AU: Fix midi output to use correct packet alignment on ARM

modules/juce_audio_plugin_client/AU/juce_AU_Wrapper.mm

@@ -1755,6 +1755,9 @@ private:
     Array<const AudioProcessorParameterGroup*> parameterGroups;
 
     //==============================================================================
+    // According to the docs, this is the maximum size of a MIDIPacketList.
+    static constexpr UInt32 packetListBytes = 65536;
+
     AudioUnitEvent auEvent;
     mutable Array<AUPreset> presetsArray;
     CriticalSection incomingMidiLock;
@@ -1762,6 +1765,7 @@ private:
     AudioTimeStamp lastTimeStamp;
     int totalInChannels, totalOutChannels;
     HeapBlock<bool> pulledSucceeded;
+    HeapBlock<MIDIPacketList> packetList { packetListBytes, 1 };
 
     ThreadLocalValue<bool> inParameterChangedCallback;
 
@@ -1858,37 +1862,55 @@ private:
 
     void pushMidiOutput (UInt32 nFrames) noexcept
     {
-        UInt32 numPackets = 0;
-        size_t dataSize = 0;
+        MIDIPacket* end = nullptr;
 
-        for (const auto metadata : midiEvents)
+        const auto init = [&]
         {
-            jassert (isPositiveAndBelow (metadata.samplePosition, nFrames));
-            ignoreUnused (nFrames);
+            end = MIDIPacketListInit (packetList);
+        };
 
-            dataSize += (size_t) metadata.numBytes;
-            ++numPackets;
-        }
-
-        MIDIPacket* p;
-        const size_t packetMembersSize     = sizeof (MIDIPacket)     - sizeof (p->data); // NB: GCC chokes on "sizeof (MidiMessage::data)"
-        const size_t packetListMembersSize = sizeof (MIDIPacketList) - sizeof (p->data);
+        const auto send = [&]
+        {
+            midiCallback.midiOutputCallback (midiCallback.userData, &lastTimeStamp, 0, packetList);
+        };
 
-        HeapBlock<MIDIPacketList> packetList;
-        packetList.malloc (packetListMembersSize + packetMembersSize * numPackets + dataSize, 1);
-        packetList->numPackets = numPackets;
+        const auto add = [&] (const MidiMessageMetadata& metadata)
+        {
+            end = MIDIPacketListAdd (packetList,
+                                     packetListBytes,
+                                     end,
+                                     static_cast<MIDITimeStamp> (metadata.samplePosition),
+                                     static_cast<ByteCount> (metadata.numBytes),
+                                     metadata.data);
+        };
 
-        p = packetList->packet;
+        init();
 
         for (const auto metadata : midiEvents)
         {
-            p->timeStamp = (MIDITimeStamp) metadata.samplePosition;
-            p->length = (UInt16) metadata.numBytes;
-            memcpy (p->data, metadata.data, (size_t) metadata.numBytes);
-            p = MIDIPacketNext (p);
+            jassert (isPositiveAndBelow (metadata.samplePosition, nFrames));
+            ignoreUnused (nFrames);
+
+            add (metadata);
+
+            if (end == nullptr)
+            {
+                send();
+                init();
+                add (metadata);
+
+                if (end == nullptr)
+                {
+                    // If this is hit, the size of this midi packet exceeds the maximum size of
+                    // a MIDIPacketList. Large SysEx messages should be broken up into smaller
+                    // chunks.
+                    jassertfalse;
+                    init();
+                }
+            }
         }
 
-        midiCallback.midiOutputCallback (midiCallback.userData, &lastTimeStamp, 0, packetList);
+        send();
     }
 
     void GetAudioBufferList (bool isInput, int busIdx, AudioBufferList*& bufferList, bool& interleaved, int& numChannels)