text: /*
   * Public libusb header file
   * Copyright © 2001 Johannes Erdfelt <johannes@erdfelt.com>
   * Copyright © 2007-2008 Daniel Drake <dsd@gentoo.org>
   * Copyright © 2012 Pete Batard <pete@akeo.ie>
   * Copyright © 2012-2018 Nathan Hjelm <hjelmn@cs.unm.edu>
   * Copyright © 2014-2020 Chris Dickens <christopher.a.dickens@gmail.com>
   * For more information, please visit: http://libusb.info
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * This library is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with this library; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  #ifndef LIBUSB_H
  #define LIBUSB_H
  
  #if defined(_MSC_VER)
  /* on MS environments, the inline keyword is available in C++ only */
  #if !defined(__cplusplus)
  #define inline __inline
  #endif
  /* ssize_t is also not available */
  #ifndef _SSIZE_T_DEFINED
  #define _SSIZE_T_DEFINED
  #include <basetsd.h>
  typedef SSIZE_T ssize_t;
  #endif /* _SSIZE_T_DEFINED */
  #endif /* _MSC_VER */
  
  #include <limits.h>
  #include <stdint.h>
  #include <sys/types.h>
  #if !defined(_MSC_VER)
  #include <sys/time.h>
  #endif
  #include <time.h>
  
  #if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L)
  #define ZERO_SIZED_ARRAY		/* [] - valid C99 code */
  #else
  #define ZERO_SIZED_ARRAY	0	/* [0] - non-standard, but usually working code */
  #endif /* __STDC_VERSION__ */
  
  /* 'interface' might be defined as a macro on Windows, so we need to
   * undefine it so as not to break the current libusb API, because
   * libusb_config_descriptor has an 'interface' member
   * As this can be problematic if you include windows.h after libusb.h
   * in your sources, we force windows.h to be included first. */
  #if defined(_WIN32) || defined(__CYGWIN__)
  #include <windows.h>
  #if defined(interface)
  #undef interface
  #endif
  #if !defined(__CYGWIN__)
  #include <winsock.h>
  #endif
  #endif /* _WIN32 || __CYGWIN__ */
  
  #if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5))
  #define LIBUSB_DEPRECATED_FOR(f) __attribute__ ((deprecated ("Use " #f " instead")))
  #elif defined(__GNUC__) && (__GNUC__ >= 3)
  #define LIBUSB_DEPRECATED_FOR(f) __attribute__ ((deprecated))
  #else
  #define LIBUSB_DEPRECATED_FOR(f)
  #endif /* __GNUC__ */
  
  #if defined(__GNUC__)
  #define LIBUSB_PACKED __attribute__ ((packed))
  #else
  #define LIBUSB_PACKED
  #endif /* __GNUC__ */
  
  /** \def LIBUSB_CALL
   * \ingroup libusb_misc
   * libusb's Windows calling convention.
   *
   * Under Windows, the selection of available compilers and configurations
   * means that, unlike other platforms, there is not <em>one true calling
   * convention</em> (calling convention: the manner in which parameters are
   * passed to functions in the generated assembly code).
   *
   * Matching the Windows API itself, libusb uses the WINAPI convention (which
   * translates to the <tt>stdcall</tt> convention) and guarantees that the
   * library is compiled in this way. The public header file also includes
   * appropriate annotations so that your own software will use the right
   * convention, even if another convention is being used by default within
   * your codebase.
   *
   * The one consideration that you must apply in your software is to mark
   * all functions which you use as libusb callbacks with this LIBUSB_CALL
   * annotation, so that they too get compiled for the correct calling
   * convention.
   *
   * On non-Windows operating systems, this macro is defined as nothing. This
   * means that you can apply it to your code without worrying about
   * cross-platform compatibility.
   */
  /* LIBUSB_CALL must be defined on both definition and declaration of libusb
   * functions. You'd think that declaration would be enough, but cygwin will
   * complain about conflicting types unless both are marked this way.
   * The placement of this macro is important too; it must appear after the
   * return type, before the function name. See internal documentation for
   * API_EXPORTED.
   */
  #if defined(_WIN32) || defined(__CYGWIN__)
  #define LIBUSB_CALL WINAPI
  #else
  #define LIBUSB_CALL
  #endif /* _WIN32 || __CYGWIN__ */
  
  /** \def LIBUSB_API_VERSION
   * \ingroup libusb_misc
   * libusb's API version.
   *
   * Since version 1.0.13, to help with feature detection, libusb defines
   * a LIBUSB_API_VERSION macro that gets increased every time there is a
   * significant change to the API, such as the introduction of a new call,
   * the definition of a new macro/enum member, or any other element that
   * libusb applications may want to detect at compilation time.
   *
   * The macro is typically used in an application as follows:
   * \code
   * #if defined(LIBUSB_API_VERSION) && (LIBUSB_API_VERSION >= 0x01001234)
   * // Use one of the newer features from the libusb API
   * #endif
   * \endcode
   *
   * Internally, LIBUSB_API_VERSION is defined as follows:
   * (libusb major << 24) | (libusb minor << 16) | (16 bit incremental)
   */
  #define LIBUSB_API_VERSION 0x01000109
  
  /* The following is kept for compatibility, but will be deprecated in the future */
  #define LIBUSBX_API_VERSION LIBUSB_API_VERSION
  
  #if defined(__cplusplus)
  extern "C" {
  #endif
  
  /**
   * \ingroup libusb_misc
   * Convert a 16-bit value from host-endian to little-endian format. On
   * little endian systems, this function does nothing. On big endian systems,
   * the bytes are swapped.
   * \param x the host-endian value to convert
   * \returns the value in little-endian byte order
   */
  static inline uint16_t libusb_cpu_to_le16(const uint16_t x)
  {
  	union {
  		uint8_t  b8[2];
  		uint16_t b16;
  	} _tmp;
  	_tmp.b8[1] = (uint8_t) (x >> 8);
  	_tmp.b8[0] = (uint8_t) (x & 0xff);
  	return _tmp.b16;
  }
  
  /** \def libusb_le16_to_cpu
   * \ingroup libusb_misc
   * Convert a 16-bit value from little-endian to host-endian format. On
   * little endian systems, this function does nothing. On big endian systems,
   * the bytes are swapped.
   * \param x the little-endian value to convert
   * \returns the value in host-endian byte order
   */
  #define libusb_le16_to_cpu libusb_cpu_to_le16
  
  /* standard USB stuff */
  
  /** \ingroup libusb_desc
   * Device and/or Interface Class codes */
  enum libusb_class_code {
  	/** In the context of a \ref libusb_device_descriptor "device descriptor",
  	 * this bDeviceClass value indicates that each interface specifies its
  	 * own class information and all interfaces operate independently.
  	 */
  	LIBUSB_CLASS_PER_INTERFACE = 0x00,
  
  	/** Audio class */
  	LIBUSB_CLASS_AUDIO = 0x01,
  
  	/** Communications class */
  	LIBUSB_CLASS_COMM = 0x02,
  
  	/** Human Interface Device class */
  	LIBUSB_CLASS_HID = 0x03,
  
  	/** Physical */
  	LIBUSB_CLASS_PHYSICAL = 0x05,
  
  	/** Image class */
  	LIBUSB_CLASS_IMAGE = 0x06,
  	LIBUSB_CLASS_PTP = 0x06, /* legacy name from libusb-0.1 usb.h */
  
  	/** Printer class */
  	LIBUSB_CLASS_PRINTER = 0x07,
  
  	/** Mass storage class */
  	LIBUSB_CLASS_MASS_STORAGE = 0x08,
  
  	/** Hub class */
  	LIBUSB_CLASS_HUB = 0x09,
  
  	/** Data class */
  	LIBUSB_CLASS_DATA = 0x0a,
  
  	/** Smart Card */
  	LIBUSB_CLASS_SMART_CARD = 0x0b,
  
  	/** Content Security */
  	LIBUSB_CLASS_CONTENT_SECURITY = 0x0d,
  
  	/** Video */
  	LIBUSB_CLASS_VIDEO = 0x0e,
  
  	/** Personal Healthcare */
  	LIBUSB_CLASS_PERSONAL_HEALTHCARE = 0x0f,
  
  	/** Diagnostic Device */
  	LIBUSB_CLASS_DIAGNOSTIC_DEVICE = 0xdc,
  
  	/** Wireless class */
  	LIBUSB_CLASS_WIRELESS = 0xe0,
  
  	/** Miscellaneous class */
  	LIBUSB_CLASS_MISCELLANEOUS = 0xef,
  
  	/** Application class */
  	LIBUSB_CLASS_APPLICATION = 0xfe,
  
  	/** Class is vendor-specific */
  	LIBUSB_CLASS_VENDOR_SPEC = 0xff
  };
  
  /** \ingroup libusb_desc
   * Descriptor types as defined by the USB specification. */
  enum libusb_descriptor_type {
  	/** Device descriptor. See libusb_device_descriptor. */
  	LIBUSB_DT_DEVICE = 0x01,
  
  	/** Configuration descriptor. See libusb_config_descriptor. */
  	LIBUSB_DT_CONFIG = 0x02,
  
  	/** String descriptor */
  	LIBUSB_DT_STRING = 0x03,
  
  	/** Interface descriptor. See libusb_interface_descriptor. */
  	LIBUSB_DT_INTERFACE = 0x04,
  
  	/** Endpoint descriptor. See libusb_endpoint_descriptor. */
  	LIBUSB_DT_ENDPOINT = 0x05,
  
  	/** BOS descriptor */
  	LIBUSB_DT_BOS = 0x0f,
  
  	/** Device Capability descriptor */
  	LIBUSB_DT_DEVICE_CAPABILITY = 0x10,
  
  	/** HID descriptor */
  	LIBUSB_DT_HID = 0x21,
  
  	/** HID report descriptor */
  	LIBUSB_DT_REPORT = 0x22,
  
  	/** Physical descriptor */
  	LIBUSB_DT_PHYSICAL = 0x23,
  
  	/** Hub descriptor */
  	LIBUSB_DT_HUB = 0x29,
  
  	/** SuperSpeed Hub descriptor */
  	LIBUSB_DT_SUPERSPEED_HUB = 0x2a,
  
  	/** SuperSpeed Endpoint Companion descriptor */
  	LIBUSB_DT_SS_ENDPOINT_COMPANION = 0x30
  };
  
  /* Descriptor sizes per descriptor type */
  #define LIBUSB_DT_DEVICE_SIZE			18
  #define LIBUSB_DT_CONFIG_SIZE			9
  #define LIBUSB_DT_INTERFACE_SIZE		9
  #define LIBUSB_DT_ENDPOINT_SIZE			7
  #define LIBUSB_DT_ENDPOINT_AUDIO_SIZE		9	/* Audio extension */
  #define LIBUSB_DT_HUB_NONVAR_SIZE		7
  #define LIBUSB_DT_SS_ENDPOINT_COMPANION_SIZE	6
  #define LIBUSB_DT_BOS_SIZE			5
  #define LIBUSB_DT_DEVICE_CAPABILITY_SIZE	3
  
