Refactor/RNG system (#476)

* Extract rng manipulation to its own file

* clang format

* Get CPU cycles since game start to use for RNG

* change a few things

* clang format

* Implement suggestions from @ricfehr3

* clang format

* Fix rebase issue

* clang format

* Create RngInfo struct to hold seed and step

* clang format

* Make a note about rng_restore system not having been tested properly yet

* Apply suggestions from @ricfehr3

Co-authored-by: Rickey <ric@rf3.xyz>

* clang format

---------

Co-authored-by: MathisMartin31 <mathis.martin31@gmail.com>
Co-authored-by: Rickey <ric@rf3.xyz>

include/game.h

@@ -175,8 +175,6 @@ void display_mult(void);
 void display_money(void);
 void set_retrigger(bool new_retrigger);
 
-u32 get_rand(void);
-
 // joker specific functions
 bool is_shortcut_joker_active(void);
 int get_straight_and_flush_size(void);

include/game_variables.h

@@ -7,6 +7,7 @@
 #define GAME_VARIABLES_H
 
 #include "blind.h"
+#include "random.h"
 
 #include <tonc.h>
 
@@ -37,8 +38,7 @@ typedef struct
     // Internal variables
 
     s32 timer; // This might already exist in libtonc but idk so i'm just making my own
-    u32 rng_seed;
-    u32 rng_step; // Position in the rng sequence.
+    RngInfo rng_info;
 
     // Variables visible by the player
 

include/random.h

@@ -0,0 +1,76 @@
+/**
+ * @file random.h
+ *
+ * @brief Common functions to handle RNG manipulation. Using this interface has three goals:
+ * 1. Make RNG repeatable so that people can share seeds and saves, and end up with the same run
+ * 2. Prevent the players from engaging in save-scumming since the pseudo-RNG is deterministic
+ * 3. Accomodate for base-36 seeds, so that we can freely chose one with alpha-numeric characters in
+ * the seed screen input
+ */
+#ifndef RANDOM_H
+#define RANDOM_H
+
+#include <tonc.h>
+
+/**
+ * @brief Hex value of "ZZZZZZ" in base 36
+ */
+#define MAX_SEED 0x81BF0FFF
+
+/**
+ * @brief Information to track and restore RNG state
+ */
+typedef struct
+{
+    /** Initial seed */
+    u32 seed;
+    /** Position in the rng sequence. */
+    u32 step;
+} RngInfo;
+
+/**
+ * @brief Starts counting CPU cycles, this will be used by rng_shuffle_seed to
+ *         generate a more random seed. To be called once on game start.
+ */
+void rng_init(void);
+
+/**
+ * @brief Update the CPU cycles counter and accumulate it into a bigger u32 `timer_acc` variable.
+ */
+void rng_update(void);
+
+/**
+ * @brief Set the rng seed to the chosen value, and reset the step counter to 0.
+ *         The seed will be capped at `MAX_SEED` for compatibility with the Seed Input screen
+ *         used to choose a seed for seeded runs.
+ *
+ * @param seed the new RNG seed
+ */
+void rng_set_seed(u32 seed);
+
+/**
+ * @brief Uses the CPU cycles counter to randomize the RNG seed as much as possible.
+ *         This will be called by the main menu and the game over screens so that
+ *         the next run's seed isn't the same as the last's.
+ *         rng_start_sampling needs to have been called, and will stop the profiling.
+ */
+void rng_shuffle_seed(void);
+
+/**
+ * @brief Get the next "randomly" generated number in the sequence from the current seed.
+ *
+ * @return u32
+ */
+u32 rng_get_u32(void);
+
+/**
+ * @brief Restore RNG info struct in the GameVariables. Sets the `seed` and seeks the
+ *         position `step` in the rng sequence.
+ *
+ * @param info RngInfo struct applied
+ *
+ * @note Consistency of the RNG after reloading the RngInfo struct has yet to be tested properly
+ */
+void rng_restore(RngInfo info);
+
+#endif // RANDOM_H

source/blind.c

@@ -4,6 +4,7 @@
 #include "game.h"
 #include "graphic_utils.h"
 #include "list.h"
+#include "random.h"
 #include "stdbool.h"
 #include "util.h"
 
