From 9800b5576ed265761999cddecc50567b93fb91de Mon Sep 17 00:00:00 2001
From: Klemen Plestenjak <plestenjak.klemen@gmail.com>
Date: Thu, 7 Dec 2023 10:42:53 +0100
Subject: [PATCH] Remove memory allocation in pathfinding

---
 engine/breeze/memory/stack_alloc.c |  2 +-
 game/game_state.h                  |  1 +
 game/main.c                        |  2 ++
 game/pathfinding.c                 | 14 ++++++--------
 game/pathfinding.h                 |  9 +++++----
 game/systems_input.c               |  6 ++++--
 6 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/engine/breeze/memory/stack_alloc.c b/engine/breeze/memory/stack_alloc.c
index b9da496..4a569d9 100644
--- a/engine/breeze/memory/stack_alloc.c
+++ b/engine/breeze/memory/stack_alloc.c
@@ -21,7 +21,7 @@ void bzStackAllocDestroy(BzStackAlloc *alloc) {
 }
 
 void *bzStackAlloc(BzStackAlloc *alloc, size_t numBytes) {
-    BZ_ASSERT(alloc->size + numBytes < alloc->size);
+    BZ_ASSERT(alloc->allocated + numBytes < alloc->size);
     void *allocated = (u8 *) alloc->memory + alloc->allocated;
     alloc->allocated += numBytes;
     return allocated;
diff --git a/game/game_state.h b/game/game_state.h
index 6eef5ed..9a911fd 100644
--- a/game/game_state.h
+++ b/game/game_state.h
@@ -57,6 +57,7 @@ typedef struct Game {
         i64 gold;
         i64 pop;
     } resources;
+    BzStackAlloc stackAlloc;
     struct {
         BzObjectPool *pathData;
     } pools;
diff --git a/game/main.c b/game/main.c
index 4c7315a..c61b581 100644
--- a/game/main.c
+++ b/game/main.c
@@ -79,6 +79,7 @@ bool init(void *userData) {
     input->unitPositions = bzArrayCreate(Position, 16);
 
 
+    game->stackAlloc = bzStackAllocCreate(10 * 1000 * 1000); // 10 MB
     // init pools
     game->pools.pathData = bzObjectPoolCreate(&(BzObjectPoolDesc) {
         .objectSize=sizeof(PathData),
@@ -189,6 +190,7 @@ void deinit(void *userData) {
     ECS = NULL;
 
     bzArrayDestroy(inputCopy.unitPositions);
+    bzStackAllocDestroy(&gameCopy.stackAlloc);
     bzObjectPoolDestroy(gameCopy.pools.pathData);
     bzSpatialGridDestroy(gameCopy.entityGrid);
 }
diff --git a/game/pathfinding.c b/game/pathfinding.c
index 0c78e5d..61d8e9c 100644
--- a/game/pathfinding.c
+++ b/game/pathfinding.c
@@ -123,6 +123,7 @@ static void heapUpdate(Heap *heap, i32 idx);
 
 bool pathfindAStar(const PathfindingDesc *desc) {
     BZ_ASSERT(desc->map);
+    BZ_ASSERT(desc->alloc);
     BzTileMap *map = desc->map;
 
     TilePosition start = {0}, target = {0};
@@ -133,18 +134,17 @@ bool pathfindAStar(const PathfindingDesc *desc) {
 
     i32 numTiles = map->width * map->height;
 
-    PathNodeRecord *closedSet = desc->closedSet;
-    if (!closedSet) closedSet = bzAlloc(sizeof(*closedSet) * numTiles);
+    PathNodeRecord *closedSet = bzStackAlloc(desc->alloc, sizeof(*closedSet) * numTiles);
     bzMemSet(closedSet, 0, sizeof(*closedSet) * numTiles);
 
+    PathNode *openSetArr = bzStackAlloc(desc->alloc, sizeof(*openSetArr) * numTiles);
     Heap openSet = {
-            .arr=desc->openSet,
+            .arr=openSetArr,
             .size=0,
             .capacity=numTiles,
             .mapWidth=map->width,
             .records=closedSet
     };
-    if (!openSet.arr) openSet.arr = bzAlloc(sizeof(*openSet.arr) * numTiles);
 
     i32 toTargetCost = dst(start, target);
     heapPush(&openSet, (PathNode) {
@@ -258,10 +258,8 @@ bool pathfindAStar(const PathfindingDesc *desc) {
         *desc->outPath = (Path) {pathData, 0};
     }
 
-    if (!desc->closedSet)
-        bzFree(closedSet);
-    if (!desc->openSet)
-        bzFree(openSet.arr);
+    bzStackAllocFree(desc->alloc, openSet.arr);
+    bzStackAllocFree(desc->alloc, closedSet);
 
     return foundPath ? pathLen : -1;
 }
diff --git a/game/pathfinding.h b/game/pathfinding.h
index 9537b72..93618b8 100644
--- a/game/pathfinding.h
+++ b/game/pathfinding.h
@@ -23,11 +23,12 @@ typedef struct PathNodeRecord {
 typedef struct PathfindingDesc {
     Position start;
     Position target;
-    BzObjectPool *pool;
+
     BzTileMap *map;
-    PathNode *openSet; // heap (size: width * height)
-    PathNodeRecord *closedSet; // size: width * height
-    Path *outPath;
+    Path      *outPath;
+
+    BzObjectPool *pool;
+    BzStackAlloc *alloc;
 } PathfindingDesc;
 
 bool pathfindAStar(const PathfindingDesc *desc);
diff --git a/game/systems_input.c b/game/systems_input.c
index 2a5e38e..820ce4b 100644
--- a/game/systems_input.c
+++ b/game/systems_input.c
@@ -138,7 +138,8 @@ void updatePlayerInput() {
                                 .target=target,
                                 .map=map,
                                 .outPath=&path,
-                                .pool=game->pools.pathData
+                                .pool=game->pools.pathData,
+                                .alloc=&game->stackAlloc
                         });
                         if (!path.paths) continue;
                         ecs_set_ptr(ECS, entity, Path, &path);
@@ -166,7 +167,8 @@ void updatePlayerInput() {
                            .target=worldPos,
                            .map=map,
                            .outPath=&path,
-                           .pool=game->pools.pathData
+                           .pool=game->pools.pathData,
+                           .alloc=&game->stackAlloc
                         });
                         if (!path.paths) continue;
                         ecs_set_ptr(ECS, entity, Path, &path);