  /* BOS descriptor sizes */
  #define LIBUSB_BT_USB_2_0_EXTENSION_SIZE	7
  #define LIBUSB_BT_SS_USB_DEVICE_CAPABILITY_SIZE	10
  #define LIBUSB_BT_CONTAINER_ID_SIZE		20
  
  /* We unwrap the BOS => define its max size */
  #define LIBUSB_DT_BOS_MAX_SIZE				\
  	(LIBUSB_DT_BOS_SIZE +				\
  	 LIBUSB_BT_USB_2_0_EXTENSION_SIZE +		\
  	 LIBUSB_BT_SS_USB_DEVICE_CAPABILITY_SIZE +	\
  	 LIBUSB_BT_CONTAINER_ID_SIZE)
  
  #define LIBUSB_ENDPOINT_ADDRESS_MASK		0x0f	/* in bEndpointAddress */
  #define LIBUSB_ENDPOINT_DIR_MASK		0x80
  
  /** \ingroup libusb_desc
   * Endpoint direction. Values for bit 7 of the
   * \ref libusb_endpoint_descriptor::bEndpointAddress "endpoint address" scheme.
   */
  enum libusb_endpoint_direction {
  	/** Out: host-to-device */
  	LIBUSB_ENDPOINT_OUT = 0x00,
  
  	/** In: device-to-host */
  	LIBUSB_ENDPOINT_IN = 0x80
  };
  
  #define LIBUSB_TRANSFER_TYPE_MASK		0x03	/* in bmAttributes */
  
  /** \ingroup libusb_desc
   * Endpoint transfer type. Values for bits 0:1 of the
   * \ref libusb_endpoint_descriptor::bmAttributes "endpoint attributes" field.
   */
  enum libusb_endpoint_transfer_type {
  	/** Control endpoint */
  	LIBUSB_ENDPOINT_TRANSFER_TYPE_CONTROL = 0x0,
  
  	/** Isochronous endpoint */
  	LIBUSB_ENDPOINT_TRANSFER_TYPE_ISOCHRONOUS = 0x1,
  
  	/** Bulk endpoint */
  	LIBUSB_ENDPOINT_TRANSFER_TYPE_BULK = 0x2,
  
  	/** Interrupt endpoint */
  	LIBUSB_ENDPOINT_TRANSFER_TYPE_INTERRUPT = 0x3
  };
  
  /** \ingroup libusb_misc
   * Standard requests, as defined in table 9-5 of the USB 3.0 specifications */
  enum libusb_standard_request {
  	/** Request status of the specific recipient */
  	LIBUSB_REQUEST_GET_STATUS = 0x00,
  
  	/** Clear or disable a specific feature */
  	LIBUSB_REQUEST_CLEAR_FEATURE = 0x01,
  
  	/* 0x02 is reserved */
  
  	/** Set or enable a specific feature */
  	LIBUSB_REQUEST_SET_FEATURE = 0x03,
  
  	/* 0x04 is reserved */
  
  	/** Set device address for all future accesses */
  	LIBUSB_REQUEST_SET_ADDRESS = 0x05,
  
  	/** Get the specified descriptor */
  	LIBUSB_REQUEST_GET_DESCRIPTOR = 0x06,
  
  	/** Used to update existing descriptors or add new descriptors */
  	LIBUSB_REQUEST_SET_DESCRIPTOR = 0x07,
  
  	/** Get the current device configuration value */
  	LIBUSB_REQUEST_GET_CONFIGURATION = 0x08,
  
  	/** Set device configuration */
  	LIBUSB_REQUEST_SET_CONFIGURATION = 0x09,
  
  	/** Return the selected alternate setting for the specified interface */
  	LIBUSB_REQUEST_GET_INTERFACE = 0x0a,
  
  	/** Select an alternate interface for the specified interface */
  	LIBUSB_REQUEST_SET_INTERFACE = 0x0b,
  
  	/** Set then report an endpoint's synchronization frame */
  	LIBUSB_REQUEST_SYNCH_FRAME = 0x0c,
  
  	/** Sets both the U1 and U2 Exit Latency */
  	LIBUSB_REQUEST_SET_SEL = 0x30,
  
  	/** Delay from the time a host transmits a packet to the time it is
  	  * received by the device. */
  	LIBUSB_SET_ISOCH_DELAY = 0x31
  };
  
  /** \ingroup libusb_misc
   * Request type bits of the
   * \ref libusb_control_setup::bmRequestType "bmRequestType" field in control
   * transfers. */
  enum libusb_request_type {
  	/** Standard */
  	LIBUSB_REQUEST_TYPE_STANDARD = (0x00 << 5),
  
  	/** Class */
  	LIBUSB_REQUEST_TYPE_CLASS = (0x01 << 5),
  
  	/** Vendor */
  	LIBUSB_REQUEST_TYPE_VENDOR = (0x02 << 5),
  
  	/** Reserved */
  	LIBUSB_REQUEST_TYPE_RESERVED = (0x03 << 5)
  };
  
  /** \ingroup libusb_misc
   * Recipient bits of the
   * \ref libusb_control_setup::bmRequestType "bmRequestType" field in control
   * transfers. Values 4 through 31 are reserved. */
  enum libusb_request_recipient {
  	/** Device */
  	LIBUSB_RECIPIENT_DEVICE = 0x00,
  
  	/** Interface */
  	LIBUSB_RECIPIENT_INTERFACE = 0x01,
  
  	/** Endpoint */
  	LIBUSB_RECIPIENT_ENDPOINT = 0x02,
  
  	/** Other */
  	LIBUSB_RECIPIENT_OTHER = 0x03
  };
  
  #define LIBUSB_ISO_SYNC_TYPE_MASK	0x0c
  
  /** \ingroup libusb_desc
   * Synchronization type for isochronous endpoints. Values for bits 2:3 of the
   * \ref libusb_endpoint_descriptor::bmAttributes "bmAttributes" field in
   * libusb_endpoint_descriptor.
   */
  enum libusb_iso_sync_type {
  	/** No synchronization */
  	LIBUSB_ISO_SYNC_TYPE_NONE = 0x0,
  
  	/** Asynchronous */
  	LIBUSB_ISO_SYNC_TYPE_ASYNC = 0x1,
  
  	/** Adaptive */
  	LIBUSB_ISO_SYNC_TYPE_ADAPTIVE = 0x2,
  
  	/** Synchronous */
  	LIBUSB_ISO_SYNC_TYPE_SYNC = 0x3
  };
  
  #define LIBUSB_ISO_USAGE_TYPE_MASK	0x30
  
  /** \ingroup libusb_desc
   * Usage type for isochronous endpoints. Values for bits 4:5 of the
   * \ref libusb_endpoint_descriptor::bmAttributes "bmAttributes" field in
   * libusb_endpoint_descriptor.
   */
  enum libusb_iso_usage_type {
  	/** Data endpoint */
  	LIBUSB_ISO_USAGE_TYPE_DATA = 0x0,
  
  	/** Feedback endpoint */
  	LIBUSB_ISO_USAGE_TYPE_FEEDBACK = 0x1,
  
  	/** Implicit feedback Data endpoint */
  	LIBUSB_ISO_USAGE_TYPE_IMPLICIT = 0x2
  };
  
  /** \ingroup libusb_desc
   * Supported speeds (wSpeedSupported) bitfield. Indicates what
   * speeds the device supports.
   */
  enum libusb_supported_speed {
  	/** Low speed operation supported (1.5MBit/s). */
  	LIBUSB_LOW_SPEED_OPERATION = (1 << 0),
  
  	/** Full speed operation supported (12MBit/s). */
  	LIBUSB_FULL_SPEED_OPERATION = (1 << 1),
  
  	/** High speed operation supported (480MBit/s). */
  	LIBUSB_HIGH_SPEED_OPERATION = (1 << 2),
  
  	/** Superspeed operation supported (5000MBit/s). */
  	LIBUSB_SUPER_SPEED_OPERATION = (1 << 3)
  };
  
  /** \ingroup libusb_desc
   * Masks for the bits of the
   * \ref libusb_usb_2_0_extension_descriptor::bmAttributes "bmAttributes" field
   * of the USB 2.0 Extension descriptor.
   */
  enum libusb_usb_2_0_extension_attributes {
  	/** Supports Link Power Management (LPM) */
  	LIBUSB_BM_LPM_SUPPORT = (1 << 1)
  };
  
  /** \ingroup libusb_desc
   * Masks for the bits of the
   * \ref libusb_ss_usb_device_capability_descriptor::bmAttributes "bmAttributes" field
   * field of the SuperSpeed USB Device Capability descriptor.
   */
  enum libusb_ss_usb_device_capability_attributes {
  	/** Supports Latency Tolerance Messages (LTM) */
  	LIBUSB_BM_LTM_SUPPORT = (1 << 1)
  };
  
  /** \ingroup libusb_desc
   * USB capability types
   */
  enum libusb_bos_type {
  	/** Wireless USB device capability */
  	LIBUSB_BT_WIRELESS_USB_DEVICE_CAPABILITY = 0x01,
  
  	/** USB 2.0 extensions */
  	LIBUSB_BT_USB_2_0_EXTENSION = 0x02,
  
  	/** SuperSpeed USB device capability */
  	LIBUSB_BT_SS_USB_DEVICE_CAPABILITY = 0x03,
  
  	/** Container ID type */
  	LIBUSB_BT_CONTAINER_ID = 0x04
  };
  
  /** \ingroup libusb_desc
   * A structure representing the standard USB device descriptor. This
   * descriptor is documented in section 9.6.1 of the USB 3.0 specification.
   * All multiple-byte fields are represented in host-endian format.
   */
  struct libusb_device_descriptor {
  	/** Size of this descriptor (in bytes) */
  	uint8_t  bLength;
  
  	/** Descriptor type. Will have value
  	 * \ref libusb_descriptor_type::LIBUSB_DT_DEVICE LIBUSB_DT_DEVICE in this
  	 * context. */
  	uint8_t  bDescriptorType;
  
  	/** USB specification release number in binary-coded decimal. A value of
  	 * 0x0200 indicates USB 2.0, 0x0110 indicates USB 1.1, etc. */
  	uint16_t bcdUSB;
  
  	/** USB-IF class code for the device. See \ref libusb_class_code. */
  	uint8_t  bDeviceClass;
  
  	/** USB-IF subclass code for the device, qualified by the bDeviceClass
  	 * value */
  	uint8_t  bDeviceSubClass;
  
  	/** USB-IF protocol code for the device, qualified by the bDeviceClass and
  	 * bDeviceSubClass values */
  	uint8_t  bDeviceProtocol;
  
  	/** Maximum packet size for endpoint 0 */
  	uint8_t  bMaxPacketSize0;
  
  	/** USB-IF vendor ID */
  	uint16_t idVendor;
  
  	/** USB-IF product ID */
  	uint16_t idProduct;
  
  	/** Device release number in binary-coded decimal */
  	uint16_t bcdDevice;
  
  	/** Index of string descriptor describing manufacturer */
  	uint8_t  iManufacturer;
  
  	/** Index of string descriptor describing product */
  	uint8_t  iProduct;
  
  	/** Index of string descriptor containing device serial number */
  	uint8_t  iSerialNumber;
  
