How to call IOCFPlugInInterface.QueryInterface() to query USB devices

Question

I want to convert this USB detector to Swift 3 https://gist.github.com/zachbadgett/471d72e83fee413d0f38

But I am stuck on this line:

let deviceInterfaceResult = plugInInterface.QueryInterface(
        plugInInterfacePtrPtr,
        CFUUIDGetUUIDBytes(kIOUSBDeviceInterfaceID),
&deviceInterfaceVoidPtr)

Cannot call value of non-function type '(@convention(c) (UnsafeMutableRawPointer?, REFIID, UnsafeMutablePointer?) -> HRESULT)!'

Source QueryInterface:

public var QueryInterface: (@convention(c) (UnsafeMutableRawPointer?, REFIID, UnsafeMutablePointer<LPVOID?>?) -> HRESULT)!

How do I call this function? Using CFNotificationCallback in Swift, or, @convention(c) blocks in Swift this answer didn't help me.

@JAL ```let deviceInterfaceResult:HRESULT = {(_: plugInInterfacePtrPtr, _: CFUUIDGetUUIDBytes(kIOUSBDeviceInterfaceID), _: &deviceInterfaceVoidPtr) -> HRESULT in }()``` not working — Arti, Dec 08 '16 at 16:31

Martin R · Accepted Answer · 2016-12-09T04:29:49.330

Cœur's answer is very close. plugInInterface.QueryInterface() expects as the last argument the address of a double-indirect pointer

UnsafeMutablePointer<UnsafeMutablePointer<IOUSBDeviceInterface>?>?

but "disguised" as a pointer to LPVOID? aka UnsafeMutableRawPointer. Consequently, the obtained pointer must be dereferenced twice. withMemoryRebound() can be used for this pointer cast.

I made some more changes to the code:

Use defer to continue with the next USB device even if the current iteration was "aborted" due to an error.
Remove unnecessary type annotations.
Use MemoryLayout<io_name_t>.size instead of 128.
Release usbDevice and the interface pointers after use to avoid memory leaks.
Move some variable declarations from the top to where they are needed.

Putting it all together:

import Foundation
import IOKit
import IOKit.usb
import IOKit.usb.IOUSBLib

print("Scanning USB Bus.....\n\n\n")

//
// These constants are not imported into Swift from IOUSBLib.h as they
// are all #define constants
//

let kIOUSBDeviceUserClientTypeID = CFUUIDGetConstantUUIDWithBytes(kCFAllocatorDefault,
                                                                  0x9d, 0xc7, 0xb7, 0x80, 0x9e, 0xc0, 0x11, 0xD4,
                                                                  0xa5, 0x4f, 0x00, 0x0a, 0x27, 0x05, 0x28, 0x61)

let kIOCFPlugInInterfaceID = CFUUIDGetConstantUUIDWithBytes(kCFAllocatorDefault,
                                                            0xC2, 0x44, 0xE8, 0x58, 0x10, 0x9C, 0x11, 0xD4,
                                                            0x91, 0xD4, 0x00, 0x50, 0xE4, 0xC6, 0x42, 0x6F)

let kIOUSBDeviceInterfaceID = CFUUIDGetConstantUUIDWithBytes(kCFAllocatorDefault,
                                                             0x5c, 0x81, 0x87, 0xd0, 0x9e, 0xf3, 0x11, 0xD4,
                                                             0x8b, 0x45, 0x00, 0x0a, 0x27, 0x05, 0x28, 0x61)


// Create dictionary with IOUSBDevice as IOProviderClass.
let matchingDictionary: NSMutableDictionary = IOServiceMatching(kIOUSBDeviceClassName)

// Get iterator for matching USB devices.
var usbIterator = io_iterator_t()
let matchingServicesResult = IOServiceGetMatchingServices(kIOMasterPortDefault, matchingDictionary, &usbIterator)
if matchingServicesResult != kIOReturnSuccess {
    print("Error getting deviceList!")
    exit(EXIT_FAILURE)
}

// Iterate devices until usbDevice == 0.
var usbDevice = IOIteratorNext(usbIterator)
while usbDevice != 0 {
    defer {
        usbDevice = IOIteratorNext(usbIterator)
    }

    // io_name_t imports to Swift as a tuple (Int8, ..., Int8) with 128 ints
    // although in device_types.h it is defined as
    //      typedef char io_name_t[128];
    var deviceNameCString = [CChar](repeating: 0, count: MemoryLayout<io_name_t>.size)
    let deviceNameResult = IORegistryEntryGetName(usbDevice, &deviceNameCString)
    if deviceNameResult != kIOReturnSuccess {
        print("Error getting device name")
        continue
    }
    let deviceName = String(cString: &deviceNameCString)
    print("USB device name: \(deviceName)")

