Add file info querying function to [coral::file_system]

source/coral/files.cpp

@@ -61,11 +61,40 @@ export namespace coral {
 	 * Platform-generalized file system interface.
 	 */
 	struct file_system {
+		/**
+		 * Errors that may occur during a file system query operation.
+		 *
+		 * [query_error::unsupported] occurs when either part or all of the query operation is not supported on the
+		 * given file system.
+		 *
+		 * [query_error::io_unavailable] is a general catch-all to report that an implementation-specific I/O error has
+		 * occured and the operation could not proceed as a result.
+		 */
+		enum class query_error {
+			unsupported,
+			io_unavailable,
+		};
+
+		/**
+		 * Various meta-information about a file in a file system.
+		 */
+		struct file_info {
+			u64 size;
+		};
+
 		virtual ~file_system() {};
 
 		/**
-		 * Attempts to read the file in `path`, calling `then` if it was successfully opened for reading and passing the
+		 * Attempts to query a file in the file system located at `path`, returning a [file_info] describing it or a
-		 * [file_reader] context along.
+		 * [query_error] if the operation failed.
+		 */
+		virtual expected<file_info, query_error> query_file(slice<char const> const & path) {
+			return query_error::unsupported;
+		}
+
+		/**
+		 * Attempts to read a file in the file system located at `path`, calling `then` if it was successfully opened
+		 * for reading and passing the [file_reader] context along.
 		 *
 		 * See [file_reader] for more information on how to read from the file.
 		 */