src/logic_signal_program.cpp

   1 /*
   2  * This file is part of OpenTTD.
   3  * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
   4  * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
   5  * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
   6  */
   7
   8 /** @file logic_signal_program.cpp Implementation of the SignalProgram class functions. */
   9
  10 #include "logic_signals.h"
  11 #include "overlay_cmd.h"
  12 #include "rail_map.h"
  13 #include "viewport_func.h"
  14
  15 #include <algorithm>
  16
  17 /**
  18  * Return the opposite of the given signal state.
  19  * @param state The original signal state to revert.
  20  * @return Green if the given argument is Red and vice versa.
  21  */
  22 static SignalState OppositeSignalState(SignalState state)
  23 {
  24         return state == SIGNAL_STATE_RED ? SIGNAL_STATE_GREEN : SIGNAL_STATE_RED;
  25 }
  26
  27 /**
  28  * The maximum number of signal programs which are evaluated in succession.
  29  */
  30 static const int MAX_LOGIC_SIGNAL_RECURSIONS = 5;
  31
  32 /**
  33  * The constructor for creating a new signal program.
  34  * @param tile The tile where the logic signal for this program is located.
  35  * @param track The track where the logic signal for this program is located.
  36  */
  37 SignalProgram::SignalProgram(TileIndex tile, Track track)
  38 {
  39         this->tile = tile;
  40         this->track = track;
  41
  42         // Default to a priority signal: if any of the linked input
  43         // signals are red, this one goes red.
  44         this->own_default_state = SIGNAL_STATE_GREEN;
  45         this->trigger_state = SIGNAL_STATE_RED;
  46         this->signal_op = SIGNAL_OP_OR;
  47
  48         this->blocked_by_train = false;
  49 }
  50
  51 /**
  52  * Add a new signal as input for this signal program.
  53  * @param tile The tile of the signal to be linked.
  54  * @param track The track of the signal to be linked.
  55  */
  56 void SignalProgram::AddLink(TileIndex tile, Track track)
  57 {
  58         const SignalReference input = GetSignalReference(tile, track);
  59
  60         if (std::find(this->linked_signals.begin(), this->linked_signals.end(), input) == this->linked_signals.end()) {
  61                 this->linked_signals.push_back(input);
  62                 _signal_link_list.push_back(std::make_pair(input, GetSignalReference(this->tile, this->track)));
  63         }
  64
  65         Overlays::Instance()->RefreshLogicSignalOverlay();
  66 }
  67
  68 /**
  69  * Remove a linked signal from this program. The link must exist.
  70  * @param tile The tile of the signal to be removed.
  71  * @param track The track of the signal to be removed.
  72  */
  73 void SignalProgram::RemoveLink(TileIndex tile, Track track)
  74 {
  75         // Refresh BEFORE because we need to know what tiles to refresh before we remove the reference to them.
  76         Overlays::Instance()->RefreshLogicSignalOverlay();
  77
  78         SignalReference input_to_remove = GetSignalReference(tile, track);
  79         const auto found_input = std::find(this->linked_signals.begin(), this->linked_signals.end(), input_to_remove);
  80
  81         assert(found_input != this->linked_signals.end());
  82
  83         this->linked_signals.erase(found_input);
  84
  85         const auto link_to_remove = std::make_pair(input_to_remove, GetSignalReference(this->tile, this->track));
  86         const auto found_link = std::find(_signal_link_list.begin(), _signal_link_list.end(), link_to_remove);
  87
  88         assert(found_link != _signal_link_list.end());
  89
  90         _signal_link_list.erase(found_link);
  91 }
  92
  93 /**
  94  * Remove all links that this signal program has.
  95  */
  96 void SignalProgram::ClearAllLinks()
  97 {
  98         // Refresh BEFORE because we need to know what tiles to refresh before we remove the reference to them.
  99         Overlays::Instance()->RefreshLogicSignalOverlay();
 100         auto this_signal = GetSignalReference(this->tile, this->track);
 101
 102         _signal_link_list.erase(std::remove_if(_signal_link_list.begin(), _signal_link_list.end(), [&](std::pair<SignalReference, SignalReference> link)
 103         {
 104                 return link.second == this_signal;
 105         }));
 106
 107         this->linked_signals.clear();
 108 }
 109
 110 /**
 111 * Return all signal input references.
 112 */
 113 const std::list<SignalReference>& SignalProgram::GetSignalReferences() const
 114 {
 115         return this->linked_signals;
 116 }
 117
 118 /**
 119  * The number of signals linked to this signal program.
 120  */
 121 size_t SignalProgram::LinkCount() const
 122 {
 123         return this->linked_signals.size();
 124 }
 125
 126 /**
 127  * This function is run when one of the signals linked to this program has changed.
 128  * It will (possibly) change the state of the signal, and then recursively change
 129  * the state of any signal linked to it.
 130  * @param depth The recursion depth, which starts at 1.
 131  */
 132 void SignalProgram::InputChanged(int depth)
 133 {
 134         // If this signal is blocked by a train, we can't do anything.
 135         if (this->blocked_by_train) {
 136                 return;
 137         }
 138
 139         const SignalState new_state = this->Evaluate();
 140
 141         if (new_state != DetermineSignalState(this->tile, this->track)) {
 142                 SetSignalStateForTrack(this->tile, this->track, new_state);
 143                 MarkTileDirtyByTile(tile);
 144
 145                 // Recursively update any signals that have this one as input.
 146                 if (depth < MAX_LOGIC_SIGNAL_RECURSIONS) {
 147                         SignalStateChanged(this->tile, this->track, depth + 1);
 148                 }
 149         }
 150 }
 151
 152 /**
 153  * The main evaluation function which determines the state of the signal linked
 154  * to this signal program. It should be short, simple and readable.
 155  */
 156 SignalState SignalProgram::Evaluate()
 157 {
 158         int trigger_states = 0, not_trigger_states = 0;
 159
 160         // We need at least one linked signal to evaluate anything.
 161         if (this->LinkCount() == 0) return this->own_default_state;
 162
 163         // Loop through all linked signals and count the states.
 164         for (auto reference : this->linked_signals) {
 165                 const TileIndex target_tile = GetTileFromSignalReference(reference);
 166                 const Track target_track = GetTrackFromSignalReference(reference);
 167                 const SignalState target_state = DetermineSignalState(target_tile, target_track);
 168
 169                 if (target_state == trigger_state) {
 170                         trigger_states++;
 171                 } else {
 172                         not_trigger_states++;
 173                 }
 174         }
 175
 176         switch (this->signal_op) {
 177                 case SIGNAL_OP_OR:
 178                         // OR is triggered if we have at least one signal of trigger color.
 179                         if (trigger_states > 0) return OppositeSignalState(this->own_default_state);
 180                         break;
 181
 182                 case SIGNAL_OP_AND:
 183                         // AND is triggered if no signals were of the 'wrong' color.
 184                         if (not_trigger_states == 0) return OppositeSignalState(this->own_default_state);
 185                         break;
 186
 187                 case SIGNAL_OP_NAND:
 188                         // NAND is triggered if we have at least one signal of the 'wrong' color.
 189                         if (not_trigger_states > 0) return OppositeSignalState(this->own_default_state);
 190                         break;
 191
 192                 case SIGNAL_OP_XOR:
 193                         // XOR is triggered if the number of signals in trigger color is uneven.
 194                         if ((trigger_states % 2) > 0) return OppositeSignalState(this->own_default_state);
 195                         break;
 196
 197                 default:
 198                         break;
 199         }
 200
 201         // Not triggered, return default color.
 202         return this->own_default_state;
 203 }