music - notes_gen.go

     1  // +build ignore
     2  
     3  package main
     4  
     5  import (
     6  	"flag"
     7  	"fmt"
     8  	"math"
     9  	"os"
    10  )
    11  
    12  var notes = [...]string{
    13  	"C",
    14  	"Cs",
    15  	"D",
    16  	"Ds",
    17  	"E",
    18  	"F",
    19  	"Fs",
    20  	"G",
    21  	"Gs",
    22  	"A",
    23  	"As",
    24  	"B",
    25  }
    26  
    27  var same = map[string]string{
    28  	"Cs": "Db",
    29  	"Ds": "Eb",
    30  	"Fs": "Gb",
    31  	"As": "Bb",
    32  }
    33  
    34  func e(message string, err error) {
    35  	if err != nil {
    36  		fmt.Println(message, err)
    37  		os.Exit(1)
    38  	}
    39  }
    40  
    41  var spaces = "                    "
    42  
    43  func main() {
    44  	var (
    45  		key    uint
    46  		pitch  float64
    47  		num    uint
    48  		output string
    49  	)
    50  	flag.UintVar(&key, "k", 49, "reference key number")
    51  	flag.Float64Var(&pitch, "p", 440, "reference key pitch")
    52  	flag.StringVar(&output, "o", "notes.go", "output file")
    53  	flag.UintVar(&num, "n", 108, "number of notes")
    54  	flag.Parse()
    55  	f, err := os.Create(output)
    56  	e("unable to create output file:", err)
    57  	_, err = fmt.Fprintf(f, "//go:generate go run notes_gen.go -k %d -p %f -n %d\n"+
    58  		"// generated with notes_gen.go\n"+
    59  		"\n"+
    60  		"package music\n"+
    61  		"\n"+
    62  		"type Note float64\n"+
    63  		"\n"+
    64  		"const (\n",
    65  		key, pitch, num)
    66  	e("error writing file header", err)
    67  
    68  	spaces = spaces[:numSize(num)+1]
    69  
    70  	semitone := math.Pow(2, float64(1)/12)
    71  	keyF := float64(key)
    72  	for i := uint(0); i < num; i++ {
    73  		note := pitch * math.Pow(semitone, float64(i)-float64(keyF)-8)
    74  		_, err = fmt.Fprintf(f, "	%s%d%sNote = %f\n", notes[i%12], i/12, spaces[uint(len(notes[i%12]))+numSize(i/12):], note)
    75  		e("error writing note", err)
    76  		if sn, ok := same[notes[i%12]]; ok {
    77  			_, err = fmt.Fprintf(f, "	%s%d%sNote = %f\n", sn, i/12, spaces[uint(len(notes[i%12]))+numSize(i/12):], note)
    78  			e("error writing note", err)
    79  		}
    80  	}
    81  	_, err = f.WriteString(")\n")
    82  	e("error writing file trailer", err)
    83  	e("error closing file", f.Close())
    84  }
    85  
    86  func numSize(n uint) uint {
    87  	var m uint = 1
    88  	for n >= 10 {
    89  		n /= 10
    90  		m++
    91  	}
    92  	return m
    93  }