1 files changed, 32 insertions, 7 deletions
diff --git a/src/corelib/tools/qhash.cpp b/src/corelib/tools/qhash.cpp
index 7200ea7993..c9271848ec 100644
--- a/src/corelib/tools/qhash.cpp
+++ b/src/corelib/tools/qhash.cpp
@@ -94,13 +94,14 @@ QT_BEGIN_NAMESPACE
     (for instance, gcc 4.4 does that even at -O0).
 */
 
-#ifdef __SSE4_2__
+#if QT_COMPILER_SUPPORTS_HERE(SSE4_2)
 static inline bool hasFastCrc32()
 {
-    return true;
+    return qCpuHasFeature(SSE4_2);
 }
 
 template <typename Char>
+QT_FUNCTION_TARGET(SSE4_2)
 static uint crc32(const Char *ptr, size_t len, uint h)
 {
     // The CRC32 instructions from Nehalem calculate a 32-bit CRC32 checksum
@@ -163,6 +164,11 @@ static inline uint hash(const uchar *p, int len, uint seed) Q_DECL_NOTHROW
     return h;
 }
 
+uint qHashBits(const void *p, size_t len, uint seed) Q_DECL_NOTHROW
+{
+    return hash(static_cast<const uchar*>(p), int(len), seed);
+}
+
 static inline uint hash(const QChar *p, int len, uint seed) Q_DECL_NOTHROW
 {
     uint h = seed;
@@ -669,6 +675,25 @@ void QHashData::checkSanity()
     Types \c T1 and \c T2 must be supported by qHash().
 */
 
+/*! \fn uint qHashBits(const void *p, size_t len, uint seed = 0)
+    \relates QHash
+    \since 5.4
+
+    Returns the hash value for the memory block of size \a len pointed
+    to by \a p, using \a seed to seed the calculation.
+
+    Use this function only to implement qHash() for your own custom
+    types. E.g., here's how you could implement a qHash() overload for
+    std::vector<int>:
+
+    \snippet code/src_corelib_tools_qhash.cpp qhashbits
+
+    It bears repeating that the implementation of qHashBits() - like
+    the qHash() overloads offered by Qt - may change at any time. You
+    \b{must not} rely on the fact that qHashBits() will give the same
+    results (for the same inputs) across different Qt versions.
+*/
+
 /*! \fn uint qHash(char key, uint seed = 0)
     \relates QHash
     \since 5.0
@@ -778,7 +803,7 @@ uint qHash(long double key, uint seed) Q_DECL_NOTHROW
 }
 #endif
 
-/*! \fn uint qHash(QChar key, uint seed = 0)
+/*! \fn uint qHash(const QChar key, uint seed = 0)
     \relates QHash
     \since 5.0
 
@@ -961,8 +986,8 @@ uint qHash(long double key, uint seed) Q_DECL_NOTHROW
 
     A QHash's key type has additional requirements other than being an
     assignable data type: it must provide operator==(), and there must also be
-    a global qHash() function that returns a hash value for an argument of the
-    key's type.
+    a qHash() function in the type's namespace that returns a hash value for an
+    argument of the key's type.
 
     The qHash() function computes a numeric value based on a key. It
     can use any algorithm imaginable, as long as it always returns
@@ -2127,8 +2152,8 @@ uint qHash(long double key, uint seed) Q_DECL_NOTHROW
     QMultiHash's key and value data types must be \l{assignable data
     types}. You cannot, for example, store a QWidget as a value;
     instead, store a QWidget *. In addition, QMultiHash's key type
-    must provide operator==(), and there must also be a global
-    qHash() function that returns a hash value for an argument of the
+    must provide operator==(), and there must also be a qHash() function
+   in the type's namespace that returns a hash value for an argument of the
     key's type. See the QHash documentation for details.
 
     \sa QHash, QHashIterator, QMutableHashIterator, QMultiMap