From 31601ffe77682dfd54958191ee18f79c772a6226 Mon Sep 17 00:00:00 2001
From: "David A. Mellis" <d.mellis@arduino.cc>
Date: Sun, 4 Jul 2010 23:31:55 +0000
Subject: [PATCH] Adding a peek() function to Stream and HardwareSerial
 (Serial).

---
 build/shared/lib/keywords.txt                     | 1 +
 hardware/arduino/cores/arduino/HardwareSerial.cpp | 9 +++++++++
 hardware/arduino/cores/arduino/HardwareSerial.h   | 1 +
 hardware/arduino/cores/arduino/Stream.h           | 1 +
 4 files changed, 12 insertions(+)

diff --git a/build/shared/lib/keywords.txt b/build/shared/lib/keywords.txt
index fbf8f3943..770acfbd8 100644
--- a/build/shared/lib/keywords.txt
+++ b/build/shared/lib/keywords.txt
@@ -163,6 +163,7 @@ Serial2	KEYWORD3	Serial
 Serial3	KEYWORD3	Serial
 begin	KEYWORD2	Serial_Begin
 end	KEYWORD2	Serial_End
+peek	KEYWORD2	Serial_Peek
 read	KEYWORD2	Serial_Read
 print	KEYWORD2	Serial_Print
 println	KEYWORD2	Serial_Println
diff --git a/hardware/arduino/cores/arduino/HardwareSerial.cpp b/hardware/arduino/cores/arduino/HardwareSerial.cpp
index 638b6d1b0..f8cdebe46 100755
--- a/hardware/arduino/cores/arduino/HardwareSerial.cpp
+++ b/hardware/arduino/cores/arduino/HardwareSerial.cpp
@@ -178,6 +178,15 @@ uint8_t HardwareSerial::available(void)
   return (RX_BUFFER_SIZE + _rx_buffer->head - _rx_buffer->tail) % RX_BUFFER_SIZE;
 }
 
+int HardwareSerial::peek(void)
+{
+  if (_rx_buffer->head == _rx_buffer->tail) {
+    return -1;
+  } else {
+    return _rx_buffer->buffer[_rx_buffer->tail];
+  }
+}
+
 int HardwareSerial::read(void)
 {
   // if the head isn't ahead of the tail, we don't have any characters
diff --git a/hardware/arduino/cores/arduino/HardwareSerial.h b/hardware/arduino/cores/arduino/HardwareSerial.h
index cae1447a0..884f9feef 100755
--- a/hardware/arduino/cores/arduino/HardwareSerial.h
+++ b/hardware/arduino/cores/arduino/HardwareSerial.h
@@ -49,6 +49,7 @@ class HardwareSerial : public Stream
     void begin(long);
     void end();
     virtual uint8_t available(void);
+    virtual int peek(void);
     virtual int read(void);
     virtual void flush(void);
     virtual void write(uint8_t);
diff --git a/hardware/arduino/cores/arduino/Stream.h b/hardware/arduino/cores/arduino/Stream.h
index 3bf5283da..1d3e50be9 100644
--- a/hardware/arduino/cores/arduino/Stream.h
+++ b/hardware/arduino/cores/arduino/Stream.h
@@ -27,6 +27,7 @@ class Stream : public Print
 {
   public:
     virtual uint8_t available() = 0;
+    virtual int peek() = 0;
     virtual int read() = 0;
     virtual void flush() = 0;
 };