  	/** Number of possible configurations */
  	uint8_t  bNumConfigurations;
  };
  
  /** \ingroup libusb_desc
   * A structure representing the standard USB endpoint descriptor. This
   * descriptor is documented in section 9.6.6 of the USB 3.0 specification.
   * All multiple-byte fields are represented in host-endian format.
   */
  struct libusb_endpoint_descriptor {
  	/** Size of this descriptor (in bytes) */
  	uint8_t  bLength;
  
  	/** Descriptor type. Will have value
  	 * \ref libusb_descriptor_type::LIBUSB_DT_ENDPOINT LIBUSB_DT_ENDPOINT in
  	 * this context. */
  	uint8_t  bDescriptorType;
  
  	/** The address of the endpoint described by this descriptor. Bits 0:3 are
  	 * the endpoint number. Bits 4:6 are reserved. Bit 7 indicates direction,
  	 * see \ref libusb_endpoint_direction. */
  	uint8_t  bEndpointAddress;
  
  	/** Attributes which apply to the endpoint when it is configured using
  	 * the bConfigurationValue. Bits 0:1 determine the transfer type and
  	 * correspond to \ref libusb_endpoint_transfer_type. Bits 2:3 are only used
  	 * for isochronous endpoints and correspond to \ref libusb_iso_sync_type.
  	 * Bits 4:5 are also only used for isochronous endpoints and correspond to
  	 * \ref libusb_iso_usage_type. Bits 6:7 are reserved. */
  	uint8_t  bmAttributes;
  
  	/** Maximum packet size this endpoint is capable of sending/receiving. */
  	uint16_t wMaxPacketSize;
  
  	/** Interval for polling endpoint for data transfers. */
  	uint8_t  bInterval;
  
  	/** For audio devices only: the rate at which synchronization feedback
  	 * is provided. */
  	uint8_t  bRefresh;
  
  	/** For audio devices only: the address if the synch endpoint */
  	uint8_t  bSynchAddress;
  
  	/** Extra descriptors. If libusb encounters unknown endpoint descriptors,
  	 * it will store them here, should you wish to parse them. */
  	const unsigned char *extra;
  
  	/** Length of the extra descriptors, in bytes. Must be non-negative. */
  	int extra_length;
  };
  
  /** \ingroup libusb_desc
   * A structure representing the standard USB interface descriptor. This
   * descriptor is documented in section 9.6.5 of the USB 3.0 specification.
   * All multiple-byte fields are represented in host-endian format.
   */
  struct libusb_interface_descriptor {
  	/** Size of this descriptor (in bytes) */
  	uint8_t  bLength;
  
  	/** Descriptor type. Will have value
  	 * \ref libusb_descriptor_type::LIBUSB_DT_INTERFACE LIBUSB_DT_INTERFACE
  	 * in this context. */
  	uint8_t  bDescriptorType;
  
  	/** Number of this interface */
  	uint8_t  bInterfaceNumber;
  
  	/** Value used to select this alternate setting for this interface */
  	uint8_t  bAlternateSetting;
  
  	/** Number of endpoints used by this interface (excluding the control
  	 * endpoint). */
  	uint8_t  bNumEndpoints;
  
  	/** USB-IF class code for this interface. See \ref libusb_class_code. */
  	uint8_t  bInterfaceClass;
  
  	/** USB-IF subclass code for this interface, qualified by the
  	 * bInterfaceClass value */
  	uint8_t  bInterfaceSubClass;
  
  	/** USB-IF protocol code for this interface, qualified by the
  	 * bInterfaceClass and bInterfaceSubClass values */
  	uint8_t  bInterfaceProtocol;
  
  	/** Index of string descriptor describing this interface */
  	uint8_t  iInterface;
  
  	/** Array of endpoint descriptors. This length of this array is determined
  	 * by the bNumEndpoints field. */
  	const struct libusb_endpoint_descriptor *endpoint;
  
  	/** Extra descriptors. If libusb encounters unknown interface descriptors,
  	 * it will store them here, should you wish to parse them. */
  	const unsigned char *extra;
  
  	/** Length of the extra descriptors, in bytes. Must be non-negative. */
  	int extra_length;
  };
  
  /** \ingroup libusb_desc
   * A collection of alternate settings for a particular USB interface.
   */
  struct libusb_interface {
  	/** Array of interface descriptors. The length of this array is determined
  	 * by the num_altsetting field. */
  	const struct libusb_interface_descriptor *altsetting;
  
  	/** The number of alternate settings that belong to this interface.
  	 * Must be non-negative. */
  	int num_altsetting;
  };
  
  /** \ingroup libusb_desc
   * A structure representing the standard USB configuration descriptor. This
   * descriptor is documented in section 9.6.3 of the USB 3.0 specification.
   * All multiple-byte fields are represented in host-endian format.
   */
  struct libusb_config_descriptor {
  	/** Size of this descriptor (in bytes) */
  	uint8_t  bLength;
  
  	/** Descriptor type. Will have value
  	 * \ref libusb_descriptor_type::LIBUSB_DT_CONFIG LIBUSB_DT_CONFIG
  	 * in this context. */
  	uint8_t  bDescriptorType;
  
  	/** Total length of data returned for this configuration */
  	uint16_t wTotalLength;
  
  	/** Number of interfaces supported by this configuration */
  	uint8_t  bNumInterfaces;
  
  	/** Identifier value for this configuration */
  	uint8_t  bConfigurationValue;
  
  	/** Index of string descriptor describing this configuration */
  	uint8_t  iConfiguration;
  
  	/** Configuration characteristics */
  	uint8_t  bmAttributes;
  
  	/** Maximum power consumption of the USB device from this bus in this
  	 * configuration when the device is fully operation. Expressed in units
  	 * of 2 mA when the device is operating in high-speed mode and in units
  	 * of 8 mA when the device is operating in super-speed mode. */
  	uint8_t  MaxPower;
  
  	/** Array of interfaces supported by this configuration. The length of
  	 * this array is determined by the bNumInterfaces field. */
  	const struct libusb_interface *interface;
  
  	/** Extra descriptors. If libusb encounters unknown configuration
  	 * descriptors, it will store them here, should you wish to parse them. */
  	const unsigned char *extra;
  
  	/** Length of the extra descriptors, in bytes. Must be non-negative. */
  	int extra_length;
  };
  
  /** \ingroup libusb_desc
   * A structure representing the superspeed endpoint companion
   * descriptor. This descriptor is documented in section 9.6.7 of
   * the USB 3.0 specification. All multiple-byte fields are represented in
   * host-endian format.
   */
  struct libusb_ss_endpoint_companion_descriptor {
  	/** Size of this descriptor (in bytes) */
  	uint8_t  bLength;
  
  	/** Descriptor type. Will have value
  	 * \ref libusb_descriptor_type::LIBUSB_DT_SS_ENDPOINT_COMPANION in
  	 * this context. */
  	uint8_t  bDescriptorType;
  
  	/** The maximum number of packets the endpoint can send or
  	 *  receive as part of a burst. */
  	uint8_t  bMaxBurst;
  
  	/** In bulk EP: bits 4:0 represents the maximum number of
  	 *  streams the EP supports. In isochronous EP: bits 1:0
  	 *  represents the Mult - a zero based value that determines
  	 *  the maximum number of packets within a service interval  */
  	uint8_t  bmAttributes;
  
  	/** The total number of bytes this EP will transfer every
  	 *  service interval. Valid only for periodic EPs. */
  	uint16_t wBytesPerInterval;
  };
  
  /** \ingroup libusb_desc
   * A generic representation of a BOS Device Capability descriptor. It is
   * advised to check bDevCapabilityType and call the matching
   * libusb_get_*_descriptor function to get a structure fully matching the type.
   */
  struct libusb_bos_dev_capability_descriptor {
  	/** Size of this descriptor (in bytes) */
  	uint8_t  bLength;
  
  	/** Descriptor type. Will have value
  	 * \ref libusb_descriptor_type::LIBUSB_DT_DEVICE_CAPABILITY
  	 * LIBUSB_DT_DEVICE_CAPABILITY in this context. */
  	uint8_t  bDescriptorType;
  
  	/** Device Capability type */
  	uint8_t  bDevCapabilityType;
  
  	/** Device Capability data (bLength - 3 bytes) */
  	uint8_t  dev_capability_data[ZERO_SIZED_ARRAY];
  };
  
  /** \ingroup libusb_desc
   * A structure representing the Binary Device Object Store (BOS) descriptor.
   * This descriptor is documented in section 9.6.2 of the USB 3.0 specification.
   * All multiple-byte fields are represented in host-endian format.
   */
  struct libusb_bos_descriptor {
  	/** Size of this descriptor (in bytes) */
  	uint8_t  bLength;
  
  	/** Descriptor type. Will have value
  	 * \ref libusb_descriptor_type::LIBUSB_DT_BOS LIBUSB_DT_BOS
  	 * in this context. */
  	uint8_t  bDescriptorType;
  
  	/** Length of this descriptor and all of its sub descriptors */
  	uint16_t wTotalLength;
  
  	/** The number of separate device capability descriptors in
  	 * the BOS */
  	uint8_t  bNumDeviceCaps;
  
  	/** bNumDeviceCap Device Capability Descriptors */
  	struct libusb_bos_dev_capability_descriptor *dev_capability[ZERO_SIZED_ARRAY];
  };
  
  /** \ingroup libusb_desc
   * A structure representing the USB 2.0 Extension descriptor
   * This descriptor is documented in section 9.6.2.1 of the USB 3.0 specification.
   * All multiple-byte fields are represented in host-endian format.
   */
  struct libusb_usb_2_0_extension_descriptor {
  	/** Size of this descriptor (in bytes) */
  	uint8_t  bLength;
  
  	/** Descriptor type. Will have value
  	 * \ref libusb_descriptor_type::LIBUSB_DT_DEVICE_CAPABILITY
  	 * LIBUSB_DT_DEVICE_CAPABILITY in this context. */
  	uint8_t  bDescriptorType;
  
  	/** Capability type. Will have value
  	 * \ref libusb_capability_type::LIBUSB_BT_USB_2_0_EXTENSION
  	 * LIBUSB_BT_USB_2_0_EXTENSION in this context. */
  	uint8_t  bDevCapabilityType;
  
  	/** Bitmap encoding of supported device level features.
  	 * A value of one in a bit location indicates a feature is
  	 * supported; a value of zero indicates it is not supported.
  	 * See \ref libusb_usb_2_0_extension_attributes. */
  	uint32_t bmAttributes;
  };
  
  /** \ingroup libusb_desc
   * A structure representing the SuperSpeed USB Device Capability descriptor
   * This descriptor is documented in section 9.6.2.2 of the USB 3.0 specification.
   * All multiple-byte fields are represented in host-endian format.
   */
  struct libusb_ss_usb_device_capability_descriptor {
  	/** Size of this descriptor (in bytes) */
  	uint8_t  bLength;
  
  	/** Descriptor type. Will have value
  	 * \ref libusb_descriptor_type::LIBUSB_DT_DEVICE_CAPABILITY
  	 * LIBUSB_DT_DEVICE_CAPABILITY in this context. */
  	uint8_t  bDescriptorType;
  
