perf(ini): Improve INI parsing performance by using std::from_chars (TheSuperHackers#2532)

Author: Caball009

Core/GameEngine/Source/Common/INI/INI.cpp

@@ -59,6 +59,17 @@
 #include "GameLogic/ScriptEngine.h"
 #include "GameLogic/Weapon.h"
 
+#if __cplusplus >= 201611L
+#define USE_STD_FROM_CHARS_PARSING 1
+#else
+#define USE_STD_FROM_CHARS_PARSING 0
+#endif
+
+#if USE_STD_FROM_CHARS_PARSING
+#include <charconv>
+#include <string_view>
+#include <type_traits>
+#endif
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 // PRIVATE DATA ///////////////////////////////////////////////////////////////////////////////////
@@ -1624,40 +1635,86 @@ void INI::initFromINIMulti( void *what, const MultiIniFieldParse& parseTableList
 	return TheScienceStore->friend_lookupScience( token );
 }
 
+#if USE_STD_FROM_CHARS_PARSING
+
+template <typename Type>
+Type scanType(std::string_view token)
+{
+	// TheSuperHackers @info std::from_chars cannot parse "-1" as uint32 so the result needs to be int64 for integers.
+	std::conditional_t<std::is_integral_v<Type>, Int64, Real> result{};
+	const auto [ptr, ec] = std::from_chars(token.data(), token.data() + token.size(), result);
+
+	if (ec != std::errc{})
+	{
+		throw INI_INVALID_DATA;
+	}
+
+	return static_cast<Type>(result);
+}
+
+#endif
+
 //-------------------------------------------------------------------------------------------------
 /*static*/ Int INI::scanInt(const char* token)
 {
+#if USE_STD_FROM_CHARS_PARSING == 1
+	return scanType<Int>(token);
+#else
 	Int value;
 	if (sscanf( token, "%d", &value ) != 1)
 		throw INI_INVALID_DATA;
+
+#if USE_STD_FROM_CHARS_PARSING == -1
+	if (value != scanType<Int>(token))
+		throw INI_INVALID_DATA;
+#endif
+
 	return value;
+#endif
 }
 
 //-------------------------------------------------------------------------------------------------
 /*static*/ UnsignedInt INI::scanUnsignedInt(const char* token)
 {
+#if USE_STD_FROM_CHARS_PARSING == 1
+	return scanType<UnsignedInt>(token);
+#else
 	UnsignedInt value;
 	if (sscanf( token, "%u", &value ) != 1)	// unsigned int is %u, not %d
 		throw INI_INVALID_DATA;
+
+#if USE_STD_FROM_CHARS_PARSING == -1
+	if (value != scanType<UnsignedInt>(token))
+		throw INI_INVALID_DATA;
+#endif
+
 	return value;
+#endif
 }
 
 //-------------------------------------------------------------------------------------------------
 /*static*/ Real INI::scanReal(const char* token)
 {
+#if USE_STD_FROM_CHARS_PARSING == 1
+	return scanType<Real>(token);
+#else
 	Real value;
 	if (sscanf( token, "%f", &value ) != 1)
 		throw INI_INVALID_DATA;
+
+#if USE_STD_FROM_CHARS_PARSING == -1
+	if (value != scanType<Real>(token))
+		throw INI_INVALID_DATA;
+#endif
+
 	return value;
+#endif
 }
 
 //-------------------------------------------------------------------------------------------------
 /*static*/ Real INI::scanPercentToReal(const char* token)
 {
-	Real value;
-	if (sscanf( token, "%f", &value ) != 1)
-		throw INI_INVALID_DATA;
-	return value / 100.0f;
+	return scanReal(token) / 100.0f;
 }
 
 //-------------------------------------------------------------------------------------------------