*	Sets the device into blocking or nonblocking mode.
 *	Can call Tcl_SetChannelError.
 *
 *-------------------------------------------------------------------
 */
static int DigestBlockModeProc(ClientData clientData, int mode) {
    DigestState *statePtr = (DigestState *) clientData;

    dprintf("Called");

    if (mode == TCL_MODE_NONBLOCKING) {
	statePtr->flags |= TLS_TCL_ASYNC;
    } else {
	statePtr->flags &= ~(TLS_TCL_ASYNC);
    }
    return 0;

 * Side effects:
 *	Deletes stored state data.
 *
 *-------------------------------------------------------------------
 */
int DigestCloseProc(ClientData clientData, Tcl_Interp *interp) {
    DigestState *statePtr = (DigestState *) clientData;

    dprintf("Called");

    /* Cancel active timer, if any */
    if (statePtr->timer != (Tcl_TimerToken) NULL) {
	Tcl_DeleteTimerHandler(statePtr->timer);
	statePtr->timer = (Tcl_TimerToken) NULL;
    }

    return 0;
}

/*
 * Same as DigestCloseProc but with individual read and write close control
 */
static int DigestClose2Proc(ClientData instanceData, Tcl_Interp *interp, int flags) {

    dprintf("Called");

    if ((flags & (TCL_CLOSE_READ | TCL_CLOSE_WRITE)) == 0) {
	return DigestCloseProc(instanceData, interp);
    }
    return EINVAL;
}

 *----------------------------------------------------------------------
 */
int DigestInputProc(ClientData clientData, char *buf, int toRead, int *errorCodePtr) {
    DigestState *statePtr = (DigestState *) clientData;
    Tcl_Channel parent;
    Tcl_Size read;
    *errorCodePtr = 0;

    dprintf("Called");

    /* Abort if nothing to process */
    if (toRead <= 0 || statePtr->self == (Tcl_Channel) NULL) {
	return 0;
    }

    /* Get bytes from underlying channel */

 *	Get data from buf and update digest
 *
 *----------------------------------------------------------------------
 */
 int DigestOutputProc(ClientData clientData, const char *buf, int toWrite, int *errorCodePtr) {
    DigestState *statePtr = (DigestState *) clientData;
    *errorCodePtr = 0;

    dprintf("Called");

    /* Abort if nothing to process */
    if (toWrite <= 0 || statePtr->self == (Tcl_Channel) NULL) {
	return 0;
    }

    /* Update hash function */

 *----------------------------------------------------------------------
 */
static int DigestSetOptionProc(ClientData clientData, Tcl_Interp *interp, const char *optionName,
	const char *optionValue) {
    DigestState *statePtr = (DigestState *) clientData;
    Tcl_Channel parent;
    Tcl_DriverSetOptionProc *setOptionProc;

    dprintf("Called");

    /* Abort if no channel */
    if (statePtr->self == (Tcl_Channel) NULL) {
	return TCL_ERROR;
    }

    /* Delegate options downstream */

 *----------------------------------------------------------------------
 */
static int DigestGetOptionProc(ClientData clientData, Tcl_Interp *interp, const char *optionName,
	Tcl_DString *optionValue) {
    DigestState *statePtr = (DigestState *) clientData;
    Tcl_Channel parent;
    Tcl_DriverGetOptionProc *getOptionProc;

    dprintf("Called");

    /* Abort if no channel */
    if (statePtr->self == (Tcl_Channel) NULL) {
	return TCL_ERROR;
    }

    /* Delegate options downstream */

 * Side effects:
 *	May call Tcl_NotifyChannel
 *
 *----------------------------------------------------------------------
 */
static void DigestTimerHandler(ClientData clientData) {
    DigestState *statePtr = (DigestState *) clientData;

    dprintf("Called");

    /* Abort if no channel */
    if (statePtr->self == (Tcl_Channel) NULL) {
	return;
    }

    /* Clear timer token */

 *
 *----------------------------------------------------------------------
 */
void DigestWatchProc(ClientData clientData, int mask) {
    DigestState *statePtr = (DigestState *) clientData;
    Tcl_Channel parent;
    Tcl_DriverWatchProc *watchProc;

    dprintf("Called");

    /* Abort if no channel */
    if (statePtr->self == (Tcl_Channel) NULL) {
	return;
    }

    /* Store OR-ed combination of TCL_READABLE, TCL_WRITABLE and TCL_EXCEPTION */

 *	None
 *
 *----------------------------------------------------------------------
 */
int DigestGetHandleProc(ClientData clientData, int direction, ClientData *handlePtr) {
    DigestState *statePtr = (DigestState *) clientData;
    Tcl_Channel parent;

    dprintf("Called");

    /* Abort if no channel */
    if (statePtr->self == (Tcl_Channel) NULL) {
	return TCL_ERROR;
    }

    parent = Tcl_GetStackedChannel(statePtr->self);

 * Side effects:
 *	Cancels any pending timer.
 *
 *----------------------------------------------------------------------
 */
int DigestNotifyProc(ClientData clientData, int interestMask) {
    DigestState *statePtr = (DigestState *) clientData;

    dprintf("Called");

    /* Skip timer event as redundant */
    if (statePtr->timer != (Tcl_TimerToken) NULL) {
	Tcl_DeleteTimerHandler(statePtr->timer);
	statePtr->timer = (Tcl_TimerToken) NULL;
    }
    return interestMask;

 * Side effects:
 *	Destroys state info structure
 *
 *-------------------------------------------------------------------
 */
void DigestCommandDeleteHandler(ClientData clientData) {
    DigestState *statePtr = (DigestState *) clientData;

    dprintf("Called");

    /* Clean-up */
    DigestStateFree(statePtr);
}

/*
 *-------------------------------------------------------------------