  	/** Capability type. Will have value
  	 * \ref libusb_capability_type::LIBUSB_BT_SS_USB_DEVICE_CAPABILITY
  	 * LIBUSB_BT_SS_USB_DEVICE_CAPABILITY in this context. */
  	uint8_t  bDevCapabilityType;
  
  	/** Bitmap encoding of supported device level features.
  	 * A value of one in a bit location indicates a feature is
  	 * supported; a value of zero indicates it is not supported.
  	 * See \ref libusb_ss_usb_device_capability_attributes. */
  	uint8_t  bmAttributes;
  
  	/** Bitmap encoding of the speed supported by this device when
  	 * operating in SuperSpeed mode. See \ref libusb_supported_speed. */
  	uint16_t wSpeedSupported;
  
  	/** The lowest speed at which all the functionality supported
  	 * by the device is available to the user. For example if the
  	 * device supports all its functionality when connected at
  	 * full speed and above then it sets this value to 1. */
  	uint8_t  bFunctionalitySupport;
  
  	/** U1 Device Exit Latency. */
  	uint8_t  bU1DevExitLat;
  
  	/** U2 Device Exit Latency. */
  	uint16_t bU2DevExitLat;
  };
  
  /** \ingroup libusb_desc
   * A structure representing the Container ID descriptor.
   * This descriptor is documented in section 9.6.2.3 of the USB 3.0 specification.
   * All multiple-byte fields, except UUIDs, are represented in host-endian format.
   */
  struct libusb_container_id_descriptor {
  	/** Size of this descriptor (in bytes) */
  	uint8_t  bLength;
  
  	/** Descriptor type. Will have value
  	 * \ref libusb_descriptor_type::LIBUSB_DT_DEVICE_CAPABILITY
  	 * LIBUSB_DT_DEVICE_CAPABILITY in this context. */
  	uint8_t  bDescriptorType;
  
  	/** Capability type. Will have value
  	 * \ref libusb_capability_type::LIBUSB_BT_CONTAINER_ID
  	 * LIBUSB_BT_CONTAINER_ID in this context. */
  	uint8_t  bDevCapabilityType;
  
  	/** Reserved field */
  	uint8_t  bReserved;
  
  	/** 128 bit UUID */
  	uint8_t  ContainerID[16];
  };
  
  /** \ingroup libusb_asyncio
   * Setup packet for control transfers. */
  #if defined(_MSC_VER) || defined(__WATCOMC__)
  #pragma pack(push, 1)
  #endif
  struct libusb_control_setup {
  	/** Request type. Bits 0:4 determine recipient, see
  	 * \ref libusb_request_recipient. Bits 5:6 determine type, see
  	 * \ref libusb_request_type. Bit 7 determines data transfer direction, see
  	 * \ref libusb_endpoint_direction.
  	 */
  	uint8_t  bmRequestType;
  
  	/** Request. If the type bits of bmRequestType are equal to
  	 * \ref libusb_request_type::LIBUSB_REQUEST_TYPE_STANDARD
  	 * "LIBUSB_REQUEST_TYPE_STANDARD" then this field refers to
  	 * \ref libusb_standard_request. For other cases, use of this field is
  	 * application-specific. */
  	uint8_t  bRequest;
  
  	/** Value. Varies according to request */
  	uint16_t wValue;
  
  	/** Index. Varies according to request, typically used to pass an index
  	 * or offset */
  	uint16_t wIndex;
  
  	/** Number of bytes to transfer */
  	uint16_t wLength;
  } LIBUSB_PACKED;
  #if defined(_MSC_VER) || defined(__WATCOMC__)
  #pragma pack(pop)
  #endif
  
  #define LIBUSB_CONTROL_SETUP_SIZE (sizeof(struct libusb_control_setup))
  
  /* libusb */
  
  struct libusb_context;
  struct libusb_device;
  struct libusb_device_handle;
  
  /** \ingroup libusb_lib
   * Structure providing the version of the libusb runtime
   */
  struct libusb_version {
  	/** Library major version. */
  	const uint16_t major;
  
  	/** Library minor version. */
  	const uint16_t minor;
  
  	/** Library micro version. */
  	const uint16_t micro;
  
  	/** Library nano version. */
  	const uint16_t nano;
  
  	/** Library release candidate suffix string, e.g. "-rc4". */
  	const char *rc;
  
  	/** For ABI compatibility only. */
  	const char *describe;
  };
  
  /** \ingroup libusb_lib
   * Structure representing a libusb session. The concept of individual libusb
   * sessions allows for your program to use two libraries (or dynamically
   * load two modules) which both independently use libusb. This will prevent
   * interference between the individual libusb users - for example
   * libusb_set_option() will not affect the other user of the library, and
   * libusb_exit() will not destroy resources that the other user is still
   * using.
   *
   * Sessions are created by libusb_init() and destroyed through libusb_exit().
   * If your application is guaranteed to only ever include a single libusb
   * user (i.e. you), you do not have to worry about contexts: pass NULL in
   * every function call where a context is required, and the default context
   * will be used. Note that libusb_set_option(NULL, ...) is special, and adds
   * an option to a list of default options for new contexts.
   *
   * For more information, see \ref libusb_contexts.
   */
  typedef struct libusb_context libusb_context;
  
  /** \ingroup libusb_dev
   * Structure representing a USB device detected on the system. This is an
   * opaque type for which you are only ever provided with a pointer, usually
   * originating from libusb_get_device_list() or libusb_hotplug_register_callback().
   *
   * Certain operations can be performed on a device, but in order to do any
   * I/O you will have to first obtain a device handle using libusb_open().
   *
   * Devices are reference counted with libusb_ref_device() and
   * libusb_unref_device(), and are freed when the reference count reaches 0.
   * New devices presented by libusb_get_device_list() have a reference count of
   * 1, and libusb_free_device_list() can optionally decrease the reference count
   * on all devices in the list. libusb_open() adds another reference which is
   * later destroyed by libusb_close().
   */
  typedef struct libusb_device libusb_device;
  
  
  /** \ingroup libusb_dev
   * Structure representing a handle on a USB device. This is an opaque type for
   * which you are only ever provided with a pointer, usually originating from
   * libusb_open().
   *
   * A device handle is used to perform I/O and other operations. When finished
   * with a device handle, you should call libusb_close().
   */
  typedef struct libusb_device_handle libusb_device_handle;
  
  /** \ingroup libusb_dev
   * Speed codes. Indicates the speed at which the device is operating.
   */
  enum libusb_speed {
  	/** The OS doesn't report or know the device speed. */
  	LIBUSB_SPEED_UNKNOWN = 0,
  
  	/** The device is operating at low speed (1.5MBit/s). */
  	LIBUSB_SPEED_LOW = 1,
  
  	/** The device is operating at full speed (12MBit/s). */
  	LIBUSB_SPEED_FULL = 2,
  
  	/** The device is operating at high speed (480MBit/s). */
  	LIBUSB_SPEED_HIGH = 3,
  
  	/** The device is operating at super speed (5000MBit/s). */
  	LIBUSB_SPEED_SUPER = 4,
  
  	/** The device is operating at super speed plus (10000MBit/s). */
  	LIBUSB_SPEED_SUPER_PLUS = 5
  };
  
  /** \ingroup libusb_misc
   * Error codes. Most libusb functions return 0 on success or one of these
   * codes on failure.
   * You can call libusb_error_name() to retrieve a string representation of an
   * error code or libusb_strerror() to get an end-user suitable description of
   * an error code.
   */
  enum libusb_error {
  	/** Success (no error) */
  	LIBUSB_SUCCESS = 0,
  
  	/** Input/output error */
  	LIBUSB_ERROR_IO = -1,
  
  	/** Invalid parameter */
  	LIBUSB_ERROR_INVALID_PARAM = -2,
  
  	/** Access denied (insufficient permissions) */
  	LIBUSB_ERROR_ACCESS = -3,
  
  	/** No such device (it may have been disconnected) */
  	LIBUSB_ERROR_NO_DEVICE = -4,
  
  	/** Entity not found */
  	LIBUSB_ERROR_NOT_FOUND = -5,
  
  	/** Resource busy */
  	LIBUSB_ERROR_BUSY = -6,
  
  	/** Operation timed out */
  	LIBUSB_ERROR_TIMEOUT = -7,
  
  	/** Overflow */
  	LIBUSB_ERROR_OVERFLOW = -8,
  
  	/** Pipe error */
  	LIBUSB_ERROR_PIPE = -9,
  
  	/** System call interrupted (perhaps due to signal) */
  	LIBUSB_ERROR_INTERRUPTED = -10,
  
  	/** Insufficient memory */
  	LIBUSB_ERROR_NO_MEM = -11,
  
  	/** Operation not supported or unimplemented on this platform */
  	LIBUSB_ERROR_NOT_SUPPORTED = -12,
  
  	/* NB: Remember to update LIBUSB_ERROR_COUNT below as well as the
  	   message strings in strerror.c when adding new error codes here. */
  
  	/** Other error */
  	LIBUSB_ERROR_OTHER = -99
  };
  
  /* Total number of error codes in enum libusb_error */
  #define LIBUSB_ERROR_COUNT 14
  
  /** \ingroup libusb_asyncio
   * Transfer type */
  enum libusb_transfer_type {
  	/** Control transfer */
  	LIBUSB_TRANSFER_TYPE_CONTROL = 0U,
  
  	/** Isochronous transfer */
  	LIBUSB_TRANSFER_TYPE_ISOCHRONOUS = 1U,
  
  	/** Bulk transfer */
  	LIBUSB_TRANSFER_TYPE_BULK = 2U,
  
  	/** Interrupt transfer */
  	LIBUSB_TRANSFER_TYPE_INTERRUPT = 3U,
  
  	/** Bulk stream transfer */
  	LIBUSB_TRANSFER_TYPE_BULK_STREAM = 4U
  };
  
  /** \ingroup libusb_asyncio
   * Transfer status codes */
  enum libusb_transfer_status {
  	/** Transfer completed without error. Note that this does not indicate
  	 * that the entire amount of requested data was transferred. */
  	LIBUSB_TRANSFER_COMPLETED,
  
  	/** Transfer failed */
  	LIBUSB_TRANSFER_ERROR,
  
  	/** Transfer timed out */
  	LIBUSB_TRANSFER_TIMED_OUT,
  
  	/** Transfer was cancelled */
  	LIBUSB_TRANSFER_CANCELLED,
  
  	/** For bulk/interrupt endpoints: halt condition detected (endpoint
  	 * stalled). For control endpoints: control request not supported. */
  	LIBUSB_TRANSFER_STALL,
  
  	/** Device was disconnected */
  	LIBUSB_TRANSFER_NO_DEVICE,
  
  	/** Device sent more data than requested */
  	LIBUSB_TRANSFER_OVERFLOW
  
  	/* NB! Remember to update libusb_error_name()
  	   when adding new status codes here. */
  };
  
  /** \ingroup libusb_asyncio
   * libusb_transfer.flags values */
  enum libusb_transfer_flags {
  	/** Report short frames as errors */
  	LIBUSB_TRANSFER_SHORT_NOT_OK = (1U << 0),
  
