Add Serial_::availableForWrite

Author: sandeepmistry

cores/arduino/USB/CDC.cpp

@@ -214,6 +214,13 @@ int Serial_::available(void)
 return (unsigned int)(CDC_SERIAL_BUFFER_SIZE + buffer->head - buffer->tail) % CDC_SERIAL_BUFFER_SIZE;
 }
 
+int Serial_::availableForWrite(void)
+{
+// return the number of bytes left in the current bank,
+// always EP size - 1, because bank is flushed on every write
+return (EPX_SIZE - 1);
+}
+
 int Serial_::peek(void)
 {
 ring_buffer *buffer = &cdc_rx_buffer;

cores/arduino/USB/USBAPI.h

@@ -54,6 +54,7 @@ class Serial_ : public Stream
 void end(void);
 
 virtual int available(void);
+virtual int availableForWrite(void);
 virtual void accept(void);
 virtual int peek(void);
 virtual int read(void);