Added preliminary printf() support to RawSerial

Author: Bogdan Marinescu

libraries/mbed/api/RawSerial.h

@@ -71,6 +71,16 @@ class RawSerial: public SerialBase {
      * @returns The char read from the serial port
      */
     int getc();
+
+    /** Write a string to the serial port
+     *
+     * @param str The string to write
+     *
+     * @returns 0 if the write succeeds, EOF for error
+     */
+    int puts(const char *str);
+
+    int printf(const char *format, ...);
 };
 
 } // namespace mbed

libraries/mbed/common/RawSerial.cpp

@@ -15,9 +15,12 @@
  */
 #include "RawSerial.h"
 #include "wait_api.h"
+#include <cstdarg>
 
 #if DEVICE_SERIAL
 
+#define STRING_STACK_LIMIT    120
+
 namespace mbed {
 
 RawSerial::RawSerial(PinName tx, PinName rx) : SerialBase(tx, rx) {
@@ -31,6 +34,34 @@ int RawSerial::putc(int c) {
     return _base_putc(c);
 }
 
+int RawSerial::puts(const char *str) {
+    while (*str)
+        putc(*str ++);
+    return 0;
+}
+
+// Experimental support for printf in RawSerial. No Stream inheritance
+// means we can't call printf() directly, so we use sprintf() instead.
+// We only call malloc() for the sprintf() buffer if the buffer
+// length is above a certain threshold, otherwise we use just the stack.
+int RawSerial::printf(const char *format, ...) {
+    std::va_list arg;
+    va_start(arg, format);
+    int len = vsnprintf(NULL, 0, format, arg);
+    if (len < STRING_STACK_LIMIT) {
+        char temp[STRING_STACK_LIMIT];
+        vsprintf(temp, format, arg);
+        puts(temp);
+    } else {
+        char *temp = new char[len + 1];
+        vsprintf(temp, format, arg);
+        puts(temp);
+        delete[] temp;
+    }
+    va_end(arg);
+    return len;
+}
+
 } // namespace mbed
 
 #endif