Microsoft Programmer's Library 1.3/Microsoft-Programers-Library-v1.3.iso/sampcode/msj/msjv4_6/unix/unixbsc.arc/IOCTL.BAS

BASIC Source File | 1989-06-19 | 7.9 KB | 276 lines

' == [ GENERAL NOTES   ] ================================================
'                                                                       =
'    This Basic program demonstrates how to interface to the     =
'    AsyncTermio device driver.  The interface used finds it's    =
'    origin on AT&T's UNIX systems.                     =
'                                    =
'    The generalized UNIX serial link interface was originally moved    =
'    to MS-DOS for C programmers that desire to port serial comm    =
'    software between MS-DOS and UNIX.                =
'                                    =
'    Most Basic programmers will tell you that Basic's COM port    =
'    management is sufficient for most applications.  We agree.    =
'    However, should you desire to use the generalized UNIX serial    =
'    port interface, Async TermIO will suffice.            =
'                                    =
'    With the OPEN COM statement, Basic provides:            =
'                                    =
'        + Speed, Parity, Stopbits, Character Length Control.    =
'        + Asynchronous buffering of input and output.        =
'        + Call back functions that are invoked on COM activity.    =
'        + Exception handling.                    =
'        + Timing.                        =
'                                    =
'    With the OPEN COM statement, Basic DOES NOT provide:        =
'                                    =
'        + Xon/Xoff Flow Control.                =
'        + The interface is not generalized across environments.    =
'            and is not portable to other operating systems.    =
'        + Not as diverse as the generalized UNIX interface.    =
'                                    =
'    The trade-offs of writing serial communications software are     =
'    discussed at length in the Async TermIO documentation.        =
'                                    =
'    Please review the publication (See Async TermIO    User's Manual)    =
'        "Portable Serial Communications Between MS-DOS & UNIX"    =
'                                    =
' =======================================================================
'                                    =
'    Copyright (c) 1988    Boulder Software Group            =
'                P.O. BOX 14200                =
'                Boulder, CO   80308-4200        =
'                                    =
'                [phone] (Voice)            =
'                [phone] (FAX)            =
'                                                                       =
' =======================================================================
'

'
' == [ INCLUDE FILES   ] ================================================
'                                                                       =
'    The include file TERMIO.H contains several constants that are    =
'    use to set flags, compare values, function declarations, etc.    =
'                                                                       =
' =======================================================================
'

    ' $INCLUDE: 'TERMIO.H'


'
' == [ TTYDEVICEIOCTL  ] ================================================
'                                                                       =
'    TtyDeviceIoctl is responsible for taking the INTEGER        =
'    FileHandle, the Command (what to do), and a Basic record    =
'    of type TtyParam.  Depending on the Command (see printed doc)    =
'    the device attributes set in the TtyParam record will be issued    =
'    to the device associated with the FileHandle.            =
'                                    =
'    It is somewhat more awkward to implement this function in    =
'    Basic than in C, however, it is possible.            =
'                                    =
' =======================================================================
'                                    =
'    NOTE:                                =
'                                    =
'    Normally the function TtyDeviceIoctl() would be named        =
'    Ioctl() (as it is in C), however, Basic reserves IOCTL        =
'    as a keyword and thus we can't use it as an identifier.        =
'                                    =
'    The name TtyDeviceIoctl() was arbitrarily chosen, the        =
'    source code is provided below, so feel free to change it    =
'    to what ever you want.  Note that TtyDeviceIoctl() will be    =
'    described as the function ioctl() in all accompanying         =
'    documentation.                            =
'                                                                       =
' =======================================================================
'
'
'
FUNCTION TtyDeviceIoctl( FileHandle AS INTEGER, Command AS INTEGER, TtyParams AS Termio ) STATIC

    DIM        TtyDevice        AS    MsdosTermio
    DIM        InRegs            AS    RegType
    DIM        OutRegs            AS    RegType


    '
    '    Make a copy of the record (struct) for the device call
    '

    TtyDevice.TtyParams    = TtyParams

    '
    '    Set the mode of the device identified by FileHandle to
    '    true binary.  The BIN bit must be set in the device attribute
    '    word inside the device driver.
    '

    IF( SetBinaryMode( FileHandle ) <> PASS ) THEN

        TtyDeviceIoctl    = FAIL
        EXIT FUNCTION

    END    IF


    '
    '    If the Command is TCSBRK, TCXONC, or TCFLSH then
    '    the argument should be passed as an integer.
    '    If this is the case, read the current value of the
    '    termio record (struct) contained internally to the
    '    device driver
    '

