Remove redundant linear sample tank pressure data

I've seen at least DivingLog do this. If you manually enter beginning and
end pressure for a tank it will either linearize the samples in between or
offer to simulate a dive (with constant SAC rate). At least the first case
is reasonably easy to detect. We throw out those samples and ensure that
we still have valid beginning and end pressure for that dive.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

1 files changed, 48 insertions, 5 deletions

diff --git a/dive.c b/dive.c
index cd797d276..31be3291d 100644
--- a/dive.c
+++ b/dive.c
@@ -236,7 +236,7 @@ static int same_rounded_pressure(pressure_t a, pressure_t b)
 
 struct dive *fixup_dive(struct dive *dive)
 {
-	int i;
+	int i,j;
 	double depthtime = 0;
 	int lasttime = 0;
 	int lastindex = -1;
@@ -244,6 +244,7 @@ struct dive *fixup_dive(struct dive *dive)
 	int maxdepth = 0, mintemp = 0;
 	int lastdepth = 0;
 	int lasttemp = 0, lastpressure = 0;
+	int pressure_delta[MAX_CYLINDERS] = {INT_MAX, };
 
 	for (i = 0; i < dive->samples; i++) {
 		struct sample *sample = dive->sample + i;
@@ -253,10 +254,25 @@ struct dive *fixup_dive(struct dive *dive)
 		int pressure = sample->cylinderpressure.mbar;
 		int index = sample->cylinderindex;
 
-		/* Remove duplicate redundant pressure information */
-		if (pressure == lastpressure && index == lastindex)
-			sample->cylinderpressure.mbar = 0;
-
+		if (index == lastindex) {
+			/* Remove duplicate redundant pressure information */
+			if (pressure == lastpressure)
+				sample->cylinderpressure.mbar = 0;
+			/* check for simply linear data in the samples
+			   +INT_MAX means uninitialized, -INT_MAX means not linear */
+			if (pressure_delta[index] != -INT_MAX && lastpressure) {
+				if (pressure_delta[index] == INT_MAX) {
+					pressure_delta[index] = abs(pressure - lastpressure);
+				} else {
+					int cur_delta = abs(pressure - lastpressure);
+					if (cur_delta && abs(cur_delta - pressure_delta[index]) > 150) {
+						/* ok the samples aren't just a linearisation
+						 * between start and end */
+						pressure_delta[index] = -INT_MAX;
+					}
+				}
+			}
+		}
 		lastindex = index;
 		lastpressure = pressure;
 
@@ -290,6 +306,33 @@ struct dive *fixup_dive(struct dive *dive)
 		lastdepth = depth;
 		lasttime = time;
 	}
+	/* if all the samples for a cylinder have pressure data that
+	 * is basically equidistant throw out the sample cylinder pressure
+	 * information but make sure we still have a valid start and end
+	 * pressure
+	 * this happens when DivingLog decides to linearalize the
+	 * pressure between beginning and end and for strange reasons
+	 * decides to put that in the sample data as if it came from
+	 * the dive computer; we don't want that (we'll visualize with
+	 * constant SAC rate instead)
+	 * WARNING WARNING - I have only seen this in single tank dives
+	 * --- maybe I should try to create a multi tank dive and see what
+	 * --- divinglog does there - but the code right now is only tested
+	 * --- for the single tank case */
+	for (j = 0; j < MAX_CYLINDERS; j++) {
+		if (abs(pressure_delta[j]) != INT_MAX) {
+			cylinder_t *cyl = dive->cylinder + j;
+			for (i = 0; i < dive->samples; i++)
+				if (dive->sample[i].cylinderindex == j)
+					dive->sample[i].cylinderpressure.mbar = 0;
+			if (! cyl->start.mbar)
+				cyl->start.mbar = cyl->sample_start.mbar;
+			if (! cyl->end.mbar)
+				cyl->end.mbar = cyl->sample_end.mbar;
+			cyl->sample_start.mbar = 0;
+			cyl->sample_end.mbar = 0;
+		}
+	}
 	if (end < 0)
 		return dive;