Three methods to get the file size of a path in Windows C++.

get_file_size.cpp

/// <summary>Values that represent the methods available to get the file size.</summary>
/// <remarks>Claude "CodeAngry" Adrian, 20 May 2012.</remarks>
typedef enum class file_size_methods {
	create_file = 1, // CreateFile, GetFileSizeEx, CloseHandle (II speed, I reliable)
	get_attributes = 2, // GetFileAttributesEx (I speed)
	find_file = 3, // FindFirstFile, FindClose (III speed)
} file_size_method;

/// <summary>Gets athe file size using the chosen method.</summary>
/// <remarks>Claude "CodeAngry" Adrian, 20 May 2012.</remarks>
/// <param name="path">Full pathname of the file.</param>
/// <param name="method">(optional) The method.</param>
/// <returns>The file size.</returns>
inline ULONGLONG get_file_size(const TCHAR* path, file_size_method method){
	if(!path || !*path){
		SetLastError(E_INVALIDARG);
		return 0;
	}

	LARGE_INTEGER file_size = { 0 };

	if(method == file_size_methods::create_file){
		HANDLE file = CreateFile(path,
			GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE, nullptr,
			OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
		if(file && file != INVALID_HANDLE_VALUE){
			if(!GetFileSizeEx(file, &file_size)){
				file_size.QuadPart = 0; // clean-up on fail
			}
			CloseHandle(file);
		}
	}else if(method == file_size_methods::find_file){
		WIN32_FIND_DATA find_data;
		HANDLE find_file = FindFirstFile(path, &find_data);
		if(find_file && find_file != INVALID_HANDLE_VALUE){
			file_size.LowPart = find_data.nFileSizeLow;
			file_size.HighPart = find_data.nFileSizeHigh;
			FindClose(find_file);
		}
	}else if(method == file_size_methods::get_attributes){
		WIN32_FILE_ATTRIBUTE_DATA file_attr_data;
		if(GetFileAttributesEx(path, GetFileExInfoStandard, &file_attr_data)){
			file_size.LowPart = file_attr_data.nFileSizeLow;
			file_size.HighPart = file_attr_data.nFileSizeHigh;
		}
	}

	return file_size.QuadPart;
}

/// <summary>Gets athe file size using the chosen method.</summary>
/// <remarks>Claude "CodeAngry" Adrian, 20 May 2012.</remarks>
/// <param name="path">Full pathname of the file.</param>
/// <param name="method">(optional) the method.</param>
/// <returns>The filesize.</returns>
inline ULONGLONG get_file_size(const std::basic_string<TCHAR>& path, file_size_method method){
	if(path.empty() || !path.front()){
		SetLastError(E_INVALIDARG);
		return 0;
	}
	return get_file_size(path.c_str(), method); // forward the call to the const TCHAR*
}