fixup: libc: implement read and write by async_read and async_write

Issue genodelabs#5302

repos/libports/src/lib/libc/vfs_plugin.cc

@@ -818,7 +818,7 @@ int Libc::Vfs_plugin::stat(char const *path, struct stat *buf)
 		return Errno(EFAULT);
 	}
 
-	typedef Vfs::Directory_service::Stat_result Result;
+	using Result = Vfs::Directory_service::Stat_result;
 
 	Vfs::Directory_service::Stat stat;
 
@@ -892,24 +892,24 @@ bool Libc::Vfs_plugin::async_read(File_descriptor  *fd,
 	}
 
 	switch (out_result) {
-		case Result::READ_ERR_WOULD_BLOCK:
-			result_errno = EWOULDBLOCK;
-			result = -1;
-			break;
-		case Result::READ_ERR_INVALID:
-			result_errno = EINVAL;
-			result = -1;
-			break;
-		case Result::READ_ERR_IO:
-			result_errno = EIO;
-			result = -1;
-		case Result::READ_OK:
-			result_errno = 0;
-			result = out_count;
-			break;
-		case Result::READ_QUEUED:
-			/* handled above, so never reached */
-			break;
+	case Result::READ_ERR_WOULD_BLOCK:
+		result_errno = EWOULDBLOCK;
+		result = -1;
+		break;
+	case Result::READ_ERR_INVALID:
+		result_errno = EINVAL;
+		result = -1;
+		break;
+	case Result::READ_ERR_IO:
+		result_errno = EIO;
+		result = -1;
+	case Result::READ_OK:
+		result_errno = 0;
+		result = out_count;
+		break;
+	case Result::READ_QUEUED:
+		/* handled above, so never reached */
+		break;
 	}
 
 	return true;
@@ -936,7 +936,6 @@ ssize_t Libc::Vfs_plugin::read(File_descriptor *fd, void *buf,
 
 	Plugin::resume_all();
 
-	/* XXX double getting the handle is a bit unfortunate */
 	Vfs::Vfs_handle *handle = vfs_handle(fd);
 	handle->advance_seek(out_count);
 
@@ -972,7 +971,6 @@ bool Libc::Vfs_plugin::async_write(File_descriptor   *fd,
 
 	if (fd->flags & O_NONBLOCK) {
 		out_result = handle->fs().write(handle, src, write_state.bytes_written);
-		// XXX are we supposed to advance seek even with a fixed-offset async write?
 		handle->advance_seek(write_state.bytes_written);
 	} else {
 		auto _fd_refers_to_continuous_file = [&]