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

    /* Update hash function */
    if (toWrite > 0 && DigestUpdate(statePtr, buf, (size_t) toWrite, 0) != TCL_OK) {
	Tcl_SetChannelError(statePtr->self, Tcl_ObjPrintf("Update failed: %s", REASON()));
	*errorCodePtr = EINVAL;
	return 0;
    }
    return toWrite;
}

    chan = Tcl_GetChannel(interp, channel, &mode);
    if (chan == (Tcl_Channel) NULL) {
	return TCL_ERROR;
    }

    /* Make sure to operate on the topmost channel */
    chan = Tcl_GetTopChannel(chan);







    /* Create state data structure */
    if ((statePtr = DigestStateNew(interp, format)) == NULL) {
	Tcl_AppendResult(interp, "Memory allocation error", (char *) NULL);
	return TCL_ERROR;
    }
    statePtr->self = chan;
    statePtr->mode = mode;

    /* Initialize hash function */
    if (DigestInitialize(interp, statePtr, md, cipher, keyObj, mac) != TCL_OK) {
	return TCL_ERROR;
    }

    /* Configure channel */
    Tcl_SetChannelOption(interp, chan, "-translation", "binary");
    if (Tcl_GetChannelBufferSize(chan) < EVP_MAX_MD_SIZE * 2) {
	Tcl_SetChannelBufferSize(chan, EVP_MAX_MD_SIZE * 2);
    }

    /* Stack channel, abort for error */
    statePtr->self = Tcl_StackChannel(interp, &digestChannelType, (ClientData) statePtr, mode, chan);
    if (statePtr->self == (Tcl_Channel) NULL) {
	DigestStateFree(statePtr);
	return TCL_ERROR;
    }

    /* Set result to channel Id */

    /* Create state data structure */
    if ((statePtr = DigestStateNew(interp, format)) == NULL) {
	Tcl_AppendResult(interp, "Memory allocation error", (char *) NULL);
	return TCL_ERROR;
    }

    /* Calc Digest, abort for error */
    if (DigestInitialize(interp, statePtr, md, cipher, keyObj, mac) != TCL_OK ||
	DigestUpdate(statePtr, data, (size_t) data_len, 1) != TCL_OK ||
	DigestFinalize(interp, statePtr, NULL) != TCL_OK) {
	DigestStateFree(statePtr);
	return TCL_ERROR;
    }

    /* Create state data structure */
    if ((statePtr = DigestStateNew(interp, format)) == NULL) {
	Tcl_AppendResult(interp, "Memory allocation error", (char *) NULL);
	return TCL_ERROR;
    }

    /* Open file channel, abort for error */
    chan = Tcl_FSOpenFileChannel(interp, inFileObj, "rb", 0444);
    if (chan == (Tcl_Channel) NULL) {
	DigestStateFree(statePtr);
	return TCL_ERROR;
    }

    /* Configure channel */