First cut

usb/usb.go

@@ -0,0 +1,76 @@
+package usb
+
+// #cgo LDFLAGS: -lusb-1.0
+// #include <libusb-1.0/libusb.h>
+import "C"
+
+import (
+	"log"
+	"reflect"
+	"runtime"
+	"unsafe"
+)
+
+type Context struct {
+	ctx *C.libusb_context
+}
+
+func (c *Context) Debug(level int) {
+	C.libusb_set_debug(c.ctx, C.int(level))
+}
+
+func NewContext() *Context {
+	c := new(Context)
+
+	log.Printf("gousb initialized")
+	if errno := C.libusb_init(&c.ctx); errno != 0 {
+		panic(usbError(errno))
+	}
+
+	// This doesn't seem to actually get called.  Sigh.
+	runtime.SetFinalizer(c, (*Context).Close)
+
+	return c
+}
+
+// ListDevices calls each with each enumerated device.  If the function returns
+// true, the device is added to the list of *DeviceInfo to return.  All of
+// these must be Closed, even if an error is also returned.
+func (c *Context) ListDevices(each func(bus, addr int, desc *Descriptor) bool) ([]*DeviceInfo, error) {
+	var list **C.libusb_device
+	cnt := C.libusb_get_device_list(c.ctx, &list)
+	if cnt < 0 {
+		return nil, usbError(cnt)
+	}
+	defer C.libusb_free_device_list(list, 1)
+
+	var slice []*C.libusb_device
+	*(*reflect.SliceHeader)(unsafe.Pointer(&slice)) = reflect.SliceHeader{
+		Data: uintptr(unsafe.Pointer(list)),
+		Len:  int(cnt),
+		Cap:  int(cnt),
+	}
+
+	ret := []*DeviceInfo{}
+	for _, dev := range slice {
+		bus := int(C.libusb_get_bus_number(dev))
+		addr := int(C.libusb_get_device_address(dev))
+		desc, err := newDescriptor(dev)
+		if err != nil {
+			return ret, err
+		}
+		if each(bus, addr, desc) {
+			ret = append(ret, newDeviceInfo(dev))
+		}
+	}
+	return ret, nil
+}
+
+func (c *Context) Close() error {
+	if c.ctx != nil {
+		C.libusb_exit(c.ctx)
+		log.Printf("gousb finished")
+	}
+	c.ctx = nil
+	return nil
+}