QAndroidFormatsInfo: fix quadratic loop (eradicates Java-style iterators)

Calling QMutableListIterator::remove() in a loop is quadratic. Use
Uniform Erasure erase_if, which is linear (uses std::remove_if under
the hoods).

Since std::remove_if() typically runs find_if() first, we can't modify
elements from within erase_if()'s predicate. Factor the modifications
to the elements into a separate loop.

Change-Id: I04f951d9b7e05f210876a2f4065b33035c94df7a
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
(cherry picked from commit 2bd1201df43a508f3f83af7b4995869fa7c4212a)
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

1 files changed, 4 insertions, 7 deletions

diff --git a/src/multimedia/platform/android/qandroidformatsinfo.cpp b/src/multimedia/platform/android/qandroidformatsinfo.cpp
index 21f7d636d..584c7a122 100644
--- a/src/multimedia/platform/android/qandroidformatsinfo.cpp
+++ b/src/multimedia/platform/android/qandroidformatsinfo.cpp
@@ -39,7 +39,6 @@
 
 #include "qandroidformatsinfo_p.h"
 
-#include <QMutableListIterator>
 #include <QtCore/qjnienvironment.h>
 #include <QtCore/qjniobject.h>
 #include <qcoreapplication.h>
@@ -70,15 +69,13 @@ QAndroidFormatInfo::QAndroidFormatInfo()
     }
 
     auto removeUnspecifiedValues = [](QList<CodecMap> &map) {
-        QMutableListIterator<CodecMap> iter(map);
-        while (iter.hasNext()) {
-            CodecMap &codec = iter.next();
+        for (CodecMap &codec : map) {
             codec.audio.removeAll(QMediaFormat::AudioCodec::Unspecified);
             codec.video.removeAll(QMediaFormat::VideoCodec::Unspecified);
-
-            if (codec.audio.size() < 1 && codec.video.size() < 1)
-                iter.remove();
         }
+        erase_if(map, [](const CodecMap &codec) {
+            return codec.audio.isEmpty() && codec.video.isEmpty();
+        });
     };
 
     {