QCryptographicHash: use a std::array to hold result (was: QByteArray)

The maximum size for a hash result is 64 atm. Even if, and esp when,
we'll get to 128 and 256 bytes in the future, there's no reason to use
dynamic memory, because the sizes will always be statically known.

So use, essentially, a std::array<char, 64> to hold the result
internally. Add a bit of convenience API on top to limit impact on the
rest of the code and add a few static_asserts that ensure this is large
enough. Then give users access to the internal buffer by adding
QByteArrayView resultView() const noexcept. The documentation snippet
is taken from QString::data(), suitably adjusted.

Use resultView() in a few places instead of result().

[ChangeLog][QtCore][QCryptographicHash] Changed to use a
statically-sized buffer internally. Added resultView() to access it.

Change-Id: I96c35e55acacbe94529446d720c18325273ffd2f
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

1 files changed, 2 insertions, 1 deletions

diff --git a/src/corelib/tools/qcryptographichash.h b/src/corelib/tools/qcryptographichash.h
index aecf8995d5..b3ab9c6126 100644
--- a/src/corelib/tools/qcryptographichash.h
+++ b/src/corelib/tools/qcryptographichash.h
@@ -102,7 +102,7 @@ public:
     explicit QCryptographicHash(Algorithm method);
     ~QCryptographicHash();
 
-    void reset();
+    void reset() noexcept;
 
 #if QT_DEPRECATED_SINCE(6, 4)
     QT_DEPRECATED_VERSION_X_6_4("Use the QByteArrayView overload instead")
@@ -115,6 +115,7 @@ public:
     bool addData(QIODevice *device);
 
     QByteArray result() const;
+    QByteArrayView resultView() const noexcept;
 
 #ifdef QT_BUILD_FUNCTIONS_REMOVED_IN_6_3
     static QByteArray hash(const QByteArray &data, Algorithm method);