Enhance sfx_handler to accomodate more formats

docs/demo.md

@@ -18,6 +18,9 @@
 * 1: Fist
 * 3: Shotgun
 
+### Music and sound effect(sfx)
+Support music and sound effects.
+
 ## Quake
 **source**: [quake-embedded](https://github.com/sysprog21/quake-embedded/)
 
@@ -47,6 +50,9 @@ make
 
 You may use the mouse to adjust the pitch and yaw angle
 
+### Music and sound effect(sfx)
+Support sound effects but not music currently because Quake needs a CD-ROM and the extracted pak file doesn't contain any music or bgm-related files.
+
 ### Limitations
 * Mouse wheel input is not supported
-* All sound functions are not implemented
+* Music related functions in Quake are not implemented

docs/syscall.md

@@ -174,7 +174,7 @@ The request is similar to how music is managed earlier in the description and su
 Music data is defined in a structure called `musicinfo_t`. The SDL2_mixer library is used by the emulator to play music using the fields `data` and `size` in the structure.
 
 #### Sound Effect(sfx)
-`sfxinfo_t` is a structure that defines sound effect data and size. The `data` and `size` fields of the structure are used to play sound effect with the SDL2_mixer library.
+`sfxinfo_t` is a structure that defines sound effect data and size. The `data` and `size` fields of the structure are used to play sound effect with the SDL2_mixer library. Currently, support sound effect of [Doom's WAV](https://doomwiki.org/wiki/Sound) format and [normal WAV](https://en.wikipedia.org/wiki/WAV) format(includes [RIFF header](https://en.wikipedia.org/wiki/Resource_Interchange_File_Format)).
 
 ### `setup_audio` - setup or shutdown sound system
 

src/syscall_sdl.c

@@ -578,12 +578,16 @@ static void *sfx_handler(void *arg)
     sound_t *sfx = (sound_t *) arg;
     uint8_t *ptr = sfx->data;
 
-    /* parsing sound */
-    ptr += 2; /* skip format */
-    ptr += 2; /* skip sample rate since SAMPLE_RATE is defined */
-    nr_sfx_samples = *(uint32_t *) ptr;
-    ptr += 4;
-    ptr += 4; /* skip pad bytes */
+    if (*ptr & 0x3) { /* Doom WAV format */
+        ptr += 2;     /* skip format */
+        ptr += 2;     /* skip sample rate since SAMPLE_RATE is defined */
+        nr_sfx_samples = *(uint32_t *) ptr;
+        ptr += 4;
+        ptr += 4;  /* skip pad bytes */
+    } else {       /* Normal WAV format*/
+        ptr += 44; /* skip RIFF header */
+        nr_sfx_samples = sfx->size - 44;
+    }
 
     memcpy(sfx_samples, ptr, sizeof(uint8_t) * nr_sfx_samples);
     sfx_chunk = Mix_QuickLoad_RAW(sfx_samples, nr_sfx_samples);
@@ -594,8 +598,11 @@ static void *sfx_handler(void *arg)
     if (chan == -1)
         return NULL;
 
-    /* multiplied by 8 because sfx->volume's max is 15 */
-    Mix_Volume(chan, sfx->volume * 8);
+    if (*ptr & 0x3) /* Doom, multiplied by 8 because sfx->volume's max is 15 */
+        Mix_Volume(chan, sfx->volume * 8);
+    else /* Quake, + 1 mod by 128 because sfx->volume's max is 255 and
+            Mix_Volume's max is 128 */
+        Mix_Volume(chan, (sfx->volume + 1) % 128);
 
     return NULL;
 }