  	/** Automatically free() transfer buffer during libusb_free_transfer().
  	 * Note that buffers allocated with libusb_dev_mem_alloc() should not
  	 * be attempted freed in this way, since free() is not an appropriate
  	 * way to release such memory. */
  	LIBUSB_TRANSFER_FREE_BUFFER = (1U << 1),
  
  	/** Automatically call libusb_free_transfer() after callback returns.
  	 * If this flag is set, it is illegal to call libusb_free_transfer()
  	 * from your transfer callback, as this will result in a double-free
  	 * when this flag is acted upon. */
  	LIBUSB_TRANSFER_FREE_TRANSFER = (1U << 2),
  
  	/** Terminate transfers that are a multiple of the endpoint's
  	 * wMaxPacketSize with an extra zero length packet. This is useful
  	 * when a device protocol mandates that each logical request is
  	 * terminated by an incomplete packet (i.e. the logical requests are
  	 * not separated by other means).
  	 *
  	 * This flag only affects host-to-device transfers to bulk and interrupt
  	 * endpoints. In other situations, it is ignored.
  	 *
  	 * This flag only affects transfers with a length that is a multiple of
  	 * the endpoint's wMaxPacketSize. On transfers of other lengths, this
  	 * flag has no effect. Therefore, if you are working with a device that
  	 * needs a ZLP whenever the end of the logical request falls on a packet
  	 * boundary, then it is sensible to set this flag on <em>every</em>
  	 * transfer (you do not have to worry about only setting it on transfers
  	 * that end on the boundary).
  	 *
  	 * This flag is currently only supported on Linux.
  	 * On other systems, libusb_submit_transfer() will return
  	 * LIBUSB_ERROR_NOT_SUPPORTED for every transfer where this flag is set.
  	 *
  	 * Available since libusb-1.0.9.
  	 */
  	LIBUSB_TRANSFER_ADD_ZERO_PACKET = (1U << 3)
  };
  
  /** \ingroup libusb_asyncio
   * Isochronous packet descriptor. */
  struct libusb_iso_packet_descriptor {
  	/** Length of data to request in this packet */
  	unsigned int length;
  
  	/** Amount of data that was actually transferred */
  	unsigned int actual_length;
  
  	/** Status code for this packet */
  	enum libusb_transfer_status status;
  };
  
  struct libusb_transfer;
  
  /** \ingroup libusb_asyncio
   * Asynchronous transfer callback function type. When submitting asynchronous
   * transfers, you pass a pointer to a callback function of this type via the
   * \ref libusb_transfer::callback "callback" member of the libusb_transfer
   * structure. libusb will call this function later, when the transfer has
   * completed or failed. See \ref libusb_asyncio for more information.
   * \param transfer The libusb_transfer struct the callback function is being
   * notified about.
   */
  typedef void (LIBUSB_CALL *libusb_transfer_cb_fn)(struct libusb_transfer *transfer);
  
  /** \ingroup libusb_asyncio
   * The generic USB transfer structure. The user populates this structure and
   * then submits it in order to request a transfer. After the transfer has
   * completed, the library populates the transfer with the results and passes
   * it back to the user.
   */
  struct libusb_transfer {
  	/** Handle of the device that this transfer will be submitted to */
  	libusb_device_handle *dev_handle;
  
  	/** A bitwise OR combination of \ref libusb_transfer_flags. */
  	uint8_t flags;
  
  	/** Address of the endpoint where this transfer will be sent. */
  	unsigned char endpoint;
  
  	/** Type of the transfer from \ref libusb_transfer_type */
  	unsigned char type;
  
  	/** Timeout for this transfer in milliseconds. A value of 0 indicates no
  	 * timeout. */
  	unsigned int timeout;
  
  	/** The status of the transfer. Read-only, and only for use within
  	 * transfer callback function.
  	 *
  	 * If this is an isochronous transfer, this field may read COMPLETED even
  	 * if there were errors in the frames. Use the
  	 * \ref libusb_iso_packet_descriptor::status "status" field in each packet
  	 * to determine if errors occurred. */
  	enum libusb_transfer_status status;
  
  	/** Length of the data buffer. Must be non-negative. */
  	int length;
  
  	/** Actual length of data that was transferred. Read-only, and only for
  	 * use within transfer callback function. Not valid for isochronous
  	 * endpoint transfers. */
  	int actual_length;
  
  	/** Callback function. This will be invoked when the transfer completes,
  	 * fails, or is cancelled. */
  	libusb_transfer_cb_fn callback;
  
  	/** User context data. Useful for associating specific data to a transfer
  	 * that can be accessed from within the callback function.
  	 *
  	 * This field may be set manually or is taken as the `user_data` parameter
  	 * of the following functions:
  	 * - libusb_fill_bulk_transfer()
  	 * - libusb_fill_bulk_stream_transfer()
  	 * - libusb_fill_control_transfer()
  	 * - libusb_fill_interrupt_transfer()
  	 * - libusb_fill_iso_transfer() */
  	void *user_data;
  
  	/** Data buffer */
  	unsigned char *buffer;
  
  	/** Number of isochronous packets. Only used for I/O with isochronous
  	 * endpoints. Must be non-negative. */
  	int num_iso_packets;
  
  	/** Isochronous packet descriptors, for isochronous transfers only. */
  	struct libusb_iso_packet_descriptor iso_packet_desc[ZERO_SIZED_ARRAY];
  };
  
  /** \ingroup libusb_misc
   * Capabilities supported by an instance of libusb on the current running
   * platform. Test if the loaded library supports a given capability by calling
   * \ref libusb_has_capability().
   */
  enum libusb_capability {
  	/** The libusb_has_capability() API is available. */
  	LIBUSB_CAP_HAS_CAPABILITY = 0x0000U,
  
  	/** Hotplug support is available on this platform. */
  	LIBUSB_CAP_HAS_HOTPLUG = 0x0001U,
  
  	/** The library can access HID devices without requiring user intervention.
  	 * Note that before being able to actually access an HID device, you may
  	 * still have to call additional libusb functions such as
  	 * \ref libusb_detach_kernel_driver(). */
  	LIBUSB_CAP_HAS_HID_ACCESS = 0x0100U,
  
  	/** The library supports detaching of the default USB driver, using
  	 * \ref libusb_detach_kernel_driver(), if one is set by the OS kernel */
  	LIBUSB_CAP_SUPPORTS_DETACH_KERNEL_DRIVER = 0x0101U
  };
  
  /** \ingroup libusb_lib
   *  Log message levels.
   */
  enum libusb_log_level {
  	/** (0) : No messages ever emitted by the library (default) */
  	LIBUSB_LOG_LEVEL_NONE = 0,
  
  	/** (1) : Error messages are emitted */
  	LIBUSB_LOG_LEVEL_ERROR = 1,
  
  	/** (2) : Warning and error messages are emitted */
  	LIBUSB_LOG_LEVEL_WARNING = 2,
  
  	/** (3) : Informational, warning and error messages are emitted */
  	LIBUSB_LOG_LEVEL_INFO = 3,
  
  	/** (4) : All messages are emitted */
  	LIBUSB_LOG_LEVEL_DEBUG = 4
  };
  
  /** \ingroup libusb_lib
   *  Log callback mode.
   *
   *  Since version 1.0.23, \ref LIBUSB_API_VERSION >= 0x01000107
   *
   * \see libusb_set_log_cb()
   */
  enum libusb_log_cb_mode {
  	/** Callback function handling all log messages. */
  	LIBUSB_LOG_CB_GLOBAL = (1 << 0),
  
  	/** Callback function handling context related log messages. */
  	LIBUSB_LOG_CB_CONTEXT = (1 << 1)
  };
  
  /** \ingroup libusb_lib
   * Callback function for handling log messages.
   * \param ctx the context which is related to the log message, or NULL if it
   * is a global log message
   * \param level the log level, see \ref libusb_log_level for a description
   * \param str the log message
   *
   * Since version 1.0.23, \ref LIBUSB_API_VERSION >= 0x01000107
   *
   * \see libusb_set_log_cb()
   */
  typedef void (LIBUSB_CALL *libusb_log_cb)(libusb_context *ctx,
  	enum libusb_log_level level, const char *str);
  
  int LIBUSB_CALL libusb_init(libusb_context **ctx);
  void LIBUSB_CALL libusb_exit(libusb_context *ctx);
  LIBUSB_DEPRECATED_FOR(libusb_set_option)
  void LIBUSB_CALL libusb_set_debug(libusb_context *ctx, int level);
  void LIBUSB_CALL libusb_set_log_cb(libusb_context *ctx, libusb_log_cb cb, int mode);
  const struct libusb_version * LIBUSB_CALL libusb_get_version(void);
  int LIBUSB_CALL libusb_has_capability(uint32_t capability);
  const char * LIBUSB_CALL libusb_error_name(int errcode);
  int LIBUSB_CALL libusb_setlocale(const char *locale);
  const char * LIBUSB_CALL libusb_strerror(int errcode);
  
  ssize_t LIBUSB_CALL libusb_get_device_list(libusb_context *ctx,
  	libusb_device ***list);
  void LIBUSB_CALL libusb_free_device_list(libusb_device **list,
  	int unref_devices);
  libusb_device * LIBUSB_CALL libusb_ref_device(libusb_device *dev);
  void LIBUSB_CALL libusb_unref_device(libusb_device *dev);
  
