Enumerating a MIDIPacketList in Swift 2.

MIDIPacketList+SequenceType.swift

extension MIDIPacketList: SequenceType {
  public typealias Generator = MIDIPacketListGenerator

  public func generate() -> Generator {
    return Generator(packetList: self)
  }
}

/**
Generator for MIDIPacketList allowing iteration over its list of MIDIPacket objects.
*/
public struct MIDIPacketListGenerator : GeneratorType {
  public typealias Element = MIDIPacket

  init(packetList: MIDIPacketList) {
    let ptr = UnsafeMutablePointer<MIDIPacket>.alloc(1)
    ptr.initialize(packetList.packet)
    self.packet = ptr
    self.count = packetList.numPackets
  }

  public mutating func next() -> Element? {
    guard self.packet != nil && self.index < self.count else { return nil }

    let lastPacket = self.packet!
    self.packet = MIDIPacketNext(self.packet!)
    self.index++
    return lastPacket.memory
  }

  // Extracted packet list info
  var count: UInt32
  var index: UInt32 = 0

  // Iteration state
  var packet: UnsafeMutablePointer<MIDIPacket>?
}