Improve tests - use offsetof to find the position of the iso packet

descriptor in the transfer struct.

usb/transfer_fakelibusb_test.go

@@ -0,0 +1,56 @@
+// Copyright 2017 the gousb Authors.  All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package usb
+
+import "sync"
+
+type fakeLibusb struct {
+	sync.Mutex
+	ts map[*libusbTransfer]chan struct{}
+}
+
+func (f *fakeLibusb) submit(t *libusbTransfer) usbError {
+	f.Lock()
+	defer f.Unlock()
+	if f.ts[t] == nil {
+		f.ts[t] = make(chan struct{})
+	}
+	close(f.ts[t])
+	return SUCCESS
+}
+
+func (f *fakeLibusb) cancel(t *libusbTransfer) usbError { return SUCCESS }
+
+func (f *fakeLibusb) waitForSubmit(t *usbTransfer) {
+	f.Lock()
+	if f.ts[t.xfer] == nil {
+		f.ts[t.xfer] = make(chan struct{})
+	}
+	ch := f.ts[t.xfer]
+	f.Unlock()
+	<-ch
+}
+
+func (f *fakeLibusb) runCallback(t *usbTransfer, cb func(*usbTransfer)) {
+	f.Lock()
+	defer f.Unlock()
+	delete(f.ts, t.xfer)
+	cb(t)
+	close(t.done)
+}
+
+func newFakeLibusb() *fakeLibusb {
+	return &fakeLibusb{ts: make(map[*libusbTransfer]chan struct{})}
+}