Add support for imperial units

Implements: https://todo.sr.ht/~tsegers/opendeco/1

8 files changed, 70 insertions, 10 deletions

diff --git a/opendeco.toml b/opendeco.toml
index 4884ee5..e549e03 100644
--- a/opendeco.toml
+++ b/opendeco.toml
@@ -2,6 +2,7 @@
 gas                 = "Air"           # Bottom gas used during the dive
 surface_pressure    = 1.01325         # Surface air pressure [bar]
 rmv                 = 20              # RMV during the dive portion of the dive [l/min]
+imperial            = false           # Use imperial units
 
 [deco]
 gflow               = 30              # Gradient factor at the first stop
diff --git a/src/deco.c b/src/deco.c
index e1ea401..349c8e5 100644
--- a/src/deco.c
+++ b/src/deco.c
@@ -9,6 +9,7 @@
 #define RND(x) (round((x) *10000) / 10000)
 
 enum ALGO ALGO_VER = ALGO_VER_DEFAULT;
+enum UNITS UNITS = UNITS_DEFAULT;
 double SURFACE_PRESSURE = SURFACE_PRESSURE_DEFAULT;
 double P_WV = P_WV_DEFAULT;
 
@@ -77,6 +78,37 @@ double msw_to_bar(double msw)
     return msw / 10;
 }
 
+double bar_to_fsw(double bar)
+{
+    return (bar / 1.01325) * 33.0;
+}
+
+double fsw_to_bar(double fsw)
+{
+    return (fsw * 1.01325) / 33.0;
+}
+
+double msw_or_fsw(double msw, double fsw)
+{
+    assert(UNITS == METRIC || UNITS == IMPERIAL);
+
+    return (UNITS == METRIC) ? msw : fsw;
+}
+
+double xsw_to_bar(double xsw)
+{
+    assert(UNITS == METRIC || UNITS == IMPERIAL);
+
+    return (UNITS == METRIC) ? msw_to_bar(xsw) : fsw_to_bar(xsw);
+}
+
+double bar_to_xsw(double bar)
+{
+    assert(UNITS == METRIC || UNITS == IMPERIAL);
+
+    return (UNITS == METRIC) ? bar_to_msw(bar) : bar_to_fsw(bar);
+}
+
 double abs_depth(double gd)
 {
     return gd + SURFACE_PRESSURE;
diff --git a/src/deco.h b/src/deco.h
index 35905ca..2500580 100644
--- a/src/deco.h
+++ b/src/deco.h
@@ -14,6 +14,7 @@
 #define P_WV_SCHR 0.0493 /* Schreiner value, Rq = 0.8, most conservative */
 
 #define ALGO_VER_DEFAULT ZHL_16C
+#define UNITS_DEFAULT METRIC
 #define SURFACE_PRESSURE_DEFAULT 1.01325
 #define P_WV_DEFAULT P_WV_BUHL
 
@@ -25,6 +26,11 @@
 #define MOD_AUTO 0
 
 /* types */
+enum UNITS {
+    METRIC,
+    IMPERIAL,
+};
+
 enum ALGO {
     ZHL_16A = 0,
     ZHL_16B = 1,
@@ -50,6 +56,7 @@ typedef struct gas_t {
 
 /* global variables */
 extern enum ALGO ALGO_VER;
+extern enum UNITS UNITS;
 extern double SURFACE_PRESSURE;
 extern double P_WV;
 
@@ -61,6 +68,11 @@ extern int LAST_STOP_AT_SIX;
 /* functions */
 double bar_to_msw(double bar);
 double msw_to_bar(double msw);
+double bar_to_fsw(double bar);
+double fsw_to_bar(double msw);
+double msw_or_fsw(double msw, double fsw);
+double xsw_to_bar(double xsw);
+double bar_to_xsw(double bar);
 double abs_depth(double gd);
 double gauge_depth(double ad);
 
diff --git a/src/opendeco-cli.c b/src/opendeco-cli.c
index 5f6b627..d8da388 100644
--- a/src/opendeco-cli.c
+++ b/src/opendeco-cli.c
@@ -26,6 +26,7 @@ static struct argp_option options[] = {
     {"gas",        'g', "STRING", 0,                   "Set the bottom gas used during the dive, defaults to Air",        2 },
     {"pressure",   'p', "NUMBER", 0,                   "Set the surface air pressure, defaults to 1.01325bar or 1atm",    3 },
     {"rmv",        'r', "NUMBER", 0,                   "Set the RMV during the dive portion of the dive, defaults to 20", 4 },
+    {"imperial",   'i', 0,        0,                   "Use imperial units (fsw)",                                        5 },
 
     {0,            0,   0,        0,                   "Deco options:",                                                   0 },
     {"gflow",      'L', "NUMBER", 0,                   "Set the gradient factor at the first stop, defaults to 30",       5 },
@@ -83,6 +84,9 @@ static error_t parse_opt(int key, char *arg, struct argp_state *state)
     case 'r':
         arguments->RMV_DIVE = arg ? atof(arg) : -1;
         break;
+    case 'i':
+        arguments->UNITS = IMPERIAL;
+        break;
     case 'L':
         arguments->gflow = arg ? atoi(arg) : -1;
         break;
diff --git a/src/opendeco-conf.c b/src/opendeco-conf.c
index e044c90..977bfc5 100644
--- a/src/opendeco-conf.c
+++ b/src/opendeco-conf.c
@@ -49,6 +49,11 @@ int opendeco_conf_parse(const char *confpath, struct arguments *arguments)
 
         if (r.ok)
             arguments->RMV_DIVE = r.u.d;
+
+        toml_datum_t i = toml_bool_in(dive, "imperial");
+
+        if (i.ok)
+            arguments->UNITS = i.u.b ? IMPERIAL : METRIC;
     }
 
     toml_table_t *deco = toml_table_in(od_conf, "deco");
diff --git a/src/opendeco-conf.h b/src/opendeco-conf.h
index 8845409..359889a 100644
--- a/src/opendeco-conf.h
+++ b/src/opendeco-conf.h
@@ -3,6 +3,8 @@
 #ifndef OPENDECOCONF_H
 #define OPENDECOCONF_H
 