    // Get plug-in interface for current USB device
    var plugInInterfacePtrPtr: UnsafeMutablePointer<UnsafeMutablePointer<IOCFPlugInInterface>?>?
    var score: Int32 = 0
    let plugInInterfaceResult = IOCreatePlugInInterfaceForService(
        usbDevice,
        kIOUSBDeviceUserClientTypeID,
        kIOCFPlugInInterfaceID,
        &plugInInterfacePtrPtr,
        &score)

    // USB device object is no longer needed.
    IOObjectRelease(usbDevice)

    // Dereference pointer for the plug-in interface
    guard plugInInterfaceResult == kIOReturnSuccess,
        let plugInInterface = plugInInterfacePtrPtr?.pointee?.pointee else {
            print("Unable to get Plug-In Interface")
            continue
    }

    // Use plug-in interface to get a device interface.
    var deviceInterfacePtrPtr: UnsafeMutablePointer<UnsafeMutablePointer<IOUSBDeviceInterface>?>?
    let deviceInterfaceResult = withUnsafeMutablePointer(to: &deviceInterfacePtrPtr) {
        $0.withMemoryRebound(to: Optional<LPVOID>.self, capacity: 1) {
            plugInInterface.QueryInterface(
                plugInInterfacePtrPtr,
                CFUUIDGetUUIDBytes(kIOUSBDeviceInterfaceID),
                $0)
        }
    }

    // Plug-in interface is no longer needed.
    _ = plugInInterface.Release(plugInInterfacePtrPtr)

    // Dereference pointer for the device interface.
    guard deviceInterfaceResult == kIOReturnSuccess,
        let deviceInterface = deviceInterfacePtrPtr?.pointee?.pointee else {
            print("Unable to get Device Interface")
            continue
    }

    // Use device interface to get vendor ID.
    var usbVendorID: UInt16 = 0
    let vendorResult = deviceInterface.GetDeviceVendor(deviceInterfacePtrPtr, &usbVendorID)

    // Device interface is no longer needed:
    _ = deviceInterface.Release(deviceInterfacePtrPtr)

    if vendorResult != kIOReturnSuccess {
        print("Unable to get device Vendor ID")
        continue
    }

    print("USB Vendor ID: \(usbVendorID)")
}

exit(EXIT_SUCCESS)

@Arti: You are welcome. I have edited the code again to fix some memory leaks. I have also taken the liberty to edit your question title, `@convention(c)` is not really relevant for this problem. — Martin R, Dec 08 '16 at 21:12

Cœur · Answer 2 · 2016-12-08T18:40:26.030

Don't know if it's correct at all, but this builds with Swift 3 and Xcode 8.0. The key was to write var deviceInterfaceVoidPtr: UnsafeMutableRawPointer? = nil.

import IOKit
import IOKit.usb
import IOKit.usb.IOUSBLib

print("Scanning USB Bus.....\n\n\n")

//
// These constants are not imported into Swift from IOUSBLib.h as they
// are all #define constants
//

let kIOUSBDeviceUserClientTypeID:   CFUUID = CFUUIDGetConstantUUIDWithBytes(kCFAllocatorDefault,
                                                                        0x9d, 0xc7, 0xb7, 0x80, 0x9e, 0xc0, 0x11, 0xD4,
                                                                        0xa5, 0x4f, 0x00, 0x0a, 0x27, 0x05, 0x28, 0x61)

let kIOCFPlugInInterfaceID:         CFUUID = CFUUIDGetConstantUUIDWithBytes(kCFAllocatorDefault,
                                                                        0xC2, 0x44, 0xE8, 0x58, 0x10, 0x9C, 0x11, 0xD4,
                                                                        0x91, 0xD4, 0x00, 0x50, 0xE4, 0xC6, 0x42, 0x6F)

let kIOUSBDeviceInterfaceID:        CFUUID = CFUUIDGetConstantUUIDWithBytes(kCFAllocatorDefault,
                                                                        0x5c, 0x81, 0x87, 0xd0, 0x9e, 0xf3, 0x11, 0xD4,
                                                                        0x8b, 0x45, 0x00, 0x0a, 0x27, 0x05, 0x28, 0x61)

var usbIterator:    io_iterator_t   = io_iterator_t()
var usbDevice:      io_service_t    = io_service_t()
var usbVendorID:    UInt16          = 0
var score:          Int32           = 0

func ptrFromAddress<T>(_ p: UnsafeMutablePointer<T>) -> UnsafeMutablePointer<T> {
    return p
}
var myInterface:IOCFPlugInInterface = IOCFPlugInInterface()
var plugInInterfacePtr: UnsafeMutablePointer<IOCFPlugInInterface>? = ptrFromAddress(&myInterface)
var plugInInterfacePtrPtr: UnsafeMutablePointer<UnsafeMutablePointer<IOCFPlugInInterface>?>? = ptrFromAddress(&plugInInterfacePtr)

