From 06871729dd93553cdc826662b33dc2303ccbaadc Mon Sep 17 00:00:00 2001
From: Gregory Nutt <gnutt@nuttx.org>
Date: Wed, 17 Apr 2013 07:40:48 -0600
Subject: [PATCH] Support for printing NaN and infinity from Andrew Tridgell

---
 libc/stdio/lib_libdtoa.c | 43 +++++++++++++++++++++++++++++++++++++---
 1 file changed, 40 insertions(+), 3 deletions(-)

diff --git a/libc/stdio/lib_libdtoa.c b/libc/stdio/lib_libdtoa.c
index a9a86817cf..7f39701271 100644
--- a/libc/stdio/lib_libdtoa.c
+++ b/libc/stdio/lib_libdtoa.c
@@ -44,6 +44,8 @@
  * Included Files
  ****************************************************************************/
 
+#include <math.h>
+
 #include "lib_internal.h"
 
 /****************************************************************************
@@ -84,6 +86,10 @@
  * Private Variables
  ****************************************************************************/
 
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
 /****************************************************************************
  * Name: zeroes
  *
@@ -103,9 +109,21 @@ static void zeroes(FAR struct lib_outstream_s *obj, int nzeroes)
 }
 
 /****************************************************************************
- * Private Functions
+ * Name: lib_dtoa_string
+ *
+ * Description:
+ *   Print the specified string
+ *
  ****************************************************************************/
 
+static void lib_dtoa_string(FAR struct lib_outstream_s *obj, const char *str)
+{
+  while (*str)
+    {
+      obj->put(obj, *str++);
+    }
+}
+
 /****************************************************************************
  * Name: lib_dtoa
  *
@@ -140,6 +158,25 @@ static void lib_dtoa(FAR struct lib_outstream_s *obj, int fmt, int prec,
   int  dsgn;            /* Unused sign indicator */
   int  i;
 
+  /* Special handling for NaN and Infinity */
+
+  if (isnan(value)) 
+    {
+      lib_dtoa_string(obj, "NaN");
+      return;
+    }
+
+  if (isinf(value))
+    {
+      if (value < 0.0d)
+        {
+          obj->put(obj, '-');
+        }
+
+      lib_dtoa_string(obj, "Infinity");
+      return;
+    }
+
   /* Non-zero... positive or negative */
 
   if (value < 0)
@@ -173,7 +210,7 @@ static void lib_dtoa(FAR struct lib_outstream_s *obj, int fmt, int prec,
 
       obj->put(obj, '0');
 
-      /* A decimal point is printed only in the alternate form or if a 
+      /* A decimal point is printed only in the alternate form or if a
        * particular precision is requested.
        */
 
@@ -227,7 +264,7 @@ static void lib_dtoa(FAR struct lib_outstream_s *obj, int fmt, int prec,
           for (i = expt; i > 0; i--)
             {
               if (*digits != '\0')
-                { 
+                {
                   obj->put(obj, *digits);
                   digits++;
                 }