Better checks for hex digits in XMLs (#279)

* Better checking

* cleanup logic and explain with a better comment

* cleanups

* last cleanup

* the last one for real

3 files changed, 39 insertions, 11 deletions

diff --git a/ZAPD/ZFile.cpp b/ZAPD/ZFile.cpp
index 0977650..ad56f98 100644
--- a/ZAPD/ZFile.cpp
+++ b/ZAPD/ZFile.cpp
@@ -213,14 +213,12 @@ void ZFile::ParseXML(tinyxml2::XMLElement* reader, const std::string& filename)
 		// Check for repeated attributes.
 		if (offsetXml != nullptr)
 		{
-			std::string offsetStr = StringHelper::Split(offsetXml, "0x")[1];
-			if (!StringHelper::HasOnlyHexDigits(offsetStr))
+			if (!StringHelper::IsValidOffset(std::string_view(offsetXml)))
 			{
 				HANDLE_ERROR(WarningType::InvalidXML,
-				             StringHelper::Sprintf("Invalid offset %s entered", offsetStr.c_str()),
-				             "");
+				             StringHelper::Sprintf("Invalid offset %s entered", offsetXml), "");
 			}
-			rawDataIndex = strtol(offsetStr.c_str(), NULL, 16);
+			rawDataIndex = strtol(offsetXml, NULL, 16);
 
 			if (offsetSet.find(offsetXml) != offsetSet.end())
 			{
diff --git a/ZAPD/ZRoom/ZNames.h b/ZAPD/ZRoom/ZNames.h
index 667407c..83c217e 100644
--- a/ZAPD/ZRoom/ZNames.h
+++ b/ZAPD/ZRoom/ZNames.h
@@ -48,11 +48,12 @@ public:
 	static std::string GetEntranceName(uint16_t id)
 	{
 		if (ZNames::GetNumEntrances() == 0 || ZNames::GetNumSpecialEntrances() == 0)
-			return StringHelper::Sprintf("0x%04X", id);	
-			
+			return StringHelper::Sprintf("0x%04X", id);
+
 		if (id < ZNames::GetNumEntrances())
 			return Globals::Instance->cfg.entranceList[id];
-		else if ((id >= 0x7FF9 && id <= 0x7FFF) && !((id - 0x7FF9U) > GetNumSpecialEntrances()))  // Special entrances
+		else if ((id >= 0x7FF9 && id <= 0x7FFF) &&
+		         !((id - 0x7FF9U) > GetNumSpecialEntrances()))  // Special entrances
 			return Globals::Instance->cfg.specialEntranceList[id - 0x7FF9];
 		else
 			return StringHelper::Sprintf("0x%04X", id);
@@ -60,5 +61,8 @@ public:
 
 	static size_t GetNumActors() { return Globals::Instance->cfg.actorList.size(); }
 	static size_t GetNumEntrances() { return Globals::Instance->cfg.entranceList.size(); }
-	static size_t GetNumSpecialEntrances() { return Globals::Instance->cfg.specialEntranceList.size(); }
+	static size_t GetNumSpecialEntrances()
+	{
+		return Globals::Instance->cfg.specialEntranceList.size();
+	}
 };
diff --git a/ZAPDUtils/Utils/StringHelper.h b/ZAPDUtils/Utils/StringHelper.h
index 8560d6b..3d32b03 100644
--- a/ZAPDUtils/Utils/StringHelper.h
+++ b/ZAPDUtils/Utils/StringHelper.h
@@ -106,9 +106,35 @@ public:
 		return std::all_of(str.begin(), str.end(), ::isdigit);
 	}
 
-	static bool HasOnlyHexDigits(const std::string& str)
+	static bool IsValidHex(std::string_view str)
 	{
-		return std::all_of(str.begin(), str.end(), ::isxdigit);
+		if (str.length() < 3)
+		{
+			return false;
+		}
+
+		if (str[0] == '0' && (str[1] == 'x' || str[1] == 'X'))
+		{
+			return std::all_of(str.begin() + 2, str.end(), ::isxdigit);
+		}
+
+		return false;
+	}
+
+	static bool IsValidOffset(std::string_view str)
+	{
+		if (str.length() == 1)
+		{
+			// 0 is a valid offset
+			return isdigit(str[0]);
+		}
+
+		return IsValidHex(str);
+	}
+
+	static bool IsValidHex(const std::string& str)
+	{
+		return IsValidHex(std::string_view(str.c_str()));
 	}
 
 	static std::string ToUpper(const std::string& str)