Add option to perform last deco stop at 6m instead of 3m

4 files changed, 24 insertions, 6 deletions

diff --git a/README.md b/README.md
index 76f1a8c..2dfd535 100644
--- a/README.md
+++ b/README.md
@@ -27,6 +27,8 @@ Implementation of Buhlmann ZH-L16 with Gradient Factors:
 
   -s                         Only switch gas at deco stops
 
+  -6                         Perform last deco stop at 6m
+
  Informational options:
 
   -?, --help                 Give this help list
diff --git a/src/deco.c b/src/deco.c
index a03ed34..204a2a7 100644
--- a/src/deco.c
+++ b/src/deco.c
@@ -15,6 +15,8 @@ double P_WV = P_WV_DEFAULT;
 double PO2_MAX = PO2_MAX_DEFAULT;
 double END_MAX = END_MAX_DEFAULT;
 
+int LAST_STOP_AT_SIX = LAST_STOP_AT_SIX_DEFAULT;
+
 typedef struct zhl_n2_t {
     double t;
     double a[3];
@@ -213,7 +215,12 @@ double round_ceiling(const decostate_t *ds, const double c)
 {
     assert(ds->ceil_multiple != 0);
 
-    return abs_depth(ds->ceil_multiple * ceil(RND(gauge_depth(c) / ds->ceil_multiple)));
+    int numbered_stop = ceil(RND(gauge_depth(c) / ds->ceil_multiple));
+
+    if (numbered_stop == 1 && LAST_STOP_AT_SIX)
+        numbered_stop = 2;
+
+    return abs_depth(ds->ceil_multiple * numbered_stop);
 }
 
 double ceiling(const decostate_t *ds, double gf)
diff --git a/src/deco.h b/src/deco.h
index 16072a1..11f6bc9 100644
--- a/src/deco.h
+++ b/src/deco.h
@@ -20,6 +20,8 @@
 #define PO2_MAX_DEFAULT 1.6
 #define END_MAX_DEFAULT 4.01325
 
+#define LAST_STOP_AT_SIX_DEFAULT 0
+
 #define MOD_AUTO 0
 
 /* types */
@@ -54,6 +56,8 @@ extern double P_WV;
 extern double PO2_MAX;
 extern double END_MAX;
 
+extern int LAST_STOP_AT_SIX;
+
 /* functions */
 double bar_to_msw(const double bar);
 double msw_to_bar(const double msw);
diff --git a/src/opendeco.c b/src/opendeco.c
index 9329383..ae95f58 100644
--- a/src/opendeco.c
+++ b/src/opendeco.c
@@ -38,6 +38,7 @@ static struct argp_option options[] = {
     {"gfhigh",     'h', "NUMBER", 0,                   "Set the gradient factor at the surface, defaults to 75",       5},
     {"decogasses", 'G', "LIST",   0,                   "Set the gasses available for deco",                            6},
     {0,            's', 0,        OPTION_ARG_OPTIONAL, "Only switch gas at deco stops",                                7},
+    {0,            '6', 0,        OPTION_ARG_OPTIONAL, "Perform last deco stop at 6m",                                 8},
     {0,            0,   0,        0,                   "Informational options:",                                       0},
     {0,            0,   0,        0,                   0,                                                              0}
 };
@@ -51,6 +52,7 @@ struct arguments {
     char *decogasses;
     double SURFACE_PRESSURE;
     int SWITCH_INTERMEDIATE;
+    int LAST_STOP_AT_SIX;
 };
 
 static error_t parse_opt(int key, char *arg, struct argp_state *state)
@@ -73,6 +75,9 @@ static error_t parse_opt(int key, char *arg, struct argp_state *state)
     case 's':
         arguments->SWITCH_INTERMEDIATE = 0;
         break;
+    case '6':
+        arguments->LAST_STOP_AT_SIX = 1;
+        break;
     case 'G':
         arguments->decogasses = arg;
         break;
@@ -174,17 +179,17 @@ int main(int argc, char *argv[])
         .gflow = 30,
         .gfhigh = 75,
         .decogasses = "",
-        .SURFACE_PRESSURE = 0,
-        .SWITCH_INTERMEDIATE = 1,
+        .SURFACE_PRESSURE = SURFACE_PRESSURE_DEFAULT,
+        .SWITCH_INTERMEDIATE = SWITCH_INTERMEDIATE_DEFAULT,
+        .LAST_STOP_AT_SIX = LAST_STOP_AT_SIX_DEFAULT,
     };
 
     argp_parse(&argp, argc, argv, 0, 0, &arguments);
 
     /* apply global options */
-    if (arguments.SURFACE_PRESSURE > 0)
-        SURFACE_PRESSURE = arguments.SURFACE_PRESSURE;
-
+    SURFACE_PRESSURE = arguments.SURFACE_PRESSURE;
     SWITCH_INTERMEDIATE = arguments.SWITCH_INTERMEDIATE;
+    LAST_STOP_AT_SIX = arguments.LAST_STOP_AT_SIX;
 
     /* setup */
     decostate_t ds;