filobsup.c

windows 2000中的UDF文件系统的驱动程序.只有读的功能,不支持未关闭的盘片.只支持UDF2.0以下版本,不支持VAT格式的UDF.

/*++

Copyright (c) 1989  Microsoft Corporation

Module Name:

    FilObSup.c

Abstract:

    This module implements the Udfs File object support routines.

Author:

    Dan Lovinger    [DanLo]     23-Sep-1996

Revision History:

--*/

#include "UdfProcs.h"

//
//  The Bug check file id for this module
//

#define BugCheckFileId                   (UDFS_BUG_CHECK_FILOBSUP)

//
//  The local debug trace level
//

#define Dbg                              (UDFS_DEBUG_LEVEL_FILOBSUP)

//
//  Local constants.
//

#define TYPE_OF_OPEN_MASK               (0x00000007)

#ifdef ALLOC_PRAGMA
#pragma alloc_text(PAGE, UdfDecodeFileObject)
#pragma alloc_text(PAGE, UdfFastDecodeFileObject)
#pragma alloc_text(PAGE, UdfSetFileObject)
#endif


VOID
UdfSetFileObject (
    IN PIRP_CONTEXT IrpContext,
    IN PFILE_OBJECT FileObject,
    IN TYPE_OF_OPEN TypeOfOpen,
    IN PFCB Fcb OPTIONAL,
    IN PCCB Ccb OPTIONAL
    )

/*++

Routine Description:

    This routine will initialize the FileObject context fields based on the
    input type and data structures.

Arguments:

    FileObject - Supplies the file object pointer being initialized.

    TypeOfOpen - Sets the type of open.

    Fcb - Fcb for this file object.  Ignored for UnopenedFileObject.

    Ccb - Ccb for the handle corresponding to this file object.  Will not
        be present for stream file objects.

Return Value:

    None.

--*/

{
    PAGED_CODE();

    //
    //  We only have values 0 to 7 available so make sure we didn't
    //  inadvertantly add a new type.
    //

    ASSERTMSG( "FileObject types exceed available bits\n", BeyondValidType <= 8 );

    //
    //  Setting a file object to type UnopenedFileObject means just
    //  clearing all of the context fields.  All the other input
    //

    if (TypeOfOpen == UnopenedFileObject) {

        FileObject->FsContext =
        FileObject->FsContext2 = NULL;

        return;
    }

    //
    //  Check that the 3 low-order bits of the Ccb are clear.
    //

    ASSERTMSG( "Ccb is not quad-aligned\n", !FlagOn( ((ULONG_PTR) Ccb), TYPE_OF_OPEN_MASK ));

    //
    //  We will or the type of open into the low order bits of FsContext2
    //  along with the Ccb value.
    //  The Fcb is stored into the FsContext field.
    //

    FileObject->FsContext = Fcb;
    FileObject->FsContext2 = Ccb;

    SetFlag( ((ULONG_PTR) FileObject->FsContext2), TypeOfOpen );

    //
    //  Set the Vpb field in the file object.
    //

    FileObject->Vpb = Fcb->Vcb->Vpb;

    return;
}



TYPE_OF_OPEN
UdfDecodeFileObject (
    IN PFILE_OBJECT FileObject,
    OUT PFCB *Fcb,
    OUT PCCB *Ccb
    )

/*++

Routine Description:

    This routine takes a file object and extracts the Fcb and Ccb (possibly NULL)
    and returns the type of open.

Arguments:

    FileObject - Supplies the file object pointer being initialized.

    Fcb - Address to store the Fcb contained in the file object.

    Ccb - Address to store the Ccb contained in the file object.

Return Value:

    TYPE_OF_OPEN - Indicates the type of file object.

--*/

{
    TYPE_OF_OPEN TypeOfOpen;

    PAGED_CODE();

    //
    //  If this is an unopened file object then return NULL for the
    //  Fcb/Ccb.  Don't trust any other values in the file object.
    //

    TypeOfOpen = (TYPE_OF_OPEN) FlagOn( (ULONG_PTR) FileObject->FsContext2,
                                        TYPE_OF_OPEN_MASK );

    if (TypeOfOpen == UnopenedFileObject) {

        *Fcb = NULL;
        *Ccb = NULL;

    } else {

        //
        //  The Fcb is pointed to by the FsContext field.  The Ccb is in
        //  FsContext2 (after clearing the low three bits).  The low three
        //  bits are the file object type.
        //

        *Fcb = FileObject->FsContext;
        *Ccb = FileObject->FsContext2;

        ClearFlag( (ULONG_PTR) *Ccb, TYPE_OF_OPEN_MASK );
    }

    //
    //  Now return the type of open.
    //

    return TypeOfOpen;
}


TYPE_OF_OPEN
UdfFastDecodeFileObject (
    IN PFILE_OBJECT FileObject,
    OUT PFCB *Fcb
    )

/*++

Routine Description:

    This procedure takes a pointer to a file object, that has already been
    opened by Udfs and does a quick decode operation.  It will only return
    a non null value if the file object is a user file open

Arguments:

    FileObject - Supplies the file object pointer being interrogated

    Fcb - Address to store Fcb if this is a user file object.  NULL
        otherwise.

Return Value:

    TYPE_OF_OPEN - type of open of this file object.

--*/

{
    PAGED_CODE();

    ASSERT_FILE_OBJECT( FileObject );

    //
    //  The Fcb is in the FsContext field.  The type of open is in the low
    //  bits of the Ccb.
    //

    *Fcb = FileObject->FsContext;

    return (TYPE_OF_OPEN) FlagOn( (ULONG_PTR) FileObject->FsContext2, TYPE_OF_OPEN_MASK );
}