    SELECT CASE ( Command )
        CASE    TCSBRK, TCXONC, TCFLSH

            '
            '    Read the current struct
            '

            TtyDevice.FileHandle    = FileHandle
            TtyDevice.Command    = Command
            TtyDevice.Arguement    = 0

            InRegs.AX        = &H4400 OR ( ReadCXBytes AND &H00FF )
            InRegs.BX        = FileHandle
            InRegs.CX        = LEN( TtyDevice )
            InRegs.DX        = VARPTR( TtyDevice )
            InRegs.DS        = VARSEG( TtyDevice )

            CALL INTERRUPT( &H0021, InRegs, OutRegs )

            IF ( ( OutRegs.Flags AND &H0001 ) <> 0 ) THEN
                TtyDeviceIoctl    = FAIL
                EXIT FUNCTION
            END IF

        CASE    TCGETS, TCSETS, TCSETAW, TCSETAF

        CASE    ELSE
            TtyDeviceIoctl    = FAIL
            EXIT FUNCTION
    END    SELECT

    '
    '    Examine the Command and determine whether to read or
    '    write bytes to using the rea MS-DOS IOCTL function call
    '

    SELECT CASE( Command )
        CASE    TCGETS
            FunctionValue        = ReadCXBytes

        CASE    TCSETS, TCSETAW, TCSETAF
            FunctionValue        = WriteCXBytes
            TtyDevice.Arguement    = 0

        '
        '    Special case: When Command is TCSETBRK, TCXONC, or
        '    TCFLSH then the Argument (TtyParams) contains an
        '    integer ( 0, 1, or 2 per the command) than can be
        '    found by referencing the first member of the structure
        '    (Ciflag) that Basic "thought" was passed.
        '

        CASE    TCSETBRK, TCXONC, TCFLSH
            FunctionValue        = WriteCXBytes
            TtyDevice.Arguement    = TtyParams.Ciflag

        CASE    ELSE
            TtyDeviceIoctl        = FAIL
            EXIT FUNCTION
    END    SELECT

    '
    '    Perform the operation on the structure via MS-DOS
    '

    TtyDevice.FileHandle    = FileHandle
    TtyDevice.Command    = Command

    InRegs.AX        = &H4400 OR ( FunctionValue AND &H00FF )
    InRegs.BX        = FileHandle
    InRegs.CX        = LEN( TtyDevice )
    InRegs.DX        = VARPTR( TtyDevice )
    InRegs.DS        = VARSEG( TtyDevice )

    CALL INTERRUPT( &H0021, InRegs, OutRegs )

    '
    '    Copy the information from the device driver to the
    '    callers record.
    '

    TtyParams    = TtyDevice.TtyParams

    '
    '    See if we failed the function call
    '

    IF ( ( OutRegs.Flags AND &H0001 ) <> 0 ) THEN
        TtyDeviceIoctl    = FAIL
        EXIT FUNCTION
    END IF


    TtyDeviceIoctl    = PASS

END    FUNCTION


'
' == [ SETBINARYMODE   ] ================================================
'                                                                       =
'    This function is used by TtyDeviceIoctl() to set binary mode    =
'    in the device's attribute block.  The user should not have to    =
'    call this function.                        =
'                                                                       =
' =======================================================================
'
'
'
FUNCTION SetBinaryMode( FileHandle AS INTEGER )

    DIM        InRegs            AS    RegType
    DIM        OutRegs            AS    RegType

    '
    '    Obtain a copy of the device attribute word from the
    '    device driver identified by FileHandle
    '

    InRegs.AX        = &H4400
    InRegs.BX        = FileHandle

    CALL INTERRUPT( &H0021, InRegs, OutRegs )

    IF ( ( OutRegs.Flags AND &H0001 ) <> 0 ) THEN
        SetBinaryMode    = FAIL
        EXIT FUNCTION
    END IF

    '
    '    Or in the bit that indicates that the device will
    '    operate in binary mode
    '

    InRegs.AX        = &H4401
    InRegs.BX        = FileHandle
    InRegs.DX        = ( OutRegs.DX AND &H00FF ) OR &H0020

    CALL INTERRUPT( &H0021, InRegs, OutRegs )

    IF ( ( OutRegs.Flags AND &H0001 ) <> 0 ) THEN
        SetBinaryMode    = FAIL
        EXIT FUNCTION
    END IF

    SetBinaryMode    = PASS

END    FUNCTION