scalestore.go RawHistoryFolder

1package config
2
3import (
4	"fmt"
5	"math"
6	"strconv"
7
8	"github.com/bnema/kvconf"
9)
10
11// ScaleStore writes output.<name>.scale into the config file, preserving
12// unrelated lines and comments.
13type ScaleStore struct{ Path string }
14
15// SaveOutputScale updates output.<name>.scale in the config file. The file is
16// replaced atomically; a symlinked config is written through to its target.
17// A new config may hold commands: only its owner reads it (0600).
18func (s ScaleStore) SaveOutputScale(output string, scale float64) error {
19	value := formatScale(scale)
20	return kvconf.SetFile(s.Path, map[string]*string{"output." + output + ".scale": &value}, 0o600)
21}
22
23// formatScale writes scales as the config expects them: a decimal when it is
24// exact (1.25), else a fraction (4/3).
25func formatScale(s float64) string {
26	n, d := int(math.Round(s*120)), 120
27	g := gcd(n, d)
28	n, d = n/g, d/g
29	den := d
30	for den%2 == 0 {
31		den /= 2
32	}
33	for den%5 == 0 {
34		den /= 5
35	}
36	if den == 1 {
37		return strconv.FormatFloat(float64(n)/float64(d), 'f', -1, 64)
38	}
39	return fmt.Sprintf("%d/%d", n, d)
40}
41
42func gcd(a, b int) int {
43	for b != 0 {
44		a, b = b, a%b
45	}
46	return a
47}