int flags;		/* Chan config flags */
	int watchMask;		/* Current WatchProc mask */
	int mode;		/* Current mode of parent channel */
	int format;		/* Output format */

	Tcl_Interp *interp;	/* Current interpreter */
	EVP_MD_CTX *ctx;	/* MD Context */
	HMAC_CTX *hctx;		/* HMAC Context */
} DigestState;

/*
 *-------------------------------------------------------------------
 *
 * DigestFree --
 *
 *	This procedure removes a digest state structure
 *
 * Returns:
 *	Nothing
 *
 * Side effects:
 *	Removes structure
 *
 *-------------------------------------------------------------------
 */
void DigestFree (DigestState *statePtr) {
    if (statePtr == (DigestState *) NULL) return;

    if (statePtr->ctx != (EVP_MD_CTX *) NULL) {
	EVP_MD_CTX_free(statePtr->ctx);
    }
    if (statePtr->hctx != (HMAC_CTX *) NULL) {
	HMAC_CTX_free(statePtr->hctx);
    }
    ckfree(statePtr);
}

/*******************************************************************/

/*
 *-------------------------------------------------------------------
 *
 * DigestFile --

	Tcl_AppendResult(interp, "Initialize digest failed: ", REASON(), NULL);
	goto error;
    }

    /* Read file data and update hash function */
    while (!Tcl_Eof(chan)) {
	int len = Tcl_ReadRaw(chan, (char *) buf, BUFFER_SIZE);
	if (len > 0) {
	    if (keyObj == NULL) {
		res = EVP_DigestUpdate(ctx, &buf, (size_t) len);
	    } else {
		res = HMAC_Update(hctx, &buf[0], (size_t) len);
	    }
	    if (!res) {
		Tcl_AppendResult(interp, "Update digest failed: ", REASON(), NULL);
		res = TCL_ERROR;
		goto error;
	    }
	}
    }

    /* Close channel */
    if (Tcl_Close(interp, chan) == TCL_ERROR) {
	chan = (Tcl_Channel) NULL;
	goto error;

    }
    return 0;
}

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
























 * DigestCloseProc --
 *
 *	This procedure is invoked by the generic IO level to perform
 *	channel-type-specific cleanup when digest channel is closed.
 *
 * Returns:
 *	TCL_OK or TCL_ERROR

 *	Read data from transform and write to buf
 *
 *----------------------------------------------------------------------
 */
int DigestInputProc(ClientData clientData, char *buf, int toRead, int *errorCodePtr) {
    DigestState *statePtr = (DigestState *) clientData;
    Tcl_Channel parent;
    int read, res;
    *errorCodePtr = 0;

    if (toRead <= 0 || statePtr->self == (Tcl_Channel) NULL) {
	return 0;
    }

    /* Get bytes from underlying channel */
    parent = Tcl_GetStackedChannel(statePtr->self);
    read = Tcl_ReadRaw(parent, buf, toRead);

    /* Add to message digest */
    if (read > 0) {
	if (statePtr->ctx != NULL) {
	    res = EVP_DigestUpdate(statePtr->ctx, buf, (size_t) read);
	} else {
	    res = HMAC_Update(statePtr->hctx, buf, (size_t) read);
	}
	if (!res) {
	    Tcl_SetChannelError(statePtr->self, Tcl_ObjPrintf("Digest update failed: %s", REASON()));
	    *errorCodePtr = EINVAL;
	    return -1;
	}
	*errorCodePtr = EAGAIN;
	read = -1;
	    
    } else if (read < 0) {
	/* Error */
	*errorCodePtr = Tcl_GetErrno();

    } else if (!(statePtr->flags & 0x10)) {
	/* EOF */
	*errorCodePtr = 0;
	unsigned char md_buf[EVP_MAX_MD_SIZE];
	unsigned int md_len = 0;

	/* Finalize hash function and calculate message digest */
	if (statePtr->ctx != NULL) {
	    res = EVP_DigestFinal_ex(statePtr->ctx, md_buf, &md_len);
	} else {
	    res = HMAC_Final(statePtr->hctx, md_buf, &md_len);
	}
	if (!res) {
	    *errorCodePtr = EINVAL;

	/* Write message digest to output channel as byte array or hex string */
	} else if (md_len > 0) {
	    if (statePtr->format == BIN_FORMAT) {
		read = md_len;
		memcpy(buf, md_buf, read);

 *
 * Side effects:
 *	Adds transform to channel and sets result to channel name or error message.
 *
 *----------------------------------------------------------------------
 */
static int
DigestChannel(Tcl_Interp *interp, const char *channel, const EVP_MD *md, int format,
	Tcl_Obj *keyObj) {
    int res, mode; /* OR-ed combination of TCL_READABLE and TCL_WRITABLE */
    Tcl_Channel chan;

