stew

a monorepo of some sort
git clone git://git.nsmpr.xyz/stew.git
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util.c (999B)

      1 #include <u.h>
      2 #include <libc.h>
      3 
      4 #include "util.h"
      5 
      6 int
      7 rune2note(Rune r)
      8 {
      9 	const Rune *keys1 =  L"zsxdcvgbhnjm,l.;/";
     10 	const Rune *keys2 =  L"q2w3er5t6y7ui9o0p[";
     11 	Rune *rp;
     12 	if ((rp = runestrchr(keys1, r)) != nil) return rp - keys1;
     13 	if ((rp = runestrchr(keys2, r)) != nil) return rp - keys2 + 12;
     14 	return -1;
     15 }
     16 
     17 double note2freq(int n)
     18 {
     19 
     20 	// TODO: convert to proper caclucations
     21 	// instead of table lookup and messy pows
     22 
     23 	/*
     24 	 * Frequencies for equal-tempered scale
     25 	 * from https://pages.mtu.edu/~suits/notefreqs.html
     26 	 */
     27 
     28 	double freq[] = {
     29 		261.63, // C-4
     30 		277.18,
     31 		293.66,
     32 		311.13,
     33 		329.63,
     34 		349.23,
     35 		369.99,
     36 		392.00,
     37 		415.30,
     38 		440.00, // A-4
     39 		466.16,
     40 		493.88,
     41 		523.25, // C-5
     42 		554.37,
     43 		587.33,
     44 		622.25,
     45 		659.25,
     46 		698.46,
     47 		739.99,
     48 		783.99,
     49 		830.61,
     50 		880.00, // A-5
     51 		932.33,
     52 		987.77,
     53 		1046.50,
     54 		1108.73,
     55 		1174.66,
     56 		1244.51,
     57 		1318.51,
     58 		1396.91 // F-6
     59 	};
     60 
     61 	int fo = 1 + (n / 12);
     62 	int fn = n % 12;
     63 	double f = freq[fn] / pow(2, 4) * pow(2, fo);
     64 	return f;
     65 }