From 838792fca41b9bccce260e9500d75549433bbe6a Mon Sep 17 00:00:00 2001
From: rtk0c <mail.tianyig@gmail.com>
Date: Sun, 18 May 2025 11:10:09 -0700
Subject: Add bounds check to set_sand()

Previously, painting didn't do it (simulation did) so there were buffer overruns
---
 src/sandbox.cpp | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

(limited to 'src/sandbox.cpp')

diff --git a/src/sandbox.cpp b/src/sandbox.cpp
index 2c09d77..64bf1db 100644
--- a/src/sandbox.cpp
+++ b/src/sandbox.cpp
@@ -60,8 +60,8 @@ static void simulate_sand_tile(Sandbox& self, int x, int y) {
     case Tile::Ti_Sand: {
         const auto below = self.gs(x, y - 1);
         if (below.so == Tile::Ti_Air) {
-            self.set_sand(x, y, below);
-            self.set_sand(x, y - 1, at0);
+            self.ss(x, y, below);
+            self.ss(x, y - 1, at0);
         } else {
             Pt loc1[]{ Pt(x - 1, y - 1), Pt(x + 1, y - 1) };
             auto bound = 2;
@@ -70,8 +70,8 @@ static void simulate_sand_tile(Sandbox& self, int x, int y) {
                 // Try going to a side
                 auto at1 = self.gs(loc1[i].x, loc1[i].y);
                 if (at1.so == Tile::Ti_Air) {
-                    self.set_sand(x, y, at1);
-                    self.set_sand(loc1[i].x, loc1[i].y, at0);
+                    self.ss(x, y, at1);
+                    self.ss(loc1[i].x, loc1[i].y, at0);
                 }
                 which = (which + 1) % bound;
             }
@@ -123,19 +123,32 @@ void Sandbox::simulate_step() {
     ++ncycle;
 }
 
+#define BOUNDS_CHECK(x, y) if (x < 0 || x >= width || y < 0 || y >= height)
+
 Tile& Sandbox::gs(int x, int y) {
-    if (x < 0 || x >= width || y < 0 || y >= height)
+    BOUNDS_CHECK(x, y) {
         return _wall_tile;
+    }
+
     return tiles[y * width + x];
 }
 
-void Sandbox::set_sand(int x, int y, Tile sand) {
+void Sandbox::ss(int x, int y, Tile sand) {
+    BOUNDS_CHECK(x, y) {
+        return;
+    }
+
+    // Update tile
     auto& target = tiles[y * width + x];
     target = sand;
-    // Set update bit if the target is after cursor
-    if (y < _y || x > _x)
-        target.updated = true;
+    target.updated = true;
+    // Update visuals
     bitmap[y * width + x] = sand.get_color();
+
+    mark_dirty(x, y);
+}
+
+void Sandbox::mark_dirty(int x, int y) {
     if (dirty_writeto == Rect())
         dirty_writeto = Rect(x, y, x, y);
     else
-- 
cgit v1.2.3-70-g09d2