@@ -139,7 +140,7 @@ enum BlindType roll_blind_type(bool showdown)
     }
 
     // roll a random blind among the unbeaten ones
-    int random_blind_idx = get_rand() % list_get_len(p_unbeaten_blinds);
+    int random_blind_idx = rng_get_u32() % list_get_len(p_unbeaten_blinds);
     Blind* random_blind = list_get_at_idx(p_unbeaten_blinds, random_blind_idx);
 
     return random_blind->type;

source/game.c

@@ -21,6 +21,7 @@
 #include "joker.h"
 #include "layout.h"
 #include "list.h"
+#include "random.h"
 #include "save.h"
 #include "selection_grid.h"
 #include "soundbank.h"
@@ -299,7 +300,8 @@ static ContainedHandTypes _contained_hands = {0};
 // Initialization of the global vars
 // clang-format off
 GameVariables g_game_vars = {
-    .timer = 0, .rng_seed = 0, .rng_step = 0,
+    .timer = 0,
+    .rng_info = {0, 0},
 
     .round = 0, .ante = 0, .money = 0,
 
@@ -629,6 +631,8 @@ static inline void jokers_update_loop(void)
 
 void game_update()
 {
+    rng_update();
+
     g_game_vars.timer++;
 
     jokers_update_loop();
@@ -654,12 +658,6 @@ void game_change_state(enum GameState new_game_state)
     }
 }
 
-u32 get_rand()
-{
-    g_game_vars.rng_step++;
-    return rand();
-}
-
 CardObject** get_hand_array(void)
 {
     return hand;
@@ -1429,7 +1427,7 @@ static inline void deck_shuffle(void)
 {
     for (int i = deck_top; i > 0; i--)
     {
-        int j = get_rand() % (i + 1);
+        int j = rng_get_u32() % (i + 1);
         Card* temp = deck[i];
         deck[i] = deck[j];
         deck[j] = temp;
@@ -1505,14 +1503,6 @@ static void game_round_on_init(void)
     game_playing_selection_grid.selection = GAME_PLAYING_INIT_SEL;
 }
 
-// General functions
-static inline void set_seed(int seed)
-{
-    srand(seed);
-    g_game_vars.rng_seed = seed;
-    g_game_vars.rng_step = 0;
-}
-
 // Playing state functions
 static void game_playing_discard_on_pressed(void)
 {
@@ -1670,7 +1660,7 @@ static bool game_playing_hand_row_on_selection_changed(
              */
             play_sfx(
                 SFX_CARD_FOCUS,
-                MM_BASE_PITCH_RATE + get_rand() % CARD_FOCUS_SFX_PITCH_OFFSET_RANGE,
+                MM_BASE_PITCH_RATE + rng_get_u32() % CARD_FOCUS_SFX_PITCH_OFFSET_RANGE,
                 SFX_DEFAULT_VOLUME
             );
         }
@@ -1690,7 +1680,7 @@ static bool game_playing_hand_row_on_selection_changed(
              */
             play_sfx(
                 SFX_CARD_FOCUS,
-                MM_BASE_PITCH_RATE + get_rand() % CARD_FOCUS_SFX_PITCH_OFFSET_RANGE,
+                MM_BASE_PITCH_RATE + rng_get_u32() % CARD_FOCUS_SFX_PITCH_OFFSET_RANGE,
                 SFX_DEFAULT_VOLUME
             );
         }
@@ -3020,8 +3010,7 @@ static void game_playing_on_update(void)
 
 void game_start(void)
 {
-    // set_seed(9); // 9 is a full house
-    set_seed(g_game_vars.rng_seed);
+    rng_shuffle_seed();
 
     affine_background_change_background(AFFINE_BG_GAME);
 

source/game/game_over.c

@@ -7,6 +7,7 @@
 #include "game/main_menu.h"
 #include "graphic_utils.h"
 #include "layout.h"
+#include "random.h"
 #include "soundbank.h"
 #include "timer.h"
 #include "util.h"
@@ -128,4 +129,5 @@ void game_over_on_exit(void)
 {
     condition = END_CONDITION_NONE;
     game_reset();
+    rng_shuffle_seed();
 }

source/game/main_menu.c

@@ -127,14 +127,6 @@ void game_main_menu_on_update(void)
     main_menu_ace->sprite_object->trotation = lu_sin((g_game_vars.timer << 8) / 2) / 3;
     card_object_update(main_menu_ace);
 
