VPM-B: add vpm-b based deco checking.

Check during the trial_ascent() if existing pressure gradient is
smaller than previously calculated max gradient. If not, ascent
is impossible from the vpm-b's point of view.

Signed-off-by: Jan Darowski <jan.darowski@gmail.com>

3 files changed, 21 insertions, 1 deletions

diff --git a/deco.c b/deco.c
index ada13fbb0..47b752ee8 100644
--- a/deco.c
+++ b/deco.c
@@ -210,6 +210,21 @@ double he_factor(int period_in_seconds, int ci)
 	return cache[ci].last_factor;
 }
 
+bool is_vpmb_ok(double pressure)
+{
+	int ci;
+	double gradient;
+	double gas_tension;
+
+	for (ci = 0; ci < 16; ++ci) {
+		gas_tension = tissue_n2_sat[ci] + tissue_he_sat[ci] + vpmb_config.other_gases_pressure;
+		gradient = gas_tension - pressure;
+		if (gradient > total_gradient[ci])
+			return false;
+	}
+	return true;
+}
+
 void vpmb_start_gradient()
 {
 	int ci;
diff --git a/dive.h b/dive.h
index d9885184e..9b44700e7 100644
--- a/dive.h
+++ b/dive.h
@@ -785,6 +785,7 @@ extern void cache_deco_state(double, char **datap);
 extern double restore_deco_state(char *data);
 extern void nuclear_regeneration(double time);
 extern void vpmb_start_gradient();
+extern bool is_vpmb_ok(double pressure);
 
 /* this should be converted to use our types */
 struct divedatapoint {
diff --git a/planner.c b/planner.c
index d376acc7c..0307ea89c 100644
--- a/planner.c
+++ b/planner.c
@@ -836,11 +836,15 @@ bool trial_ascent(int trial_depth, int stoplevel, int avg_depth, int bottom_time
 		tissue_tolerance = add_segment(depth_to_mbar(trial_depth, &displayed_dive) / 1000.0,
 					       gasmix,
 					       TIMESTEP, po2, &displayed_dive, prefs.decosac);
-		if (deco_allowed_depth(tissue_tolerance, surface_pressure, &displayed_dive, 1) > trial_depth - deltad) {
+		if (prefs.deco_mode != VPMB && deco_allowed_depth(tissue_tolerance, surface_pressure, &displayed_dive, 1) > trial_depth - deltad) {
 			/* We should have stopped */
 			clear_to_ascend = false;
 			break;
 		}
+		if (prefs.deco_mode == VPMB && (!is_vpmb_ok(depth_to_mbar(trial_depth, &displayed_dive) / 1000.0))){
+			clear_to_ascend = false;
+			break;
+		}
 		trial_depth -= deltad;
 	}
 	restore_deco_state(trial_cache);