  int LIBUSB_CALL libusb_get_configuration(libusb_device_handle *dev,
  	int *config);
  int LIBUSB_CALL libusb_get_device_descriptor(libusb_device *dev,
  	struct libusb_device_descriptor *desc);
  int LIBUSB_CALL libusb_get_active_config_descriptor(libusb_device *dev,
  	struct libusb_config_descriptor **config);
  int LIBUSB_CALL libusb_get_config_descriptor(libusb_device *dev,
  	uint8_t config_index, struct libusb_config_descriptor **config);
  int LIBUSB_CALL libusb_get_config_descriptor_by_value(libusb_device *dev,
  	uint8_t bConfigurationValue, struct libusb_config_descriptor **config);
  void LIBUSB_CALL libusb_free_config_descriptor(
  	struct libusb_config_descriptor *config);
  int LIBUSB_CALL libusb_get_ss_endpoint_companion_descriptor(
  	libusb_context *ctx,
  	const struct libusb_endpoint_descriptor *endpoint,
  	struct libusb_ss_endpoint_companion_descriptor **ep_comp);
  void LIBUSB_CALL libusb_free_ss_endpoint_companion_descriptor(
  	struct libusb_ss_endpoint_companion_descriptor *ep_comp);
  int LIBUSB_CALL libusb_get_bos_descriptor(libusb_device_handle *dev_handle,
  	struct libusb_bos_descriptor **bos);
  void LIBUSB_CALL libusb_free_bos_descriptor(struct libusb_bos_descriptor *bos);
  int LIBUSB_CALL libusb_get_usb_2_0_extension_descriptor(
  	libusb_context *ctx,
  	struct libusb_bos_dev_capability_descriptor *dev_cap,
  	struct libusb_usb_2_0_extension_descriptor **usb_2_0_extension);
  void LIBUSB_CALL libusb_free_usb_2_0_extension_descriptor(
  	struct libusb_usb_2_0_extension_descriptor *usb_2_0_extension);
  int LIBUSB_CALL libusb_get_ss_usb_device_capability_descriptor(
  	libusb_context *ctx,
  	struct libusb_bos_dev_capability_descriptor *dev_cap,
  	struct libusb_ss_usb_device_capability_descriptor **ss_usb_device_cap);
  void LIBUSB_CALL libusb_free_ss_usb_device_capability_descriptor(
  	struct libusb_ss_usb_device_capability_descriptor *ss_usb_device_cap);
  int LIBUSB_CALL libusb_get_container_id_descriptor(libusb_context *ctx,
  	struct libusb_bos_dev_capability_descriptor *dev_cap,
  	struct libusb_container_id_descriptor **container_id);
  void LIBUSB_CALL libusb_free_container_id_descriptor(
  	struct libusb_container_id_descriptor *container_id);
  uint8_t LIBUSB_CALL libusb_get_bus_number(libusb_device *dev);
  uint8_t LIBUSB_CALL libusb_get_port_number(libusb_device *dev);
  int LIBUSB_CALL libusb_get_port_numbers(libusb_device *dev, uint8_t *port_numbers, int port_numbers_len);
  LIBUSB_DEPRECATED_FOR(libusb_get_port_numbers)
  int LIBUSB_CALL libusb_get_port_path(libusb_context *ctx, libusb_device *dev, uint8_t *path, uint8_t path_length);
  libusb_device * LIBUSB_CALL libusb_get_parent(libusb_device *dev);
  uint8_t LIBUSB_CALL libusb_get_device_address(libusb_device *dev);
  int LIBUSB_CALL libusb_get_device_speed(libusb_device *dev);
  int LIBUSB_CALL libusb_get_max_packet_size(libusb_device *dev,
  	unsigned char endpoint);
  int LIBUSB_CALL libusb_get_max_iso_packet_size(libusb_device *dev,
  	unsigned char endpoint);
  
  int LIBUSB_CALL libusb_wrap_sys_device(libusb_context *ctx, intptr_t sys_dev, libusb_device_handle **dev_handle);
  int LIBUSB_CALL libusb_open(libusb_device *dev, libusb_device_handle **dev_handle);
  void LIBUSB_CALL libusb_close(libusb_device_handle *dev_handle);
  libusb_device * LIBUSB_CALL libusb_get_device(libusb_device_handle *dev_handle);
  
  int LIBUSB_CALL libusb_set_configuration(libusb_device_handle *dev_handle,
  	int configuration);
  int LIBUSB_CALL libusb_claim_interface(libusb_device_handle *dev_handle,
  	int interface_number);
  int LIBUSB_CALL libusb_release_interface(libusb_device_handle *dev_handle,
  	int interface_number);
  
  libusb_device_handle * LIBUSB_CALL libusb_open_device_with_vid_pid(
  	libusb_context *ctx, uint16_t vendor_id, uint16_t product_id);
  
  int LIBUSB_CALL libusb_set_interface_alt_setting(libusb_device_handle *dev_handle,
  	int interface_number, int alternate_setting);
  int LIBUSB_CALL libusb_clear_halt(libusb_device_handle *dev_handle,
  	unsigned char endpoint);
  int LIBUSB_CALL libusb_reset_device(libusb_device_handle *dev_handle);
  
  int LIBUSB_CALL libusb_alloc_streams(libusb_device_handle *dev_handle,
  	uint32_t num_streams, unsigned char *endpoints, int num_endpoints);
  int LIBUSB_CALL libusb_free_streams(libusb_device_handle *dev_handle,
  	unsigned char *endpoints, int num_endpoints);
  
  unsigned char * LIBUSB_CALL libusb_dev_mem_alloc(libusb_device_handle *dev_handle,
  	size_t length);
  int LIBUSB_CALL libusb_dev_mem_free(libusb_device_handle *dev_handle,
  	unsigned char *buffer, size_t length);
  
  int LIBUSB_CALL libusb_kernel_driver_active(libusb_device_handle *dev_handle,
  	int interface_number);
  int LIBUSB_CALL libusb_detach_kernel_driver(libusb_device_handle *dev_handle,
  	int interface_number);
  int LIBUSB_CALL libusb_attach_kernel_driver(libusb_device_handle *dev_handle,
  	int interface_number);
  int LIBUSB_CALL libusb_set_auto_detach_kernel_driver(
  	libusb_device_handle *dev_handle, int enable);
  
  /* async I/O */
  
  /** \ingroup libusb_asyncio
   * Get the data section of a control transfer. This convenience function is here
   * to remind you that the data does not start until 8 bytes into the actual
   * buffer, as the setup packet comes first.
   *
   * Calling this function only makes sense from a transfer callback function,
   * or situations where you have already allocated a suitably sized buffer at
   * transfer->buffer.
   *
   * \param transfer a transfer
   * \returns pointer to the first byte of the data section
   */
  static inline unsigned char *libusb_control_transfer_get_data(
  	struct libusb_transfer *transfer)
  {
  	return transfer->buffer + LIBUSB_CONTROL_SETUP_SIZE;
  }
  
  /** \ingroup libusb_asyncio
   * Get the control setup packet of a control transfer. This convenience
   * function is here to remind you that the control setup occupies the first
   * 8 bytes of the transfer data buffer.
   *
   * Calling this function only makes sense from a transfer callback function,
   * or situations where you have already allocated a suitably sized buffer at
   * transfer->buffer.
   *
   * \param transfer a transfer
   * \returns a casted pointer to the start of the transfer data buffer
   */
  static inline struct libusb_control_setup *libusb_control_transfer_get_setup(
  	struct libusb_transfer *transfer)
  {
  	return (struct libusb_control_setup *)(void *)transfer->buffer;
  }
  
  /** \ingroup libusb_asyncio
   * Helper function to populate the setup packet (first 8 bytes of the data
   * buffer) for a control transfer. The wIndex, wValue and wLength values should
   * be given in host-endian byte order.
   *
   * \param buffer buffer to output the setup packet into
   * This pointer must be aligned to at least 2 bytes boundary.
   * \param bmRequestType see the
   * \ref libusb_control_setup::bmRequestType "bmRequestType" field of
   * \ref libusb_control_setup
   * \param bRequest see the
   * \ref libusb_control_setup::bRequest "bRequest" field of
   * \ref libusb_control_setup
   * \param wValue see the
   * \ref libusb_control_setup::wValue "wValue" field of
   * \ref libusb_control_setup
   * \param wIndex see the
   * \ref libusb_control_setup::wIndex "wIndex" field of
   * \ref libusb_control_setup
   * \param wLength see the
   * \ref libusb_control_setup::wLength "wLength" field of
   * \ref libusb_control_setup
   */
  static inline void libusb_fill_control_setup(unsigned char *buffer,
  	uint8_t bmRequestType, uint8_t bRequest, uint16_t wValue, uint16_t wIndex,
  	uint16_t wLength)
  {
  	struct libusb_control_setup *setup = (struct libusb_control_setup *)(void *)buffer;
  	setup->bmRequestType = bmRequestType;
  	setup->bRequest = bRequest;
  	setup->wValue = libusb_cpu_to_le16(wValue);
  	setup->wIndex = libusb_cpu_to_le16(wIndex);
  	setup->wLength = libusb_cpu_to_le16(wLength);
  }
  
  struct libusb_transfer * LIBUSB_CALL libusb_alloc_transfer(int iso_packets);
  int LIBUSB_CALL libusb_submit_transfer(struct libusb_transfer *transfer);
  int LIBUSB_CALL libusb_cancel_transfer(struct libusb_transfer *transfer);
  void LIBUSB_CALL libusb_free_transfer(struct libusb_transfer *transfer);
  void LIBUSB_CALL libusb_transfer_set_stream_id(
  	struct libusb_transfer *transfer, uint32_t stream_id);
  uint32_t LIBUSB_CALL libusb_transfer_get_stream_id(
  	struct libusb_transfer *transfer);
  
  /** \ingroup libusb_asyncio
   * Helper function to populate the required \ref libusb_transfer fields
   * for a control transfer.
   *
   * If you pass a transfer buffer to this function, the first 8 bytes will
   * be interpreted as a control setup packet, and the wLength field will be
   * used to automatically populate the \ref libusb_transfer::length "length"
   * field of the transfer. Therefore the recommended approach is:
   * -# Allocate a suitably sized data buffer (including space for control setup)
   * -# Call libusb_fill_control_setup()
   * -# If this is a host-to-device transfer with a data stage, put the data
   *    in place after the setup packet
   * -# Call this function
   * -# Call libusb_submit_transfer()
   *
   * It is also legal to pass a NULL buffer to this function, in which case this
   * function will not attempt to populate the length field. Remember that you
   * must then populate the buffer and length fields later.
   *
   * \param transfer the transfer to populate
   * \param dev_handle handle of the device that will handle the transfer
   * \param buffer data buffer. If provided, this function will interpret the
   * first 8 bytes as a setup packet and infer the transfer length from that.
   * This pointer must be aligned to at least 2 bytes boundary.
   * \param callback callback function to be invoked on transfer completion
   * \param user_data user data to pass to callback function
   * \param timeout timeout for the transfer in milliseconds
   */
  static inline void libusb_fill_control_transfer(
  	struct libusb_transfer *transfer, libusb_device_handle *dev_handle,
  	unsigned char *buffer, libusb_transfer_cb_fn callback, void *user_data,
  	unsigned int timeout)
  {
  	struct libusb_control_setup *setup = (struct libusb_control_setup *)(void *)buffer;
  	transfer->dev_handle = dev_handle;
  	transfer->endpoint = 0;
  	transfer->type = LIBUSB_TRANSFER_TYPE_CONTROL;
  	transfer->timeout = timeout;
  	transfer->buffer = buffer;
  	if (setup)
  		transfer->length = (int) (LIBUSB_CONTROL_SETUP_SIZE
  			+ libusb_le16_to_cpu(setup->wLength));
  	transfer->user_data = user_data;
  	transfer->callback = callback;
  }
  
  /** \ingroup libusb_asyncio
   * Helper function to populate the required \ref libusb_transfer fields
   * for a bulk transfer.
   *
   * \param transfer the transfer to populate
   * \param dev_handle handle of the device that will handle the transfer
   * \param endpoint address of the endpoint where this transfer will be sent
   * \param buffer data buffer
   * \param length length of data buffer
   * \param callback callback function to be invoked on transfer completion
   * \param user_data user data to pass to callback function
   * \param timeout timeout for the transfer in milliseconds
   */
  static inline void libusb_fill_bulk_transfer(struct libusb_transfer *transfer,
  	libusb_device_handle *dev_handle, unsigned char endpoint,
  	unsigned char *buffer, int length, libusb_transfer_cb_fn callback,
  	void *user_data, unsigned int timeout)
  {
  	transfer->dev_handle = dev_handle;
  	transfer->endpoint = endpoint;
  	transfer->type = LIBUSB_TRANSFER_TYPE_BULK;
  	transfer->timeout = timeout;
  	transfer->buffer = buffer;
  	transfer->length = length;
  	transfer->user_data = user_data;
  	transfer->callback = callback;
  }
  
