Avoid overflowing parseFloat()'s internal 'value'

edgar-bonet · edgar-bonet · commit 61975114e344 · 2021-01-25T13:49:52.000+01:00
If more than 309 digits are provided to Stream::parseFloat() (more than
39 on AVR), the internal variable 'value' would overflow to infinity. We
avoid this by not storing the parsed number as an integer-in-a-float.
diff --git a/api/Stream.cpp b/api/Stream.cpp
@@ -179,9 +179,12 @@ float Stream::parseFloat(LookaheadMode lookahead, char ignore)
     else if (c == '.')
       isFraction = true;
     else if(c >= '0' && c <= '9')  {      // is c a digit?
-      value = value * 10 + c - '0';
-      if(isFraction)
-         fraction *= 0.1;
+      if(isFraction) {
+        fraction *= 0.1;
+        value = value + fraction * (c - '0');
+      } else {
+        value = value * 10 + c - '0';
+      }
     }
     read();  // consume the character we got with peek
     c = timedPeek();
@@ -191,9 +194,6 @@ float Stream::parseFloat(LookaheadMode lookahead, char ignore)
   if(isNegative)
     value = -value;
 
-  if(isFraction)
-    value *= fraction;
-
   return value;
 }
 
