hid-mac.c

/*******************************************************
 HIDAPI - Multi-Platform library for
 communication with HID devices.

 Alan Ott
 Signal 11 Software

 2010-07-03

 Copyright 2010, All Rights Reserved.

 At the discretion of the user of this library,
 this software may be licensed under the terms of the
 GNU General Public License v3, a BSD-Style license, or the
 original HIDAPI license as outlined in the LICENSE.txt,
 LICENSE-gpl3.txt, LICENSE-bsd.txt, and LICENSE-orig.txt
 files located at the root of the source distribution.
 These files may also be found in the public source
 code repository located at:
        http://github.com/signal11/hidapi .
********************************************************/

/* See Apple Technical Note TN2187 for details on IOHidManager. */

#include <IOKit/hid/IOHIDManager.h>
#include <IOKit/hid/IOHIDKeys.h>
#include <IOKit/IOKitLib.h>
#include <CoreFoundation/CoreFoundation.h>
#include <wchar.h>
#include <locale.h>
#include <pthread.h>
#include <sys/time.h>
#include <unistd.h>
#include <dlfcn.h>

#include "hidapi.h"

/* Barrier implementation because Mac OSX doesn't have pthread_barrier.
   It also doesn't have clock_gettime(). So much for POSIX and SUSv2.
   This implementation came from Brent Priddy and was posted on
   StackOverflow. It is used with his permission. */
typedef int pthread_barrierattr_t;
typedef struct pthread_barrier {
    pthread_mutex_t mutex;
    pthread_cond_t cond;
    int count;
    int trip_count;
} pthread_barrier_t;

static int pthread_barrier_init(pthread_barrier_t *barrier, const pthread_barrierattr_t *attr, unsigned int count)
{
  if(count == 0) {
    errno = EINVAL;
    return -1;
  }

  if(pthread_mutex_init(&barrier->mutex, 0) < 0) {
    return -1;
  }
  if(pthread_cond_init(&barrier->cond, 0) < 0) {
    pthread_mutex_destroy(&barrier->mutex);
    return -1;
  }
  barrier->trip_count = count;
  barrier->count = 0;

  return 0;
}

static int pthread_barrier_destroy(pthread_barrier_t *barrier)
{
  pthread_cond_destroy(&barrier->cond);
  pthread_mutex_destroy(&barrier->mutex);
  return 0;
}

static int pthread_barrier_wait(pthread_barrier_t *barrier)
{
  pthread_mutex_lock(&barrier->mutex);
  ++(barrier->count);
  if(barrier->count >= barrier->trip_count)
  {
    barrier->count = 0;
    pthread_cond_broadcast(&barrier->cond);
    pthread_mutex_unlock(&barrier->mutex);
    return 1;
  }
  else
  {
    pthread_cond_wait(&barrier->cond, &(barrier->mutex));
    pthread_mutex_unlock(&barrier->mutex);
    return 0;
  }
}

static int return_data(hid_device *dev, unsigned char *data, size_t length);

/* Linked List of input reports received from the device. */
struct input_report {
  uint8_t *data;
  size_t len;
  struct input_report *next;
};

struct hid_device_ {
  IOHIDDeviceRef device_handle;
  int blocking;
  int uses_numbered_reports;
  int disconnected;
  CFStringRef run_loop_mode;
  CFRunLoopRef run_loop;
  CFRunLoopSourceRef source;
  uint8_t *input_report_buf;
  CFIndex max_input_report_len;
  struct input_report *input_reports;

  pthread_t thread;
  pthread_mutex_t mutex; /* Protects input_reports */
  pthread_cond_t condition;
  pthread_barrier_t barrier; /* Ensures correct startup sequence */
  pthread_barrier_t shutdown_barrier; /* Ensures correct shutdown sequence */
  int shutdown_thread;
};

static hid_device *new_hid_device(void)
{
  hid_device *dev = calloc(1, sizeof(hid_device));
  dev->device_handle = NULL;
  dev->blocking = 1;
  dev->uses_numbered_reports = 0;
  dev->disconnected = 0;
  dev->run_loop_mode = NULL;
  dev->run_loop = NULL;
  dev->source = NULL;
  dev->input_report_buf = NULL;
  dev->input_reports = NULL;
  dev->shutdown_thread = 0;

