libsmet: a new convert_to_double implementation, based on strtod from the...

libsmet: a new convert_to_double implementation, based on strtod from the cstdlib, cuts conversion time to about a fourth of the stringstream implementation.

meteoio/plugins/libsmet.cc

@@ -82,11 +82,14 @@ bool SMETCommon::initStaticData()
 
 double SMETCommon::convert_to_double(const std::string& in_string)
 {
-	istringstream ss(in_string);
-	double value;
-	if (!(ss >> value)) throw SMETException("Value \"" + in_string + "\" cannot be converted to double", SMET_AT);
+	char* end;
+	double value = strtod(in_string.c_str(),&end);
 
-	return value;
+	if (*end == '\0') {
+		return value;
+	} else {
+		throw SMETException("Value \"" + in_string + "\" cannot be converted to double", SMET_AT);
+	}
 }
 
 int SMETCommon::convert_to_int(const std::string& in_string)

meteoio/plugins/libsmet.h

@@ -21,6 +21,7 @@
 #include <meteoio/IOUtils.h> //HACK: move FileIndexer in a plugins specific file
 
 #include <cmath>
+#include <cstdlib>
 #include <string>
 #include <sstream>
 #include <iostream>