Add helper 'for_each_dive()' dive iterator

It's an easy thing to do, but the for-loop ends up being pretty ugly, so
hide it behind the macro.

It would be even prettier with one of the (few) useful C99 features:
local for-loop variables.  However, gcc needs special command line
options, and other compilers may not do it at all. So instead of doing

   #define for_each_dive(_x) \
      for (int _i = 0; ((_x) = get_dive(_i)) != NULL; _i++)

we require that the user declare the index iterator too, and the use
syntax becomes

   for_each_dive(idx, dive) {
	... use idx/dive here ...
   }

And hey, maybe somebody actually will want to use the index, so maybe
that's not all bad.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

dive.h

@@ -295,6 +295,16 @@ static inline struct dive *get_dive(unsigned int nr)
 	return dive_table.dives[nr];
 }
 
+/*
+ * Iterate over each dive, with the first parameter being the index
+ * iterator variable, and the second one being the dive one.
+ *
+ * I don't think anybody really wants the index, and we could make
+ * it local to the for-loop, but that would make us requires C99.
+ */
+#define for_each_dive(_i,_x) \
+	for ((_i) = 0; ((_x) = get_dive(_i)) != NULL; (_i)++)
+
 extern void parse_xml_init(void);
 extern void parse_xml_buffer(const char *url, const char *buf, int size, GError **error);
 extern void set_filename(const char *filename);

divelist.c

@@ -85,7 +85,7 @@ void dump_selection(void)
 	struct dive *dive;
 
 	printf("currently selected are %d dives:", amount_selected);
-	for (i = 0; (dive = get_dive(i)) != NULL; i++) {
+	for_each_dive(i, dive) {
 		if (dive->selected)
 			printf(" %d", i);
 	}

info.c

@@ -519,7 +519,7 @@ int edit_multi_dive_info(struct dive *single_dive)
 			int i;
 			struct dive *dive;
 
-			for (i = 0; (dive = get_dive(i)) != NULL; i++) {
+			for_each_dive(i, dive) {
 				if (dive == master || !dive->selected)
 					continue;
 				/* copy all "info" fields */

statistics.c

@@ -151,7 +151,7 @@ void process_selected_dives(void)
 	memset(&stats_selection, 0, sizeof(stats_selection));
 
 	nr = 0;
-	for (i = 0; (dive = get_dive(i)) != NULL; ++i) {
+	for_each_dive(i, dive) {
 		if (dive->selected) {
 			process_dive(dive, &stats_selection);
 			nr++;