/* Constants */
const char *hex = "0123456789ABCDEF";

/* Macros */
#define BUFFER_SIZE 65536
#define BIN_FORMAT 0
#define HEX_FORMAT 1
#define CHAN_EOF 0x10

/*
 * This structure describes the per-instance state of an SSL channel.
 *
 * The SSL processing context is maintained here, in the ClientData
 */
typedef struct DigestState {

/*
 *-------------------------------------------------------------------
 *
 * DigestCloseProc --
 *
 *	This procedure is invoked by the generic IO level to perform
 *	channel-type-specific cleanup when channel is closed. All
 *	queued output is flushed prior to calling this function.
 *
 * Returns:

 *	0 if successful or POSIX error code if failed.
 *
 * Side effects:
 *	Writes digest to output and closes the channel. Stores error
 *	messages in interp result.
 *
 *-------------------------------------------------------------------
 */
int DigestCloseProc(ClientData clientData, Tcl_Interp *interp) {
    DigestState *statePtr = (DigestState *) clientData;


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

    /* Clean-up */
    DigestFree(statePtr);
    return 0;
}

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

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

/*
 *----------------------------------------------------------------------
 *
 * DigestInputProc --
 *
 *	Called by the generic IO system to read data from transform and
 *	place in buf.
 *
 * Returns:
 *	Total bytes read or -1 for an error along with a POSIX error
 *	code in errorCodePtr. Use EAGAIN for nonblocking and no data.
 *
 * Side effects:
 *	Read data from transform and write to buf
 *
 *----------------------------------------------------------------------
 */
int DigestInputProc(ClientData clientData, char *buf, int toRead, int *errorCodePtr) {

	    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;
	}
	/* This is correct */
	read = -1;
	*errorCodePtr = EAGAIN;
	    
    } else if (read < 0) {
	/* Error */
	*errorCodePtr = Tcl_GetErrno();

    } else if (!(statePtr->flags & CHAN_EOF)) {
	/* 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) {

		    *ptr++ = hex[(md_buf[i] >> 4) & 0x0F];
		    *ptr++ = hex[md_buf[i] & 0x0F];
		}
		read = md_len*2;
		memcpy(buf, hex_buf, read);
	    }
	}
	statePtr->flags |= CHAN_EOF;
    }
    return read;
}

/*
 *----------------------------------------------------------------------
 *
 * DigestOutputProc --
 *
 *	Called by the generic IO system to write data in buf to transform.
 *
 * Returns:
 *	Total bytes written or -1 for an error along with a POSIX error
 *	code in errorCodePtr. Use EAGAIN for nonblocking and can't write data.
 *
 * Side effects:
 *	Get data from buf and update digest
 *
 *----------------------------------------------------------------------
 */
 int DigestOutputProc(ClientData clientData, const char *buf, int toWrite, int *errorCodePtr) {
    DigestState *statePtr = (DigestState *) clientData;
    *errorCodePtr = 0;
    int res;

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

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

/*
 *----------------------------------------------------------------------
 *
 * DigestSetOptionProc --
 *
 *	Called by the generic IO system to set channel option name to value.
 *
 * Returns:
 *	TCL_OK if successful or TCL_ERROR if failed along with an error
 *	message in interp and Tcl_SetErrno.
 *
 * Side effects:
 *	Updates channel option to new value.
 *
 *----------------------------------------------------------------------
 */
static int DigestSetOptionProc(ClientData clientData, Tcl_Interp *interp, const char *optionName,

    /* Delegate options downstream */
    parent = Tcl_GetStackedChannel(statePtr->self);
    setOptionProc = Tcl_ChannelSetOptionProc(Tcl_GetChannelType(parent));
    if (setOptionProc != NULL) {
	return (*setOptionProc)(Tcl_GetChannelInstanceData(parent), interp, optionName, optionValue);
    } else {
	Tcl_SetErrno(EINVAL);
	return Tcl_BadChannelOption(interp, optionName, NULL);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * DigestGetOptionProc --
 *
 *	Called by the generic IO system to get channel option name's value.
 *
 * Returns:
 *	TCL_OK if successful or TCL_ERROR if failed along with an error
 *	message in interp and Tcl_SetErrno.
 *
 * Side effects:
 *	Sets result to option's value
 *
 *----------------------------------------------------------------------
 */
static int DigestGetOptionProc(ClientData clientData, Tcl_Interp *interp, const char *optionName,

    parent = Tcl_GetStackedChannel(statePtr->self);
    getOptionProc = Tcl_ChannelGetOptionProc(Tcl_GetChannelType(parent));
    if (getOptionProc != NULL) {
	return (*getOptionProc)(Tcl_GetChannelInstanceData(parent), interp, optionName, optionValue);
    } else if (optionName == (char*) NULL) {
	/* Request is query for all options, this is ok. */
	return TCL_OK;
    } else {
	Tcl_SetErrno(EINVAL);

	return Tcl_BadChannelOption(interp, optionName, NULL);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * DigestTimerHandler --
 *

 *
 * DigestGetHandleProc --
 *
 *	Called from Tcl_GetChannelHandle to retrieve OS specific file handle
 *	from inside this channel. Not used for transformations?
 *
 * Returns:
 *	TCL_OK for success or TCL_ERROR for error or if not supported. If
 *	direction is TCL_READABLE, sets handlePtr to the handle used for
 *	input, or if TCL_WRITABLE sets to the handle used for output.
 *
 * Side effects:
 *	None
 *
 *----------------------------------------------------------------------
 */
int DigestGetHandleProc(ClientData clientData, int direction, ClientData *handlePtr) {