QByteArrayList: add indexOf(const char*) overload

This avoids memory allocation and data copying in e.g.
QObject::property().

Detected by heaptrack's "Temporary allocations" counter in an
application using the breeze widget style (many animations).

Change-Id: Iabdb58a3e504cb121cce906ef707b0722de89df6
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

2 files changed, 26 insertions, 0 deletions

diff --git a/src/corelib/tools/qbytearraylist.cpp b/src/corelib/tools/qbytearraylist.cpp
index c815e766ab..d04555ed4d 100644
--- a/src/corelib/tools/qbytearraylist.cpp
+++ b/src/corelib/tools/qbytearraylist.cpp
@@ -150,4 +150,26 @@ QByteArray QtPrivate::QByteArrayList_join(const QByteArrayList *that, const char
     return res;
 }
 
+/*!
+    \fn int QByteArrayList::indexOf(const char *needle, int from) const
+
+    Returns the index position of the first occurrence of \a needle in
+    the list, searching forward from index position \a from. Returns
+    -1 if no item matched.
+
+    \a needle must be NUL-terminated.
+
+    This overload doesn't require creating a QByteArray, thus saving a
+    memory allocation and some CPU time.
+
+    \since 5.13
+    \overload
+*/
+
+int QtPrivate::QByteArrayList_indexOf(const QByteArrayList *that, const char *needle, int from)
+{
+    const auto it = std::find_if(that->begin() + from, that->end(), [needle](const QByteArray &item) { return item == needle; });
+    return it == that->end() ? -1 : int(std::distance(that->begin(), it));
+}
+
 QT_END_NAMESPACE
diff --git a/src/corelib/tools/qbytearraylist.h b/src/corelib/tools/qbytearraylist.h
index be94bc1d40..d69e8bb54b 100644
--- a/src/corelib/tools/qbytearraylist.h
+++ b/src/corelib/tools/qbytearraylist.h
@@ -55,6 +55,7 @@ typedef QList<QByteArray> QByteArrayList;
 
 namespace QtPrivate {
     QByteArray Q_CORE_EXPORT QByteArrayList_join(const QByteArrayList *that, const char *separator, int separatorLength);
+    int Q_CORE_EXPORT QByteArrayList_indexOf(const QByteArrayList *that, const char *needle, int from);
 }
 #endif
 
@@ -76,6 +77,9 @@ public:
     inline QByteArray join(char sep) const
     { return QtPrivate::QByteArrayList_join(self(), &sep, 1); }
 
+    inline int indexOf(const char *needle, int from = 0) const
+    { return QtPrivate::QByteArrayList_indexOf(self(), needle, from); }
+
 private:
     typedef QList<QByteArray> Self;
     Self *self() { return static_cast<Self *>(this); }