Drive gameplay with audio instead of timer

audio.c

@@ -1,14 +1,30 @@
 #include <audio.h>
 #include <stdio.h>
 
+void audioCallback(void *userdata, uint8_t *stream, int len) {
+    AudioContext *aud;
+    SDL_assert(len == 834 * 4);
+
+    aud = userdata;
+    if (!aud->filled) {
+        /* too little data, play silence */
+        SDL_memset4(stream, 0, 834);
+        return;
+    }
+    SDL_memcpy4(stream, aud->buffers[aud->current], 834);
+    ++aud->current;
+    aud->current %= 2;
+    aud->filled -= 1;
+} 
+
 int audioInit(AudioContext *aud) {
     SDL_AudioSpec spec;
     spec.freq = 41700;
     spec.format = AUDIO_S16;
     spec.channels = 2;
-    spec.samples = 1024;
+    spec.samples = 834;
-    spec.callback = NULL;
+    spec.callback = &audioCallback;
-    spec.userdata = NULL;
+    spec.userdata = aud;
 
     aud->id = SDL_OpenAudioDevice(NULL, 0, &spec, NULL, 0);
     aud->paused = true;
@@ -16,21 +32,34 @@ int audioInit(AudioContext *aud) {
         fprintf(stderr, "could not open audio device: %s\n", SDL_GetError());
         return -1;
     }
+    aud->current = 0;
+    aud->filled = 0;
     return 0;
 }
 
 int audioUpdate(AudioContext *aud, void *data, uint32_t bytes) {
+    int filled;
     if (!aud->id) return -1;
+    SDL_assert(bytes == 834 * 4);
 
-    if (SDL_QueueAudio(aud->id, data, bytes)) {
+    SDL_LockAudioDevice(aud->id);
-        fprintf(stderr, "could not write audio: %s\n", SDL_GetError());
+    if (aud->filled < 2) {
-        return -1;
+        int next = (aud->current + aud->filled) % 2;
+        SDL_memcpy4(aud->buffers[next], data, bytes / 4);
+        aud->filled += 1;
     }
+    filled = aud->filled;
+    SDL_UnlockAudioDevice(aud->id);
 
     if (aud->paused) {
         SDL_PauseAudioDevice(aud->id, false);
         aud->paused = false;
     }
 
+    while (filled > 1) {
+        SDL_Delay(0);
+        filled = aud->filled;
+    }
+
     return 0;
 }

audio.h

@@ -7,6 +7,9 @@
 typedef struct {
     SDL_AudioDeviceID id;
     bool paused;
+    uint32_t buffers[2][834];
+    int current;
+    int filled;
 } AudioContext;
 
 int audioInit(AudioContext *aud);

game.c

@@ -6,19 +6,6 @@
 #include <stdbool.h>
 #include <time.h>
 
-int sleepNanos(long int ns) {
-    struct timespec time;
-    if (ns < 0) return 0;
-    time.tv_sec = ns / 1000000000;
-    time.tv_nsec = ns % 1000000000;
-    return nanosleep(&time, NULL);
-}
-long int tickNs() {
-    struct timespec time;
-    clock_gettime(CLOCK_MONOTONIC, &time);
-    return (time.tv_sec * 1000000000) + time.tv_nsec;
-}
-
 typedef struct {
     GraphicsContext *gfx;
     AudioContext aud;
@@ -52,7 +39,6 @@ int runGame(VB *sim, GraphicsContext *gfx) {
     SDL_Event event;
     GameState state;
     ControllerState ctrl;
-    uint64_t ticks, prevTicks;
 
     state.gfx = gfx;
     audioInit(&state.aud);
@@ -67,10 +53,7 @@ int runGame(VB *sim, GraphicsContext *gfx) {
 
     while (1) {
         clocks = MAX_STEP_CLOCKS;
-        prevTicks = tickNs();
         vbEmulate(sim, &clocks);
-        ticks = tickNs();
-        sleepNanos(((MAX_STEP_CLOCKS - clocks) * 50) - (ticks - prevTicks));
 
         while (SDL_PollEvent(&event)) {
             if (event.type == SDL_QUIT) {

makefile

@@ -28,17 +28,15 @@ output/%.o: %.c
 	@mkdir -p output
 	@$(CC) -c -o $@ $< -I . \
 		-I shrooms-vb-core/core $(SDL2FLAGS) \
-		-D _POSIX_C_SOURCE=199309L \
 		-O3 -flto -fno-strict-aliasing \
-		-Werror -std=c11 -Wall -Wextra -Wpedantic
+		-Werror -std=c90 -Wall -Wextra -Wpedantic
 
 output/vb.o: shrooms-vb-core/core/vb.c
 	@mkdir -p output
 	@$(CC) -c -o $@ $< -I . \
 		-I shrooms-vb-core/core $(SDL2FLAGS) \
-		-D _POSIX_C_SOURCE=199309L \
 		-O3 -flto -fno-strict-aliasing \
-		-Werror -std=c11 -Wall -Wextra -Wpedantic
+		-Werror -std=c90 -Wall -Wextra -Wpedantic
 
 output/%.o: assets/%.bin
 	@mkdir -p output