  /** \ingroup libusb_asyncio
   * Helper function to populate the required \ref libusb_transfer fields
   * for a bulk transfer using bulk streams.
   *
   * Since version 1.0.19, \ref LIBUSB_API_VERSION >= 0x01000103
   *
   * \param transfer the transfer to populate
   * \param dev_handle handle of the device that will handle the transfer
   * \param endpoint address of the endpoint where this transfer will be sent
   * \param stream_id bulk stream id for this transfer
   * \param buffer data buffer
   * \param length length of data buffer
   * \param callback callback function to be invoked on transfer completion
   * \param user_data user data to pass to callback function
   * \param timeout timeout for the transfer in milliseconds
   */
  static inline void libusb_fill_bulk_stream_transfer(
  	struct libusb_transfer *transfer, libusb_device_handle *dev_handle,
  	unsigned char endpoint, uint32_t stream_id,
  	unsigned char *buffer, int length, libusb_transfer_cb_fn callback,
  	void *user_data, unsigned int timeout)
  {
  	libusb_fill_bulk_transfer(transfer, dev_handle, endpoint, buffer,
  				  length, callback, user_data, timeout);
  	transfer->type = LIBUSB_TRANSFER_TYPE_BULK_STREAM;
  	libusb_transfer_set_stream_id(transfer, stream_id);
  }
  
  /** \ingroup libusb_asyncio
   * Helper function to populate the required \ref libusb_transfer fields
   * for an interrupt transfer.
   *
   * \param transfer the transfer to populate
   * \param dev_handle handle of the device that will handle the transfer
   * \param endpoint address of the endpoint where this transfer will be sent
   * \param buffer data buffer
   * \param length length of data buffer
   * \param callback callback function to be invoked on transfer completion
   * \param user_data user data to pass to callback function
   * \param timeout timeout for the transfer in milliseconds
   */
  static inline void libusb_fill_interrupt_transfer(
  	struct libusb_transfer *transfer, libusb_device_handle *dev_handle,
  	unsigned char endpoint, unsigned char *buffer, int length,
  	libusb_transfer_cb_fn callback, void *user_data, unsigned int timeout)
  {
  	transfer->dev_handle = dev_handle;
  	transfer->endpoint = endpoint;
  	transfer->type = LIBUSB_TRANSFER_TYPE_INTERRUPT;
  	transfer->timeout = timeout;
  	transfer->buffer = buffer;
  	transfer->length = length;
  	transfer->user_data = user_data;
  	transfer->callback = callback;
  }
  
  /** \ingroup libusb_asyncio
   * Helper function to populate the required \ref libusb_transfer fields
   * for an isochronous transfer.
   *
   * \param transfer the transfer to populate
   * \param dev_handle handle of the device that will handle the transfer
   * \param endpoint address of the endpoint where this transfer will be sent
   * \param buffer data buffer
   * \param length length of data buffer
   * \param num_iso_packets the number of isochronous packets
   * \param callback callback function to be invoked on transfer completion
   * \param user_data user data to pass to callback function
   * \param timeout timeout for the transfer in milliseconds
   */
  static inline void libusb_fill_iso_transfer(struct libusb_transfer *transfer,
  	libusb_device_handle *dev_handle, unsigned char endpoint,
  	unsigned char *buffer, int length, int num_iso_packets,
  	libusb_transfer_cb_fn callback, void *user_data, unsigned int timeout)
  {
  	transfer->dev_handle = dev_handle;
  	transfer->endpoint = endpoint;
  	transfer->type = LIBUSB_TRANSFER_TYPE_ISOCHRONOUS;
  	transfer->timeout = timeout;
  	transfer->buffer = buffer;
  	transfer->length = length;
  	transfer->num_iso_packets = num_iso_packets;
  	transfer->user_data = user_data;
  	transfer->callback = callback;
  }
  
  /** \ingroup libusb_asyncio
   * Convenience function to set the length of all packets in an isochronous
   * transfer, based on the num_iso_packets field in the transfer structure.
   *
   * \param transfer a transfer
   * \param length the length to set in each isochronous packet descriptor
   * \see libusb_get_max_packet_size()
   */
  static inline void libusb_set_iso_packet_lengths(
  	struct libusb_transfer *transfer, unsigned int length)
  {
  	int i;
  
  	for (i = 0; i < transfer->num_iso_packets; i++)
  		transfer->iso_packet_desc[i].length = length;
  }
  
  /** \ingroup libusb_asyncio
   * Convenience function to locate the position of an isochronous packet
   * within the buffer of an isochronous transfer.
   *
   * This is a thorough function which loops through all preceding packets,
   * accumulating their lengths to find the position of the specified packet.
   * Typically you will assign equal lengths to each packet in the transfer,
   * and hence the above method is sub-optimal. You may wish to use
   * libusb_get_iso_packet_buffer_simple() instead.
   *
   * \param transfer a transfer
   * \param packet the packet to return the address of
   * \returns the base address of the packet buffer inside the transfer buffer,
   * or NULL if the packet does not exist.
   * \see libusb_get_iso_packet_buffer_simple()
   */
  static inline unsigned char *libusb_get_iso_packet_buffer(
  	struct libusb_transfer *transfer, unsigned int packet)
  {
  	int i;
  	size_t offset = 0;
  	int _packet;
  
  	/* oops..slight bug in the API. packet is an unsigned int, but we use
  	 * signed integers almost everywhere else. range-check and convert to
  	 * signed to avoid compiler warnings. FIXME for libusb-2. */
  	if (packet > INT_MAX)
  		return NULL;
  	_packet = (int) packet;
  
  	if (_packet >= transfer->num_iso_packets)
  		return NULL;
  
  	for (i = 0; i < _packet; i++)
  		offset += transfer->iso_packet_desc[i].length;
  
  	return transfer->buffer + offset;
  }
  
  /** \ingroup libusb_asyncio
   * Convenience function to locate the position of an isochronous packet
   * within the buffer of an isochronous transfer, for transfers where each
   * packet is of identical size.
   *
   * This function relies on the assumption that every packet within the transfer
   * is of identical size to the first packet. Calculating the location of
   * the packet buffer is then just a simple calculation:
   * <tt>buffer + (packet_size * packet)</tt>
   *
   * Do not use this function on transfers other than those that have identical
   * packet lengths for each packet.
   *
   * \param transfer a transfer
   * \param packet the packet to return the address of
   * \returns the base address of the packet buffer inside the transfer buffer,
   * or NULL if the packet does not exist.
   * \see libusb_get_iso_packet_buffer()
   */
  static inline unsigned char *libusb_get_iso_packet_buffer_simple(
  	struct libusb_transfer *transfer, unsigned int packet)
  {
  	int _packet;
  
  	/* oops..slight bug in the API. packet is an unsigned int, but we use
  	 * signed integers almost everywhere else. range-check and convert to
  	 * signed to avoid compiler warnings. FIXME for libusb-2. */
  	if (packet > INT_MAX)
  		return NULL;
  	_packet = (int) packet;
  
  	if (_packet >= transfer->num_iso_packets)
  		return NULL;
  
  	return transfer->buffer + ((int) transfer->iso_packet_desc[0].length * _packet);
  }
  
  /* sync I/O */
  
  int LIBUSB_CALL libusb_control_transfer(libusb_device_handle *dev_handle,
  	uint8_t request_type, uint8_t bRequest, uint16_t wValue, uint16_t wIndex,
  	unsigned char *data, uint16_t wLength, unsigned int timeout);
  
  int LIBUSB_CALL libusb_bulk_transfer(libusb_device_handle *dev_handle,
  	unsigned char endpoint, unsigned char *data, int length,
  	int *actual_length, unsigned int timeout);
  
  int LIBUSB_CALL libusb_interrupt_transfer(libusb_device_handle *dev_handle,
  	unsigned char endpoint, unsigned char *data, int length,
  	int *actual_length, unsigned int timeout);
  
  /** \ingroup libusb_desc
   * Retrieve a descriptor from the default control pipe.
   * This is a convenience function which formulates the appropriate control
   * message to retrieve the descriptor.
   *
   * \param dev_handle a device handle
   * \param desc_type the descriptor type, see \ref libusb_descriptor_type
   * \param desc_index the index of the descriptor to retrieve
   * \param data output buffer for descriptor
   * \param length size of data buffer
   * \returns number of bytes returned in data, or LIBUSB_ERROR code on failure
   */
  static inline int libusb_get_descriptor(libusb_device_handle *dev_handle,
  	uint8_t desc_type, uint8_t desc_index, unsigned char *data, int length)
  {
  	return libusb_control_transfer(dev_handle, LIBUSB_ENDPOINT_IN,
  		LIBUSB_REQUEST_GET_DESCRIPTOR, (uint16_t) ((desc_type << 8) | desc_index),
  		0, data, (uint16_t) length, 1000);
  }
  
  /** \ingroup libusb_desc
   * Retrieve a descriptor from a device.
   * This is a convenience function which formulates the appropriate control
   * message to retrieve the descriptor. The string returned is Unicode, as
   * detailed in the USB specifications.
   *
   * \param dev_handle a device handle
   * \param desc_index the index of the descriptor to retrieve
   * \param langid the language ID for the string descriptor
   * \param data output buffer for descriptor
   * \param length size of data buffer
   * \returns number of bytes returned in data, or LIBUSB_ERROR code on failure
   * \see libusb_get_string_descriptor_ascii()
   */
  static inline int libusb_get_string_descriptor(libusb_device_handle *dev_handle,
  	uint8_t desc_index, uint16_t langid, unsigned char *data, int length)
  {
  	return libusb_control_transfer(dev_handle, LIBUSB_ENDPOINT_IN,
  		LIBUSB_REQUEST_GET_DESCRIPTOR, (uint16_t)((LIBUSB_DT_STRING << 8) | desc_index),
  		langid, data, (uint16_t) length, 1000);
  }
  
  int LIBUSB_CALL libusb_get_string_descriptor_ascii(libusb_device_handle *dev_handle,
  	uint8_t desc_index, unsigned char *data, int length);
  
  /* polling and timeouts */
  
  int LIBUSB_CALL libusb_try_lock_events(libusb_context *ctx);
  void LIBUSB_CALL libusb_lock_events(libusb_context *ctx);
  void LIBUSB_CALL libusb_unlock_events(libusb_context *ctx);
  int LIBUSB_CALL libusb_event_handling_ok(libusb_context *ctx);
  int LIBUSB_CALL libusb_event_handler_active(libusb_context *ctx);
  void LIBUSB_CALL libusb_interrupt_event_handler(libusb_context *ctx);
  void LIBUSB_CALL libusb_lock_event_waiters(libusb_context *ctx);
  void LIBUSB_CALL libusb_unlock_event_waiters(libusb_context *ctx);
  int LIBUSB_CALL libusb_wait_for_event(libusb_context *ctx, struct timeval *tv);
  
  int LIBUSB_CALL libusb_handle_events_timeout(libusb_context *ctx,
  	struct timeval *tv);
  int LIBUSB_CALL libusb_handle_events_timeout_completed(libusb_context *ctx,
  	struct timeval *tv, int *completed);
  int LIBUSB_CALL libusb_handle_events(libusb_context *ctx);
  int LIBUSB_CALL libusb_handle_events_completed(libusb_context *ctx, int *completed);
  int LIBUSB_CALL libusb_handle_events_locked(libusb_context *ctx,
  	struct timeval *tv);
  int LIBUSB_CALL libusb_pollfds_handle_timeouts(libusb_context *ctx);
  int LIBUSB_CALL libusb_get_next_timeout(libusb_context *ctx,
  	struct timeval *tv);
  
