From 06f50ed77949cee495a1d8d98fec16648a5c8ea9 Mon Sep 17 00:00:00 2001
From: "Juan J. Martinez" <jjm@usebox.net>
Date: Mon, 15 May 2023 12:31:46 +0100
Subject: Added OPL3 support

---
 tr8vm.c | 86 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)

(limited to 'tr8vm.c')

diff --git a/tr8vm.c b/tr8vm.c
index e75ba9f..fd64c0f 100644
--- a/tr8vm.c
+++ b/tr8vm.c
@@ -27,6 +27,7 @@
 #include <string.h>
 
 #include "SDL.h"
+#include "opl3.h"
 
 #include "vm.h"
 
@@ -42,6 +43,10 @@
 #define WINDOW_W (TR8_W * WINDOW_SCALE)
 #define WINDOW_H (TR8_H * WINDOW_SCALE)
 
+#define TR8_SAMPLE_RATE     44100
+#define TR8_SAMPLE_CHANNELS 1
+#define TR8_SAMPLE_SIZE     1024
+
 static void resize_full_screen(SDL_Window *win, SDL_Renderer *renderer, int fullscreen, SDL_Rect *s)
 {
     if (!fullscreen)
@@ -157,6 +162,26 @@ static void update_ctl(SDL_Event *ev)
     }
 }
 
+SDL_mutex *amutex = NULL;
+
+opl3_chip opl;
+uint8_t snd_reg[2] = { 0 };
+
+static void audio_callback(void *userdata, uint8_t *stream, int32_t len)
+{
+    if (!SDL_LockMutex(amutex))
+    {
+        SDL_memset(stream, 0, len);
+        while (len >= 2)
+        {
+            OPL3_GenerateResampled((opl3_chip *)userdata, (int16_t *)stream);
+            stream += 2;
+            len -= 2;
+        }
+        SDL_UnlockMutex(amutex);
+    }
+}
+
 uint8_t blt_set = 0;
 uint8_t blt_paramc = 0;
 uint8_t blt_param[6] = { 0 };
@@ -240,6 +265,34 @@ uint8_t port(uint8_t p, uint8_t v)
             blt_param[blt_paramc++] = v;
             return p;
 
+        /* sound register selector primary */
+        case 0xc0:
+            snd_reg[0] = v & 0xff;
+            return p;
+
+        /* sound data primary */
+        case 0xc1:
+            if (!SDL_LockMutex(amutex))
+            {
+                OPL3_WriteReg(&opl, snd_reg[0], v);
+                SDL_UnlockMutex(amutex);
+            }
+            return p;
+
+        /* sound register selector secondary */
+        case 0xc2:
+            snd_reg[1] = v & 0xff;
+            return p;
+
+        /* sound data secondary */
+        case 0xc3:
+            if (!SDL_LockMutex(amutex))
+            {
+                OPL3_WriteReg(&opl, 0x100 | snd_reg[1], v);
+                SDL_UnlockMutex(amutex);
+            }
+            return p;
+
         /* controller 1 */
         case 0xf0:
             return ctl[0];
@@ -298,6 +351,33 @@ int main(int argc, char *argv[])
         return 1;
     }
 
+    /* init audio */
+    OPL3_Reset(&opl, TR8_SAMPLE_RATE);
+
+    amutex = SDL_CreateMutex();
+    if (!amutex)
+    {
+        fprintf(stderr, "Failed to create mutex: %s\n", SDL_GetError());
+        return 1;
+    }
+
+    SDL_AudioSpec audio_spec, audio_want;
+
+    SDL_memset(&audio_want, 0, sizeof(audio_want));
+
+    audio_want.freq = TR8_SAMPLE_RATE,
+    audio_want.format = AUDIO_S16,
+    audio_want.channels = TR8_SAMPLE_CHANNELS,
+    audio_want.callback = audio_callback,
+    audio_want.userdata = (void *)&opl;
+    audio_want.samples = TR8_SAMPLE_SIZE;
+
+    SDL_AudioDeviceID audio = SDL_OpenAudioDevice(NULL, 0, &audio_want, &audio_spec, 0);
+    if (audio == 0)
+        fprintf(stderr, "Failed to open audio: %s\n", SDL_GetError());
+    else
+        SDL_PauseAudioDevice(audio, 0);
+
     SDL_Window *screen = SDL_CreateWindow(APP_NAME " " APP_VERSION,
                                           SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
                                           WINDOW_W, WINDOW_H,
@@ -411,6 +491,12 @@ int main(int argc, char *argv[])
     if (fb)
         SDL_DestroyTexture(fb);
 
+    if (audio > 0)
+        SDL_CloseAudioDevice(audio);
+
+    if (amutex)
+        SDL_DestroyMutex(amutex);
+
     SDL_DestroyRenderer(renderer);
     SDL_DestroyWindow(screen);
 
-- 
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