Adding Serial.flush() command.

targets/arduino/HardwareSerial.cpp

@@ -54,6 +54,11 @@ int HardwareSerial::read(void)
   return serialRead();
 }
 
+void HardwareSerial::flush()
+{
+  serialFlush();
+}
+
 void HardwareSerial::print(char c)
 {
   printByte(c);

targets/arduino/HardwareSerial.h

@@ -38,6 +38,7 @@ class HardwareSerial
     void begin(long);
     uint8_t available(void);
     int read(void);
+    void flush(void);
     void print(char);
     void print(char[]);
     void print(uint8_t);

targets/arduino/wiring.c

@@ -306,6 +306,16 @@ int serialRead()
 	}
 }
 
+void serialFlush()
+{
+	// don't reverse this or there may be problems if the RX interrupt
+	// occurs after reading the value of rx_buffer_head but before writing
+	// the value to rx_buffer_tail; the previous value of rx_buffer_head
+	// may be written to rx_buffer_tail, making it appear as if the buffer
+	// were full, not empty.
+	rx_buffer_head = rx_buffer_tail;
+}
+
 #if defined(__AVR_ATmega168__)
 SIGNAL(SIG_USART_RECV)
 #else

targets/arduino/wiring.h

@@ -76,6 +76,7 @@ void beginSerial(long);
 void serialWrite(unsigned char);
 int serialAvailable();
 int serialRead();
+void serialFlush();
 void printMode(int);
 void printByte(unsigned char c);
 void printNewline();