Add support for dtostrf()

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Show output from successful compile
 - `--min-free-space=N` command-line argument to fail if free space is below requred value
 - Add `_BV()` macro.
+- Support for `dtostrf()`
 
 ### Changed
 - Fix copy/paste error to allow additional warnings for a platform

SampleProjects/TestSomething/test/stdlib.cpp

@@ -43,4 +43,12 @@ unittest(library_tests_itoa)
 
 }
 
+unittest(library_tests_dtostrf)
+{
+  float num = 123.456;
+  char buffer[10];
+  dtostrf(num, 7, 3, buffer);
+  assertEqual(strncmp(buffer, "123.456", sizeof(buffer)), 0);
+}
+
 unittest_main()

cpp/arduino/stdlib.cpp

@@ -18,6 +18,7 @@
 **            is out of range.
 */
 
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -59,3 +60,22 @@ char *itoa(int N, char *str, int base)
       return str;
 }
 #endif
+
+ /*
+ The dtostrf() function converts the double value passed in val into
+ an ASCII representationthat will be stored under s. The caller is
+ responsible for providing sufficient storage in s.
+
+ Conversion is done in the format “[-]d.ddd”. The minimum field width
+ of the output string (including the ‘.’ and the possible sign for
+ negative values) is given in width, and prec determines the number of
+ digits after the decimal sign. width is signed value, negative for
+ left adjustment.
+
+ The dtostrf() function returns the pointer to the converted string s.
+ */
+
+ char *dtostrf(double __val, signed char __width, unsigned char __prec, char *__s) {
+       sprintf(__s, "%*.*f", __width, __prec, __val);
+       return __s;
+ }

cpp/arduino/stdlib.h

@@ -12,3 +12,6 @@
  * https://stackoverflow.com/questions/190229/where-is-the-itoa-function-in-linux
  */
 char *itoa(int val, char *s, int radix);
+
+ // another function provided by Arduino
+ char * 	dtostrf(double __val, signed char __width, unsigned char __prec, char *__s);