"Cancel" Implementation(windows only): Cancels all pending read and write operation from an other thread.

Unix also need add something like this.

include/serial/impl/win.h

@@ -66,6 +66,9 @@ public:
   void
   open ();
 
+  void
+  cancel();
+
   void
   close ();
 

include/serial/serial.h

@@ -211,6 +211,10 @@ public:
   bool
   isOpen () const;
 
+  /*! Cancels all pending read and write operation. */
+  void
+  cancel();
+
   /*! Closes the serial port. */
   void
   close ();

src/impl/win.cc

@@ -274,9 +274,27 @@ Serial::SerialImpl::reconfigurePort ()
   }
 }
 
+void
+Serial::SerialImpl::cancel()
+{
+  if (is_open_ == true) {
+     if (fd_ != INVALID_HANDLE_VALUE) {
+        int ret;
+        ret = CancelIoEx(fd_, NULL);
+        DWORD last_error = GetLastError();
+        if (ret == 0 && last_error != ERROR_NOT_FOUND) {
+          stringstream ss;
+          ss << "Error while canceling serial port: " << last_error;
+          THROW(IOException, ss.str().c_str());
+        }
+      }
+  }
+}
+
 void
 Serial::SerialImpl::close ()
 {
+  this->cancel();
   if (is_open_ == true) {
     if (fd_ != INVALID_HANDLE_VALUE) {
       int ret;

src/serial.cc

@@ -83,6 +83,12 @@ Serial::open ()
   pimpl_->open ();
 }
 
+void
+Serial::cancel()
+{
+  pimpl_->cancel();
+}
+
 void
 Serial::close ()
 {