Merge pull request #44968 from John-Candlebury/fix-road-infinite-loop

Remove posible infinite loop in place_roads
CleverRaven · Oct 20, 2020 · ea096c2 · ea096c2
2 parents e6cd482 + 8927eba
commit ea096c2
Showing 1 changed file with 42 additions and 21 deletions.
diff --git a/src/overmap.cpp b/src/overmap.cpp
@@ -2745,34 +2745,55 @@ void overmap::place_roads( const overmap *north, const overmap *east, const over
         tripoint_om_omt tmp;
         // Populate viable_roads with one point for each neighborless side.
         // Make sure these points don't conflict with rivers.
-        // TODO: In theory this is a potential infinite loop...
+
+        std::array < int, OMAPX - 20 > omap_num;
+        for( int i = 0; i < 160; i++ ) {
+            omap_num[i] = i + 10;
+        }
+
         if( north == nullptr ) {
-            do {
-                tmp = tripoint_om_omt( rng( 10, OMAPX - 11 ), 0, 0 );
-            } while( is_river( ter( tmp ) ) || is_river( ter( tmp + point_east ) ) ||
-                     is_river( ter( tmp + point_west ) ) );
-            viable_roads.push_back( tmp );
+            std::shuffle( omap_num.begin(), omap_num.end(), rng_get_engine() );
+            for( const auto &i : omap_num ) {
+                tmp = tripoint_om_omt( i, 0, 0 );
+                if( !( is_river( ter( tmp ) ) || is_river( ter( tmp + point_east ) ) ||
+                       is_river( ter( tmp + point_west ) ) ) ) {
+                    viable_roads.push_back( tmp );
+                    break;
+                }
+            }
         }
         if( east == nullptr ) {
-            do {
-                tmp = tripoint_om_omt( OMAPX - 1, rng( 10, OMAPY - 11 ), 0 );
-            } while( is_river( ter( tmp ) ) || is_river( ter( tmp + point_north ) ) ||
-                     is_river( ter( tmp + point_south ) ) );
-            viable_roads.push_back( tmp );
+            std::shuffle( omap_num.begin(), omap_num.end(), rng_get_engine() );
+            for( const auto &i : omap_num ) {
+                tmp = tripoint_om_omt( OMAPX - 1, i, 0 );
+                if( !( is_river( ter( tmp ) ) || is_river( ter( tmp + point_north ) ) ||
+                       is_river( ter( tmp + point_south ) ) ) ) {
+                    viable_roads.push_back( tmp );
+                    break;
+                }
+            }
         }
         if( south == nullptr ) {
-            do {
-                tmp = tripoint_om_omt( rng( 10, OMAPX - 11 ), OMAPY - 1, 0 );
-            } while( is_river( ter( tmp ) ) || is_river( ter( tmp + point_east ) ) ||
-                     is_river( ter( tmp + point_west ) ) );
-            viable_roads.push_back( tmp );
+            std::shuffle( omap_num.begin(), omap_num.end(), rng_get_engine() );
+            for( const auto &i : omap_num ) {
+                tmp = tripoint_om_omt( i, OMAPY - 1, 0 );
+                if( !( is_river( ter( tmp ) ) || is_river( ter( tmp + point_east ) ) ||
+                       is_river( ter( tmp + point_west ) ) ) ) {
+                    viable_roads.push_back( tmp );
+                    break;
+                }
+            }
         }
         if( west == nullptr ) {
-            do {
-                tmp = tripoint_om_omt( 0, rng( 10, OMAPY - 11 ), 0 );
-            } while( is_river( ter( tmp ) ) || is_river( ter( tmp + point_north ) ) ||
-                     is_river( ter( tmp + point_south ) ) );
-            viable_roads.push_back( tmp );
+            std::shuffle( omap_num.begin(), omap_num.end(), rng_get_engine() );
+            for( const auto &i : omap_num ) {
+                tmp = tripoint_om_omt( 0, i, 0 );
+                if( !( is_river( ter( tmp ) ) || is_river( ter( tmp + point_north ) ) ||
+                       is_river( ter( tmp + point_south ) ) ) ) {
+                    viable_roads.push_back( tmp );
+                    break;
+                }
+            }
         }
         while( roads_out.size() < 2 && !viable_roads.empty() ) {
             roads_out.push_back( random_entry_removed( viable_roads ) );