cameo: added KiCad Gerber input and path merging

- Makefile (OBJS): added gerber.o
- cameo.c (usage, main): new option -g to process input a KiCad Gerber
- gerber.h, gerber.c (gerber_read): parse Gerber files as generated by KiCad
- path.h, path.c (path_reverse_inplace, points_eq, attr_eq, path_connect):
  merge sets of paths with equal endpoints into single paths

cameo/path.c

@@ -147,6 +147,20 @@ struct path *path_reverse(const struct path *path)
 }
 
 
+static void path_reverse_inplace(struct path *path)
+{
+	struct point *points = NULL, *p, *next;
+
+	path->last = path->first;
+	for (p = path->first; p; p = next) {
+		next = p->next;
+		p->next = points;
+		points = p;
+	}
+	path->first = points;
+}
+
+
 static struct point *offset_point(const struct point *a, const struct point *b,
     const struct point *c, double off, int left)
 {
@@ -331,3 +345,54 @@ struct path *path_find_leftmost(struct path *path)
 	}
 	return best;
 }
+
+
+static int points_eq(const struct point *a, const struct point *b)
+{
+	return a->x == b->x && a->y == b->y && a->z == b->z;
+}
+
+
+static int attr_eq(const struct path *a, const struct path *b)
+{
+	return a->r_tool == b->r_tool && a->outside == b->outside &&
+	    a->notch == b->notch;
+}
+
+
+struct path *path_connect(struct path *path)
+{
+	struct path **a, **b;
+	struct path *tmp;
+
+again:
+	for (a = &path; *a; a = &(*a)->next)
+		for (b = &(*a)->next; *b; b = &(*b)->next) {
+			if (!attr_eq(*a, *b))
+				continue;
+			if (points_eq((*a)->last, (*b)->last))
+				path_reverse_inplace(*b);
+			if (points_eq((*a)->last, (*b)->first)) {
+				(*a)->last->next = (*b)->first->next;
+				(*a)->last = (*b)->last;
+				free((*b)->first);
+				tmp = *b;
+				*b = tmp->next;
+				free(tmp);
+				goto again;
+			}
+			if (points_eq((*a)->first, (*b)->first))
+				path_reverse_inplace(*b);
+			if (points_eq((*a)->first, (*b)->last)) {
+				(*b)->last->next = (*a)->first->next;
+				(*b)->last = (*a)->last;
+				free((*a)->first);
+				tmp = *a;
+				*a = *b;
+				free(tmp);
+				*b = (*b)->next;
+				goto again;
+			}
+		}
+	return path;
+}