diff options
author | Marc Mutz <marc.mutz@kdab.com> | 2014-02-12 14:10:35 +0100 |
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committer | The Qt Project <gerrit-noreply@qt-project.org> | 2014-02-28 21:27:41 +0100 |
commit | 12372960f8ab3c50231c4f5c21aa6a87c69e9915 (patch) | |
tree | d4aec4dbfb80f621e2f48c83dfa5a76e2ea7caf4 /src/corelib/tools/qhash.cpp | |
parent | f4ffe2a2439928992c3f44085e81686d4f911417 (diff) |
Add qHashBits(), a hash function for a memory block
The function arguments have been chosen to avoid caller-side casting of
argument types, when passing object addresses and type sizeof()s.
[ChangeLog][QtCore] Added qHashBits() to aid implementing qHash() overloads
for custom types.
Change-Id: I983a8560769bb27e489f23ebb6db51850ddd65f2
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Diffstat (limited to 'src/corelib/tools/qhash.cpp')
-rw-r--r-- | src/corelib/tools/qhash.cpp | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/src/corelib/tools/qhash.cpp b/src/corelib/tools/qhash.cpp index a5d14a3535..65c88d35ab 100644 --- a/src/corelib/tools/qhash.cpp +++ b/src/corelib/tools/qhash.cpp @@ -163,6 +163,11 @@ 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 +674,25 @@ 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 |