Remove is_air() and convert its users to gasmix

Also make gasname() and get_gas_string() global functions (which allows us
to delete code elsewhere).

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

dive.c

@@ -546,7 +546,7 @@ void sanitize_gasmix(struct gasmix *mix)
 		if (!o2)
 			return;
 		/* 20.8% to 21% O2 is just air */
-		if (is_air(o2, he)) {
+		if (gasmix_is_air(mix)) {
 			mix->o2.permille = 0;
 			return;
 		}

dive.h

@@ -108,14 +108,11 @@ extern void sanitize_gasmix(struct gasmix *mix);
 extern int gasmix_distance(const struct gasmix *a, const struct gasmix *b);
 extern struct gasmix *get_gasmix_from_event(struct event *ev);
 
-static inline bool is_air(int o2, int he)
-{
-	return (he == 0) && (o2 == 0 || ((o2 >= O2_IN_AIR - 1) && (o2 <= O2_IN_AIR + 1)));
-}
-
 static inline bool gasmix_is_air(const struct gasmix *gasmix)
 {
-	return is_air(gasmix->o2.permille, gasmix->he.permille);
+	int o2 = gasmix->o2.permille;
+	int he = gasmix->he.permille;
+	return (he == 0) && (o2 == 0 || ((o2 >= O2_IN_AIR - 1) && (o2 <= O2_IN_AIR + 1)));
 }
 
 /* in the planner we use a null gasmix to indicate that we keep using the gas as before
@@ -140,6 +137,9 @@ static inline depth_t gas_mod(struct gasmix *mix, pressure_t po2_limit) {
 	return depth;
 }
 
+void get_gas_string(const struct gasmix *gasmix, char *text, int len);
+const char *gasname(const struct gasmix *gasmix);
+
 struct sample {
 	duration_t time;
 	depth_t depth;

equipment.c

@@ -97,6 +97,24 @@ bool cylinder_is_used(struct dive *d, cylinder_t *cyl)
 	return false;
 }
 
+void get_gas_string(const struct gasmix *gasmix, char *text, int len)
+{
+	if (gasmix_is_air(gasmix))
+		snprintf(text, len, "%s", translate("gettextFromC", "air"));
+	else if (get_he(gasmix) == 0)
+		snprintf(text, len, translate("gettextFromC", "EAN%d"), (get_o2(gasmix) + 5) / 10);
+	else
+		snprintf(text, len, "(%d/%d)", (get_o2(gasmix) + 5) / 10, (get_he(gasmix) + 5) / 10);
+}
+
+/* Returns a static char buffer - only good for immediate use by printf etc */
+const char *gasname(const struct gasmix *gasmix)
+{
+	static char gas[64];
+	get_gas_string(gasmix, gas, sizeof(gas));
+	return gas;
+}
+
 bool weightsystem_none(void *_data)
 {
 	weightsystem_t *ws = _data;

planner.c

@@ -93,24 +93,6 @@ int get_gasidx(struct dive *dive, struct gasmix *mix)
 	return -1;
 }
 
-static void get_gas_string(const struct gasmix *gasmix, char *text, int len)
-{
-	if (gasmix_is_air(gasmix))
-		snprintf(text, len, "%s", translate("gettextFromC", "air"));
-	else if (get_he(gasmix) == 0)
-		snprintf(text, len, translate("gettextFromC", "EAN%d"), (get_o2(gasmix) + 5) / 10);
-	else
-		snprintf(text, len, "(%d/%d)", (get_o2(gasmix) + 5) / 10, (get_he(gasmix) + 5) / 10);
-}
-
-/* Returns a static char buffer - only good for immediate use by printf etc */
-static const char *gasname(const struct gasmix *gasmix)
-{
-	static char gas[64];
-	get_gas_string(gasmix, gas, sizeof(gas));
-	return gas;
-}
-
 double interpolate_transition(struct dive *dive, int t0, int t1, int d0, int d1, const struct gasmix *gasmix, int ppo2)
 {
 	int j;

statistics.c

@@ -337,7 +337,6 @@ char *get_gaslist(struct dive *dive)
 {
 	int idx, offset = 0;
 	static char buf[MAXBUF];
-	int o2, he;
 
 	buf[0] = '\0';
 	for (idx = 0; idx < MAX_CYLINDERS; idx++) {
@@ -345,20 +344,11 @@ char *get_gaslist(struct dive *dive)
 		if (!is_gas_used(dive, idx))
 			continue;
 		cyl = &dive->cylinder[idx];
-		o2 = get_o2(&cyl->gasmix);
-		he = get_he(&cyl->gasmix);
 		if (offset > 0) {
 			strncpy(buf + offset, "\n", MAXBUF - offset);
 			offset = strlen(buf);
 		}
-		if (is_air(o2, he))
+		strncpy(buf + offset, gasname(&cyl->gasmix), MAXBUF - offset);
-			strncpy(buf + offset, translate("gettextFromC", "air"), MAXBUF - offset);
-		else if (he == 0)
-			snprintf(buf + offset, MAXBUF - offset,
-				 translate("gettextFromC", "EAN%d"), (o2 + 5) / 10);
-		else
-			snprintf(buf + offset, MAXBUF - offset,
-				 "%d/%d", (o2 + 5) / 10, (he + 5) / 10);
 		offset = strlen(buf);
 	}
 	if (*buf == '\0')