-    // Seed randomization
-    g_game_vars.rng_seed++;
-    // If the keys have changed, make it more pseudo-random
-    if (key_curr_state() != key_prev_state())
-    {
-        g_game_vars.rng_seed *= 2;
-    }
-
     selection_grid_process_input(&main_menu_selection_grid);
 }
 

source/game/shop.c

@@ -17,6 +17,7 @@
 #include "joker.h"
 #include "layout.h"
 #include "list.h"
+#include "random.h"
 #include "save.h"
 #include "soundbank.h"
 #include "timer.h"
@@ -196,7 +197,7 @@ static inline int game_shop_get_rand_available_joker_id(void)
         return UNDEFINED;
 
     int matching_joker_ids[jokers_avail_size];
-    int fallback_random_idx = get_rand() % jokers_avail_size;
+    int fallback_random_idx = rng_get_u32() % jokers_avail_size;
     int fallback_random_joker_id = UNDEFINED;
     int match_count = 0;
 
@@ -215,8 +216,8 @@ static inline int game_shop_get_rand_available_joker_id(void)
         }
     }
 
-    int selected_joker_id =
-        (match_count > 0) ? matching_joker_ids[get_rand() % match_count] : fallback_random_joker_id;
+    int selected_joker_id = (match_count > 0) ? matching_joker_ids[rng_get_u32() % match_count]
+                                              : fallback_random_joker_id;
 
     return selected_joker_id;
 }

source/joker.c

@@ -5,6 +5,7 @@
 #include "graphic_utils.h"
 #include "joker_gfx.h"
 #include "pool.h"
+#include "random.h"
 #include "soundbank.h"
 #include "util.h"
 
@@ -368,7 +369,7 @@ Sprite* joker_object_get_sprite(JokerObject* joker_object)
 int joker_get_random_rarity()
 {
     int joker_rarity = 0;
-    int rarity_roll = get_rand() % 100;
+    int rarity_roll = rng_get_u32() % 100;
     if (rarity_roll < COMMON_JOKER_CHANCE)
     {
         joker_rarity = COMMON_JOKER;

source/joker_effects.c

@@ -4,6 +4,7 @@
 #include "joker.h"
 #include "list.h"
 #include "pool.h"
+#include "random.h"
 #include "util.h"
 
 #include <stdlib.h>
@@ -563,7 +564,7 @@ static u32 misprint_joker_effect(
 
     *joker_effect = &shared_joker_effect;
 
-    (*joker_effect)->mult = get_rand() % (MISPRINT_MAX_MULT + 1);
+    (*joker_effect)->mult = rng_get_u32() % (MISPRINT_MAX_MULT + 1);
 
     return JOKER_EFFECT_FLAG_MULT;
 }
@@ -776,7 +777,7 @@ static u32 reserved_parking_joker_effect(
 
     u32 effect_flags_ret = JOKER_EFFECT_FLAG_NONE;
 
-    if ((get_rand() % 2 == 0) && card_is_face(scored_card))
+    if ((rng_get_u32() % 2 == 0) && card_is_face(scored_card))
     {
         *joker_effect = &shared_joker_effect;
 
@@ -798,7 +799,7 @@ static u32 business_card_joker_effect(
 
     u32 effect_flags_ret = JOKER_EFFECT_FLAG_NONE;
 
-    if ((get_rand() % 2 == 0) && card_is_face(scored_card))
+    if ((rng_get_u32() % 2 == 0) && card_is_face(scored_card))
     {
         *joker_effect = &shared_joker_effect;
 

source/main.c

@@ -6,6 +6,7 @@
 #include "gbalatro_sys8.h"
 #include "graphic_utils.h"
 #include "joker.h"
+#include "random.h"
 #include "save.h"
 #include "sprite.h"
 
@@ -24,6 +25,8 @@
 
 void init()
 {
+    rng_init();
+
     irq_init(NULL);
     irq_add(II_VBLANK, mmVBlank);
     irq_add(II_HBLANK, affine_background_hblank);

source/random.c

@@ -0,0 +1,50 @@
+#include "random.h"
+
+#include "game_variables.h"
+
+#include <stdlib.h>
+#include <tonc.h>
+
+// Accumulate timer 1 into a bigger variable so we can generate more diverse seeds
+static u32 timer_acc = 0;
+
+// Timers usage docs: https://gbadev.net/tonc/timers.html
+void rng_init(void)
+{
+    REG_TM1D = 0;
+    REG_TM1CNT = TM_FREQ_1 | TM_ENABLE; // using timer with x1 prescale
+}
+
+void rng_update(void)
+{
+    timer_acc += (u32)REG_TM1D;
+}
+
+void rng_set_seed(u32 seed)
+{
+    g_game_vars.rng_info.seed = seed % (MAX_SEED + 1);
+    g_game_vars.rng_info.step = 0;
+    srand(g_game_vars.rng_info.seed);
+}
+
+void rng_shuffle_seed(void)
+{
+    rng_set_seed(timer_acc);
+}
+
+u32 rng_get_u32(void)
+{
+    g_game_vars.rng_info.step++;
+    return rand();
+}
+
+void rng_restore(RngInfo info)
+{
+    g_game_vars.rng_info = info;
+
+    srand(g_game_vars.rng_info.seed);
+    for (u32 i = 0; i < g_game_vars.rng_info.step; i++)
+    {
+        (void)rng_get_u32();
+    }
+}

