1 files changed, 73 insertions, 0 deletions
diff --git a/nyqsrc/sndmax.c b/nyqsrc/sndmax.c
new file mode 100644
index 0000000..a91297b
--- /dev/null
+++ b/nyqsrc/sndmax.c
@@ -0,0 +1,73 @@
+/* sndmax.c -- computes the maximum amplitude in a sound */
+
+
+/* CHANGE LOG
+ * --------------------------------------------------------------------
+ * 28Apr03  dm  min->MIN; fix compiler warning
+ * 31Jan07 rbd  handle negative scale factors
+ */
+
+#ifdef UNIX
+#include "sys/types.h"
+#endif	
+#include <stdio.h>
+/* #include "snd.h" */
+#include "xlisp.h"
+#include "sound.h"
+#include "falloc.h"
+#include "sndmax.h"
+#include "extern.h"
+
+double sound_max(LVAL snd_expr, long n)
+{
+    LVAL s_as_lval;
+    sound_type s = NULL;
+    long blocklen;
+    sample_block_values_type sbufp;
+    register double maximum = 0;
+
+    s_as_lval = xleval(snd_expr);
+    /* BE CAREFUL - DO NOT ALLOW GC TO RUN WHILE LVAL IS UNPROTECTED */
+    if (exttypep(s_as_lval, a_sound)) {
+        /* if snd_expr was simply a symbol, then s now points to
+        a shared sound_node.  If we read samples from it, then
+        the sound bound to the symbol will be destroyed, so
+        copy it first.  If snd_expr was a real expression that
+        computed a new value, then the next garbage collection
+        will reclaim the sound_node.  We need to make the new
+        sound reachable by the garbage collector to that any
+        lisp data reachable from the sound do not get collected.
+        To make the sound reachable, we need to allocate a node,
+        and the GC might run, so we need to protect the OLD s
+        but then make it unreachable.
+        We will let the GC collect the sound in the end.
+        */
+        xlprot1(s_as_lval);
+        s = sound_copy(getsound(s_as_lval));
+        s_as_lval = cvsound(s);	/* destroys only ref. to original */
+        /* printf("sound_max: copy is %x, lval %x\n", s, s_as_lval); */
+        while (n > 0) {
+            long togo, j;
+            sample_block_type sampblock = 
+              sound_get_next(s, &blocklen);
+            if (sampblock == zero_block || blocklen == 0) {
+                break;
+            }
+            togo = MIN(blocklen, n);
+            sbufp = sampblock->samples;
+            for (j = 0; j < togo; j++) {
+                register double samp = *sbufp++;
+                if (samp > maximum) maximum = samp;
+                else if (-samp > maximum) maximum = -samp;
+            }
+            n -= togo;
+        }
+        xlpop();
+    } else {
+        xlerror("sound_max: expression did not return a sound",
+                 s_as_lval);
+    }
+    return fabs(maximum * s->scale);
+}
+
+