Introduce A2L methods

The memory allocation for sr_datafeed_logic is broken, the memory
will never be freed. #994 is used to handle this issue.

Makefile.am

@@ -50,6 +50,7 @@ lib_LTLIBRARIES = libsigrok.la
 # Backend files
 libsigrok_la_SOURCES = \
 	src/backend.c \
+	src/conversion.c \
 	src/device.c \
 	src/session.c \
 	src/session_file.c \

bindings/cxx/classes.cpp

@@ -1287,6 +1287,48 @@ vector<const QuantityFlag *> Analog::mq_flags() const
 	return QuantityFlag::flags_from_mask(_structure->meaning->mqflags);
 }
 
+shared_ptr<Logic> Analog::get_logic_via_threshold(float threshold,
+	uint8_t *data_ptr) const
+{
+	auto datafeed = g_new(struct sr_datafeed_logic, 1);
+	datafeed->length = num_samples();
+	datafeed->unitsize = 1;
+
+	if (data_ptr)
+		datafeed->data = data_ptr;
+	else
+		datafeed->data = g_malloc(datafeed->length);
+
+	shared_ptr<Logic> logic =
+		shared_ptr<Logic>{new Logic{datafeed}, default_delete<Logic>{}};
+
+	check(sr_a2l_threshold(_structure, threshold,
+		(uint8_t*)datafeed->data, datafeed->length));
+
+	return logic;
+}
+
+shared_ptr<Logic> Analog::get_logic_via_schmitt_trigger(float lo_thr,
+	float hi_thr, uint8_t *state, uint8_t *data_ptr) const
+{
+	auto datafeed = g_new(struct sr_datafeed_logic, 1);
+	datafeed->length = num_samples();
+	datafeed->unitsize = 1;
+
+	if (data_ptr)
+		datafeed->data = data_ptr;
+	else
+		datafeed->data = g_malloc(datafeed->length);
+
+	shared_ptr<Logic> logic =
+		shared_ptr<Logic>{new Logic{datafeed}, default_delete<Logic>{}};
+
+	check(sr_a2l_schmitt_trigger(_structure, lo_thr, hi_thr, state,
+		(uint8_t*)datafeed->data, datafeed->length));
+
+	return logic;
+}
+
 Rational::Rational(const struct sr_rational *structure) :
 	_structure(structure)
 {

bindings/cxx/include/libsigrokcxx/libsigrokcxx.hpp

@@ -758,6 +758,8 @@ private:
 	const struct sr_datafeed_logic *_structure;
 
 	friend class Packet;
+	friend class Analog;
+	friend struct std::default_delete<Logic>;
 };
 
 /** Payload of a datafeed packet with analog data */
@@ -803,6 +805,34 @@ public:
 	const Unit *unit() const;
 	/** Measurement flags associated with the samples in this packet. */
 	vector<const QuantityFlag *> mq_flags() const;
+	/**
+	 * Provides a Logic packet that contains a conversion of the analog
+	 * data using a simple threshold.
+	 *
+	 * @param threshold Threshold to use.
+	 * @param data_ptr Pointer to num_samples() bytes where the logic
+	 *                 samples are stored. When nullptr, memory for
+	 *                 logic->data_pointer() will be allocated and must
+	 *                 be freed by the caller.
+	 */
+	shared_ptr<Logic> get_logic_via_threshold(float threshold,
+		uint8_t *data_ptr=nullptr) const;
+	/**
+	 * Provides a Logic packet that contains a conversion of the analog
+	 * data using a Schmitt-Trigger.
+	 *
+	 * @param lo_thr Low threshold to use (anything below this is low).
+	 * @param hi_thr High threshold to use (anything above this is high).
+	 * @param state Points to a byte that contains the current state of the
+	 *              converter. For best results, set to value of logic
+	 *              sample n-1.
+	 * @param data_ptr Pointer to num_samples() bytes where the logic
+	 *                 samples are stored. When nullptr, memory for
+	 *                 logic->data_pointer() will be allocated and must be
+	 *                 freed by the caller.
+	 */
+	shared_ptr<Logic> get_logic_via_schmitt_trigger(float lo_thr,
+		float hi_thr, uint8_t *state, uint8_t *data_ptr=nullptr) const;
 private:
 	explicit Analog(const struct sr_datafeed_analog *structure);
 	~Analog();

include/libsigrok/proto.h

@@ -50,6 +50,14 @@ SR_API GSList *sr_buildinfo_libs_get(void);
 SR_API char *sr_buildinfo_host_get(void);
 SR_API char *sr_buildinfo_scpi_backends_get(void);
 