  /* Thread objects */
  pthread_mutex_init(&dev->mutex, NULL);
  pthread_cond_init(&dev->condition, NULL);
  pthread_barrier_init(&dev->barrier, NULL, 2);
  pthread_barrier_init(&dev->shutdown_barrier, NULL, 2);

  return dev;
}

static void free_hid_device(hid_device *dev)
{
  if (!dev)
    return;

  /* Delete any input reports still left over. */
  struct input_report *rpt = dev->input_reports;
  while (rpt) {
    struct input_report *next = rpt->next;
    free(rpt->data);
    free(rpt);
    rpt = next;
  }

  /* Free the string and the report buffer. The check for NULL
     is necessary here as CFRelease() doesn't handle NULL like
     free() and others do. */
  if (dev->run_loop_mode)
    CFRelease(dev->run_loop_mode);
  if (dev->source)
    CFRelease(dev->source);
  free(dev->input_report_buf);

  /* Clean up the thread objects */
  pthread_barrier_destroy(&dev->shutdown_barrier);
  pthread_barrier_destroy(&dev->barrier);
  pthread_cond_destroy(&dev->condition);
  pthread_mutex_destroy(&dev->mutex);

  /* Free the structure itself. */
  free(dev);
}

static  IOHIDManagerRef hid_mgr = 0x0;


#if 0
static void register_error(hid_device *device, const char *op)
{

}
#endif


static int32_t get_int_property(IOHIDDeviceRef device, CFStringRef key)
{
  CFTypeRef ref;
  int32_t value;

  ref = IOHIDDeviceGetProperty(device, key);
  if (ref) {
    if (CFGetTypeID(ref) == CFNumberGetTypeID()) {
      CFNumberGetValue((CFNumberRef) ref, kCFNumberSInt32Type, &value);
      return value;
    }
  }
  return 0;
}

static unsigned short get_vendor_id(IOHIDDeviceRef device)
{
  return get_int_property(device, CFSTR(kIOHIDVendorIDKey));
}

static unsigned short get_product_id(IOHIDDeviceRef device)
{
  return get_int_property(device, CFSTR(kIOHIDProductIDKey));
}

static int32_t get_max_report_length(IOHIDDeviceRef device)
{
  return get_int_property(device, CFSTR(kIOHIDMaxInputReportSizeKey));
}

static int get_string_property(IOHIDDeviceRef device, CFStringRef prop, wchar_t *buf, size_t len)
{
  CFStringRef str;

  if (!len)
    return 0;

  str = IOHIDDeviceGetProperty(device, prop);

  buf[0] = 0;

  if (str) {
    CFIndex str_len = CFStringGetLength(str);
    CFRange range;
    CFIndex used_buf_len;
    CFIndex chars_copied;

    len --;

    range.location = 0;
    range.length = ((size_t)str_len > len)? len: (size_t)str_len;
    chars_copied = CFStringGetBytes(str,
      range,
      kCFStringEncodingUTF32LE,
      (char)'?',
      FALSE,
      (UInt8*)buf,
      len * sizeof(wchar_t),
      &used_buf_len);

    if (chars_copied == len)
      buf[len] = 0; /* len is decremented above */
    else
      buf[chars_copied] = 0;

    return 0;
  }
  else
    return -1;

}

static int get_serial_number(IOHIDDeviceRef device, wchar_t *buf, size_t len)
{
  return get_string_property(device, CFSTR(kIOHIDSerialNumberKey), buf, len);
}

static int get_manufacturer_string(IOHIDDeviceRef device, wchar_t *buf, size_t len)
{
  return get_string_property(device, CFSTR(kIOHIDManufacturerKey), buf, len);
}

static int get_product_string(IOHIDDeviceRef device, wchar_t *buf, size_t len)
{
  return get_string_property(device, CFSTR(kIOHIDProductKey), buf, len);
}


/* Implementation of wcsdup() for Mac. */
static wchar_t *dup_wcs(const wchar_t *s)
{
  size_t len = wcslen(s);
  wchar_t *ret = malloc((len+1)*sizeof(wchar_t));
  wcscpy(ret, s);

  return ret;
}

/* hidapi_IOHIDDeviceGetService()
 *
 * Return the io_service_t corresponding to a given IOHIDDeviceRef, either by:
 * - on OS X 10.6 and above, calling IOHIDDeviceGetService()
 * - on OS X 10.5, extract it from the IOHIDDevice struct
 */
static io_service_t hidapi_IOHIDDeviceGetService(IOHIDDeviceRef device)
{
  static void *iokit_framework = NULL;
  static io_service_t (*dynamic_IOHIDDeviceGetService)(IOHIDDeviceRef device) = NULL;

