-%02d", row++) << QString("abc𝐀𝐁𝐂def𝐃𝐄𝐅") << true;
+    QTest::addRow("valid-%02d", row++) << (QString("abc") + QChar(0x0000) + QString("def")) << true;
+    QTest::addRow("valid-%02d", row++) << (QString("abc") + QChar(0xFFFF) + QString("def")) << true;
+    // check that BOM presence doesn't make any difference
+    QTest::addRow("valid-%02d", row++) << (QString() + QChar(0xFEFF) + QString("abc𝐀𝐁𝐂def𝐃𝐄𝐅")) << true;
+    QTest::addRow("valid-%02d", row++) << (QString() + QChar(0xFFFE) + QString("abc𝐀𝐁𝐂def𝐃𝐄𝐅")) << true;
+
+    row = 0;
+    QTest::addRow("stray-high-%02d", row++) << (QString() + QChar(0xD800)) << false;
+    QTest::addRow("stray-high-%02d", row++) << (QString() + QString("abc") + QChar(0xD800)) << false;
+    QTest::addRow("stray-high-%02d", row++) << (QString() + QChar(0xD800) + QString("def")) << false;
+    QTest::addRow("stray-high-%02d", row++) << (QString() + QString("abc") + QChar(0xD800) + QString("def")) << false;
+    QTest::addRow("stray-high-%02d", row++) << (QString() + QChar(0xD800) + QChar(0xD800)) << false;
+    QTest::addRow("stray-high-%02d", row++) << (QString() + QString("abc") + QChar(0xD800) + QChar(0xD800)) << false;
+    QTest::addRow("stray-high-%02d", row++) << (QString() + QChar(0xD800) + QChar(0xD800) + QString("def")) << false;
+    QTest::addRow("stray-high-%02d", row++) << (QString() + QString("abc") + QChar(0xD800) + QChar(0xD800) + QString("def")) << false;
+
+    row = 0;
+    QTest::addRow("stray-low-%02d", row++) << (QString() + QChar(0xDC00)) << false;
+    QTest::addRow("stray-low-%02d", row++) << (QString() + QString("abc") + QChar(0xDC00)) << false;
+    QTest::addRow("stray-low-%02d", row++) << (QString() + QChar(0xDC00) + QString("def")) << false;
+    QTest::addRow("stray-low-%02d", row++) << (QString() + QString("abc") + QChar(0xDC00) + QString("def")) << false;
+    QTest::addRow("stray-low-%02d", row++) << (QString() + QChar(0xDC00) + QChar(0xDC00)) << false;
+    QTest::addRow("stray-low-%02d", row++) << (QString() + QString("abc") + QChar(0xDC00) + QChar(0xDC00)) << false;
+    QTest::addRow("stray-low-%02d", row++) << (QString() + QChar(0xDC00) + QChar(0xDC00) + QString("def")) << false;
+    QTest::addRow("stray-low-%02d", row++) << (QString() + QString("abc") + QChar(0xDC00) + QChar(0xDC00) + QString("def")) << false;
+}
+
+void tst_QString::isValidUtf16()
+{
+    QFETCH(QString, string);
+    QTEST(string.isValidUtf16(), "valid");
+}
+
 QTEST_APPLESS_MAIN(tst_QString)
 
 #include "tst_qstring.moc"