Add a purge() method

serial-core/src/lib.rs

@@ -274,6 +274,19 @@ pub enum FlowControl {
     FlowHardware,
 }
 
+/// Queues available to purge.
+#[derive(Debug,Copy,Clone,PartialEq,Eq)]
+pub enum Queue {
+    /// Receive queue.
+    Input,
+
+    /// Transmit queue.
+    Output,
+
+    /// Both the input and output queues.
+    Both,
+}
+
 /// A trait for implementing serial devices.
 ///
 /// This trait is meant to be used to implement new serial port devices. To use a serial port
@@ -346,6 +359,12 @@ pub trait SerialDevice: io::Read + io::Write {
     /// Sets the timeout for future I/O operations.
     fn set_timeout(&mut self, timeout: Duration) -> ::Result<()>;
 
+    /// Purges the send or receive queue.
+    ///
+    /// Clears any data that has been queued for sending or receiving. The data is discarded
+    /// without being sent or received.
+    fn purge(&mut self, queue: Queue) -> ::Result<()>;
+
     /// Sets the state of the RTS (Request To Send) control signal.
     ///
     /// Setting a value of `true` asserts the RTS control signal. `false` clears the signal.
@@ -494,6 +513,12 @@ pub trait SerialPort: io::Read + io::Write {
     /// ```
     fn reconfigure(&mut self, setup: &Fn(&mut SerialPortSettings) -> ::Result<()>) -> ::Result<()>;
 
+    /// Purges the send or receive queue.
+    ///
+    /// Clears any data that has been queued for sending or receiving. The data is discarded
+    /// without being sent or received.
+    fn purge(&mut self, queue: Queue) -> ::Result<()>;
+
     /// Sets the state of the RTS (Request To Send) control signal.
     ///
     /// Setting a value of `true` asserts the RTS control signal. `false` clears the signal.
@@ -602,6 +627,10 @@ impl<T> SerialPort for T
         T::write_settings(self, &device_settings)
     }
 
+    fn purge(&mut self, queue: Queue) -> ::Result<()> {
+        T::purge(self, queue)
+    }
+
     fn set_rts(&mut self, level: bool) -> ::Result<()> {
         T::set_rts(self, level)
     }

serial-windows/src/com.rs

@@ -183,6 +183,21 @@ impl SerialDevice for COMPort {
         Ok(())
     }
 
+    fn purge(&mut self, queue: core::Queue) -> core::Result<()> {
+        use core::Queue::*;
+
+        let flags = match queue {
+            Input => PURGE_RXCLEAR,
+            Output => PURGE_TXCLEAR,
+            Both => PURGE_RXCLEAR | PURGE_TXCLEAR,
+        };
+
+        match unsafe { PurgeComm(self.handle, flags) } {
+            0 => Err(error::last_os_error()),
+            _ => Ok(()),
+        }
+    }
+
     fn set_rts(&mut self, level: bool) -> core::Result<()> {
         if level {
             self.escape_comm_function(SETRTS)

serial-windows/src/ffi.rs

@@ -133,6 +133,10 @@ pub const MS_DSR_ON:  DWORD = 0x0020;
 pub const MS_RING_ON: DWORD = 0x0040;
 pub const MS_RLSD_ON: DWORD = 0x0080;
 
+// PurgeComm values
+pub const PURGE_RXCLEAR: DWORD = 0x0008;
+pub const PURGE_TXCLEAR: DWORD = 0x0004;
+
 #[derive(Copy,Clone,Debug)]
 #[repr(C)]
 pub struct COMMTIMEOUTS {
@@ -166,6 +170,7 @@ extern "system" {
                      lpOverlapped: LPOVERLAPPED)
                      -> BOOL;
     pub fn FlushFileBuffers(hFile: HANDLE) -> BOOL;
+    pub fn PurgeComm(hFile: HANDLE, dwFlags: DWORD) -> BOOL;
 
     pub fn GetCommState(hFile: HANDLE, lpDCB: *mut DCB) -> BOOL;
     pub fn SetCommState(hFile: HANDLE, lpDCB: *const DCB) -> BOOL;