  /* Use dlopen()/dlsym() to get a pointer to IOHIDDeviceGetService() if it exists.
   * If any of these steps fail, dynamic_IOHIDDeviceGetService will be left NULL
   * and the fallback method will be used.
   */
  if (iokit_framework == NULL) {
    iokit_framework = dlopen("/System/Library/IOKit.framework/IOKit", RTLD_LAZY);

    if (iokit_framework != NULL)
      dynamic_IOHIDDeviceGetService = dlsym(iokit_framework, "IOHIDDeviceGetService");
  }

  if (dynamic_IOHIDDeviceGetService != NULL) {
    /* Running on OS X 10.6 and above: IOHIDDeviceGetService() exists */
    return dynamic_IOHIDDeviceGetService(device);
  }
  else
  {
    /* Running on OS X 10.5: IOHIDDeviceGetService() doesn't exist.
     *
     * Be naughty and pull the service out of the IOHIDDevice.
     * IOHIDDevice is an opaque struct not exposed to applications, but its
     * layout is stable through all available versions of OS X.
     * Tested and working on OS X 10.5.8 i386, x86_64, and ppc.
     */
    struct IOHIDDevice_internal {
      /* The first field of the IOHIDDevice struct is a
       * CFRuntimeBase (which is a private CF struct).
       *
       * a, b, and c are the 3 fields that make up a CFRuntimeBase.
       * See http://opensource.apple.com/source/CF/CF-476.18/CFRuntime.h
       *
       * The second field of the IOHIDDevice is the io_service_t we're looking for.
       */
      uintptr_t a;
      uint8_t b[4];
#if __LP64__
      uint32_t c;
#endif
      io_service_t service;
    };
    struct IOHIDDevice_internal *tmp = (struct IOHIDDevice_internal *)device;

    return tmp->service;
  }
}

/* Initialize the IOHIDManager. Return 0 for success and -1 for failure. */
static int init_hid_manager(void)
{
  /* Initialize all the HID Manager Objects */
  hid_mgr = IOHIDManagerCreate(kCFAllocatorDefault, kIOHIDOptionsTypeNone);
  if (hid_mgr) {
    IOHIDManagerSetDeviceMatching(hid_mgr, NULL);
    IOHIDManagerScheduleWithRunLoop(hid_mgr, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode);
    return 0;
  }

  return -1;
}

/* Initialize the IOHIDManager if necessary. This is the public function, and
   it is safe to call this function repeatedly. Return 0 for success and -1
   for failure. */
int HID_API_EXPORT hid_init(void)
{
  if (!hid_mgr) {
    return init_hid_manager();
  }

  /* Already initialized. */
  return 0;
}

int HID_API_EXPORT hid_exit(void)
{
  if (hid_mgr) {
    /* Close the HID manager. */
    IOHIDManagerClose(hid_mgr, kIOHIDOptionsTypeNone);
    CFRelease(hid_mgr);
    hid_mgr = NULL;
  }

  return 0;
}

static void process_pending_events(void) {
  SInt32 res;
  do {
    res = CFRunLoopRunInMode(kCFRunLoopDefaultMode, 0.001, FALSE);
  } while(res != kCFRunLoopRunFinished && res != kCFRunLoopRunTimedOut);
}

struct hid_device_info  HID_API_EXPORT *hid_enumerate(unsigned short vendor_id, unsigned short product_id)
{
  struct hid_device_info *root = NULL; /* return object */
  struct hid_device_info *cur_dev = NULL;
  CFIndex num_devices;
  int i;

  /* Set up the HID Manager if it hasn't been done */
  if (hid_init() < 0)
    return NULL;

  /* give the IOHIDManager a chance to update itself */
  process_pending_events();

  /* Get a list of the Devices */
  IOHIDManagerSetDeviceMatching(hid_mgr, NULL);
  CFSetRef device_set = IOHIDManagerCopyDevices(hid_mgr);

  /* Convert the list into a C array so we can iterate easily. */
  num_devices = CFSetGetCount(device_set);
  IOHIDDeviceRef *device_array = calloc(num_devices, sizeof(IOHIDDeviceRef));
  CFSetGetValues(device_set, (const void **) device_array);

  /* Iterate over each device, making an entry for it. */
  for (i = 0; i < num_devices; i++) {
    unsigned short dev_vid;
    unsigned short dev_pid;
    #define BUF_LEN 256
    wchar_t buf[BUF_LEN];

