From 9ddc5c4a6690094c4886197e624101f6a7fe13c1 Mon Sep 17 00:00:00 2001
From: veclavtalica <veclavtalica@tutamail.com>
Date: Sun, 26 Jan 2025 02:37:21 +0300
Subject: [PATCH] twn_timer.c: time limiter for game ticks

---
 CMakeLists.txt               |  1 +
 src/system/linux/twn_timer.c | 71 ++++++++++++++++++++++++++++++++++++
 src/system/twn_timer.h       | 10 +++++
 src/twn_loop.c               |  3 ++
 4 files changed, 85 insertions(+)
 create mode 100644 src/system/linux/twn_timer.c
 create mode 100644 src/system/twn_timer.h

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 060b34b..6fc0c0c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -68,6 +68,7 @@ add_subdirectory(third-party/libxm ${CMAKE_CURRENT_BINARY_DIR}/third-party/libxm
 if(LINUX)
         set(SYSTEM_SOURCE_FILES
                 src/system/linux/twn_elf.c
+                src/system/linux/twn_timer.c
                 $<$<BOOL:${TWN_FEATURE_DYNLIB_GAME}>:src/game_object/twn_linux_game_object.c>)
 elseif(WIN32)
         set(SYSTEM_SOURCE_FILES
diff --git a/src/system/linux/twn_timer.c b/src/system/linux/twn_timer.c
new file mode 100644
index 0000000..3fc51e9
--- /dev/null
+++ b/src/system/linux/twn_timer.c
@@ -0,0 +1,71 @@
+#include "../twn_timer.h"
+#include "twn_engine_context_c.h"
+
+#include <SDL_messagebox.h>
+
+#include <signal.h>
+#include <stdint.h>
+#include <time.h>
+#include <unistd.h>
+#include <stdbool.h>
+
+
+static timer_t            timerid;
+static sigset_t           mask;
+static struct sigaction   sa;
+static struct sigevent    sev;
+
+static bool created;
+
+
+/* stop application */
+static void sanity_timer_handler(int sig, siginfo_t *si, void *uc) {
+    (void)uc; (void)sig; (void)si;
+    SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR,
+                             "sanity timer", "Your game tick exceeded its allocated time, application is closing",
+                             ctx.window);
+    raise(SIGKILL);
+}
+
+
+bool start_sanity_timer(uint64_t milliseconds_to_expire) {
+    if (!created) {
+        sa.sa_flags = SA_SIGINFO;
+        sa.sa_sigaction = sanity_timer_handler;
+        sigemptyset(&sa.sa_mask);
+        if (sigaction(SIGRTMIN, &sa, NULL) == -1)
+            goto ERR_SIGACTION;
+
+       sev.sigev_notify = SIGEV_SIGNAL;
+       sev.sigev_signo = SIGRTMIN;
+       sev.sigev_value.sival_ptr = &timerid;
+       if (timer_create(CLOCK_MONOTONIC, &sev, &timerid) == -1)
+            goto ERR_TIMERCREATE;
+
+        created = true;
+
+    ERR_TIMERCREATE:
+    // ERR_SIGPROCMASK:
+    ERR_SIGACTION:
+        return false;
+    }
+
+    struct itimerspec its = {0};
+    its.it_value.tv_sec = milliseconds_to_expire / 1000;
+    its.it_value.tv_nsec = (milliseconds_to_expire * 1000000 % 1000000000);
+    if (timer_settime(timerid, 0, &its, NULL) == -1)
+        return false;
+
+    return true;
+}
+
+
+bool end_sanity_timer(void) {
+    struct itimerspec its = {0};
+    its.it_value.tv_sec = 0;
+    its.it_value.tv_nsec = 0;
+    if (timer_settime(timerid, 0, &its, NULL) == -1)
+        return false;
+
+    return false;
+}
diff --git a/src/system/twn_timer.h b/src/system/twn_timer.h
new file mode 100644
index 0000000..2cabcaf
--- /dev/null
+++ b/src/system/twn_timer.h
@@ -0,0 +1,10 @@
+#ifndef TWN_TIMER_H
+#define TWN_TIMER_H
+
+#include <stdbool.h>
+#include <stdbit.h>
+
+bool start_sanity_timer(uint64_t milliseconds_to_expire);
+bool end_sanity_timer(void);
+
+#endif // TWN_TIMER_H
diff --git a/src/twn_loop.c b/src/twn_loop.c
index f3b1849..ab49e36 100644
--- a/src/twn_loop.c
+++ b/src/twn_loop.c
@@ -5,6 +5,7 @@
 #include "twn_util_c.h"
 #include "twn_game_object_c.h"
 #include "twn_textures_c.h"
+#include "system/twn_timer.h"
 
 #include <SDL2/SDL.h>
 #include <physfs.h>
@@ -216,7 +217,9 @@ static void main_loop(void) {
         input_state_update(&ctx.input);
 
         profile_start("game tick");
+        start_sanity_timer(2000);
         game_object_tick();
+        end_sanity_timer();
         profile_end("game tick");
 
         input_state_update_postframe(&ctx.input);