    DigestState *statePtr;
    EVP_MD_CTX *ctx = (EVP_MD_CTX *) NULL;
    HMAC_CTX *hctx = (HMAC_CTX *) NULL;

    /* Validate args */
    if (channel == (const char *) NULL || md == (const EVP_MD *) NULL) {
	return TCL_ERROR;
    }

    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 internal storage structure */

    statePtr = (DigestState *) ckalloc((unsigned) sizeof(DigestState));
    if (statePtr != NULL) {
	memset(statePtr, 0, sizeof(DigestState));
	statePtr->self	= chan;		/* This socket channel */
	statePtr->timer = (Tcl_TimerToken) NULL;	/* Timer to flush data */
	statePtr->flags = 0;		/* Chan config flags */
	statePtr->watchMask = 0;	/* Current WatchProc mask */
	statePtr->mode	= mode;		/* Current mode of parent channel */
	statePtr->format = format;	/* Output format */
	statePtr->interp = interp;	/* Current interpreter */
	statePtr->ctx = ctx;		/* MD Context */
	statePtr->hctx = hctx;		/* HMAC Context */
	statePtr->mac = NULL;		/* MAC Context */
    } else {
	Tcl_AppendResult(interp, "Initialize digest error: memory allocation failure", (char *) NULL);
	return TCL_ERROR;
    }

    /* Create message digest context */
    if (keyObj == NULL) {
	ctx = EVP_MD_CTX_new();
    } else {
	hctx = HMAC_CTX_new();
    }
    if (ctx != NULL || hctx != NULL) {
	statePtr->ctx = ctx;
	statePtr->hctx = hctx;
    } else {
	Tcl_AppendResult(interp, "Create digest context failed: ", REASON(), NULL);
	DigestFree(statePtr);
	return TCL_ERROR;
    }

    /* Initialize hash function */
    if (keyObj == NULL) {
	res = EVP_DigestInit_ex(ctx, md, NULL);
    } else {
	int key_len;
	unsigned char *key = Tcl_GetByteArrayFromObj(keyObj, &key_len);
	res = HMAC_Init_ex(hctx, (const void *) key, key_len, md, NULL);
    }
    if (!res) {

	Tcl_AppendResult(interp, "Initialize digest failed: ", REASON(), (char *) NULL);

	DigestFree(statePtr);
	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 */
    statePtr->self = Tcl_StackChannel(interp, &digestChannelType, (ClientData) statePtr, mode, chan);
    if (statePtr->self == (Tcl_Channel) NULL) {

	DigestFree(statePtr);
	return TCL_ERROR;
    }

    Tcl_SetResult(interp, (char *) Tcl_GetChannelName(chan), TCL_VOLATILE);
    return TCL_OK;
}

    data = Tcl_GetByteArrayFromObj(objv[1], &len);
    if (data == NULL || len == 0) {
	Tcl_SetResult(interp, "No data", NULL);
	return TCL_ERROR;
    }

    /* Calculate digest based on hash function */
    if (keyObj == (Tcl_Obj *) NULL) {
	res = EVP_Digest(data, (size_t) len, md_buf, &md_len, md, NULL);
    } else {
	unsigned char *key, *hmac = NULL;
	int key_len;

	key = Tcl_GetByteArrayFromObj(keyObj, &key_len);
	hmac = HMAC(md, (const void *) key, key_len, (const unsigned char *) data,
	    (size_t) len, md_buf, &md_len);
	res = (hmac != NULL);
    }

 * Side effects:
 *	Sets result to message digest or error message
 *
 *-------------------------------------------------------------------
 */
static int
DigestObjCmd(ClientData clientData, Tcl_Interp *interp, int objc, Tcl_Obj *const objv[]) {
    int idx, len, format = HEX_FORMAT, key_len = 0, data_len = 0, res = TCL_OK;
    const char *digestname, *channel = NULL;
    Tcl_Obj *dataObj = NULL, *fileObj = NULL, *keyObj = NULL;
    unsigned char *key = NULL;
    const EVP_MD *md;

    Tcl_ResetResult(interp);

    /* If no option for last arg, then its the data */
    if (idx < objc) {
	dataObj = objv[idx];
    }

    /* Calc digest on file, stacked channel, or data blob */
    if (fileObj != NULL) {
	res = DigestFile(interp, fileObj, md, format, keyObj);
    } else if (channel != NULL) {
	res = DigestChannel(interp, channel, md, format, keyObj);
    } else if (dataObj != NULL) {
	Tcl_Obj *objs[2];
	objs[0] = NULL;
	objs[1] = dataObj;
	res = DigestHashFunction(interp, 2, objs, md, format, keyObj);
    }


    return res;
}

/*
 *-------------------------------------------------------------------
 *
 * Message Digest Convenience Commands --
 *