    IOHIDDeviceRef dev = device_array[i];

        if (!dev) {
            continue;
        }
    dev_vid = get_vendor_id(dev);
    dev_pid = get_product_id(dev);

    /* Check the VID/PID against the arguments */
    if ((vendor_id == 0x0 || vendor_id == dev_vid) &&
        (product_id == 0x0 || product_id == dev_pid)) {
      struct hid_device_info *tmp;
      io_object_t iokit_dev;
      kern_return_t res;
      io_string_t path;

      /* VID/PID match. Create the record. */
      tmp = malloc(sizeof(struct hid_device_info));
      if (cur_dev) {
        cur_dev->next = tmp;
      }
      else {
        root = tmp;
      }
      cur_dev = tmp;

      /* Get the Usage Page and Usage for this device. */
      cur_dev->usage_page = get_int_property(dev, CFSTR(kIOHIDPrimaryUsagePageKey));
      cur_dev->usage = get_int_property(dev, CFSTR(kIOHIDPrimaryUsageKey));

      /* Fill out the record */
      cur_dev->next = NULL;

      /* Fill in the path (IOService plane) */
      iokit_dev = hidapi_IOHIDDeviceGetService(dev);
      res = IORegistryEntryGetPath(iokit_dev, kIOServicePlane, path);
      if (res == KERN_SUCCESS)
        cur_dev->path = strdup(path);
      else
        cur_dev->path = strdup("");

      /* Serial Number */
      get_serial_number(dev, buf, BUF_LEN);
      cur_dev->serial_number = dup_wcs(buf);

      /* Manufacturer and Product strings */
      get_manufacturer_string(dev, buf, BUF_LEN);
      cur_dev->manufacturer_string = dup_wcs(buf);
      get_product_string(dev, buf, BUF_LEN);
      cur_dev->product_string = dup_wcs(buf);

      /* VID/PID */
      cur_dev->vendor_id = dev_vid;
      cur_dev->product_id = dev_pid;

      /* Release Number */
      cur_dev->release_number = get_int_property(dev, CFSTR(kIOHIDVersionNumberKey));

      /* Interface Number (Unsupported on Mac)*/
      cur_dev->interface_number = -1;
    }
  }

  free(device_array);
  CFRelease(device_set);

  return root;
}

void  HID_API_EXPORT hid_free_enumeration(struct hid_device_info *devs)
{
  /* This function is identical to the Linux version. Platform independent. */
  struct hid_device_info *d = devs;
  while (d) {
    struct hid_device_info *next = d->next;
    free(d->path);
    free(d->serial_number);
    free(d->manufacturer_string);
    free(d->product_string);
    free(d);
    d = next;
  }
}

hid_device * HID_API_EXPORT hid_open(unsigned short vendor_id, unsigned short product_id, const wchar_t *serial_number)
{
  /* This function is identical to the Linux version. Platform independent. */
  struct hid_device_info *devs, *cur_dev;
  const char *path_to_open = NULL;
  hid_device * handle = NULL;

  devs = hid_enumerate(vendor_id, product_id);
  cur_dev = devs;
  while (cur_dev) {
    if (cur_dev->vendor_id == vendor_id &&
        cur_dev->product_id == product_id) {
      if (serial_number) {
        if (wcscmp(serial_number, cur_dev->serial_number) == 0) {
          path_to_open = cur_dev->path;
          break;
        }
      }
      else {
        path_to_open = cur_dev->path;
        break;
      }
    }
    cur_dev = cur_dev->next;
  }

  if (path_to_open) {
    /* Open the device */
    handle = hid_open_path(path_to_open);
  }

  hid_free_enumeration(devs);

  return handle;
}

static void hid_device_removal_callback(void *context, IOReturn result,
                                        void *sender)
{
  /* Stop the Run Loop for this device. */
  hid_device *d = context;

  d->disconnected = 1;
  CFRunLoopStop(d->run_loop);
}

/* The Run Loop calls this function for each input report received.
   This function puts the data into a linked list to be picked up by
   hid_read(). */
static void hid_report_callback(void *context, IOReturn result, void *sender,
                         IOHIDReportType report_type, uint32_t report_id,
                         uint8_t *report, CFIndex report_length)
{
  struct input_report *rpt;
  hid_device *dev = context;

