From c259e35348ee7beeab02fca646ceca15c532864b Mon Sep 17 00:00:00 2001
From: Miloslav Ciz <drummyfish@disroot.org>
Date: Thu, 9 Jan 2025 15:34:14 +0100
Subject: [PATCH] Add map hash

---
 TODO.txt |  1 +
 assets.h |  6 +++---
 map.h    | 25 ++++++++++++++++++++++++-
 racing.h |  2 --
 4 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/TODO.txt b/TODO.txt
index bd01f01..02786ca 100644
--- a/TODO.txt
+++ b/TODO.txt
@@ -1,5 +1,6 @@
 =========== GENERAL ==============
 
+- the horizon on background seems too low? maybe add setting to shift it a bit?
 - add argc/argv to gameInit? could be used to quickly start maps, verify
   replays etc.
 - maybe each map could have a target time embedded: when beaten, the map would
diff --git a/assets.h b/assets.h
index cf11b5f..ed417b8 100644
--- a/assets.h
+++ b/assets.h
@@ -40,16 +40,16 @@ static const char *LCR_texts[] =
 
 static const char *LCR_internalResourceFile =
   "Mtestmap;"
-  "0 :*H1k0J"
+  "1 :*H1k0"
 
   ":=s0s0 :fd190" // big concrete
 
-  ":+v0n0"
   ":+w0o0"
+  ":+v0n0"
   ":!x0n0"
 
-  ":=s0B0 :fd910" // concrete wall
   ":^s1A0 :fk110" // ramps before wall
+  ":=s0B0 :fd910" // concrete wall
 
   ":nu0j1 :ly0j1 :AA0j1 "
 
diff --git a/map.h b/map.h
index a548f8c..96f3806 100644
--- a/map.h
+++ b/map.h
@@ -151,7 +151,8 @@ struct
 
   uint8_t environment;
   uint8_t checkpointCount;
-  // TODO: name, desc? possibly as a single '\n' separated string?
+
+  uint32_t hash;       ///< Hash of the processed binary map.
 } LCR_currentMap;
 
 void LCR_makeMapBlock(uint8_t type, uint8_t x, uint8_t y, uint8_t z,
@@ -353,6 +354,25 @@ int _LCR_mapCharToCoord(char c)
   return -1;
 }
 
+void _LCR_mapComputeHash(void)
+{
+  LCR_LOG1("computing map hash");
+
+  const uint8_t *data = LCR_currentMap.startPos;
+
+  LCR_currentMap.hash = 11 + LCR_currentMap.environment;
+
+  for (int i = 0; i < LCR_currentMap.blockCount * LCR_BLOCK_SIZE + 4; ++i)
+  {
+    LCR_currentMap.hash = LCR_currentMap.hash * 101 + *data;
+    data = i != 3 ? data + 1 : LCR_currentMap.blocks;
+  }
+
+  LCR_currentMap.hash *= 251;
+  LCR_currentMap.hash = ((LCR_currentMap.hash << 19) |
+    (LCR_currentMap.hash >> 13)) * 113;
+}
+
 uint8_t LCR_mapLoadFromStr(char (*getNextCharFunc)(void))
 {
   LCR_LOG0("loading map string");
@@ -368,6 +388,7 @@ uint8_t LCR_mapLoadFromStr(char (*getNextCharFunc)(void))
   LCR_currentMap.checkpointCount = 0;
   LCR_currentMap.blockCount = 0;
   LCR_currentMap.environment = 0;
+  LCR_currentMap.hash = 0;
 
   c = getNextCharFunc();
 
@@ -495,6 +516,8 @@ uint8_t LCR_mapLoadFromStr(char (*getNextCharFunc)(void))
   for (int i = 0; i < LCR_MAP_BLOCK_CACHE_SIZE; ++i)
     _LCR_mapBlockCache[i] = 0xffffffff;
 
+  _LCR_mapComputeHash();
+
   LCR_LOG2("map loaded")
 
   LCR_mapReset();
diff --git a/racing.h b/racing.h
index 5057d44..8bd4ef5 100644
--- a/racing.h
+++ b/racing.h
@@ -45,11 +45,9 @@ typedef int32_t LCR_GameUnit;  ///< abstract game unit
 #define LCR_CAR_DRIFT_THRESHOLD_1 (LCR_GAME_UNIT / 4)
 #define LCR_CAR_DRIFT_THRESHOLD_0 (LCR_GAME_UNIT / 200)
 
-
 #define LCR_CAR_CRASH_SPEED_DIFF 25
 #define LCR_CAR_CRASH_SPEED_THRESHOLD 70
 
-
 // multipliers (in 8ths) of friction and acceleration on concrete:
 #define LCR_CAR_GRASS_FACTOR 5
 #define LCR_CAR_DIRT_FACTOR 3