Wrap tick API

This avoids to use the SDL timer API directly, and will allow to handle
generic ticks (possibly negative).

app/meson.build

@@ -25,6 +25,7 @@ src = [
     'src/util/process.c',
     'src/util/str_util.c',
     'src/util/thread.c',
+    'src/util/tick.c',
 ]
 
 if host_machine.system() == 'windows'

app/src/fps_counter.c

@@ -1,11 +1,10 @@
 #include "fps_counter.h"
 
 #include <assert.h>
-#include <SDL2/SDL_timer.h>
 
 #include "util/log.h"
 
-#define FPS_COUNTER_INTERVAL_MS 1000
+#define FPS_COUNTER_INTERVAL SC_TICK_FROM_SEC(1)
 
 bool
 fps_counter_init(struct fps_counter *counter) {
@@ -47,7 +46,7 @@ set_started(struct fps_counter *counter, bool started) {
 static void
 display_fps(struct fps_counter *counter) {
     unsigned rendered_per_second =
-        counter->nr_rendered * 1000 / FPS_COUNTER_INTERVAL_MS;
+        counter->nr_rendered * SC_TICK_FREQ / FPS_COUNTER_INTERVAL;
     if (counter->nr_skipped) {
         LOGI("%u fps (+%u frames skipped)", rendered_per_second,
                                             counter->nr_skipped);
@@ -68,8 +67,8 @@ check_interval_expired(struct fps_counter *counter, uint32_t now) {
     counter->nr_skipped = 0;
     // add a multiple of the interval
     uint32_t elapsed_slices =
-        (now - counter->next_timestamp) / FPS_COUNTER_INTERVAL_MS + 1;
-    counter->next_timestamp += FPS_COUNTER_INTERVAL_MS * elapsed_slices;
+        (now - counter->next_timestamp) / FPS_COUNTER_INTERVAL + 1;
+    counter->next_timestamp += FPS_COUNTER_INTERVAL * elapsed_slices;
 }
 
 static int
@@ -82,11 +81,11 @@ run_fps_counter(void *data) {
             sc_cond_wait(&counter->state_cond, &counter->mutex);
         }
         while (!counter->interrupted && is_started(counter)) {
-            uint32_t now = SDL_GetTicks();
+            sc_tick now = sc_tick_now();
             check_interval_expired(counter, now);
 
             assert(counter->next_timestamp > now);
-            uint32_t remaining = counter->next_timestamp - now;
+            sc_tick remaining = counter->next_timestamp - now;
 
             // ignore the reason (timeout or signaled), we just loop anyway
             sc_cond_timedwait(&counter->state_cond, &counter->mutex, remaining);
@@ -99,7 +98,7 @@ run_fps_counter(void *data) {
 bool
 fps_counter_start(struct fps_counter *counter) {
     sc_mutex_lock(&counter->mutex);
-    counter->next_timestamp = SDL_GetTicks() + FPS_COUNTER_INTERVAL_MS;
+    counter->next_timestamp = sc_tick_now() + FPS_COUNTER_INTERVAL;
     counter->nr_rendered = 0;
     counter->nr_skipped = 0;
     sc_mutex_unlock(&counter->mutex);
@@ -165,7 +164,7 @@ fps_counter_add_rendered_frame(struct fps_counter *counter) {
     }
 
     sc_mutex_lock(&counter->mutex);
-    uint32_t now = SDL_GetTicks();
+    sc_tick now = sc_tick_now();
     check_interval_expired(counter, now);
     ++counter->nr_rendered;
     sc_mutex_unlock(&counter->mutex);
@@ -178,7 +177,7 @@ fps_counter_add_skipped_frame(struct fps_counter *counter) {
     }
 
     sc_mutex_lock(&counter->mutex);
-    uint32_t now = SDL_GetTicks();
+    sc_tick now = sc_tick_now();
     check_interval_expired(counter, now);
     ++counter->nr_skipped;
     sc_mutex_unlock(&counter->mutex);

