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
{
	enum General_error { ERR_FD_INVALID, NUM_GENERAL_ERRORS };


	/***********
	 ** Write **
	 ***********/

	/*
	 * Exception, thrown when, for example, 'alloc_packet()' or
	 * 'submit_packet()' failed in the VFS plugin. The caller can try again
	 * after a previous VFS request is completed.
	 */
	struct Insufficient_buffer { };

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

	virtual Write_result write(Vfs_handle *vfs_handle,
	                           char const *buf, file_size buf_size,
	                           file_size &out_count) = 0;


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

	enum Read_result { READ_ERR_AGAIN,     READ_ERR_WOULD_BLOCK,
	                   READ_ERR_INVALID,   READ_ERR_IO,
	                   READ_ERR_INTERRUPT, 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 *, file_size)
	{
		return true;
	}

	virtual Read_result complete_read(Vfs_handle *, char * /* dst */,
	                                  file_size   /* in count */,
	                                  file_size & /* out count */) = 0;

	/**
	 * Return true if the handle has readable data
	 */
	virtual bool read_ready(Vfs_handle *) = 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 = NUM_GENERAL_ERRORS,
	                        FTRUNCATE_ERR_INTERRUPT, FTRUNCATE_ERR_NO_SPACE,
	                        FTRUNCATE_OK };

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


	/***********
	 ** Ioctl **
	 ***********/

	enum Ioctl_result { IOCTL_ERR_INVALID, IOCTL_ERR_NOTTY, IOCTL_OK };

	enum Ioctl_opcode { IOCTL_OP_UNDEFINED, IOCTL_OP_TIOCGWINSZ,
	                    IOCTL_OP_TIOCSETAF, IOCTL_OP_TIOCSETAW,
	                    IOCTL_OP_FIONBIO,   IOCTL_OP_DIOCGMEDIASIZE };

	enum Ioctl_value { IOCTL_VAL_NULL, IOCTL_VAL_ECHO, IOCTL_VAL_ECHONL };

	typedef unsigned long Ioctl_arg;

	struct Ioctl_out
	{
		union
		{
			/* if request was 'IOCTL_OP_TIOCGWINSZ' */
			struct {
				int rows;
				int columns;
			} tiocgwinsz;

			/* if request was 'IOCTL_OP_DIOCGMEDIASIZE' */
			struct {
				/* disk size rounded up to sector size in bytes*/
				file_size size;

			} diocgmediasize;
		};
	};

	virtual Ioctl_result ioctl(Vfs_handle *, Ioctl_opcode, Ioctl_arg, Ioctl_out &)
	{
		/*
		 * This method is only needed in file systems which actually implement a
		 * device and is therefore false by default.
		 */
		return IOCTL_ERR_INVALID;
	}


	/**
	 * Return true if an unblocking condition of the file is satisfied
	 *
	 * \param rd  if true, check for data available for reading
	 * \param wr  if true, check for readiness for writing
	 * \param ex  if true, check for exceptions
	 */
	virtual bool check_unblock(Vfs_handle *, bool /* rd */, bool /* wr */, bool /* ex */)
	{ return true; }

	virtual void register_read_ready_sigh(Vfs_handle *, Signal_context_capability)
	{ }

	/**********
	 ** 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_ */