+/*--- conversion.c ----------------------------------------------------------*/
+
+SR_API int sr_a2l_threshold(const struct sr_datafeed_analog *analog,
+		float threshold, uint8_t *output, uint64_t count);
+SR_API int sr_a2l_schmitt_trigger(const struct sr_datafeed_analog *analog,
+		float lo_thr, float hi_thr, uint8_t *state, uint8_t *output,
+		uint64_t count);
+
 /*--- log.c -----------------------------------------------------------------*/
 
 typedef int (*sr_log_callback)(void *cb_data, int loglevel,

src/conversion.c

@@ -0,0 +1,107 @@
+/*
+ * This file is part of the libsigrok project.
+ *
+ * Copyright (C) 2017 Soeren Apel <soeren@apelpie.net>
+ *
+ * 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, see <http://www.gnu.org/licenses/>.
+ */
+
+/**
+ * @file
+ *
+ * Conversion helper functions.
+ */
+
+#include <libsigrok/libsigrok.h>
+#include "libsigrok-internal.h"
+
+#define LOG_PREFIX "conv"
+
+/**
+ * Convert analog values to logic values by using a fixed threshold.
+ *
+ * @param[in] analog The analog input values.
+ * @param[in] threshold The threshold to use.
+ * @param[out] output The converted output values; either 0 or 1. Must provide
+ *                    space for count bytes.
+ * @param[in] count The number of samples to process.
+ *
+ * @return SR_OK on success or SR_ERR on failure.
+ */
+SR_API int sr_a2l_threshold(const struct sr_datafeed_analog *analog,
+		float threshold, uint8_t *output, uint64_t count)
+{
+	float *input;
+
+	if (!analog->encoding->is_float) {
+		input = g_try_malloc(sizeof(float) * count);
+		if (!input)
+			return SR_ERR;
+
+		sr_analog_to_float(analog, input);
+	} else
+		input = analog->data;
+
+	for (uint64_t i = 0; i < count; i++)
+		output[i] = (input[i] >= threshold) ? 1 : 0;
+
+	if (!analog->encoding->is_float)
+		g_free(input);
+
+	return SR_OK;
+}
+
+/**
+ * Convert analog values to logic values by using a Schmitt-trigger algorithm.
+ *
+ * @param analog The analog input values.
+ * @param lo_thr The low threshold - result becomes 0 below it.
+ * @param lo_thr The high threshold - result becomes 1 above it.
+ * @param state The internal converter state. Must contain the state of logic
+ *        sample n-1, will contain the state of logic sample n+count upon exit.
+ * @param output The converted output values; either 0 or 1. Must provide
+ *        space for count bytes.
+ * @param count The number of samples to process.
+ *
+ * @return SR_OK on success or SR_ERR on failure.
+ */
+SR_API int sr_a2l_schmitt_trigger(const struct sr_datafeed_analog *analog,
+		float lo_thr, float hi_thr, uint8_t *state, uint8_t *output,
+		uint64_t count)
+{
+	float *input;
+
+	if (!analog->encoding->is_float) {
+		input = g_try_malloc(sizeof(float) * count);
+		if (!input)
+			return SR_ERR;
+
+		sr_analog_to_float(analog, input);
+	} else
+		input = analog->data;
+
+	for (uint64_t i = 0; i < count; i++) {
+		if (input[i] < lo_thr)
+			*state = 0;
+		else if (input[i] > hi_thr)
+			*state = 1;
+
+		output[i] = *state;
+	}
+
+	if (!analog->encoding->is_float)
+		g_free(input);
+
+	return SR_OK;
+}