Windows: Add new API calls to DLL .def file

[libusbx.git] / libusb / libusb.h

/*
 * Public libusbx header file
 * Copyright © 2007-2008 Daniel Drake <dsd@gentoo.org>
 * Copyright © 2001 Johannes Erdfelt <johannes@erdfelt.com>
 *
 * 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

#ifdef _MSC_VER
/* on MS environments, the inline keyword is available in C++ only */
#define inline __inline
/* ssize_t is also not available (copy/paste from MinGW) */
#ifndef _SSIZE_T_DEFINED
#define _SSIZE_T_DEFINED
#undef ssize_t
#ifdef _WIN64
  typedef __int64 ssize_t;
#else
  typedef int ssize_t;
#endif /* _WIN64 */
#endif /* _SSIZE_T_DEFINED */
#endif /* _MSC_VER */

/* stdint.h is also not usually available on MS */
#if defined(_MSC_VER) && (_MSC_VER < 1600) && (!defined(_STDINT)) && (!defined(_STDINT_H))
typedef unsigned __int8   uint8_t;
typedef unsigned __int16  uint16_t;
typedef unsigned __int32  uint32_t;
#else
#include <stdint.h>
#endif

#include <sys/types.h>
#include <time.h>
#include <limits.h>

#if defined(__linux) || defined(__APPLE__) || defined(__CYGWIN__)
#include <sys/time.h>
#endif

/* 'interface' might be defined as a macro on Windows, so we need to
 * undefine it so as not to break the current libusbx 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
#endif

/** \def LIBUSB_CALL
 * \ingroup misc
 * libusbx'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 funcions in the generated assembly code).
 *
 * Matching the Windows API itself, libusbx 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 libusbx 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 libusbx
 * 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

#ifdef __cplusplus
extern "C" {
#endif

/** \def libusb_cpu_to_le16
 * \ingroup 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] = x >> 8;
        _tmp.b8[0] = x & 0xff;
        return _tmp.b16;
}

/** \def libusb_le16_to_cpu
 * \ingroup 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 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 = 0,

        /** Audio class */
        LIBUSB_CLASS_AUDIO = 1,

        /** Communications class */
        LIBUSB_CLASS_COMM = 2,

        /** Human Interface Device class */
        LIBUSB_CLASS_HID = 3,

        /** Physical */
        LIBUSB_CLASS_PHYSICAL = 5,

        /** Printer class */
        LIBUSB_CLASS_PRINTER = 7,

        /** Image class */
        LIBUSB_CLASS_PTP = 6, /* legacy name from libusb-0.1 usb.h */
        LIBUSB_CLASS_IMAGE = 6,

        /** Mass storage class */
        LIBUSB_CLASS_MASS_STORAGE = 8,

        /** Hub class */
        LIBUSB_CLASS_HUB = 9,

        /** Data class */
        LIBUSB_CLASS_DATA = 10,

        /** 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,

        /** Application class */
        LIBUSB_CLASS_APPLICATION = 0xfe,

        /** Class is vendor-specific */
        LIBUSB_CLASS_VENDOR_SPEC = 0xff
};

/** \ingroup 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,

        /** 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,
};

/* 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_ENDPOINT_ADDRESS_MASK    0x0f    /* in bEndpointAddress */
#define LIBUSB_ENDPOINT_DIR_MASK                0x80

/** \ingroup desc
 * Endpoint direction. Values for bit 7 of the
 * \ref libusb_endpoint_descriptor::bEndpointAddress "endpoint address" scheme.
 */
enum libusb_endpoint_direction {
        /** In: device-to-host */
        LIBUSB_ENDPOINT_IN = 0x80,

        /** Out: host-to-device */
        LIBUSB_ENDPOINT_OUT = 0x00
};

#define LIBUSB_TRANSFER_TYPE_MASK                       0x03    /* in bmAttributes */

/** \ingroup desc
 * Endpoint transfer type. Values for bits 0:1 of the
 * \ref libusb_endpoint_descriptor::bmAttributes "endpoint attributes" field.
 */
enum libusb_transfer_type {
        /** Control endpoint */
        LIBUSB_TRANSFER_TYPE_CONTROL = 0,

