1 files changed, 137 insertions, 0 deletions
diff --git a/reference/C/CONTRIB/SNIP/playlib.c b/reference/C/CONTRIB/SNIP/playlib.c
new file mode 100755
index 0000000..5ac3ddd
--- /dev/null
+++ b/reference/C/CONTRIB/SNIP/playlib.c
@@ -0,0 +1,137 @@
+/*
+**  PLAYLIB.C
+**
+**  Public domain for TC only by Lynn R. Lively
+**  Modified by Bob Stout
+*/
+
+#include <dos.h>
+#include <stdlib.h>
+#include "sound.h"
+
+#ifdef __ZTC__
+ #include <int.h>
+ #define interrupt
+#else
+ static void (interrupt far *n_oldtmint) (void);
+#endif
+
+#define TIMER_TICK_INTR 0x1c
+
+static NOTE *     n_buff;
+static unsigned   n_buff_sz;
+static NOTE *     n_head;
+static NOTE *     n_tail;
+static unsigned   play_duration;
+static unsigned   play_freq;
+
+/*
+** Add note to note buff. Return = 1 (note added), 0 (Out of note buff)
+*/
+
+int playb_note (unsigned freq, unsigned duration)
+{
+      if (++n_tail == (n_buff + n_buff_sz))
+            n_tail = n_buff;
+
+      if (n_tail == n_head)
+      {
+            --n_tail;
+            return (0);
+      }
+
+      n_tail->freq     = freq;
+      n_tail->duration = duration;
+
+      return (1);
+}
+
+/*
+** ISR for background music.
+*/
+
+#ifndef __ZTC__
+ static void interrupt far play_intr (void)
+#else
+ static int play_intr (struct INT_DATA *idp)
+#endif
+{
+      int_off ();
+
+#ifndef __ZTC__
+      (*n_oldtmint) ();                   /* Call Old timer interrupt.  */
+#else
+      int_prev(idp);
+#endif
+
+      if (play_duration == 0)
+      {
+            soundoff ();
+
+            if (++n_head == (n_buff + n_buff_sz))
+                  n_head = n_buff;
+
+            if (n_head == n_tail)
+            {
+                  --n_head;
+                  int_on ();
+                  return;
+            }
+
+            play_duration = n_head->duration;
+            if (0 != (play_freq = n_head->freq))
+                  soundon();
+            dosound (play_freq);
+      }
+      else  --play_duration;
+
+      int_on ();
+
+#ifdef __ZTC__
+      return 1;                           /* Don't chain                */
+#endif
+}
+
+/*
+** Call this function to init background music. buff_sz is number of
+** notes in the note buffer. Returns pointer to buff or NULL if
+** out of heap space.
+*/
+
+NOTE * playb_open (unsigned buff_sz)
+{
+      n_buff =
+      n_head =
+      n_tail =  (NOTE *) calloc (buff_sz, sizeof (NOTE));
+
+      if (n_buff != (NOTE *) NULL)
+      {
+            n_buff_sz     = buff_sz;
+
+            play_duration =
+            play_freq     = 0;
+            
+#ifdef __ZTC__
+            int_intercept(TIMER_TICK_INTR, play_intr, 256);
+#else
+            n_oldtmint    = getvect (TIMER_TICK_INTR);
+            setvect (TIMER_TICK_INTR, play_intr);
+#endif
+      }
+      return (n_buff);
+}
+
+/*
+** Return things to normal and free allocated space.
+*/
+
+void playb_close (void)
+{
+      soundoff ();
+#ifndef __ZTC__
+      setvect (TIMER_TICK_INTR, n_oldtmint);
+#else
+      int_restore(TIMER_TICK_INTR);
+#endif
+      free (n_buff);
+}