From 2c29409f6c7dd7cbacd7027b4afcc08546fa7a66 Mon Sep 17 00:00:00 2001
From: Ian Munsie <darkstarsword@gmail.com>
Date: Mon, 10 Sep 2012 03:51:13 +1000
Subject: [PATCH] Replace floating point arithmetic causing freeze with 64bit
 integer arithmetic

It seems that sem_GetTicks sometimes returns NAN. If this happens when
resuming the game (i.e. from Start60HZ), than the start variable can be
set to NAN, which causes this test in CheckTimers to never succeed:
while ((end - start) >= update_ticks_pc)

So it never runs Game60hzcall and therefore appears to freeze.

Using gdb to change start to a real number less than end allows zsnes to
continue.

See this forum post for more details:
http://board.zsnes.com/phpBB3/viewtopic.php?f=3&t=2337&p=225071#p225071

This patch changes it to use a 64bit integer instead of floating point
arithmetic to avoid hitting these cases.

Also, remove the unused start2, end2, and update_ticks_pc2 variables.

Signed-off-by: Ian Munsie <darkstarsword@gmail.com>
---
 src/linux/sdllink.c |   35 ++++++++++++-----------------------
 1 file changed, 12 insertions(+), 23 deletions(-)

diff --git a/src/linux/sdllink.c b/src/linux/sdllink.c
index 4274c9d..eece048 100644
--- a/src/linux/sdllink.c
+++ b/src/linux/sdllink.c
@@ -111,23 +111,23 @@ static BYTE IsActivated = 1;
 
 /* TIMER VARIABLES/MACROS */
 // millisecond per world update
-#define UPDATE_TICKS_GAME (1000.0/59.948743718592964824120603015060)
-#define UPDATE_TICKS_GAMEPAL (20.0)
-#define UPDATE_TICKS_GUI (1000.0/36.0)
-#define UPDATE_TICKS_UDP (1000.0/60.0)
+#define UPDATE_TICKS_GAME (1000000.0/59.948743718592964824120603015060)
+#define UPDATE_TICKS_GAMEPAL (20000)
+#define UPDATE_TICKS_GUI (1000000/36)
+#define UPDATE_TICKS_UDP (1000000/60)
 
 int T60HZEnabled = 0;
 int T36HZEnabled = 0;
-float end, end2;
-float start, start2;
-float update_ticks_pc, update_ticks_pc2;
+unsigned long long end;
+unsigned long long start;
+unsigned long long update_ticks_pc;
 
 // Used for semaphore code
 static SDL_sem *sem_frames = NULL;
 static struct timeval sem_start;
 void sem_sleep_rdy(void);
 void sem_sleep_die(void);
-float sem_GetTicks(void);
+unsigned long long sem_GetTicks(void);
 
 extern unsigned char romispal;
 
@@ -830,7 +830,6 @@ int startgame()
 
 void Start60HZ(void)
 {
-  update_ticks_pc2 = UPDATE_TICKS_UDP;
   if (romispal == 1)
   {
     update_ticks_pc = UPDATE_TICKS_GAMEPAL;
@@ -842,7 +841,6 @@ void Start60HZ(void)
 
   // Restore timer data from semaphore data
   start = sem_GetTicks();
-  start2 = sem_GetTicks();
   T36HZEnabled = 0;
   T60HZEnabled = 1;
 }
@@ -854,12 +852,10 @@ void Stop60HZ(void)
 
 void Start36HZ(void)
 {
-  update_ticks_pc2 = UPDATE_TICKS_UDP;
   update_ticks_pc = UPDATE_TICKS_GUI;
 
   // Restore timer data from semaphore data
   start = sem_GetTicks();
-  start2 = sem_GetTicks();
   T60HZEnabled = 0;
   T36HZEnabled = 1;
 }
@@ -1097,14 +1093,6 @@ void initwinvideo(void)
 
 void CheckTimers(void)
 {
-  //QueryPerformanceCounter((LARGE_INTEGER*)&end2);
-  end2 = sem_GetTicks();
-
-  while ((end2 - start2) >= update_ticks_pc2)
-  {
-    start2 += update_ticks_pc2;
-  }
-
   if (T60HZEnabled)
   {
     //QueryPerformanceCounter((LARGE_INTEGER*)&end);
@@ -1306,13 +1294,14 @@ void __attribute__ ((stdcall, constructor)) sem_StartTicks()
   gettimeofday(&sem_start, NULL);
 }
 
-float sem_GetTicks()
+unsigned long long sem_GetTicks()
 {
   struct timeval now;
-  float ticks;
+  unsigned long long ticks;
 
   gettimeofday(&now, NULL);
-  ticks=((float)(now.tv_sec-sem_start.tv_sec))*1000.f+((float)(now.tv_usec-sem_start.tv_usec))*.001f;
+  ticks = (now.tv_sec - sem_start.tv_sec) * 1000000 +
+	  (now.tv_usec - sem_start.tv_usec);
   return(ticks);
 }
 
-- 
1.7.10.4