// From: CFPlugInCOM.h: public typealias LPVOID =  UnsafeMutablePointer<Void>()
var deviceInterfaceVoidPtr: UnsafeMutableRawPointer? = nil

// create dictionary with IOUSBDevice as IOProviderClass
let matchingDictionary: NSMutableDictionary = IOServiceMatching(kIOUSBDeviceClassName)

// get iterator for matching USB devices
let matchingServicesResult = IOServiceGetMatchingServices(kIOMasterPortDefault, matchingDictionary, &usbIterator)
if matchingServicesResult != kIOReturnSuccess {
    print("Error getting deviceList!")
    exit(EXIT_FAILURE)
}

// usbDevice = 0 when finished iterating all devices
repeat {
    usbDevice = IOIteratorNext(usbIterator)
    // io_name_t imports to swift as a tuple (Int8, ..., Int8) 128 ints
    // although in device_types.h it's defined:
    // typedef  char io_name_t[128];
    var deviceNameCString: [CChar] = [CChar](repeating: 0, count: 128)
    let deviceNameResult = IORegistryEntryGetName(usbDevice, &deviceNameCString)

    if deviceNameResult != kIOReturnSuccess {
        print("Error getting device name")
        exit(EXIT_FAILURE)
    }

    let deviceName = String(cString: &deviceNameCString)
    print("usb Device Name: \(deviceName)")

    // Get plugInInterface for current USB device
    let plugInInterfaceResult = IOCreatePlugInInterfaceForService(
        usbDevice,
        kIOUSBDeviceUserClientTypeID,
        kIOCFPlugInInterfaceID,
        &plugInInterfacePtrPtr,
        &score)

    if (plugInInterfacePtrPtr == nil) || (plugInInterfaceResult != kIOReturnSuccess) {
        print("Unable to get Plug-In Interface")
        continue
    }

    // dereference pointer for the plug in interface
    let plugInInterface: IOCFPlugInInterface = plugInInterfacePtrPtr!.pointee!.pointee

    // use plug in interface to get a device interface
    // public var QueryInterface: (@convention(c) (UnsafeMutablePointer<Void>, REFIID, UnsafeMutablePointer<LPVOID>) -> HRESULT)!

    let deviceInterfaceResult = plugInInterface.QueryInterface(
        plugInInterfacePtrPtr,
        CFUUIDGetUUIDBytes(kIOUSBDeviceInterfaceID),
        &deviceInterfaceVoidPtr)

    if (deviceInterfaceResult != kIOReturnSuccess) || (deviceInterfaceVoidPtr == nil) {
        print("Unable to get Device Interface")
        exit(EXIT_FAILURE)
    }

    // dereference the IOUSBDeviceInterface struct from pointer var after
    // converting from a void to a IOUSBDeviceInterface pointer
    let opaquePtr = OpaquePointer(deviceInterfaceVoidPtr!)
    let deviceInterface = UnsafeMutablePointer<IOUSBDeviceInterface>(opaquePtr).pointee

    // get USB Vendor ID --> CRASH
    let vendorResult = deviceInterface.GetDeviceVendor(deviceInterfaceVoidPtr!, &usbVendorID)

    if vendorResult != kIOReturnSuccess {
        print("Unable to get Device Vendor ID")
        exit(EXIT_FAILURE)
    }

    print("usb Vendor ID: \(usbVendorID)")

    usbDevice = IOIteratorNext(usbIterator)
} while (usbDevice != 0)

exit(EXIT_SUCCESS)

Also, please note that according to gist comment from cellininicholas, you should remove one of the two occurrences of

usbDevice = IOIteratorNext(usbIterator)

oh, it is shame. I forgot import `IOKit` that is why i have a lot of troubles. — Arti, Dec 08 '16 at 18:56
I get crash here: ```// get USB Vendor ID --> CRASH let vendorResult = deviceInterface.GetDeviceVendor(deviceInterfaceVoidPtr!, &usbVendorID)``` — Arti, Dec 08 '16 at 19:16
Well, the crash was in the original gist I think. Let's compliment Martin for his much better answer. :) — Cœur, Dec 09 '16 at 02:06

How to call IOCFPlugInInterface.QueryInterface() to query USB devices

2 Answers2