        /** Isochronous endpoint */
        LIBUSB_TRANSFER_TYPE_ISOCHRONOUS = 1,

        /** Bulk endpoint */
        LIBUSB_TRANSFER_TYPE_BULK = 2,

        /** Interrupt endpoint */
        LIBUSB_TRANSFER_TYPE_INTERRUPT = 3
};

/** \ingroup misc
 * Standard requests, as defined in table 9-3 of the USB2 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,
};

/** \ingroup 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 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 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 = 0,

        /** Asynchronous */
        LIBUSB_ISO_SYNC_TYPE_ASYNC = 1,

        /** Adaptive */
        LIBUSB_ISO_SYNC_TYPE_ADAPTIVE = 2,

        /** Synchronous */
        LIBUSB_ISO_SYNC_TYPE_SYNC = 3
};

#define LIBUSB_ISO_USAGE_TYPE_MASK 0x30

/** \ingroup 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 = 0,

        /** Feedback endpoint */
        LIBUSB_ISO_USAGE_TYPE_FEEDBACK = 1,

        /** Implicit feedback Data endpoint */
        LIBUSB_ISO_USAGE_TYPE_IMPLICIT = 2,
};

/** \ingroup desc
 * A structure representing the standard USB device descriptor. This
 * descriptor is documented in section 9.6.1 of the USB 2.0 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 desc
 * A structure representing the standard USB endpoint descriptor. This
 * descriptor is documented in section 9.6.3 of the USB 2.0 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_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 libusbx 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. */
        int extra_length;
};

/** \ingroup desc
 * A structure representing the standard USB interface descriptor. This
 * descriptor is documented in section 9.6.5 of the USB 2.0 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 libusbx 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. */
        int extra_length;
};

/** \ingroup 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 */
        int num_altsetting;
};

/** \ingroup desc
 * A structure representing the standard USB configuration descriptor. This
 * descriptor is documented in section 9.6.3 of the USB 2.0 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 opreation. Expressed in units
         * of 2 mA. */
        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 libusbx 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. */
        int extra_length;
};

/** \ingroup asyncio
 * Setup packet for control transfers. */
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;
};

#define LIBUSB_CONTROL_SETUP_SIZE (sizeof(struct libusb_control_setup))

/* libusbx */

struct libusb_context;
struct libusb_device;
struct libusb_device_handle;

/** \ingroup lib
 * Structure providing the version of the libusbx 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 lib
 * Structure representing a libusbx session. The concept of individual libusbx
 * 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 libusbx users - for example
 * libusb_set_debug() 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 libusbx
 * user (i.e. you), you do not have to worry about contexts: pass NULL in
 * every function call where a context is required. The default context
 * will be used.
 *
 * For more information, see \ref contexts.
 */
typedef struct libusb_context libusb_context;

/** \ingroup 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().
 *
 * 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_device_ref() and
 * libusb_device_unref(), 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 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 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,
};

/** \ingroup misc
 * Error codes. Most libusbx functions return 0 on success or one of these
 * codes on failure.
 * You can call \ref libusb_error_name() to retrieve a string representation
 * 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_name()
           when adding new error codes here. */

        /** Other error */
        LIBUSB_ERROR_OTHER = -99,
};

/** \ingroup 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,
};

/** \ingroup asyncio
 * libusb_transfer.flags values */
enum libusb_transfer_flags {
        /** Report short frames as errors */
        LIBUSB_TRANSFER_SHORT_NOT_OK = 1<<0,

        /** Automatically free() transfer buffer during libusb_free_transfer() */
        LIBUSB_TRANSFER_FREE_BUFFER = 1<<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 = 1<<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 = 1 << 3,
};

/** \ingroup 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 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. libusbx will call this function later, when the transfer has
 * completed or failed. See \ref 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 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 endpoint from \ref libusb_transfer_type */
        unsigned char type;

        /** Timeout for this transfer in millseconds. 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 */
        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 to pass to the callback function. */
        void *user_data;

        /** Data buffer */
        unsigned char *buffer;

