MIDI2Transport

MIDI I/O abstraction layer. Production CoreMIDI implementation and MockTransport for testing.

MIDITransport Protocol

The core protocol that abstracts MIDI I/O operations. Both production and test implementations conform to this protocol.

Required Methods

Required Properties

CoreMIDITransport

Production implementation using Apple's CoreMIDI framework.

// Create transport
let transport = try CoreMIDITransport(clientName: "MyApp")

// Connect to all sources
try await transport.connectToAllSources()

// Send data
let data: [UInt8] = [0xF0, 0x7E, 0x7F, ...]
try await transport.send(data, to: destinationID)

// Receive data
for await received in transport.received {
    print("Received \(received.data.count) bytes from \(received.sourceID)")
}

// Handle setup changes (device connected/disconnected)
for await _ in transport.setupChanged {
    print("MIDI setup changed")
    // Refresh device list
}

LoopbackTransport

In-process loopback transport for testing initiator-responder communication without CoreMIDI. New in v1.0.5.

// Create a loopback pair
let (initiatorTransport, responderTransport) = LoopbackTransport.createPair()

// Messages sent on one transport are received on the other
try await initiatorTransport.send(data, to: destinationID)
// → responderTransport.received will emit this data

try await responderTransport.send(replyData, to: destinationID)
// → initiatorTransport.received will emit this data

Use Cases

With MockDevice

let (initiatorTransport, responderTransport) = LoopbackTransport.createPair()

// Create mock device on responder side
let mockDevice = MockDevice(transport: responderTransport, preset: .korgModulePro)
try await mockDevice.start()

// Create managers on initiator side
let ciManager = CIManager(transport: initiatorTransport, ...)
let peManager = PEManager(transport: initiatorTransport, ...)
try await ciManager.start()

// Discovery and PE operations work seamlessly
await ciManager.startDiscovery()
let response = try await peManager.get("DeviceInfo", from: mockDevice.handle)

MockMIDITransport

Mock implementation for unit testing without real MIDI hardware.

// Create mock transport
let mockTransport = MockMIDITransport()

// Add mock endpoints
await mockTransport.addMockSource(MIDISourceInfo(
    sourceID: MIDISourceID(1),
    name: "Test Device",
    uniqueID: 12345
))
await mockTransport.addMockDestination(MIDIDestinationInfo(
    destinationID: MIDIDestinationID(1),
    name: "Test Device",
    uniqueID: 12345
))

// Simulate receiving data
await mockTransport.simulateReceive(
    [0xF0, 0x7E, 0x7F, ...],
    from: MIDISourceID(1)
)

// Check sent messages
let sent = await mockTransport.sentMessages
XCTAssertEqual(sent.count, 1)
XCTAssertEqual(sent[0].data, expectedData)

Test Helpers

Endpoint Types

MIDISourceID / MIDIDestinationID

Type-safe wrappers for CoreMIDI endpoint references.

public struct MIDISourceID: Sendable, Hashable {
    public let value: UInt32
}

public struct MIDIDestinationID: Sendable, Hashable {
    public let value: UInt32
}

MIDISourceInfo / MIDIDestinationInfo

Endpoint metadata including name, manufacturer, and persistent ID.

MIDIReceivedData

Incoming MIDI data with source information.

public struct MIDIReceivedData: Sendable {
    public let data: [UInt8]       // Raw MIDI bytes
    public let sourceID: MIDISourceID?  // Source endpoint
    public let timestamp: UInt64    // CoreMIDI timestamp
}

Error Types