  /* Make a new Input Report object */
  rpt = calloc(1, sizeof(struct input_report));
  rpt->data = calloc(1, report_length);
  memcpy(rpt->data, report, report_length);
  rpt->len = report_length;
  rpt->next = NULL;

  /* Lock this section */
  pthread_mutex_lock(&dev->mutex);

  /* Attach the new report object to the end of the list. */
  if (dev->input_reports == NULL) {
    /* The list is empty. Put it at the root. */
    dev->input_reports = rpt;
  }
  else {
    /* Find the end of the list and attach. */
    struct input_report *cur = dev->input_reports;
    int num_queued = 0;
    while (cur->next != NULL) {
      cur = cur->next;
      num_queued++;
    }
    cur->next = rpt;

    /* Pop one off if we've reached 30 in the queue. This
       way we don't grow forever if the user never reads
       anything from the device. */
    if (num_queued > 30) {
      return_data(dev, NULL, 0);
    }
  }

  /* Signal a waiting thread that there is data. */
  pthread_cond_signal(&dev->condition);

  /* Unlock */
  pthread_mutex_unlock(&dev->mutex);

}

/* This gets called when the read_thread's run loop gets signaled by
   hid_close(), and serves to stop the read_thread's run loop. */
static void perform_signal_callback(void *context)
{
  hid_device *dev = context;
  CFRunLoopStop(dev->run_loop); /*TODO: CFRunLoopGetCurrent()*/
}

static void *read_thread(void *param)
{
  hid_device *dev = param;
  SInt32 code;

  /* Move the device's run loop to this thread. */
  IOHIDDeviceScheduleWithRunLoop(dev->device_handle, CFRunLoopGetCurrent(), dev->run_loop_mode);

  /* Create the RunLoopSource which is used to signal the
     event loop to stop when hid_close() is called. */
  CFRunLoopSourceContext ctx;
  memset(&ctx, 0, sizeof(ctx));
  ctx.version = 0;
  ctx.info = dev;
  ctx.perform = &perform_signal_callback;
  dev->source = CFRunLoopSourceCreate(kCFAllocatorDefault, 0/*order*/, &ctx);
  CFRunLoopAddSource(CFRunLoopGetCurrent(), dev->source, dev->run_loop_mode);

  /* Store off the Run Loop so it can be stopped from hid_close()
     and on device disconnection. */
  dev->run_loop = CFRunLoopGetCurrent();

  /* Notify the main thread that the read thread is up and running. */
  pthread_barrier_wait(&dev->barrier);

  /* Run the Event Loop. CFRunLoopRunInMode() will dispatch HID input
     reports into the hid_report_callback(). */
  while (!dev->shutdown_thread && !dev->disconnected) {
    code = CFRunLoopRunInMode(dev->run_loop_mode, 1000/*sec*/, FALSE);
    /* Return if the device has been disconnected */
    if (code == kCFRunLoopRunFinished) {
      dev->disconnected = 1;
      break;
    }


    /* Break if The Run Loop returns Finished or Stopped. */
    if (code != kCFRunLoopRunTimedOut &&
        code != kCFRunLoopRunHandledSource) {
      /* There was some kind of error. Setting
         shutdown seems to make sense, but
         there may be something else more appropriate */
      dev->shutdown_thread = 1;
      break;
    }
  }

  /* Now that the read thread is stopping, Wake any threads which are
     waiting on data (in hid_read_timeout()). Do this under a mutex to
     make sure that a thread which is about to go to sleep waiting on
     the condition actually will go to sleep before the condition is
     signaled. */
  pthread_mutex_lock(&dev->mutex);
  pthread_cond_broadcast(&dev->condition);
  pthread_mutex_unlock(&dev->mutex);

  /* Wait here until hid_close() is called and makes it past
     the call to CFRunLoopWakeUp(). This thread still needs to
     be valid when that function is called on the other thread. */
  pthread_barrier_wait(&dev->shutdown_barrier);

  return NULL;
}

/* hid_open_path()
 *
 * path must be a valid path to an IOHIDDevice in the IOService plane
 * Example: "IOService:/AppleACPIPlatformExpert/PCI0@0/AppleACPIPCI/EHC1@1D,7/AppleUSBEHCI/PLAYSTATION(R)3 Controller@fd120000/IOUSBInterface@0/IOUSBHIDDriver"
 */
hid_device * HID_API_EXPORT hid_open_path(const char *path)
{
  hid_device *dev = NULL;
  io_registry_entry_t entry = MACH_PORT_NULL;

  dev = new_hid_device();

