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iolink.def
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1996-08-29
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DEFINITION MODULE IOLink;
(* Types and procedures giving the standard implementation of channels *)
FROM IOChan IMPORT ChanId, DeviceErrNum, ChanExceptions;
FROM IOConsts IMPORT ReadResults;
FROM ChanConsts IMPORT FlagSet;
FROM SYSTEM IMPORT ADDRESS;
(* Devices need to identify themselves in order to allow a check to be made
that device-dependent operations are applied only for channels opened to
that device: *)
TYPE
DeviceId; (* values of this type are used to identify new device modules
and are normally obtained by them during their intialization *)
PROCEDURE AllocateDeviceId (VAR did : DeviceId);
(* Allocates a unique value of type DeviceId and assigns this value to
the parameter did *)
(* a new device module open procedure obtains a channel by calling MakeChan *)
PROCEDURE MakeChan ( did : DeviceId;
VAR cid : ChanId);
(* Attempts to make a new channel for the device module identified by did.
If no more channels can be made, the identity of the bad channel is
assigned to cid. Otherwise, the identity ofa new channel is assigned to
cid. *)
(* If a channel is allocated but the call of the device module open
procedure is not successful, and on a successful call of a device module
close procedure, the device module unmakes the channel and returns the
value identifying the bad channel to its client: *)
PROCEDURE UnMakeChan ( did : DeviceId;
VAR cid : ChanId);
(* If the device module identified by the parameter did is not the module that
made the channel identified by the parameter cid, the exception wrongDevice
is raised.
Otherwise, the channel is deallocated and the value identifying the bad
channel is assigned to cid. *)
(* If the call of the device module open procedure is successful, the
device module obtains a pointer to a device table for the channel, which
will have been initialized by MakeChan. It then changes the fields of the
device table to install its own values for the device data, supported
operations, and flags, and returns to its client the identity of the
channel. *)
TYPE
DeviceTablePtr = POINTER TO DeviceTable;
(* Values of this type are used to refer to device tables *)
(* Device modules supply procedures of the following types: *)
TYPE
LookProc = PROCEDURE (DeviceTablePtr, VAR CHAR, VAR ReadResults);
SkipProc = PROCEDURE (DeviceTablePtr);
SkipLookProc = PROCEDURE (DeviceTablePtr, VAR CHAR, VAR ReadResults);
TextReadProc = PROCEDURE (DeviceTablePtr, ADDRESS, CARDINAL, VAR CARDINAL);
TextWriteProc = PROCEDURE (DeviceTablePtr, ADDRESS, CARDINAL);
WriteLnProc = PROCEDURE (DeviceTablePtr);
RawReadProc = PROCEDURE (DeviceTablePtr, ADDRESS, CARDINAL, VAR CARDINAL);
RawWriteProc = PROCEDURE (DeviceTablePtr, ADDRESS, CARDINAL);
GetNameProc = PROCEDURE (DeviceTablePtr, VAR ARRAY OF CHAR);
ResetProc = PROCEDURE (DeviceTablePtr);
FlushProc = PROCEDURE (DeviceTablePtr);
FreeProc = PROCEDURE (DeviceTablePtr);
(* Carry out the operations involved in closing the corresponding
channel, including flushing buffers, but do not unmake the channel.
This procedure is called for each open channel at program termination. *)
TYPE
DeviceData = ADDRESS;
DeviceTable = RECORD (* Initialized by MakeChan to: *)
cd : DeviceData; (* the value NIL *)
did : DeviceId; (* the value given to MakeChan *)
cid : ChanId; (* the identity of the channel *)
result : ReadResults; (* the value notKnown *)
errNum : DeviceErrNum; (* undefined *)
flags : FlagSet; (* FlagSet{} *)
doLook : LookProc; (* raise exception notAvailable *)
doSkip : SkipProc; (* raise exception notAvailable *)
doSkipLook : SkipLookProc; (* raise exception notAvailable *)
doTextRead : TextReadProc; (* raise exception notAvailable *)
doTextWrite : TextWriteProc; (* raise exception notAvailable *)
doLnWrite : WriteLnProc; (* raise exception notAvailable *)
doRawRead : RawReadProc; (* raise exception notAvailable *)
doRawWrite : RawWriteProc; (* raise exception notAvailable *)
doGetName : GetNameProc; (* return the empty string *)
doReset : ResetProc; (* do nothing *)
doFlush : FlushProc; (* do nothing *)
doFree : FreeProc; (* do nothing *)
END;
(* The pointer to the device table for a channel is obtained using the
following procedure: *)
PROCEDURE DeviceTablePtrValue (cid : ChanId;
did : DeviceId): DeviceTablePtr;
(* If the device module identified by the parameter did is not the module
that made the channel identified by the parameter cid, the exception
wrongDevice is raised.
Otherwise, a pointer to the device table for the channel is returned. *)
(* A device module can ask if it opened a given channel. It does this
to implement a corresponding enquiry function that is exported from the
device module: *)
PROCEDURE IsDevice (cid : ChanId;
did : DeviceId): BOOLEAN;
(* Tests if the device module identified by the parameter did is the
module that made the channel identified by the parameter cid. *)
TYPE
DevExceptionRange = ChanExceptions; (* [notAvailable .. textParseError] *)
PROCEDURE RAISEdevException (cid : ChanId;
did : DeviceId;
x : DevExceptionRange;
s : ARRAY OF CHAR);
(* If the device module identified by the parameter did is not the module
that made the channel identified by the parameter cid, the exception
wrongDevice is raised. Otherwise the given exception is raised and the
string value of the parameter s is included in the exception message. *)
PROCEDURE IsIOException (): BOOLEAN;
(* Returns TRUE if the current coroutine is in the exceptional execution state
because of the raising of an exception from ChanExceptions
Otherwise returns FALSE *)
PROCEDURE IOException (): ChanExceptions;
(* If the current coroutine is in the exceptional execution state because of
the raising of an exception from ChanExceptions, returns the corresponding
enumeration value, and otherwise raises an exception. *)
END IOLink.