Windows Driver Development | windows driver samples | cdfs file system driver | C++

Sample Code

windows driver samples/ cdfs file system driver/ C++/ filobsup.c/

/*++
 
Copyright (c) 1989-2000 Microsoft Corporation
 
Module Name:
 
    FilObSup.c
 
Abstract:
 
    This module implements the Cdfs File object support routines.
 
 
--*/
 
#include "CdProcs.h"
 
//
//  The Bug check file id for this module
//
 
#define BugCheckFileId                   (CDFS_BUG_CHECK_FILOBSUP)
 
//
//  Local constants.
//
 
#define TYPE_OF_OPEN_MASK               (0x00000007)
 
#ifdef ALLOC_PRAGMA
#pragma alloc_text(PAGE, CdDecodeFileObject)
#pragma alloc_text(PAGE, CdFastDecodeFileObject)
#pragma alloc_text(PAGE, CdSetFileObject)
#endif
 
 
_When_(TypeOfOpen == UnopenedFileObject, _At_(Fcb, _In_opt_))
_When_(TypeOfOpen != UnopenedFileObject, _At_(Fcb, _In_))
VOID
CdSetFileObject (
    _In_ PIRP_CONTEXT IrpContext,
    _Inout_ PFILE_OBJECT FileObject,
    _In_ TYPE_OF_OPEN TypeOfOpen,
    PFCB Fcb,
    _In_opt_ PCCB Ccb
    )
 
/*++
 
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();
 
    UNREFERENCED_PARAMETER( IrpContext );
 
    //
    //  We only have values 0 to 7 available so make sure we didn't
    //  inadvertantly add a new type.
    //
 
    NT_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.
    //
 
    NT_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;
 
#pragma warning( suppress: 4213 )
    SetFlag( ((ULONG_PTR) FileObject->FsContext2), TypeOfOpen );
 
    //
    //  Set the Vpb field in the file object.
    //
 
    FileObject->Vpb = Fcb->Vcb->Vpb;
 
    return;
}
 
 
_When_(return == UnopenedFileObject, _At_(*Fcb, _Post_null_))
_When_(return != UnopenedFileObject, _At_(Fcb, _Outptr_))
_When_(return == UnopenedFileObject, _At_(*Ccb, _Post_null_))
_When_(return != UnopenedFileObject, _At_(Ccb, _Outptr_))
TYPE_OF_OPEN
CdDecodeFileObject (
    _In_ PIRP_CONTEXT IrpContext,
    _In_ PFILE_OBJECT FileObject,
    PFCB *Fcb,
    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();
 
    UNREFERENCED_PARAMETER( IrpContext );
 
    //
    //  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;
         
#pragma warning( suppress: 4213 )
        ClearFlag( (ULONG_PTR) *Ccb, TYPE_OF_OPEN_MASK );
    }
 
    //
    //  Now return the type of open.
    //
 
    return TypeOfOpen;
}
 

TYPE_OF_OPEN
CdFastDecodeFileObject (
    _In_ PFILE_OBJECT FileObject,
    _Out_ PFCB *Fcb
    )
 
/*++
 
Routine Description:
 
    This procedure takes a pointer to a file object, that has already been
    opened by Cdfs 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 );
}
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