  /* Set up the HID Manager if it hasn't been done */
  if (hid_init() < 0)
    return NULL;

  /* Get the IORegistry entry for the given path */
  entry = IORegistryEntryFromPath(kIOMasterPortDefault, path);
  if (entry == MACH_PORT_NULL) {
    /* Path wasn't valid (maybe device was removed?) */
    goto return_error;
  }

  /* Create an IOHIDDevice for the entry */
  dev->device_handle = IOHIDDeviceCreate(kCFAllocatorDefault, entry);
  if (dev->device_handle == NULL) {
    /* Error creating the HID device */
    goto return_error;
  }

  /* Open the IOHIDDevice */
  IOReturn ret = IOHIDDeviceOpen(dev->device_handle, kIOHIDOptionsTypeSeizeDevice);
  if (ret == kIOReturnSuccess) {
    char str[32];

    /* Create the buffers for receiving data */
    dev->max_input_report_len = (CFIndex) get_max_report_length(dev->device_handle);
    dev->input_report_buf = calloc(dev->max_input_report_len, sizeof(uint8_t));

    /* Create the Run Loop Mode for this device.
       printing the reference seems to work. */
    sprintf(str, "HIDAPI_%p", dev->device_handle);
    dev->run_loop_mode =
      CFStringCreateWithCString(NULL, str, kCFStringEncodingASCII);

    /* Attach the device to a Run Loop */
    IOHIDDeviceRegisterInputReportCallback(
      dev->device_handle, dev->input_report_buf, dev->max_input_report_len,
      &hid_report_callback, dev);
    IOHIDDeviceRegisterRemovalCallback(dev->device_handle, hid_device_removal_callback, dev);

    /* Start the read thread */
    pthread_create(&dev->thread, NULL, read_thread, dev);

    /* Wait here for the read thread to be initialized. */
    pthread_barrier_wait(&dev->barrier);

    IOObjectRelease(entry);
    return dev;
  }
  else {
    goto return_error;
  }

return_error:
  if (dev->device_handle != NULL)
    CFRelease(dev->device_handle);

  if (entry != MACH_PORT_NULL)
    IOObjectRelease(entry);

  free_hid_device(dev);
  return NULL;
}

static int set_report(hid_device *dev, IOHIDReportType type, const unsigned char *data, size_t length)
{
  const unsigned char *data_to_send;
  size_t length_to_send;
  IOReturn res;

  /* Return if the device has been disconnected. */
  if (dev->disconnected)
    return -1;

  if (data[0] == 0x0) {
    /* Not using numbered Reports.
       Don't send the report number. */
    data_to_send = data+1;
    length_to_send = length-1;
  }
  else {
    /* Using numbered Reports.
       Send the Report Number */
    data_to_send = data;
    length_to_send = length;
  }

  if (!dev->disconnected) {
    res = IOHIDDeviceSetReport(dev->device_handle,
             type,
             data[0], /* Report ID*/
             data_to_send, length_to_send);

    if (res == kIOReturnSuccess) {
      return length;
    }
    else
      return -1;
  }

  return -1;
}

int HID_API_EXPORT hid_write(hid_device *dev, const unsigned char *data, size_t length)
{
  return set_report(dev, kIOHIDReportTypeOutput, data, length);
}

/* Helper function, so that this isn't duplicated in hid_read(). */
static int return_data(hid_device *dev, unsigned char *data, size_t length)
{
  /* Copy the data out of the linked list item (rpt) into the
     return buffer (data), and delete the liked list item. */
  struct input_report *rpt = dev->input_reports;
  size_t len = (length < rpt->len)? length: rpt->len;
  memcpy(data, rpt->data, len);
  dev->input_reports = rpt->next;
  free(rpt->data);
  free(rpt);
  return len;
}

static int cond_wait(const hid_device *dev, pthread_cond_t *cond, pthread_mutex_t *mutex)
{
  while (!dev->input_reports) {
    int res = pthread_cond_wait(cond, mutex);
    if (res != 0)
      return res;

    /* A res of 0 means we may have been signaled or it may
       be a spurious wakeup. Check to see that there's acutally
       data in the queue before returning, and if not, go back
       to sleep. See the pthread_cond_timedwait() man page for
       details. */

    if (dev->shutdown_thread || dev->disconnected)
      return -1;
  }

  return 0;
}

static int cond_timedwait(const hid_device *dev, pthread_cond_t *cond, pthread_mutex_t *mutex, const struct timespec *abstime)
{
  while (!dev->input_reports) {
    int res = pthread_cond_timedwait(cond, mutex, abstime);
    if (res != 0)
      return res;

