telecom: Add the data set comparison algorithm from the Telecom Profiles.

The first half of the telecom algorithm from G.8275.1 and G.8275.2
differs from the one in 1588, making use of profile specific
"localPriority" attributes.

Signed-off-by: Richard Cochran <richardcochran@gmail.com>

bmc.h

@@ -55,4 +55,16 @@ int dscmp(struct dataset *a, struct dataset *b);
  */
 int dscmp2(struct dataset *a, struct dataset *b);
 
+/**
+ * Compare two data sets using the algorithm defined in the Telecom
+ * Profiles according to ITU-T G.8275.1 and G.8275.2.
+ *
+ * @param a A dataset to compare.
+ * @param b A dataset to compare.
+ * @return An integer less than, equal to, or greater than zero
+ *         if the dataset @a a is found, respectively, to be
+ *         less than, to match, or be greater than @a b.
+ */
+int telecom_dscmp(struct dataset *a, struct dataset *b);
+
 #endif

makefile

@@ -25,7 +25,7 @@ LDLIBS	= -lm -lrt $(EXTRA_LDFLAGS)
 PRG	= ptp4l hwstamp_ctl nsm phc2sys phc_ctl pmc timemaster
 OBJ     = bmc.o clock.o clockadj.o clockcheck.o config.o fault.o \
  filter.o fsm.o hash.o linreg.o mave.o mmedian.o msg.o ntpshm.o nullf.o phc.o \
- pi.o port.o print.o ptp4l.o raw.o rtnl.o servo.o sk.o stats.o tlv.o \
+ pi.o port.o print.o ptp4l.o raw.o rtnl.o servo.o sk.o stats.o telecom.o tlv.o \
  transport.o tsproc.o udp.o udp6.o uds.o util.o version.o
 
 OBJECTS	= $(OBJ) hwstamp_ctl.o nsm.o phc2sys.o phc_ctl.o pmc.o pmc_common.o \

telecom.c

@@ -0,0 +1,73 @@
+/**
+ * @file telecom.c
+ * @note Copyright (C) 2017 Richard Cochran <richardcochran@gmail.com>
+ *
+ * Derived from code in bmc.c.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA.
+ */
+#include <string.h>
+
+#include "bmc.h"
+#include "ds.h"
+
+int telecom_dscmp(struct dataset *a, struct dataset *b)
+{
+	int diff;
+
+	if (a == b)
+		return 0;
+	if (a && !b)
+		return A_BETTER;
+	if (b && !a)
+		return B_BETTER;
+
+	if (a->quality.clockClass < b->quality.clockClass)
+		return A_BETTER;
+	if (a->quality.clockClass > b->quality.clockClass)
+		return B_BETTER;
+
+	if (a->quality.clockAccuracy < b->quality.clockAccuracy)
+		return A_BETTER;
+	if (a->quality.clockAccuracy > b->quality.clockAccuracy)
+		return B_BETTER;
+
+	if (a->quality.offsetScaledLogVariance <
+	    b->quality.offsetScaledLogVariance)
+		return A_BETTER;
+	if (a->quality.offsetScaledLogVariance >
+	    b->quality.offsetScaledLogVariance)
+		return B_BETTER;
+
+	if (a->priority2 < b->priority2)
+		return A_BETTER;
+	if (a->priority2 > b->priority2)
+		return B_BETTER;
+
+	if (a->localPriority < b->localPriority)
+		return A_BETTER;
+	if (a->localPriority > b->localPriority)
+		return B_BETTER;
+
+	if (a->quality.clockClass <= 127)
+		return dscmp2(a, b);
+
+	diff = memcmp(&a->identity, &b->identity, sizeof(a->identity));
+
+	if (!diff)
+		return dscmp2(a, b);
+
+	return diff < 0 ? A_BETTER : B_BETTER;
+}