playing test audio works now

.gitignore

@@ -1,3 +1,4 @@
 
 *.exe
 *.dll
+reload-trigger

ampler.c

@@ -2,19 +2,103 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdint.h>
 
 #include <SDL2/SDL.h>
 
-int ampler_main(SDL_Window *w, SDL_Renderer *r, void **u_data) {
-	SDL_Event e;
+#define SAMPLE_RATE (44100)
+#define CHANNELS (2)
+#define FRAME_SAMPLES (SAMPLE_RATE / 60)
+
+typedef uint8_t s8;
+typedef uint16_t s16;
+
+typedef struct Ampler_state Ampler_state;
+struct Ampler_state {
+	int size;
+	SDL_AudioDeviceID playdev;
+	s8 track_l[SAMPLE_RATE * 120]; // 2 minutes
+	s8 track_r[SAMPLE_RATE * 120]; // 2 minutes
+};
+
+int audio_frame(Ampler_state *state) {
+	int queued = SDL_GetQueuedAudioSize(state -> playdev);
+	queued /= sizeof s16; // queued is in bytes
+
+	if(queued > FRAME_SAMPLES * CHANNELS * 2) return 0;
+	// else puts("queued audio.");
+
+	s16 silence[FRAME_SAMPLES * CHANNELS] = { 0 };
+	for (int i = 0; i < FRAME_SAMPLES; i += CHANNELS) {
+		int vol = 10;
+		silence[i] = (i/2) * vol - FRAME_SAMPLES / 2;
+		silence[i + 1] = (i/2) * vol - FRAME_SAMPLES / 2;
+	}
+	if(SDL_QueueAudio(state -> playdev, silence, sizeof silence))
+		puts(SDL_GetError());
+
+	return 1; // audio was qued
+}
+
+Ampler_state *init() {
+	Ampler_state *state = malloc(sizeof Ampler_state);
+	SDL_memset(state, 0, sizeof Ampler_state);
+
+	state -> size = sizeof Ampler_state;
+
+	SDL_AudioSpec want = { 0 }, have = { 0 };
+	want.freq = SAMPLE_RATE;
+	want.format = AUDIO_S16;
+	want.channels = CHANNELS;
+	want.samples = 512;
+	want.callback = NULL; // use que funcs
+	want.userdata = NULL;
+
+	state -> playdev = SDL_OpenAudioDevice(
+		NULL, // default device
+		0, // not capture
+		&want,
+		&have,
+		0 // no changes allowed
+	);
+	if(!(state -> playdev))
+		puts(SDL_GetError());
+
+	puts("init.");
+	return state;
+}
+
+int ampler_main(SDL_Window *w, SDL_Renderer *r, Ampler_state **u_data) {
+	if(*u_data == NULL) *u_data = init();
+
+	int old_size = (*u_data) -> size, new_size = sizeof Ampler_state;
+	if(old_size < new_size) {
+		printf("increasing size. %i to %i\n", old_size, new_size);
+		Ampler_state *nu = malloc(new_size);
+		SDL_memset(nu, 0, new_size);
+		SDL_memcpy(nu, *u_data, old_size);
+		nu -> size = new_size;
+		free(*u_data);
+		*u_data = nu;
+	}
+
+	Ampler_state *state = *u_data;
+
+	SDL_PauseAudioDevice(state -> playdev, 0); // unpause audio
 	while (1) {
+		SDL_Event e;
 		while(SDL_PollEvent(&e))
 			if (e.type == SDL_QUIT)
 				return 1;
+
+		audio_frame(state);
+		// draw_frame(w, r, state);
+
 		SDL_RenderPresent(r);
 		SDL_Delay(1);
 
 		if (!remove("reload-trigger")) {
+			SDL_PauseAudioDevice(state -> playdev, 1); // pause audio
 			puts("removed reload-trigger, reloading...");
 			return 0;
 		}

audio.c

@@ -0,0 +1,21 @@
+// audio.c
+
+int audio_frame(Ampler_state *state) {
+	int queued = SDL_GetQueuedAudioSize(state -> playdev);
+	queued /= sizeof s16; // queued is in bytes
+
+	if(queued > FRAME_SAMPLES * CHANNELS * 2) return 0;
+	// else puts("queued audio.");
+
+	s16 silence[FRAME_SAMPLES * CHANNELS] = { 0 };
+	for (int i = 0; i < FRAME_SAMPLES; i += CHANNELS) {
+		int vol = 10;
+		silence[i] = (i/2) * vol - FRAME_SAMPLES / 2;
+		silence[i + 1] = (i/2) * vol - FRAME_SAMPLES / 2;
+	}
+	if(SDL_QueueAudio(state -> playdev, silence, sizeof silence))
+		puts(SDL_GetError());
+
+	return 1; // audio was qued
+}
+