/*
 * Copyright (c) 1998-2005 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */

/*!
 * @header IOFilterScheme
 * @abstract
 * This header contains the IOFilterScheme class definition.
 */

#ifndef _IOFILTERSCHEME_H
#define _IOFILTERSCHEME_H

/*!
 * @defined kIOFilterSchemeClass
 * @abstract
 * The name of the IOFilterScheme class.
 * @discussion
 * kIOFilterSchemeClass is the name of the IOFilterScheme class.
 */

#define kIOFilterSchemeClass "IOFilterScheme"

#ifdef KERNEL
#ifdef __cplusplus

/*
 * Kernel
 */

#include <IOKit/storage/IOMedia.h>
#include <IOKit/storage/IOStorage.h>

/*!
 * @class IOFilterScheme
 * @abstract
 * The common base class for all filter scheme
 * objects.
 * @discussion
 * The IOFilterScheme class is the common base class for all filter scheme
 * objects.  It extends the IOStorage class by implementing the appropriate
 * open and close semantics for filter objects (standard semantics are act
 * as a relay for incoming opens, producing one outgoing open for each
 * incoming open).  It also implements the default read and write semantics,
 * which pass all reads and writes through to the provider media unprocessed.
 * For simple schemes, the default behavior is sufficient.  More complex
 * filter schemes such as RAID will want to do extra processing for reads
 * and writes.
 */

class IOFilterScheme : public IOStorage
{
    OSDeclareDefaultStructors(IOFilterScheme);

protected:

    struct ExpansionData { /* */ };
    ExpansionData * _expansionData;

    /*!
     * @function handleOpen
     * @discussion
     * The handleOpen method grants or denies permission to access this object
     * to an interested client.  The argument is an IOStorageAccess value that
     * specifies the level of access desired -- reader or reader-writer.
     *
     * This method can be invoked to upgrade or downgrade the access level for
     * an existing client as well.  The previous access level will prevail for
     * upgrades that fail, of course.   A downgrade should never fail.  If the
     * new access level should be the same as the old for a given client, this
     * method will do nothing and return success.  In all cases, one, singular
     * close-per-client is expected for all opens-per-client received.
     *
     * This implementation replaces the IOService definition of handleOpen().
     * @param client
     * Client requesting the open.
     * @param options
     * Options for the open.  Set to zero.
     * @param access
     * Access level for the open.  Set to kIOStorageAccessReader or
     * kIOStorageAccessReaderWriter.
     * @result
     * Returns true if the open was successful, false otherwise.
     */

    virtual bool handleOpen(IOService *  client,
                            IOOptionBits options,
                            void *       access);

    /*!
     * @function handleIsOpen
     * @discussion
     * The handleIsOpen method determines whether the specified client, or any
     * client if none is specified, presently has an open on this object.
     *
     * This implementation replaces the IOService definition of handleIsOpen().
     * @param client
     * Client to check the open state of.  Set to zero to check the open state
     * of all clients.
     * @result
     * Returns true if the client was (or clients were) open, false otherwise.
     */

    virtual bool handleIsOpen(const IOService * client) const;

    /*!
     * @function handleClose
     * @discussion
     * The handleClose method closes the client's access to this object.
     *
     * This implementation replaces the IOService definition of handleClose().
     * @param client
     * Client requesting the close.
     * @param options
     * Options for the close.  Set to zero.
     */

    virtual void handleClose(IOService * client, IOOptionBits options);

public:

    using IOStorage::read;
    using IOStorage::write;

    /*!
     * @function read
     * @discussion
     * Read data from the storage object at the specified byte offset into the
     * specified buffer, asynchronously.   When the read completes, the caller
     * will be notified via the specified completion action.
     *
     * The buffer will be retained for the duration of the read.
     *
     * For simple filter schemes, the default behavior is to simply pass the
     * read through to the provider media.  More complex filter schemes such
     * as RAID will need to do extra processing here.
     * @param client
     * Client requesting the read.
     * @param byteStart
     * Starting byte offset for the data transfer.
     * @param buffer
     * Buffer for the data transfer.  The size of the buffer implies the size of
     * the data transfer.
     * @param completion
     * Completion routine to call once the data transfer is complete.
     */

    virtual void read(IOService *          client,
                      UInt64               byteStart,
                      IOMemoryDescriptor * buffer,
                      IOStorageCompletion  completion);

    /*!
     * @function write
     * @discussion
     * Write data into the storage object at the specified byte offset from the
     * specified buffer, asynchronously.   When the write completes, the caller
     * will be notified via the specified completion action.
     *
     * The buffer will be retained for the duration of the write.
     *
     * For simple filter schemes, the default behavior is to simply pass the
     * write through to the provider media. More complex filter schemes such
     * as RAID will need to do extra processing here.
     * @param client
     * Client requesting the write.
     * @param byteStart
     * Starting byte offset for the data transfer.
     * @param buffer
     * Buffer for the data transfer.  The size of the buffer implies the size of
     * the data transfer.
     * @param completion
     * Completion routine to call once the data transfer is complete.
     */

    virtual void write(IOService *          client,
                       UInt64               byteStart,
                       IOMemoryDescriptor * buffer,
                       IOStorageCompletion  completion);

    /*!
     * @function synchronizeCache
     * @discussion
     * Flush the cached data in the storage object, if any, synchronously.
     * @param client
     * Client requesting the cache synchronization.
     * @result
     * Returns the status of the cache synchronization.
     */

    virtual IOReturn synchronizeCache(IOService * client);

    /*
     * Obtain this object's provider.  We override the superclass's method
     * to return a more specific subclass of OSObject -- an IOMedia.  This
     * method serves simply as a convenience to subclass developers.
     */

    virtual IOMedia * getProvider() const;

    OSMetaClassDeclareReservedUnused(IOFilterScheme,  0);
    OSMetaClassDeclareReservedUnused(IOFilterScheme,  1);
    OSMetaClassDeclareReservedUnused(IOFilterScheme,  2);
    OSMetaClassDeclareReservedUnused(IOFilterScheme,  3);
    OSMetaClassDeclareReservedUnused(IOFilterScheme,  4);
    OSMetaClassDeclareReservedUnused(IOFilterScheme,  5);
    OSMetaClassDeclareReservedUnused(IOFilterScheme,  6);
    OSMetaClassDeclareReservedUnused(IOFilterScheme,  7);
    OSMetaClassDeclareReservedUnused(IOFilterScheme,  8);
    OSMetaClassDeclareReservedUnused(IOFilterScheme,  9);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 10);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 11);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 12);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 13);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 14);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 15);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 16);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 17);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 18);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 19);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 20);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 21);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 22);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 23);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 24);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 25);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 26);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 27);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 28);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 29);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 30);
    OSMetaClassDeclareReservedUnused(IOFilterScheme, 31);
};

#endif /* __cplusplus */
#endif /* KERNEL */
#endif /* !_IOFILTERSCHEME_H */
