genode/repos/os/include/vfs/file_io_service.h

/*
 * \brief  Interface for operations provided by file I/O service
 * \author Norman Feske
 * \author Emery Hemingway
 * \author Christian Helmuth
 * \date   2011-02-17
 */

/*
 * Copyright (C) 2011-2017 Genode Labs GmbH
 *
 * This file is part of the Genode OS framework, which is distributed
 * under the terms of the GNU Affero General Public License version 3.
 */

#ifndef _INCLUDE__VFS__FILE_IO_SERVICE_H_
#define _INCLUDE__VFS__FILE_IO_SERVICE_H_

#include <vfs/vfs_handle.h>

namespace Vfs { struct File_io_service; }


struct Vfs::File_io_service : Interface
{
	/***********
	 ** Write **
	 ***********/

	enum Write_result { WRITE_ERR_WOULD_BLOCK, WRITE_ERR_INVALID,
	                    WRITE_ERR_IO,          WRITE_OK };

	virtual Write_result write(Vfs_handle *vfs_handle, Const_byte_range_ptr const &,
	                           size_t &out_count) = 0;


	/**********
	 ** Read **
	 **********/

	enum Read_result { READ_ERR_WOULD_BLOCK, READ_ERR_INVALID,
	                   READ_ERR_IO,          READ_QUEUED,
	                   READ_OK };

	/**
	 * Queue read operation
	 *
	 * \return false if queue is full
	 *
	 * If the queue is full, the caller can try again after a previous VFS
	 * request is completed.
	 */
	virtual bool queue_read(Vfs_handle *, size_t)
	{
		return true;
	}

	virtual Read_result complete_read(Vfs_handle *, Byte_range_ptr const &dst,
	                                  size_t &out_count) = 0;

	/**
	 * Return true if the handle has readable data
	 */
	virtual bool read_ready(Vfs_handle const &) const = 0;

	/**
	 * Return true if the handle might accept a write operation
	 */
	virtual bool write_ready(Vfs_handle const &) const = 0;

	/**
	 * Explicitly indicate interest in read-ready for a handle
	 *
	 * For example, the file-system-session plugin can then send READ_READY
	 * packets to the server.
	 *
	 * \return false if notification setup failed
	 */
	virtual bool notify_read_ready(Vfs_handle *) { return true; }


	/***************
	 ** Ftruncate **
	 ***************/

	enum Ftruncate_result { FTRUNCATE_ERR_NO_PERM,  FTRUNCATE_ERR_INTERRUPT,
	                        FTRUNCATE_ERR_NO_SPACE, FTRUNCATE_OK };

	virtual Ftruncate_result ftruncate(Vfs_handle *vfs_handle, file_size len) = 0;


	/**********
	 ** Sync **
	 **********/

	enum Sync_result { SYNC_QUEUED, SYNC_ERR_INVALID, SYNC_OK };

	/**
	 * Queue sync operation
	 *
	 * \return false if queue is full
	 *
	 * If the queue is full, the caller can try again after a previous VFS
	 * request is completed.
	 */
	virtual bool queue_sync(Vfs_handle *) { return true; }

	virtual Sync_result complete_sync(Vfs_handle *) { return SYNC_OK; }

	/***********************
	 ** Modification time **
	 ***********************/

	/**
	 * Update the modification time of a file
	 *
	 * \return true if update attempt was successful
	 */
	virtual bool update_modification_timestamp(Vfs_handle *, Vfs::Timestamp)
	{
		return true;
	}
};

#endif /* _INCLUDE__VFS__FILE_IO_SERVICE_H_ */