stew

commit cd9a4a89bf37fefa23fc85f97ab421797e803e82
parent e1e23b060a8b2933eddb1a77d192a4467a06d324
Author: rpa <rpa@laika>
Date:   Fri, 13 Jan 2023 17:18:53 +0000

wave: add missing util.c

Diffstat:
A
src/wave/util.c
 | 
63
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 63 insertions(+), 0 deletions(-)
diff --git a/src/wave/util.c b/src/wave/util.c
@@ -0,0 +1,63 @@
+#include <u.h>
+#include <libc.h>
+
+#include "util.h"
+
+int
+rune2note(Rune r)
+{
+	const Rune *keys1 =  L"zsxdcvgbhnjm,l.;/";
+	const Rune *keys2 =  L"q2w3er5t6y7ui9o0p[";
+	Rune *rp;
+	if ((rp = runestrchr(keys1, r)) != nil) return rp - keys1;
+	if ((rp = runestrchr(keys2, r)) != nil) return rp - keys2 + 12;
+	return -1;
+}
+
+int note2freq(int n)
+{
+
+	/*
+	 * Frequencies for equal-tempered scale
+	 * from https://pages.mtu.edu/~suits/notefreqs.html
+	 */
+
+	double freq[] = {
+		261.63, // C-4
+		277.18,
+		293.66,
+		311.13,
+		329.63,
+		349.23,
+		369.99,
+		392.00,
+		415.30,
+		440.00, // A-4
+		466.16,
+		493.88,
+		523.25, // C-5
+		554.37,
+		587.33,
+		622.25,
+		659.25,
+		698.46,
+		739.99,
+		783.99,
+		830.61,
+		880.00, // A-5
+		932.33,
+		987.77,
+		1046.50,
+		1108.73,
+		1174.66,
+		1244.51,
+		1318.51,
+		1396.91 // F-6
+	};
+
+	int s = sizeof(freq) / sizeof(double);
+	int fo = 1 + (n / s);
+	int fn = n % s;
+	double f = freq[fn];// / 16 * fo;
+	return f;
+}