From 2081371d861e659192eff905acba75e443bb9c79 Mon Sep 17 00:00:00 2001
From: Steffan Andrews <stef@orchetect.com>
Date: Mon, 13 Jun 2022 01:36:32 -0700
Subject: [PATCH] `.send(events:)`: Improved reliability of sending SysEx in a
 multi-event array when using old Core MIDI API

---
 .../MIDIPacketList Utilities.swift            |  1 +
 .../MIDIIOSendsMIDIMessagesProtocol.swift     | 10 +++-
 .../Integration Tests/Round Trip Tests.swift  |  6 ++-
 Tests/MIDIKitTests/Tests Helpers.swift        | 53 +++++++++++++++++++
 4 files changed, 66 insertions(+), 4 deletions(-)
 create mode 100644 Tests/MIDIKitTests/Tests Helpers.swift

diff --git a/Sources/MIDIKit/IO/Core MIDI/MIDIPacketLIst/MIDIPacketList Utilities.swift b/Sources/MIDIKit/IO/Core MIDI/MIDIPacketLIst/MIDIPacketList Utilities.swift
index 310d4dee16..3f72c46953 100644
--- a/Sources/MIDIKit/IO/Core MIDI/MIDIPacketLIst/MIDIPacketList Utilities.swift	
+++ b/Sources/MIDIKit/IO/Core MIDI/MIDIPacketLIst/MIDIPacketList Utilities.swift	
@@ -74,6 +74,7 @@ extension UnsafeMutablePointer where Pointee == MIDIPacketList {
     /// Assembles an array of `Byte` arrays into Core MIDI `MIDIPacket`s and wraps them in a `MIDIPacketList`.
     ///
     /// - Note: You must deallocate the pointer when finished with it.
+    /// - Note: System Exclusive messages must each be packed in a dedicated MIDIPacketList with no other events, otherwise MIDIPacketList may fail.
     @inline(__always)
     internal init(data: [[MIDI.Byte]]) throws {
         
diff --git a/Sources/MIDIKit/IO/Managed/Protocols/MIDIIOSendsMIDIMessagesProtocol.swift b/Sources/MIDIKit/IO/Managed/Protocols/MIDIIOSendsMIDIMessagesProtocol.swift
index aab5b8acc6..e18d211b16 100644
--- a/Sources/MIDIKit/IO/Managed/Protocols/MIDIIOSendsMIDIMessagesProtocol.swift
+++ b/Sources/MIDIKit/IO/Managed/Protocols/MIDIIOSendsMIDIMessagesProtocol.swift
@@ -152,7 +152,14 @@ extension _MIDIIOSendsMIDIMessagesProtocol {
         
         switch api {
         case .legacyCoreMIDI:
-            try send(rawMessages: events.map { $0.midi1RawBytes })
+            if events.contains(where: { $0.isSystemExclusive }) {
+                // System Exclusive events must be the only event in a MIDIPacketList
+                // so force each event to be sent in its own packet
+                try events.forEach { try send(event: $0) }
+            } else {
+                // combine events into a single MIDIPacketList
+                try send(rawMessages: events.map { $0.midi1RawBytes })
+            }
             
         case .newCoreMIDI:
             guard #available(macOS 11, iOS 14, macCatalyst 14, tvOS 14, watchOS 7, *) else {
@@ -172,4 +179,3 @@ extension _MIDIIOSendsMIDIMessagesProtocol {
     }
     
 }
-
diff --git a/Tests/MIDIKitTests/Integration Tests/Round Trip Tests.swift b/Tests/MIDIKitTests/Integration Tests/Round Trip Tests.swift
index d27d0e881d..bd40ef5c6d 100644
--- a/Tests/MIDIKitTests/Integration Tests/Round Trip Tests.swift	
+++ b/Tests/MIDIKitTests/Integration Tests/Round Trip Tests.swift	
@@ -262,8 +262,10 @@ open class RoundTrip_Tests_Base: XCTestCase {
         
         receivedEvents.reserveCapacity(sourceEvents.count)
         
-        for event in sourceEvents {
-            try output.send(event: event)
+        // send several events at once to test packing
+        // multiple packets into a single MIDIPacketList / MIDIEventList
+        for eventGroup in sourceEvents.split(every: 2) {
+            try output.send(events: Array(eventGroup))
         }
         
         wait(sec: 0.5)
diff --git a/Tests/MIDIKitTests/Tests Helpers.swift b/Tests/MIDIKitTests/Tests Helpers.swift
new file mode 100644
index 0000000000..70cda8242f
--- /dev/null
+++ b/Tests/MIDIKitTests/Tests Helpers.swift	
@@ -0,0 +1,53 @@
+/// ------------------------------------------------------------------------------------
+/// ------------------------------------------------------------------------------------
+/// Borrowed from [OTCore 1.4.1](https://github.com/orchetect/OTCore) under MIT license.
+/// Methods herein are unit tested in OTCore, so no unit tests are necessary in MIDIKit.
+/// ------------------------------------------------------------------------------------
+/// ------------------------------------------------------------------------------------
+
+#if shouldTestCurrentPlatform
+
+import Foundation
+
+extension Collection {
+    
+    /// **OTCore:**
+    /// Splits a `Collection` or `String` into groups of `length` characters, grouping from left-to-right. If `backwards` is true, right-to-left.
+    @_disfavoredOverload
+    internal func split(every: Int,
+                        backwards: Bool = false) -> [SubSequence] {
+        
+        var result: [SubSequence] = []
+        
+        for i in stride(from: 0, to: count, by: every) {
+            
+            switch backwards {
+            case true:
+                let offsetEndIndex = index(endIndex, offsetBy: -i)
+                let offsetStartIndex = index(offsetEndIndex,
+                                             offsetBy: -every,
+                                             limitedBy: startIndex)
+                ?? startIndex
+                
+                result.insert(self[offsetStartIndex..<offsetEndIndex], at: 0)
+                
+            case false:
+                let offsetStartIndex = index(startIndex, offsetBy: i)
+                let offsetEndIndex = index(offsetStartIndex,
+                                           offsetBy: every,
+                                           limitedBy: endIndex)
+                ?? endIndex
+                
+                result.append(self[offsetStartIndex..<offsetEndIndex])
+                
+            }
+            
+        }
+        
+        return result
+        
+    }
+    
+}
+
+#endif