source/save.c

@@ -105,8 +105,8 @@ typedef struct JokerObjectSaveData
  * 2    | 'L'    | ' '    | 'D'    | 'A'    | -            | -
  * 3    | 'T'    | 'A'    | ' '    | '-'    | -            | -
  * 4    | T[0]   | T[1]   | T[2]   | T[3]   | GLOB TIMER   | The global timer used for animations thoughout the game
- * 5    | SED[0] | SED[1] | SED[2] | SED[3] | RNG SEED     | The seed used for RNG, either randomly shuffled or chosen by the player at game start
- * 6    | STP[0] | STP[1] | STP[2] | STP[3] | RNG STEP     | The current position in the RNG sequence for the given seed, since the start of the run
+ * 5    | RNG[0] | RNG[1] | RNG[2] | RNG[3] | RNG INFO     | RNG Info struct, containing the seed used for RNG, either randomly shuffled or chosen by the player
+ * 6    | RNG[4] | RNG[5] | RNG[6] | RNG[7] | -            | at game start, and the current position in the RNG sequence for the given seed, since the start of the run
  * 7    | RND[0] | RND[1] | RND[2] | RND[3] | ROUND        | What Round we are about to start
  * 8    | ANT[0] | ANT[1] | ANT[2] | ANT[3] | ANTE         | What Ante we are on
  * 9    | MNY[0] | MNY[1] | MNY[2] | MNY[3] | MONEY        | How much money we currently have left
@@ -127,8 +127,7 @@ typedef struct SaveGame
 {
     char tag_internal[SAVE_LABEL_SIZE];
     s32 timer;
-    u32 rng_seed;
-    u32 rng_step;
+    RngInfo rng_info;
     int round;
     int ante;
     int money;
@@ -168,8 +167,7 @@ static const SaveOptions SaveOptions_default = {
 static const SaveGame SaveGame_default = {
     .tag_internal = "-INTERNAL DATA -",
     .timer = 0,
-    .rng_seed = 0,
-    .rng_step = 0,
+    .rng_info = {0, 0},
     .round = 0,
     .ante = 0,
     .money = 0,
@@ -328,8 +326,7 @@ void save_game(void)
     // Fixed data
 
     game.timer = g_game_vars.timer;
-    game.rng_seed = g_game_vars.rng_seed;
-    game.rng_step = g_game_vars.rng_step;
+    game.rng_info = g_game_vars.rng_info;
     game.round = g_game_vars.round;
     game.ante = g_game_vars.ante;
     game.money = g_game_vars.money;
@@ -370,17 +367,10 @@ void load_game(void)
     read_sram(GAME_ADDRESS, (u8*)&game, sizeof(game));
 
     g_game_vars.timer = game.timer;
-    g_game_vars.rng_seed = game.rng_seed;
-    g_game_vars.rng_step = game.rng_step;
+    rng_restore(game.rng_info);
     g_game_vars.round = game.round;
     g_game_vars.ante = game.ante;
     g_game_vars.money = game.money;
 
     // TODO: load Jokers from stored minimal data
-
-    // return to where we were in the random sequence so that the run stays reproducible
-    for (u32 i = 0; i < g_game_vars.rng_step; i++)
-    {
-        (void)rand();
-    }
 }

source/sprite.c

@@ -5,6 +5,7 @@
 #include "game_variables.h"
 #include "graphic_utils.h"
 #include "pool.h"
+#include "random.h"
 #include "soundbank.h"
 #include "util.h"
 
@@ -330,7 +331,7 @@ void sprite_object_set_focus(SpriteObject* sprite_object, bool focus)
 
     play_sfx(
         SFX_CARD_FOCUS,
-        MM_BASE_PITCH_RATE + get_rand() % CARD_FOCUS_SFX_PITCH_OFFSET_RANGE,
+        MM_BASE_PITCH_RATE + rng_get_u32() % CARD_FOCUS_SFX_PITCH_OFFSET_RANGE,
         SFX_DEFAULT_VOLUME
     );
     sprite_object->ty = sprite_object->ty + int2fx((focus ? -1 : 1) * SPRITE_FOCUS_RAISE_PX);