twn_audio.c: .wav support and scratch channels

src/twn_audio_c.h

@@ -13,9 +13,12 @@
 
 #define AUDIO_FREQUENCY 48000
 
-
+/* TODO: specify which PCM formats are usable with WAV */
+/* TODO: specify limitations of libxm */
+/* TODO: specify limitations of stb_vorbis */
 typedef enum AudioFileType {
     AUDIO_FILE_TYPE_OGG,
+    AUDIO_FILE_TYPE_WAV,
     AUDIO_FILE_TYPE_XM,
     AUDIO_FILE_TYPE_COUNT,
     AUDIO_FILE_TYPE_UNKNOWN,
@@ -30,6 +33,12 @@ union AudioContext {
         uint8_t channel_count;
     } vorbis;
 
+    struct {
+        void *samples;
+        SDL_AudioSpec spec;
+        size_t position;
+    } wav;
+
     struct {
         xm_context_t *handle;
     } xm;
@@ -44,6 +53,7 @@ typedef struct AudioChannel {
     bool repeat;
     float volume;
     float panning;
+    bool finished;
 } AudioChannel;