  /** \ingroup libusb_poll
   * File descriptor for polling
   */
  struct libusb_pollfd {
  	/** Numeric file descriptor */
  	int fd;
  
  	/** Event flags to poll for from <poll.h>. POLLIN indicates that you
  	 * should monitor this file descriptor for becoming ready to read from,
  	 * and POLLOUT indicates that you should monitor this file descriptor for
  	 * nonblocking write readiness. */
  	short events;
  };
  
  /** \ingroup libusb_poll
   * Callback function, invoked when a new file descriptor should be added
   * to the set of file descriptors monitored for events.
   * \param fd the new file descriptor
   * \param events events to monitor for, see \ref libusb_pollfd for a
   * description
   * \param user_data User data pointer specified in
   * libusb_set_pollfd_notifiers() call
   * \see libusb_set_pollfd_notifiers()
   */
  typedef void (LIBUSB_CALL *libusb_pollfd_added_cb)(int fd, short events,
  	void *user_data);
  
  /** \ingroup libusb_poll
   * Callback function, invoked when a file descriptor should be removed from
   * the set of file descriptors being monitored for events. After returning
   * from this callback, do not use that file descriptor again.
   * \param fd the file descriptor to stop monitoring
   * \param user_data User data pointer specified in
   * libusb_set_pollfd_notifiers() call
   * \see libusb_set_pollfd_notifiers()
   */
  typedef void (LIBUSB_CALL *libusb_pollfd_removed_cb)(int fd, void *user_data);
  
  const struct libusb_pollfd ** LIBUSB_CALL libusb_get_pollfds(
  	libusb_context *ctx);
  void LIBUSB_CALL libusb_free_pollfds(const struct libusb_pollfd **pollfds);
  void LIBUSB_CALL libusb_set_pollfd_notifiers(libusb_context *ctx,
  	libusb_pollfd_added_cb added_cb, libusb_pollfd_removed_cb removed_cb,
  	void *user_data);
  
  /** \ingroup libusb_hotplug
   * Callback handle.
   *
   * Callbacks handles are generated by libusb_hotplug_register_callback()
   * and can be used to deregister callbacks. Callback handles are unique
   * per libusb_context and it is safe to call libusb_hotplug_deregister_callback()
   * on an already deregistered callback.
   *
   * Since version 1.0.16, \ref LIBUSB_API_VERSION >= 0x01000102
   *
   * For more information, see \ref libusb_hotplug.
   */
  typedef int libusb_hotplug_callback_handle;
  
  /** \ingroup libusb_hotplug
   *
   * Since version 1.0.16, \ref LIBUSB_API_VERSION >= 0x01000102
   *
   * Hotplug events */
  typedef enum {
  	/** A device has been plugged in and is ready to use */
  	LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED = (1 << 0),
  
  	/** A device has left and is no longer available.
  	 * It is the user's responsibility to call libusb_close on any handle associated with a disconnected device.
  	 * It is safe to call libusb_get_device_descriptor on a device that has left */
  	LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT = (1 << 1)
  } libusb_hotplug_event;
  
  /** \ingroup libusb_hotplug
   *
   * Since version 1.0.16, \ref LIBUSB_API_VERSION >= 0x01000102
   *
   * Hotplug flags */
  typedef enum {
  	/** Arm the callback and fire it for all matching currently attached devices. */
  	LIBUSB_HOTPLUG_ENUMERATE = (1 << 0)
  } libusb_hotplug_flag;
  
  /** \ingroup libusb_hotplug
   * Convenience macro when not using any flags */
  #define LIBUSB_HOTPLUG_NO_FLAGS 0
  
  /** \ingroup libusb_hotplug
   * Wildcard matching for hotplug events */
  #define LIBUSB_HOTPLUG_MATCH_ANY -1
  
  /** \ingroup libusb_hotplug
   * Hotplug callback function type. When requesting hotplug event notifications,
   * you pass a pointer to a callback function of this type.
   *
   * This callback may be called by an internal event thread and as such it is
   * recommended the callback do minimal processing before returning.
   *
   * libusb will call this function later, when a matching event had happened on
   * a matching device. See \ref libusb_hotplug for more information.
   *
   * It is safe to call either libusb_hotplug_register_callback() or
   * libusb_hotplug_deregister_callback() from within a callback function.
   *
   * Since version 1.0.16, \ref LIBUSB_API_VERSION >= 0x01000102
   *
   * \param ctx            context of this notification
   * \param device         libusb_device this event occurred on
   * \param event          event that occurred
   * \param user_data      user data provided when this callback was registered
   * \returns bool whether this callback is finished processing events.
   *                       returning 1 will cause this callback to be deregistered
   */
  typedef int (LIBUSB_CALL *libusb_hotplug_callback_fn)(libusb_context *ctx,
  	libusb_device *device, libusb_hotplug_event event, void *user_data);
  
  /** \ingroup libusb_hotplug
   * Register a hotplug callback function
   *
   * Register a callback with the libusb_context. The callback will fire
   * when a matching event occurs on a matching device. The callback is
   * armed until either it is deregistered with libusb_hotplug_deregister_callback()
   * or the supplied callback returns 1 to indicate it is finished processing events.
   *
   * If the \ref LIBUSB_HOTPLUG_ENUMERATE is passed the callback will be
   * called with a \ref LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED for all devices
   * already plugged into the machine. Note that libusb modifies its internal
   * device list from a separate thread, while calling hotplug callbacks from
   * libusb_handle_events(), so it is possible for a device to already be present
   * on, or removed from, its internal device list, while the hotplug callbacks
   * still need to be dispatched. This means that when using \ref
   * LIBUSB_HOTPLUG_ENUMERATE, your callback may be called twice for the arrival
   * of the same device, once from libusb_hotplug_register_callback() and once
   * from libusb_handle_events(); and/or your callback may be called for the
   * removal of a device for which an arrived call was never made.
   *
   * Since version 1.0.16, \ref LIBUSB_API_VERSION >= 0x01000102
   *
   * \param[in] ctx context to register this callback with
   * \param[in] events bitwise or of hotplug events that will trigger this callback.
   *            See \ref libusb_hotplug_event
   * \param[in] flags bitwise or of hotplug flags that affect registration.
   *            See \ref libusb_hotplug_flag
   * \param[in] vendor_id the vendor id to match or \ref LIBUSB_HOTPLUG_MATCH_ANY
   * \param[in] product_id the product id to match or \ref LIBUSB_HOTPLUG_MATCH_ANY
   * \param[in] dev_class the device class to match or \ref LIBUSB_HOTPLUG_MATCH_ANY
   * \param[in] cb_fn the function to be invoked on a matching event/device
   * \param[in] user_data user data to pass to the callback function
   * \param[out] callback_handle pointer to store the handle of the allocated callback (can be NULL)
   * \returns LIBUSB_SUCCESS on success LIBUSB_ERROR code on failure
   */
  int LIBUSB_CALL libusb_hotplug_register_callback(libusb_context *ctx,
  	int events, int flags,
  	int vendor_id, int product_id, int dev_class,
  	libusb_hotplug_callback_fn cb_fn, void *user_data,
  	libusb_hotplug_callback_handle *callback_handle);
  
  /** \ingroup libusb_hotplug
   * Deregisters a hotplug callback.
   *
   * Deregister a callback from a libusb_context. This function is safe to call from within
   * a hotplug callback.
   *
   * Since version 1.0.16, \ref LIBUSB_API_VERSION >= 0x01000102
   *
   * \param[in] ctx context this callback is registered with
   * \param[in] callback_handle the handle of the callback to deregister
   */
  void LIBUSB_CALL libusb_hotplug_deregister_callback(libusb_context *ctx,
  	libusb_hotplug_callback_handle callback_handle);
  
  /** \ingroup libusb_hotplug
   * Gets the user_data associated with a hotplug callback.
   *
   * Since version v1.0.24 \ref LIBUSB_API_VERSION >= 0x01000108
   *
   * \param[in] ctx context this callback is registered with
   * \param[in] callback_handle the handle of the callback to get the user_data of
   */
  void * LIBUSB_CALL libusb_hotplug_get_user_data(libusb_context *ctx,
  	libusb_hotplug_callback_handle callback_handle);
  
  /** \ingroup libusb_lib
   * Available option values for libusb_set_option().
   */
  enum libusb_option {
  	/** Set the log message verbosity.
  	 *
  	 * The default level is LIBUSB_LOG_LEVEL_NONE, which means no messages are ever
  	 * printed. If you choose to increase the message verbosity level, ensure
  	 * that your application does not close the stderr file descriptor.
  	 *
  	 * You are advised to use level LIBUSB_LOG_LEVEL_WARNING. libusb is conservative
  	 * with its message logging and most of the time, will only log messages that
  	 * explain error conditions and other oddities. This will help you debug
  	 * your software.
  	 *
  	 * If the LIBUSB_DEBUG environment variable was set when libusb was
  	 * initialized, this function does nothing: the message verbosity is fixed
  	 * to the value in the environment variable.
  	 *
  	 * If libusb was compiled without any message logging, this function does
  	 * nothing: you'll never get any messages.
  	 *
  	 * If libusb was compiled with verbose debug message logging, this function
  	 * does nothing: you'll always get messages from all levels.
  	 */
  	LIBUSB_OPTION_LOG_LEVEL = 0,
  
  	/** Use the UsbDk backend for a specific context, if available.
  	 *
  	 * This option should be set immediately after calling libusb_init(), otherwise
  	 * unspecified behavior may occur.
  	 *
  	 * Only valid on Windows.
  	 */
  	LIBUSB_OPTION_USE_USBDK = 1,
  
  	/** Do not scan for devices
  	 *
  	 * With this option set, libusb will skip scanning devices in
  	 * libusb_init(). Must be set before calling libusb_init().
  	 *
  	 * Hotplug functionality will also be deactivated.
  	 *
  	 * The option is useful in combination with libusb_wrap_sys_device(),
  	 * which can access a device directly without prior device scanning.
  	 *
  	 * This is typically needed on Android, where access to USB devices
  	 * is limited.
  	 *
  	 * For LIBUSB_API_VERSION 0x01000108 it was called LIBUSB_OPTION_WEAK_AUTHORITY
  	 *
  	 * Only valid on Linux.
  	 */
  	LIBUSB_OPTION_NO_DEVICE_DISCOVERY = 2,
  
  #define LIBUSB_OPTION_WEAK_AUTHORITY LIBUSB_OPTION_NO_DEVICE_DISCOVERY
  
  	LIBUSB_OPTION_MAX = 3
  };
  
  int LIBUSB_CALL libusb_set_option(libusb_context *ctx, enum libusb_option option, ...);
  
  #if defined(__cplusplus)
  }
  #endif
  
  #endif
  