Stanza: Make E2eeMetadata optional to avoid allocation

Avoids an allocation of the E2eeMetadataPrivate object when it's not
used.

It doesn't use optional<E2eeMetadata> directly because that wouldn't
avoid the allocation and takes up 16 bytes instead of 8.

This concept could be generalized and used elsewhere in the code
(e.g. extended addresses in the stanza are unused 99% of the time).

1 files changed, 23 insertions, 5 deletions

diff --git a/src/base/QXmppStanza.cpp b/src/base/QXmppStanza.cpp
index 25b9baac..3aff0404 100644
--- a/src/base/QXmppStanza.cpp
+++ b/src/base/QXmppStanza.cpp
@@ -525,6 +525,24 @@ QXmppE2eeMetadata::QXmppE2eeMetadata(const QXmppE2eeMetadata &other) = default;
 
 QXmppE2eeMetadata::~QXmppE2eeMetadata() = default;
 
+/// \cond
+QXmppE2eeMetadata::QXmppE2eeMetadata(const std::optional<QXmppE2eeMetadata> &other)
+    : d(nullptr)
+{
+    if (other) {
+        *this = *other;
+    }
+}
+
+std::optional<QXmppE2eeMetadata> QXmppE2eeMetadata::toOptional() const
+{
+    if (d) {
+        return *this;
+    }
+    return {};
+}
+/// \endcond
+
 ///
 /// Assigns \a other to this end-to-end encryption metadata class.
 ///
@@ -618,7 +636,7 @@ public:
     QXmppStanza::Error error;
     QXmppElementList extensions;
     QList<QXmppExtendedAddress> extendedAddresses;
-    QXmppE2eeMetadata e2eeMetadata;
+    QXmppE2eeMetadata e2eeMetadata = QXmppE2eeMetadata(std::nullopt);
 };
 
 ///
@@ -776,9 +794,9 @@ void QXmppStanza::setExtendedAddresses(const QList<QXmppExtendedAddress> &addres
 ///
 /// \since QXmpp 1.5
 ///
-QXmppE2eeMetadata QXmppStanza::e2eeMetadata() const
+std::optional<QXmppE2eeMetadata> QXmppStanza::e2eeMetadata() const
 {
-    return d->e2eeMetadata;
+    return d->e2eeMetadata.toOptional();
 }
 
 ///
@@ -786,9 +804,9 @@ QXmppE2eeMetadata QXmppStanza::e2eeMetadata() const
 ///
 /// \since QXmpp 1.5
 ///
-void QXmppStanza::setE2eeMetadata(const QXmppE2eeMetadata &e2eeMetadata)
+void QXmppStanza::setE2eeMetadata(const std::optional<QXmppE2eeMetadata> &e2eeMetadata)
 {
-    d->e2eeMetadata = e2eeMetadata;
+    d->e2eeMetadata = QXmppE2eeMetadata(e2eeMetadata);
 }
 
 /// \cond