1 files changed, 24 insertions, 0 deletions
diff --git a/core/gaspressures.c b/core/gaspressures.c
index 1b191369b..72c6d4a57 100644
--- a/core/gaspressures.c
+++ b/core/gaspressures.c
@@ -25,6 +25,30 @@
 #include "gaspressures.h"
 #include "pref.h"
 
+/*
+ * simple structure to track the beginning and end tank pressure as
+ * well as the integral of depth over time spent while we have no
+ * pressure reading from the tank */
+typedef struct pr_track_struct pr_track_t;
+struct pr_track_struct {
+	int start;
+	int end;
+	int t_start;
+	int t_end;
+	int pressure_time;
+	pr_track_t *next;
+};
+
+typedef struct pr_interpolate_struct pr_interpolate_t;
+struct pr_interpolate_struct {
+	int start;
+	int end;
+	int pressure_time;
+	int acc_pressure_time;
+};
+
+enum interpolation_strategy {SAC, TIME, CONSTANT};
+
 static pr_track_t *pr_track_alloc(int start, int t_start)
 {
 	pr_track_t *pt = malloc(sizeof(pr_track_t));