qHash: implement chunked hashing of QLatin1StringView

So that it hashes to the same value as QString{,View}.

In order to test this, you must either run on a CPU other than ARM and
x86, or disable the AES hasher. I did that and can confirm siphash and
murmurhash do work with on-the-fly conversion from Latin-1.

Change-Id: I664b9f014ffc48cbb49bfffd17b03e5e62ec4e89
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

2 files changed, 50 insertions, 4 deletions

diff --git a/tests/auto/corelib/tools/qhash/tst_qhash.cpp b/tests/auto/corelib/tools/qhash/tst_qhash.cpp
index 6b7b5955df..b3dbdfa40c 100644
--- a/tests/auto/corelib/tools/qhash/tst_qhash.cpp
+++ b/tests/auto/corelib/tools/qhash/tst_qhash.cpp
@@ -42,6 +42,7 @@ private slots:
     void heterogeneousSearchConstKey();
     void heterogeneousSearchByteArray();
     void heterogeneousSearchString();
+    void heterogeneousSearchLatin1String();
 
     void rehash_isnt_quadratic();
     void dont_need_default_constructor();
@@ -54,6 +55,7 @@ private slots:
     void qmultihashHeterogeneousSearchConstKey();
     void qmultihashHeterogeneousSearchByteArray();
     void qmultihashHeterogeneousSearchString();
+    void qmultihashHeterogeneousSearchLatin1String();
 
     void compare();
     void compare2();
@@ -1221,15 +1223,17 @@ template <> struct HeterogeneousSearchTestHelper<HeterogeneousHashingType>
 using HeterogeneousHashingType = QString;
 #endif
 
-template <template <typename, typename> class Hash, typename String, typename View>
-static void heterogeneousSearchTest(const QList<std::remove_const_t<String>> &keys)
+template <template <typename, typename> class Hash, typename String, typename View, typename Converter>
+static void heterogeneousSearchTest(const QList<std::remove_const_t<String>> &keys, Converter conv)
 {
 #ifdef __cpp_concepts
     using Helper = HeterogeneousSearchTestHelper<View>;
     String key = keys.last();
     String otherKey = keys.first();
-    View keyView(key);
-    View otherKeyView(otherKey);
+    auto keyHolder = conv(key);
+    auto otherKeyHolder = conv(otherKey);
+    View keyView(keyHolder);
+    View otherKeyView(otherKeyHolder);
 
     Hash<String, qsizetype> hash;
     static constexpr bool IsMultiHash = !std::is_same_v<decltype(hash.remove(String())), bool>;
@@ -1332,10 +1336,29 @@ static void heterogeneousSearchTest(const QList<std::remove_const_t<String>> &ke
     Helper::checkCounter();
 #else
     Q_UNUSED(keys);
+    Q_UNUSED(conv);
     QSKIP("This feature requires C++20 (concepts)");
 #endif
 }
 
+template <template <typename, typename> class Hash, typename String, typename View>
+static void heterogeneousSearchTest(const QList<std::remove_const_t<String>> &keys)
+{
+    heterogeneousSearchTest<Hash, String, View>(keys, [](const String &s) { return View(s); });
+}
+
+template <template <typename, typename> class Hash, typename T>
+static void heterogeneousSearchLatin1String(T)
+{
+    if constexpr (!T::value) {
+        QSKIP("QLatin1StringView and QString do not have the same hash on this platform");
+    } else {
+        // similar to the above
+        auto toLatin1 = [](const QString &s) { return s.toLatin1(); };
+        heterogeneousSearchTest<Hash, QString, QLatin1StringView>({ "Hello", {}, "World" }, toLatin1);
+    }
+}
+
 void tst_QHash::heterogeneousSearch()
 {
     heterogeneousSearchTest<QHash, QString, HeterogeneousHashingType>({ "Hello", {}, "World" });
@@ -1357,6 +1380,11 @@ void tst_QHash::heterogeneousSearchString()
     heterogeneousSearchTest<QHash, QString, QStringView>({ "Hello", {}, "World" });
 }
 
+void tst_QHash::heterogeneousSearchLatin1String()
+{
+    ::heterogeneousSearchLatin1String<QHash>(QHashHeterogeneousSearch<QString, QLatin1StringView>{});
+}
+
 void tst_QHash::compare()
 {
     QHash<int, QString> hash1,hash2;
@@ -2346,6 +2374,11 @@ void tst_QHash::qmultihashHeterogeneousSearchString()
     heterogeneousSearchTest<QMultiHash, QString, QStringView>({ "Hello", {}, "World" });
 }
 
+void tst_QHash::qmultihashHeterogeneousSearchLatin1String()
+{
+    ::heterogeneousSearchLatin1String<QMultiHash>(QHashHeterogeneousSearch<QString, QLatin1StringView>{});
+}
+
 void tst_QHash::keys_values_uniqueKeys()
 {
     QMultiHash<QString, int> hash;
diff --git a/tests/auto/corelib/tools/qhashfunctions/tst_qhashfunctions.cpp b/tests/auto/corelib/tools/qhashfunctions/tst_qhashfunctions.cpp
index b9a7d88056..fdb2b37346 100644
--- a/tests/auto/corelib/tools/qhashfunctions/tst_qhashfunctions.cpp
+++ b/tests/auto/corelib/tools/qhashfunctions/tst_qhashfunctions.cpp
@@ -321,6 +321,19 @@ void tst_QHashFunctions::stringConsistency()
 
     QCOMPARE(qHash(sv, seed), qHash(value, seed));
     QCOMPARE(qHash(u8bav, seed), qHash(u8ba, seed));
+
+    if (seed || QT_VERSION_MAJOR > 6) {
+        QByteArray l1ba = value.toLatin1();
+        QLatin1StringView l1sv(l1ba.data(), l1ba.size());
+#ifdef Q_PROCESSOR_ARM
+        // zero-extending aeshash not implemented on ARM
+#elif defined(Q_PROCESSOR_X86)
+        // zero-extending aeshash not implemented on x86
+#else
+        if (value == l1sv)
+            QCOMPARE(qHash(l1sv, seed), qHash(value, seed));
+#endif
+    }
 }
 
 void tst_QHashFunctions::qhash()