Add new software trigger as a library-wide facility.

This is strictly an internal feature, for use by drivers for hardware
that doesn't have its own trigger mechanism.

Makefile.am

@@ -33,6 +33,7 @@ libsigrok_la_SOURCES = \
 	session_driver.c \
 	hwdriver.c \
 	trigger.c \
+	soft-trigger.c \
 	strutil.c \
 	log.c \
 	version.c \

libsigrok-internal.h

@@ -332,6 +332,23 @@ SR_PRIV int sr_atod(const char *str, double *ret);
 SR_PRIV int sr_atof(const char *str, float *ret);
 SR_PRIV int sr_atof_ascii(const char *str, float *ret);
 
+/*--- soft-trigger.c --------------------------------------------------------*/
+
+struct soft_trigger_logic {
+	const struct sr_dev_inst *sdi;
+	const struct sr_trigger *trigger;
+	int count;
+	int unitsize;
+	int cur_stage;
+	uint8_t *prev_sample;
+};
+
+SR_PRIV struct soft_trigger_logic *soft_trigger_logic_new(
+		const struct sr_dev_inst *sdi, struct sr_trigger *trigger);
+SR_PRIV void soft_trigger_logic_free(struct soft_trigger_logic *st);
+SR_PRIV int soft_trigger_logic_check(struct soft_trigger_logic *st, uint8_t *buf,
+		int len);
+
 /*--- hardware/common/serial.c ----------------------------------------------*/
 
 #ifdef HAVE_LIBSERIALPORT

soft-trigger.c

@@ -0,0 +1,147 @@
+/*
+ * This file is part of the libsigrok project.
+ *
+ * Copyright (C) 2014 Bert Vermeulen <bert@biot.com>
+ *
+ * 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 3 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, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <string.h>
+#include "libsigrok.h"
+#include "libsigrok-internal.h"
+
+/* @cond PRIVATE */
+#define LOG_PREFIX "soft-trigger"
+/* @endcond */
+
+SR_PRIV struct soft_trigger_logic *soft_trigger_logic_new(
+		const struct sr_dev_inst *sdi, struct sr_trigger *trigger)
+{
+	struct soft_trigger_logic *stl;
+
+	stl = g_malloc0(sizeof(struct soft_trigger_logic));
+	stl->sdi = sdi;
+	stl->trigger = trigger;
+	stl->unitsize = (g_slist_length(sdi->channels) + 7) / 8;
+	stl->prev_sample = g_malloc0(stl->unitsize);
+
+	return stl;
+}
+
+SR_PRIV void soft_trigger_logic_free(struct soft_trigger_logic *stl)
+{
+	g_free(stl->prev_sample);
+	g_free(stl);
+}
+
+static gboolean logic_check_match(struct soft_trigger_logic *stl,
+		uint8_t *sample, struct sr_trigger_match *match)
+{
+	int bit, prev_bit;
+	gboolean result;
+
+	stl->count++;
+	result = FALSE;
+	bit = *(sample + match->channel->index / 8)
+			& (1 << (match->channel->index % 8));
+	if (match->match == SR_TRIGGER_ZERO)
+		result = bit == 0;
+	else if (match->match == SR_TRIGGER_ONE)
+		result = bit != 0;
+	else {
+		/* Edge matches. */
+		if (stl->count == 1)
+			/* First sample, don't have enough for an edge match yet. */
+			return FALSE;
+		prev_bit = *(stl->prev_sample + match->channel->index / 8)
+				& (1 << (match->channel->index % 8));
+		if (match->match == SR_TRIGGER_RISING)
+			result = prev_bit == 0 && bit != 0;
+		else if (match->match == SR_TRIGGER_FALLING)
+			result = prev_bit != 0 && bit == 0;
+		else if (match->match == SR_TRIGGER_EDGE)
+			result = prev_bit != bit;
+	}
+
+	return result;
+}
+
+/* Returns the offset (in samples) within buf of where the trigger
+ * occurred, or -1 if not triggered. */
+SR_PRIV int soft_trigger_logic_check(struct soft_trigger_logic *stl,
+		uint8_t *buf, int len)
+{
+	struct sr_datafeed_packet packet;
+	struct sr_trigger_stage *stage;
+	struct sr_trigger_match *match;
+	GSList *l, *l_stage;
+	int offset;
+	int i;
+	gboolean match_found;
+
+	offset = -1;
+	for (i = 0; i < len; i += stl->unitsize) {
+		l_stage = g_slist_nth(stl->trigger->stages, stl->cur_stage);
+		stage = l_stage->data;
+		if (!stage->matches)
+			/* No matches supplied, client error. */
+			return SR_ERR_ARG;
+
+		match_found = TRUE;
+		for (l = stage->matches; l; l = l->next) {
+			match = l->data;
+			if (!match->channel->enabled)
+				/* Ignore disabled channels with a trigger. */
+				continue;
+			if (!logic_check_match(stl, buf + i, match)) {
+				match_found = FALSE;
+				break;
+			}
+		}
+		memcpy(stl->prev_sample, buf + i, stl->unitsize);
+		if (match_found) {
+			/* Matched on the current stage. */
+			if (l_stage->next) {
+				/* Advance to next stage. */
+				stl->cur_stage++;
+			} else {
+				/* Matched on last stage, fire trigger. */
+				offset = i / stl->unitsize;
+
+				packet.type = SR_DF_TRIGGER;
+				packet.payload = NULL;
+				sr_session_send(stl->sdi, &packet);
+				break;
+			}
+		} else if (stl->cur_stage > 0) {
+			/*
+			 * We had a match at an earlier stage, but failed on the
+			 * current stage. However, we may have a match on this
+			 * stage in the next bit -- trigger on 0001 will fail on
+			 * seeing 00001, so we need to go back to stage 0 -- but
+			 * at the next sample from the one that matched originally,
+			 * which the counter increment at the end of the loop
+			 * takes care of.
+			 */
+			i -= stl->cur_stage * stl->unitsize;
+			if (i < -1)
+				i = -1; /* Oops, went back past this buffer. */
+			/* Reset trigger stage. */
+			stl->cur_stage = 0;
+		}
+	}
+
+	return offset;
+}
+