Author: sveinung
Date: Sun Mar 19 11:13:16 2017
New Revision: 35128

URL: http://svn.gna.org/viewcvs/freeciv?rev=35128&view=rev
Log:
action_prob_vs_X(): quick check target distance.

Make all the action_prob_vs_X() functions fail fast if the target is to far
away. This makes the behavior of action_prob_vs_units() (action probability
against unit stack) standard so the remaining action_prob_vs_X() functions
becomes ready for target specific unknowns.

See hrm Feature #644053

Modified:
    branches/S3_0/common/actions.c

Modified: branches/S3_0/common/actions.c
URL: 
http://svn.gna.org/viewcvs/freeciv/branches/S3_0/common/actions.c?rev=35128&r1=35127&r2=35128&view=diff
==============================================================================
--- branches/S3_0/common/actions.c      (original)
+++ branches/S3_0/common/actions.c      Sun Mar 19 11:13:16 2017
@@ -1730,7 +1730,12 @@
   case ATK_UNIT:
     /* The Freeciv code for all actions that is controlled by action
      * enablers and targets a unit assumes that the acting
-     * player can see the target unit. */
+     * player can see the target unit.
+     * Examples:
+     * - action_prob_vs_unit()'s quick check that the distance between actor
+     *   and target is acceptable would leak distance to target unit if the
+     *   target unit can't be seen.
+     */
     if (!can_player_see_unit(actor_player, target_unit)) {
       return TRI_NO;
     }
@@ -3057,6 +3062,15 @@
     return ACTPROB_IMPOSSIBLE;
   }
 
+  /* Doesn't leak information about city position since an unknown city
+   * can't be targeted and a city can't move. */
+  if (!action_id_distance_accepted(action_id,
+          real_map_distance(unit_tile(actor_unit),
+                            city_tile(target_city)))) {
+    /* No point in continuing. */
+    return ACTPROB_IMPOSSIBLE;
+  }
+
   target_building = tgt_city_local_building(target_city);
   target_utype = tgt_city_local_utype(target_city);
 
@@ -3101,6 +3115,15 @@
                         action_target_kind_name(ATK_UNIT));
 
   if (!unit_can_do_action(actor_unit, action_id)) {
+    /* No point in continuing. */
+    return ACTPROB_IMPOSSIBLE;
+  }
+
+  /* Doesn't leak information about unit position since an unseen unit can't
+   * be targeted. */
+  if (!action_id_distance_accepted(action_id,
+          real_map_distance(unit_tile(actor_unit),
+                            unit_tile(target_unit)))) {
     /* No point in continuing. */
     return ACTPROB_IMPOSSIBLE;
   }
@@ -3152,6 +3175,8 @@
     return ACTPROB_IMPOSSIBLE;
   }
 
+  /* Doesn't leak information about unit stack position since it is
+   * specified as a tile and an unknown tile's position is known. */
   if (!action_id_distance_accepted(action_id,
                                    real_map_distance(unit_tile(actor_unit),
                                                      target_tile))) {
@@ -3250,6 +3275,15 @@
     return ACTPROB_IMPOSSIBLE;
   }
 
+  /* Doesn't leak information about unit stack position since an unknown
+   * tile's position is known. */
+  if (!action_id_distance_accepted(action_id,
+                                   real_map_distance(unit_tile(actor_unit),
+                                                     target_tile))) {
+    /* No point in continuing. */
+    return ACTPROB_IMPOSSIBLE;
+  }
+
   return action_prob(action_id,
                      unit_owner(actor_unit), tile_city(actor_tile),
                      NULL, actor_tile, actor_unit, NULL,
@@ -3271,6 +3305,8 @@
     /* Can't do the action when the actor is missing. */
     return ACTPROB_IMPOSSIBLE;
   }
+
+  /* No point in checking distance to target. It is always 0. */
 
   fc_assert_ret_val_msg(AAK_UNIT == action_id_get_actor_kind(action_id),
                         ACTPROB_IMPOSSIBLE,


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