    /* A res of 0 means we may have been signaled or it may
       be a spurious wakeup. Check to see that there's acutally
       data in the queue before returning, and if not, go back
       to sleep. See the pthread_cond_timedwait() man page for
       details. */

    if (dev->shutdown_thread || dev->disconnected)
      return -1;
  }

  return 0;

}

int HID_API_EXPORT hid_read_timeout(hid_device *dev, unsigned char *data, size_t length, int milliseconds)
{
  int bytes_read = -1;

  /* Lock the access to the report list. */
  pthread_mutex_lock(&dev->mutex);

  /* There's an input report queued up. Return it. */
  if (dev->input_reports) {
    /* Return the first one */
    bytes_read = return_data(dev, data, length);
    goto ret;
  }

  /* Return if the device has been disconnected. */
  if (dev->disconnected) {
    bytes_read = -1;
    goto ret;
  }

  if (dev->shutdown_thread) {
    /* This means the device has been closed (or there
       has been an error. An error code of -1 should
       be returned. */
    bytes_read = -1;
    goto ret;
  }

  /* There is no data. Go to sleep and wait for data. */

  if (milliseconds == -1) {
    /* Blocking */
    int res;
    res = cond_wait(dev, &dev->condition, &dev->mutex);
    if (res == 0)
      bytes_read = return_data(dev, data, length);
    else {
      /* There was an error, or a device disconnection. */
      bytes_read = -1;
    }
  }
  else if (milliseconds > 0) {
    /* Non-blocking, but called with timeout. */
    int res;
    struct timespec ts;
    struct timeval tv;
    gettimeofday(&tv, NULL);
    TIMEVAL_TO_TIMESPEC(&tv, &ts);
    ts.tv_sec += milliseconds / 1000;
    ts.tv_nsec += (milliseconds % 1000) * 1000000;
    if (ts.tv_nsec >= 1000000000L) {
      ts.tv_sec++;
      ts.tv_nsec -= 1000000000L;
    }

    res = cond_timedwait(dev, &dev->condition, &dev->mutex, &ts);
    if (res == 0)
      bytes_read = return_data(dev, data, length);
    else if (res == ETIMEDOUT)
      bytes_read = 0;
    else
      bytes_read = -1;
  }
  else {
    /* Purely non-blocking */
    bytes_read = 0;
  }

ret:
  /* Unlock */
  pthread_mutex_unlock(&dev->mutex);
  return bytes_read;
}

int HID_API_EXPORT hid_read(hid_device *dev, unsigned char *data, size_t length)
{
  return hid_read_timeout(dev, data, length, (dev->blocking)? -1: 0);
}

int HID_API_EXPORT hid_set_nonblocking(hid_device *dev, int nonblock)
{
  /* All Nonblocking operation is handled by the library. */
  dev->blocking = !nonblock;

  return 0;
}

int HID_API_EXPORT hid_send_feature_report(hid_device *dev, const unsigned char *data, size_t length)
{
  return set_report(dev, kIOHIDReportTypeFeature, data, length);
}

int HID_API_EXPORT hid_get_feature_report(hid_device *dev, unsigned char *data, size_t length)
{
  CFIndex len = length;
  IOReturn res;

  /* Return if the device has been unplugged. */
  if (dev->disconnected)
    return -1;

  res = IOHIDDeviceGetReport(dev->device_handle,
                             kIOHIDReportTypeFeature,
                             data[0], /* Report ID */
                             data, &len);
  if (res == kIOReturnSuccess)
    return len;
  else
    return -1;
}


void HID_API_EXPORT hid_close(hid_device *dev)
{
  if (!dev)
    return;

  /* Disconnect the report callback before close. */
  if (!dev->disconnected) {
    IOHIDDeviceRegisterInputReportCallback(
      dev->device_handle, dev->input_report_buf, dev->max_input_report_len,
      NULL, dev);
    IOHIDDeviceRegisterRemovalCallback(dev->device_handle, NULL, dev);
    IOHIDDeviceUnscheduleFromRunLoop(dev->device_handle, dev->run_loop, dev->run_loop_mode);
    IOHIDDeviceScheduleWithRunLoop(dev->device_handle, CFRunLoopGetMain(), kCFRunLoopDefaultMode);
  }