+#include "deco.h"
+
 #ifndef VERSION
 #define VERSION "unknown version"
 #endif
@@ -21,6 +23,7 @@ struct arguments {
     double RMV_DIVE;
     double RMV_DECO;
     int SHOW_TRAVEL;
+    enum UNITS UNITS;
 };
 
 int opendeco_conf_parse(const char *confpath, struct arguments *arguments);
diff --git a/src/opendeco.c b/src/opendeco.c
index 029a81f..fe9a1d1 100644
--- a/src/opendeco.c
+++ b/src/opendeco.c
@@ -12,7 +12,7 @@
 #include "output.h"
 #include "schedule.h"
 
-#define MOD_OXY (abs_depth(msw_to_bar(6)))
+#define MOD_OXY (abs_depth(xsw_to_bar(msw_or_fsw(6, 20))))
 
 #define RMV_DIVE_DEFAULT 20
 #define RMV_DECO_DEFAULT 15
@@ -154,6 +154,7 @@ int main(int argc, char *argv[])
         .RMV_DIVE = RMV_DIVE_DEFAULT,
         .RMV_DECO = RMV_DECO_DEFAULT,
         .SHOW_TRAVEL = SHOW_TRAVEL_DEFAULT,
+        .UNITS = UNITS_DEFAULT,
     };
 
     opendeco_conf_parse("opendeco.toml", &arguments);
@@ -166,11 +167,12 @@ int main(int argc, char *argv[])
     RMV_DIVE = arguments.RMV_DIVE;
     RMV_DECO = arguments.RMV_DECO;
     SHOW_TRAVEL = arguments.SHOW_TRAVEL;
+    UNITS = arguments.UNITS;
 
     /* setup */
     decostate_t ds;
-    init_decostate(&ds, arguments.gflow, arguments.gfhigh, msw_to_bar(3));
-    double dec_per_min = msw_to_bar(9);
+    init_decostate(&ds, arguments.gflow, arguments.gfhigh, xsw_to_bar(msw_or_fsw(3, 10)));
+    double dec_per_min = xsw_to_bar(msw_or_fsw(9, 30));
 
     gas_t bottom_gas;
     scan_gas(&bottom_gas, arguments.gas);
@@ -184,12 +186,12 @@ int main(int argc, char *argv[])
             deco_gasses[i].mod = MOD_OXY;
 
     /* simulate dive */
-    double descent_time = msw_to_bar(arguments.depth) / dec_per_min;
+    double descent_time = xsw_to_bar(arguments.depth) / dec_per_min;
     double bottom_time = max(1, arguments.time - descent_time);
 
     waypoint_t waypoints[] = {
-        {.depth = abs_depth(msw_to_bar(arguments.depth)), .time = descent_time, &bottom_gas},
-        {.depth = abs_depth(msw_to_bar(arguments.depth)), .time = bottom_time,  &bottom_gas},
+        {.depth = abs_depth(xsw_to_bar(arguments.depth)), .time = descent_time, &bottom_gas},
+        {.depth = abs_depth(xsw_to_bar(arguments.depth)), .time = bottom_time,  &bottom_gas},
     };
 
     waypoint_callback_t print_segment_callback = {
diff --git a/src/output.c b/src/output.c
index 52b45dd..5997f31 100644
--- a/src/output.c
+++ b/src/output.c
@@ -69,8 +69,8 @@ void print_planline(wchar_t sign, double depth, double time, double runtime, con
 
     static gas_t last_gas;
 
-    const int depth_m = round(bar_to_msw(gauge_depth(depth)));
-    const int ead_m = round(bar_to_msw(max(0, gauge_depth(ead(depth, gas)))));
+    const int depth_x = round(bar_to_xsw(gauge_depth(depth)));
+    const int ead_x = round(bar_to_xsw(max(0, gauge_depth(ead(depth, gas)))));
 
     wchar_t swi = L' ';
 
@@ -86,14 +86,15 @@ void print_planline(wchar_t sign, double depth, double time, double runtime, con
 
     /* only print ead and pO2 on stops */
     if (sign == LVL) {
-        snprintf(eadbuf, 4, "%3i", ead_m);
+        snprintf(eadbuf, 4, "%3i", ead_x);
         snprintf(pO2buf, 5, "%4.2f", ppO2(depth, gas));
     } else {
         snprintf(eadbuf, 4, "%3s", "-");
         snprintf(pO2buf, 5, "%4s", "-");
     }
 
-    wprintf(L" %lc  %4im  %8s  %-7s  %lc %-9s  %s  %s\n", sign, depth_m, timbuf, runbuf, swi, gasbuf, pO2buf, eadbuf);
+    wprintf(L" %lc  %4i%s  %8s  %-7s  %lc %-9s  %s  %s\n", sign, depth_x, (UNITS == METRIC) ? "m" : "ft", timbuf,
+            runbuf, swi, gasbuf, pO2buf, eadbuf);
 }
 
 void print_planfoot(const decostate_t *ds)