Issue details

The struct definition for MIDIPacketList is wrong and only seems to work by accident on 32bit platforms.
When calling getPacket() on a MIDIPacketList struct the returned packet is off by 4 byte on a 64bit platform.

Example:
On 32bit

• Pointer of list: 6106767000
• Pointer of getPacket().getHandle(): 6106767004

On 64bit

• Pointer of list: 6106767000
• Pointer of getPacket().getHandle(): 6106767008
  Therefore all the data of the MIDIPacket is invalid on 64bit platforms.

The issue is that the packet is not referenced by ref in the original header - therefore the offset is always 4 byte (the numPackets field)

Reproduction steps/code

• Receive midi data using CoreMidi
• The length of any midi packet is way too long on 64bit platforms which shows the off by 4.

Configuration

Build Tools:

• Gradle plugin

Versions:

• Robovm: 2.3.7-SNAPSHOT
• XCode: 10.2.1
• JDK: 1.8.0_181

Build Targets:
iPhone 8 (64 bit)

Workaround

As of now I'm reading the packet with an hardcoded 4 byte offset but that's pretty ugly..

long listPointer = pktlist.getHandle();
MIDIPacket packet = MIDIPacket.toStruct(MIDIPacket.class, listPointer + 4);