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// usb - Self contained USB and HID library for Go
// Copyright 2017 The library Authors
//
// 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 3 of the License, or (at your option) any
// later version.
//
// The 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 the library. If not, see <http://www.gnu.org/licenses/>.
// +build freebsd,cgo linux,cgo darwin,!ios,cgo windows,cgo
package usb
/*
#include <stdlib.h>
#include "./hidapi/hidapi/hidapi.h"
*/
import "C"
import (
"errors"
"runtime"
"sync"
"unsafe"
)
// enumerateHid returns a list of all the HID devices attached to the system which
// match the vendor and product id:
// - If the vendor id is set to 0 then any vendor matches.
// - If the product id is set to 0 then any product matches.
// - If the vendor and product id are both 0, all HID devices are returned.
func enumerateHid(vendorID uint16, productID uint16) ([]DeviceInfo, error) {
// Gather all device infos and ensure they are freed before returning
head := C.hid_enumerate(C.ushort(vendorID), C.ushort(productID))
if head == nil {
return nil, nil
}
defer C.hid_free_enumeration(head)
// Iterate the list and retrieve the device details
var infos []DeviceInfo
for ; head != nil; head = head.next {
info := DeviceInfo{
Path: C.GoString(head.path),
VendorID: uint16(head.vendor_id),
ProductID: uint16(head.product_id),
Release: uint16(head.release_number),
UsagePage: uint16(head.usage_page),
Usage: uint16(head.usage),
Interface: int(head.interface_number),
}
if head.serial_number != nil {
info.Serial, _ = wcharTToString(head.serial_number)
}
if head.product_string != nil {
info.Product, _ = wcharTToString(head.product_string)
}
if head.manufacturer_string != nil {
info.Manufacturer, _ = wcharTToString(head.manufacturer_string)
}
infos = append(infos, info)
}
return infos, nil
}
// openHid connects to an HID device by its path name.
func openHid(info DeviceInfo) (*hidDevice, error) {
path := C.CString(info.Path)
defer C.free(unsafe.Pointer(path))
device := C.hid_open_path(path)
if device == nil {
return nil, errors.New("hidapi: failed to open device")
}
return &hidDevice{
DeviceInfo: info,
device: device,
}, nil
}
// hidDevice is a live HID USB connected device handle.
type hidDevice struct {
DeviceInfo // Embed the infos for easier access
device *C.hid_device // Low level HID device to communicate through
lock sync.Mutex
}
// Close releases the HID USB device handle.
func (dev *hidDevice) Close() error {
dev.lock.Lock()
defer dev.lock.Unlock()
if dev.device != nil {
C.hid_close(dev.device)
dev.device = nil
}
return nil
}
// Write sends an output report to a HID device.
//
// Write will send the data on the first OUT endpoint, if one exists. If it does
// not, it will send the data through the Control Endpoint (Endpoint 0).
func (dev *hidDevice) Write(b []byte) (int, error) {
// Abort if nothing to write
if len(b) == 0 {
return 0, nil
}
// Abort if device closed in between
dev.lock.Lock()
device := dev.device
dev.lock.Unlock()
if device == nil {
return 0, ErrDeviceClosed
}
// Prepend a HID report ID on Windows, other OSes don't need it
var report []byte
if runtime.GOOS == "windows" {
report = append([]byte{0x00}, b...)
} else {
report = b
}
// Execute the write operation
written := int(C.hid_write(device, (*C.uchar)(&report[0]), C.size_t(len(report))))
if written == -1 {
// If the write failed, verify if closed or other error
dev.lock.Lock()
device = dev.device
dev.lock.Unlock()
if device == nil {
return 0, ErrDeviceClosed
}
// Device not closed, some other error occurred
message := C.hid_error(device)
if message == nil {
return 0, errors.New("hidapi: unknown failure")
}
failure, _ := wcharTToString(message)
return 0, errors.New("hidapi: " + failure)
}
return written, nil
}
// Read retrieves an input report from a HID device.
func (dev *hidDevice) Read(b []byte) (int, error) {
// Aborth if nothing to read
if len(b) == 0 {
return 0, nil
}
// Abort if device closed in between
dev.lock.Lock()
device := dev.device
dev.lock.Unlock()
if device == nil {
return 0, ErrDeviceClosed
}
// Execute the read operation
read := int(C.hid_read(device, (*C.uchar)(&b[0]), C.size_t(len(b))))
if read == -1 {
// If the read failed, verify if closed or other error
dev.lock.Lock()
device = dev.device
dev.lock.Unlock()
if device == nil {
return 0, ErrDeviceClosed
}
// Device not closed, some other error occurred
message := C.hid_error(device)
if message == nil {
return 0, errors.New("hidapi: unknown failure")
}
failure, _ := wcharTToString(message)
return 0, errors.New("hidapi: " + failure)
}
return read, nil
}
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