STYLE: Reduce buf size, remove builder.Reset() calls from NumberToString

Various style improvements of the implementation of the
`NumberToString<TValue>` specializations for floating point numbers:

 - Did clean up the #include's.
 - Removed unnecessary builder.Reset() calls. (`StringBuilder::Reset()` only just sets the internal position to zero, but that is already taken care of by the constructor of `StringBuilder`.)
 - Added local helper function, `FloatingPointNumberToString(val)`, sharing code between `float` and `double` specialization.
 - Reduced size of local buffer (`buf`) from 256 to 32 chars.

Author: N-Dekker

Modules/Core/Common/src/itkNumberToString.cxx

@@ -16,45 +16,66 @@
  *
  *=========================================================================*/
 #include "itkNumberToString.h"
-#include "itkNumericTraits.h"
-#include "double-conversion/double-conversion.h"
+#include "double-conversion/double-to-string.h"
 
 #include <sstream>
 
-namespace itk
+namespace
 {
 
-template <>
+bool
+ConvertToShortest(const double_conversion::DoubleToStringConverter & converter,
+                  const double                                       val,
+                  double_conversion::StringBuilder &                 builder)
+{
+  return converter.ToShortest(val, &builder);
+}
+
+bool
+ConvertToShortest(const double_conversion::DoubleToStringConverter & converter,
+                  const float                                        val,
+                  double_conversion::StringBuilder &                 builder)
+{
+  // Call the converter member function that is specific for single-precision `float`.
+  return converter.ToShortestSingle(val, &builder);
+}
+
+template <typename TValue>
 std::string
-NumberToString<double>::operator()(double val) const
+FloatingPointNumberToString(const TValue val)
 {
-  char                                               buf[256];
-  const double_conversion::DoubleToStringConverter & converter =
-    double_conversion::DoubleToStringConverter::EcmaScriptConverter();
+  // Declare a buffer, large enough for strings like:
+  // "-100000000000000000000" (-1e20, either float or double, 23 chars)
+  // "-1.7976931348623157e+308" (-DBL_MAX, 25 chars)
+  // "-0.0000033333333333333333" (-3e-005/9.0, 26 chars)
+  char buf[32];
+
   double_conversion::StringBuilder builder(buf, sizeof(buf));
-  builder.Reset();
-  if (!converter.ToShortest(val, &builder))
+
+  if (!ConvertToShortest(double_conversion::DoubleToStringConverter::EcmaScriptConverter(), val, builder))
   {
     itkGenericExceptionMacro(<< "Conversion failed for " << val);
   }
   return std::string(builder.Finalize());
 }
 
+} // namespace
+
+namespace itk
+{
+
 template <>
 std::string
-NumberToString<float>::operator()(float val) const
+NumberToString<double>::operator()(double val) const
 {
-  char                                               buf[256];
-  const double_conversion::DoubleToStringConverter & converter =
-    double_conversion::DoubleToStringConverter::EcmaScriptConverter();
+  return FloatingPointNumberToString(val);
+}
 
-  double_conversion::StringBuilder builder(buf, sizeof(buf));
-  builder.Reset();
-  if (!converter.ToShortestSingle(val, &builder))
-  {
-    itkGenericExceptionMacro(<< "Conversion failed for " << val);
-  }
-  return std::string(builder.Finalize());
+template <>
+std::string
+NumberToString<float>::operator()(float val) const
+{
+  return FloatingPointNumberToString(val);
 }
 
 } // namespace itk