        /** Number of isochronous packets. Only used for I/O with isochronous
         * endpoints. */
        int num_iso_packets;

        /** Isochronous packet descriptors, for isochronous transfers only. */
        struct libusb_iso_packet_descriptor iso_packet_desc
#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L)
        [] /* valid C99 code */
#else
        [0] /* non-standard, but usually working code */
#endif
        ;
};

/** \ingroup misc
 * Capabilities supported by this instance of libusb. 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 = 0,
};

/** \ingroup lib
 *  Log message levels.
 *  - LOG_LEVEL_NONE (0)    : no messages ever printed by the library (default)
 *  - LOG_LEVEL_ERROR (1)   : error messages are printed to stderr
 *  - LOG_LEVEL_WARNING (2) : warning and error messages are printed to stderr
 *  - LOG_LEVEL_INFO (3)    : informational messages are printed to stdout, warning
 *    and error messages are printed to stderr
 *  - LOG_LEVEL_DEBUG (4)   : debug and informational messages are printed to stdout,
 *    warnings and errors to stderr
 */
enum usbi_log_level {
        LOG_LEVEL_NONE = 0,
        LOG_LEVEL_ERROR,
        LOG_LEVEL_WARNING,
        LOG_LEVEL_INFO,
        LOG_LEVEL_DEBUG,
};

int LIBUSB_CALL libusb_init(libusb_context **ctx);
void LIBUSB_CALL libusb_exit(libusb_context *ctx);
void LIBUSB_CALL libusb_set_debug(libusb_context *ctx, int level);
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);

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);
uint8_t LIBUSB_CALL libusb_get_bus_number(libusb_device *dev);
uint8_t LIBUSB_CALL libusb_get_port_number(libusb_device *dev);
libusb_device * LIBUSB_CALL libusb_get_parent(libusb_device *dev);
int LIBUSB_CALL libusb_get_port_path(libusb_context *ctx, libusb_device *dev, uint8_t* path, uint8_t path_length);
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_open(libusb_device *dev, libusb_device_handle **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,
        int configuration);
int LIBUSB_CALL libusb_claim_interface(libusb_device_handle *dev,
        int interface_number);
int LIBUSB_CALL libusb_release_interface(libusb_device_handle *dev,
        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,
        int interface_number, int alternate_setting);
int LIBUSB_CALL libusb_clear_halt(libusb_device_handle *dev,
        unsigned char endpoint);
int LIBUSB_CALL libusb_reset_device(libusb_device_handle *dev);

int LIBUSB_CALL libusb_kernel_driver_active(libusb_device_handle *dev,
        int interface_number);
int LIBUSB_CALL libusb_detach_kernel_driver(libusb_device_handle *dev,
        int interface_number);
int LIBUSB_CALL libusb_attach_kernel_driver(libusb_device_handle *dev,
        int interface_number);

/* async I/O */

/** \ingroup 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 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 *) transfer->buffer;
}

/** \ingroup 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
 * \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 *) 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);

/** \ingroup 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.
 * \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 *) 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 = LIBUSB_CONTROL_SETUP_SIZE
                        + libusb_le16_to_cpu(setup->wLength);
        transfer->user_data = user_data;
        transfer->callback = callback;
}

/** \ingroup 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 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 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 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 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 = 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 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 = packet;

        if (_packet >= transfer->num_iso_packets)
                return NULL;

        return transfer->buffer + (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 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 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,
        uint8_t desc_type, uint8_t desc_index, unsigned char *data, int length)
{
        return libusb_control_transfer(dev, LIBUSB_ENDPOINT_IN,
                LIBUSB_REQUEST_GET_DESCRIPTOR, (desc_type << 8) | desc_index, 0, data,
                (uint16_t) length, 1000);
}

/** \ingroup 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 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,
        uint8_t desc_index, uint16_t langid, unsigned char *data, int length)
{
        return libusb_control_transfer(dev, 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,
        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_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 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 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 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_set_pollfd_notifiers(libusb_context *ctx,
        libusb_pollfd_added_cb added_cb, libusb_pollfd_removed_cb removed_cb,
        void *user_data);

#ifdef __cplusplus
}
#endif

#endif