Add a method to BetterStream and FastSerial that can be used to report

the amount of data that can be written without blocking.



git-svn-id: https://arducopter.googlecode.com/svn/trunk@2549 f9c3cf11-9bcb-44bc-f272-b75c42450872

libraries/FastSerial/BetterStream.cpp

@@ -12,6 +12,7 @@
 // Enhancements to the Arduino Stream class.
 //
 
+#include <limits.h>
 #include "BetterStream.h"
 
 // Stream extensions////////////////////////////////////////////////////////////
@@ -52,3 +53,9 @@ BetterStream::_printf_P(const prog_char *fmt, ...)
         va_end(ap);
 }
 
+int
+BetterStream::space(void)
+{
+        // by default claim that there is always space
+        return(INT_MAX);
+}

libraries/FastSerial/BetterStream.h

@@ -28,6 +28,8 @@ public:
         void            _printf_P(const prog_char *, ...);
                 __attribute__ ((format(__printf__, 2, 3)));
 
+        virtual int     space(void);
+
 #define printf_P(fmt, ...) _printf_P((const prog_char *)fmt, ## __VA_ARGS__)
 
 private:

libraries/FastSerial/FastSerial.cpp

@@ -142,6 +142,13 @@ int FastSerial::available(void)
 	return ((_rxBuffer->head - _rxBuffer->tail) & _rxBuffer->mask);
 }
 
+int FastSerial::space(void)
+{
+	if (!_open)
+		return (-1);
+	return (((_rxBuffer->tail - _rxBuffer->head) & _rxBuffer->mask) - 1);
+}
+
 int FastSerial::read(void)
 {
 	uint8_t c;

libraries/FastSerial/FastSerial.h

@@ -110,6 +110,7 @@ public:
 	virtual void begin(long baud);
 	virtual void end(void);
 	virtual int available(void);
+	virtual int space(void);
 	virtual int read(void);
 	virtual int peek(void);
 	virtual void flush(void);