  /* Cause read_thread() to stop. */
  dev->shutdown_thread = 1;

  /* Wake up the run thread's event loop so that the thread can exit. */
  CFRunLoopSourceSignal(dev->source);
  CFRunLoopWakeUp(dev->run_loop);

  /* Notify the read thread that it can shut down now. */
  pthread_barrier_wait(&dev->shutdown_barrier);

  /* Wait for read_thread() to end. */
  pthread_join(dev->thread, NULL);

  /* Close the OS handle to the device, but only if it's not
     been unplugged. If it's been unplugged, then calling
     IOHIDDeviceClose() will crash. */
  if (!dev->disconnected) {
    IOHIDDeviceClose(dev->device_handle, kIOHIDOptionsTypeSeizeDevice);
  }

  /* Clear out the queue of received reports. */
  pthread_mutex_lock(&dev->mutex);
  while (dev->input_reports) {
    return_data(dev, NULL, 0);
  }
  pthread_mutex_unlock(&dev->mutex);
  CFRelease(dev->device_handle);

  free_hid_device(dev);
}

int HID_API_EXPORT_CALL hid_get_manufacturer_string(hid_device *dev, wchar_t *string, size_t maxlen)
{
  return get_manufacturer_string(dev->device_handle, string, maxlen);
}

int HID_API_EXPORT_CALL hid_get_product_string(hid_device *dev, wchar_t *string, size_t maxlen)
{
  return get_product_string(dev->device_handle, string, maxlen);
}

int HID_API_EXPORT_CALL hid_get_serial_number_string(hid_device *dev, wchar_t *string, size_t maxlen)
{
  return get_serial_number(dev->device_handle, string, maxlen);
}

int HID_API_EXPORT_CALL hid_get_indexed_string(hid_device *dev, int string_index, wchar_t *string, size_t maxlen)
{
  /* TODO: */

  return 0;
}


HID_API_EXPORT const wchar_t * HID_API_CALL  hid_error(hid_device *dev)
{
  /* TODO: */

  return NULL;
}







#if 0
static int32_t get_location_id(IOHIDDeviceRef device)
{
  return get_int_property(device, CFSTR(kIOHIDLocationIDKey));
}

static int32_t get_usage(IOHIDDeviceRef device)
{
  int32_t res;
  res = get_int_property(device, CFSTR(kIOHIDDeviceUsageKey));
  if (!res)
    res = get_int_property(device, CFSTR(kIOHIDPrimaryUsageKey));
  return res;
}

static int32_t get_usage_page(IOHIDDeviceRef device)
{
  int32_t res;
  res = get_int_property(device, CFSTR(kIOHIDDeviceUsagePageKey));
  if (!res)
    res = get_int_property(device, CFSTR(kIOHIDPrimaryUsagePageKey));
  return res;
}

static int get_transport(IOHIDDeviceRef device, wchar_t *buf, size_t len)
{
  return get_string_property(device, CFSTR(kIOHIDTransportKey), buf, len);
}


int main(void)
{
  IOHIDManagerRef mgr;
  int i;

  mgr = IOHIDManagerCreate(kCFAllocatorDefault, kIOHIDOptionsTypeNone);
  IOHIDManagerSetDeviceMatching(mgr, NULL);
  IOHIDManagerOpen(mgr, kIOHIDOptionsTypeNone);

  CFSetRef device_set = IOHIDManagerCopyDevices(mgr);

  CFIndex num_devices = CFSetGetCount(device_set);
  IOHIDDeviceRef *device_array = calloc(num_devices, sizeof(IOHIDDeviceRef));
  CFSetGetValues(device_set, (const void **) device_array);

  for (i = 0; i < num_devices; i++) {
    IOHIDDeviceRef dev = device_array[i];
    printf("Device: %p\n", dev);
    printf("  %04hx %04hx\n", get_vendor_id(dev), get_product_id(dev));

    wchar_t serial[256], buf[256];
    char cbuf[256];
    get_serial_number(dev, serial, 256);


    printf("  Serial: %ls\n", serial);
    printf("  Loc: %ld\n", get_location_id(dev));
    get_transport(dev, buf, 256);
    printf("  Trans: %ls\n", buf);
    make_path(dev, cbuf, 256);
    printf("  Path: %s\n", cbuf);

  }

  return 0;
}
#endif