Core/File: Add OpenMode::Defer

include/Nazara/Core/Enums.hpp

@@ -97,6 +97,7 @@ namespace Nz
 		NotOpen,    // Use the current mod of opening
 
 		Append,     // Disable writing on existing parts and put the cursor at the end
+		Defer,      // Defer file opening until a read/write operation is performed on it
 		Lock,       // Disable modifying the file before it is open
 		MustExist,  // Fail if the file doesn't exists, even if opened in write mode
 		ReadOnly,   // Open in read only

include/Nazara/Core/File.hpp

@@ -60,6 +60,7 @@ namespace Nz
 			static bool WriteWhole(const std::filesystem::path& path, const void* data, std::size_t size);
 
 		private:
+			inline bool CheckFileOpening();
 			void FlushStream() override;
 			std::size_t ReadBlock(void* buffer, std::size_t size) override;
 			bool SeekStreamCursor(UInt64 offset) override;

include/Nazara/Core/File.inl

@@ -33,6 +33,20 @@ namespace Nz
 	{
 		return Nz::ComputeHash(hash, File(filePath));
 	}
+
+	inline bool File::CheckFileOpening()
+	{
+		if (m_openMode.Test(OpenMode::Defer))
+		{
+			if (!Open(m_filePath, m_openMode & ~OpenMode::Defer))
+			{
+				NazaraError("failed to open file");
+				return false;
+			}
+		}
+
+		return true;
+	}
 }
 
 #include <Nazara/Core/DebugOff.hpp>