app/src/fps_counter.h

@@ -24,7 +24,7 @@ struct fps_counter {
     bool interrupted;
     unsigned nr_rendered;
     unsigned nr_skipped;
-    uint32_t next_timestamp;
+    sc_tick next_timestamp;
 };
 
 bool

app/src/server.c

@@ -554,10 +554,10 @@ server_stop(struct server *server) {
     sc_mutex_lock(&server->mutex);
     bool signaled = false;
     if (!server->process_terminated) {
-#define WATCHDOG_DELAY_MS 1000
+#define WATCHDOG_DELAY SC_TICK_FROM_SEC(1)
         signaled = sc_cond_timedwait(&server->process_terminated_cond,
                                      &server->mutex,
-                                     WATCHDOG_DELAY_MS);
+                                     WATCHDOG_DELAY);
     }
     sc_mutex_unlock(&server->mutex);
 

app/src/util/thread.c

@@ -123,7 +123,12 @@ sc_cond_wait(sc_cond *cond, sc_mutex *mutex) {
 }
 
 bool
-sc_cond_timedwait(sc_cond *cond, sc_mutex *mutex, uint32_t ms) {
+sc_cond_timedwait(sc_cond *cond, sc_mutex *mutex, sc_tick delay) {
+    if (delay < 0) {
+        return false; // timeout
+    }
+
+    uint32_t ms = SC_TICK_TO_MS(delay);
     int r = SDL_CondWaitTimeout(cond->cond, mutex->mutex, ms);
 #ifndef NDEBUG
     if (r < 0) {

app/src/util/thread.h

@@ -5,7 +5,8 @@
 
 #include <stdatomic.h>
 #include <stdbool.h>
-#include <stdint.h>
+
+#include "tick.h"
 
 /* Forward declarations */
 typedef struct SDL_Thread SDL_Thread;
@@ -72,7 +73,7 @@ sc_cond_wait(sc_cond *cond, sc_mutex *mutex);
 
 // return true on signaled, false on timeout
 bool
-sc_cond_timedwait(sc_cond *cond, sc_mutex *mutex, uint32_t ms);
+sc_cond_timedwait(sc_cond *cond, sc_mutex *mutex, sc_tick ms);
 
 void
 sc_cond_signal(sc_cond *cond);

app/src/util/tick.c

@@ -0,0 +1,16 @@
+#include "tick.h"
+
+#include <SDL2/SDL_timer.h>
+
+sc_tick
+sc_tick_now(void) {
+    // SDL_GetTicks() resolution is in milliseconds, but sc_tick are expressed
+    // in microseconds to store PTS without precision loss.
+    //
+    // As an alternative, SDL_GetPerformanceCounter() and
+    // SDL_GetPerformanceFrequency() could be used, but:
+    //  - the conversions (avoiding overflow) are expansive, since the
+    //    frequency is not known at compile time;
+    //  - in practice, we don't need more precision for now.
+    return (sc_tick) SDL_GetTicks() * 1000;
+}

app/src/util/tick.h

@@ -0,0 +1,20 @@
+#ifndef SC_TICK_H
+#define SC_TICK_H
+
+#include <stdint.h>
+
+typedef int64_t sc_tick;
+#define SC_TICK_FREQ 1000000 // microsecond
+
+// To be adapted if SC_TICK_FREQ changes
+#define SC_TICK_TO_US(tick) (tick)
+#define SC_TICK_TO_MS(tick) ((tick) / 1000)
+#define SC_TICK_TO_SEC(tick) ((tick) / 1000000)
+#define SC_TICK_FROM_US(us) (us)
+#define SC_TICK_FROM_MS(ms) ((ms) * 1000)
+#define SC_TICK_FROM_SEC(sec) ((sec) * 1000000)
+
+sc_tick
+sc_tick_now(void);
+
+#endif