From da2446283aaf3be344ba772738333058a17eca0f Mon Sep 17 00:00:00 2001
From: Jef Driesen <jef@libdivecomputer.org>
Date: Fri, 18 Jun 2021 20:36:31 +0200
Subject: [PATCH] Move the unit conversion to the last moment

Processing the data in device units, and performing the unit conversion
only at the very last moment, avoids the need for intermediate floating
point math and thus possible rounding errors. In practice this is not
really an important issue, except for some case where a negative zero
value was returned.
---
 src/uwatec_smart_parser.c | 30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/src/uwatec_smart_parser.c b/src/uwatec_smart_parser.c
index be74b1c..dd867e4 100644
--- a/src/uwatec_smart_parser.c
+++ b/src/uwatec_smart_parser.c
@@ -940,9 +940,9 @@ uwatec_smart_parse (uwatec_smart_parser_t *parser, dc_sample_callback_t callback
 	unsigned int rbt = 99;
 	unsigned int tank = 0;
 	unsigned int gasmix = 0;
-	double depth = 0, depth_calibration = 0;
-	double temperature = 0;
-	double pressure = 0;
+	unsigned int depth = 0, depth_calibration = 0;
+	int temperature = 0;
+	unsigned int pressure = 0;
 	unsigned int heartrate = 0;
 	unsigned int bearing = 0;
 	unsigned int bookmark = 0;
@@ -1026,8 +1026,8 @@ uwatec_smart_parse (uwatec_smart_parser_t *parser, dc_sample_callback_t callback
 		const uwatec_smart_event_info_t *events = NULL;
 		switch (table[id].type) {
 		case PRESSURE_DEPTH:
-			pressure += ((signed char) ((svalue >> NBITS) & 0xFF)) / 4.0;
-			depth += ((signed char) (svalue & 0xFF)) / 50.0;
+			pressure += (signed char) ((svalue >> NBITS) & 0xFF);
+			depth += (signed char) (svalue & 0xFF);
 			complete = 1;
 			break;
 		case RBT:
@@ -1040,37 +1040,37 @@ uwatec_smart_parse (uwatec_smart_parser_t *parser, dc_sample_callback_t callback
 			break;
 		case TEMPERATURE:
 			if (table[id].absolute) {
-				temperature = svalue / 2.5;
+				temperature = svalue;
 				have_temperature = 1;
 			} else {
-				temperature += svalue / 2.5;
+				temperature += svalue;
 			}
 			break;
 		case PRESSURE:
 			if (table[id].absolute) {
 				if (parser->trimix) {
 					tank = (value & 0xF000) >> 12;
-					pressure = (value & 0x0FFF) / 4.0;
+					pressure = (value & 0x0FFF);
 				} else {
 					tank = table[id].index;
-					pressure = value / 4.0;
+					pressure = value;
 				}
 				have_pressure = 1;
 				gasmix = tank;
 			} else {
-				pressure += svalue / 4.0;
+				pressure += svalue;
 			}
 			break;
 		case DEPTH:
 			if (table[id].absolute) {
-				depth = value / 50.0;
+				depth = value;
 				if (!calibrated) {
 					calibrated = 1;
 					depth_calibration = depth;
 				}
 				have_depth = 1;
 			} else {
-				depth += svalue / 50.0;
+				depth += svalue;
 			}
 			complete = 1;
 			break;
@@ -1195,7 +1195,7 @@ uwatec_smart_parse (uwatec_smart_parser_t *parser, dc_sample_callback_t callback
 			}
 
 			if (have_temperature) {
-				sample.temperature = temperature;
+				sample.temperature = temperature / 2.5;
 				if (callback) callback (DC_SAMPLE_TEMPERATURE, sample, userdata);
 			}
 
@@ -1216,7 +1216,7 @@ uwatec_smart_parse (uwatec_smart_parser_t *parser, dc_sample_callback_t callback
 				idx = uwatec_smart_find_tank(parser, tank);
 				if (idx < parser->ntanks) {
 					sample.pressure.tank = idx;
-					sample.pressure.value = pressure;
+					sample.pressure.value = pressure / 4.0;
 					if (callback) callback (DC_SAMPLE_PRESSURE, sample, userdata);
 				}
 			}
@@ -1233,7 +1233,7 @@ uwatec_smart_parse (uwatec_smart_parser_t *parser, dc_sample_callback_t callback
 			}
 
 			if (have_depth) {
-				sample.depth = (depth - depth_calibration) / salinity;
+				sample.depth = (depth - depth_calibration) / 50.0 / salinity;
 				if (callback) callback (DC_SAMPLE_DEPTH, sample, userdata);
 			}