Add printf to print class

api/Print.cpp

@@ -233,6 +233,34 @@ size_t Print::println(const Printable& x)
   return n;
 }
 
+static int16_t printf_putchar(char c, FILE *fp)
+{
+  ((class Print *)(fdev_get_udata(fp)))->write((uint8_t)c);
+  return 0;
+}
+
+int16_t Print::printf(const char *format, ...)
+{
+  FILE f;
+  va_list ap;
+
+  fdev_setup_stream(&f, printf_putchar, NULL, _FDEV_SETUP_WRITE);
+  fdev_set_udata(&f, this);
+  va_start(ap, format);
+  return vfprintf(&f, format, ap);
+}
+
+int16_t Print::printf(const __FlashStringHelper *format, ...)
+{
+  FILE f;
+  va_list ap;
+
+  fdev_setup_stream(&f, printf_putchar, NULL, _FDEV_SETUP_WRITE);
+  fdev_set_udata(&f, this);
+  va_start(ap, format);
+  return vfprintf_P(&f, (const char *)format, ap);
+}
+
 // Private Methods /////////////////////////////////////////////////////////////
 
 size_t Print::printNumber(unsigned long n, uint8_t base)

api/Print.h

@@ -20,7 +20,7 @@
 
 #include <inttypes.h>
 #include <stdio.h> // for size_t
-
+#include <stdarg.h>
 #include "String.h"
 #include "Printable.h"
 
@@ -82,5 +82,8 @@ class Print
     size_t println(double, int = 2);
     size_t println(const Printable&);
     size_t println(void);
+
+    int16_t printf(const char *format, ...);
+    int16_t printf(const __FlashStringHelper *format, ...);
 };