adb: fix spurious usb write failure on Windows.

We were accidentally returning 0 instead of the number of bytes written
whenever we wrote a USB packet that had a size that was a multiple of
the USB packet size, which resulted in the device getting kicked.

Bug: http://b/113070258
Test: python test_device.py
Change-Id: Ib3d6415545e90e1f4730afc8ad8713d10bb1534a

adb/client/usb_windows.cpp

@@ -357,7 +357,8 @@ int usb_write(usb_handle* handle, const void* data, int len) {
 
     if (handle->zero_mask && (len & handle->zero_mask) == 0) {
         // Send a zero length packet
-        if (!AdbWriteEndpointSync(handle->adb_write_pipe, (void*)data, 0, &written, time_out)) {
+        unsigned long dummy;
+        if (!AdbWriteEndpointSync(handle->adb_write_pipe, (void*)data, 0, &dummy, time_out)) {
             D("AdbWriteEndpointSync of zero length packet failed: %s",
               android::base::SystemErrorCodeToString(GetLastError()).c_str());
             err = EIO;

adb/test_device.py

@@ -1302,6 +1302,37 @@ class DeviceOfflineTest(DeviceTest):
                 self.assertEqual(length, len(stdout) - 4)
                 self.assertEqual(stdout, "\0" * length + "foo\n")
 
+    def test_zero_packet(self):
+        """Test for http://b/113070258
+
+        Make sure that we don't blow up when sending USB transfers that line up
+        exactly with the USB packet size.
+        """
+
+        local_port = int(self.device.forward("tcp:0", "tcp:12345"))
+        try:
+            for size in [512, 1024]:
+                def listener():
+                    cmd = ["echo foo | nc -l -p 12345; echo done"]
+                    rc, stdout, stderr = self.device.shell_nocheck(cmd)
+
+                thread = threading.Thread(target=listener)
+                thread.start()
+
+                # Wait a bit to let the shell command start.
+                time.sleep(0.25)
+
+                sock = socket.create_connection(("localhost", local_port))
+                with contextlib.closing(sock):
+                    bytesWritten = sock.send("a" * size)
+                    self.assertEqual(size, bytesWritten)
+                    readBytes = sock.recv(4096)
+                    self.assertEqual("foo\n", readBytes)
+
+                thread.join()
+        finally:
+            self.device.forward_remove("tcp:{}".format(local_port))
+
 
 def main():
     random.seed(0)