forked from maddyblue/moggio
/
seek.go
71 lines (64 loc) · 1.13 KB
/
seek.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
package server
import (
"errors"
"time"
)
type Seek struct {
b []float32
pos int
sr time.Duration
f func(int) ([]float32, error)
}
func NewSeek(canSeek bool, sr time.Duration, f func(int) ([]float32, error)) *Seek {
s := Seek{
f: f,
sr: sr,
}
if canSeek {
s.b = make([]float32, 4096)
}
return &s
}
func (s *Seek) Read(n int) (b []float32, err error) {
if s.b == nil {
b, err = s.f(n)
s.pos += len(b)
return
}
for len(s.b)-s.pos < n {
b, err = s.f(n)
s.b = append(s.b, b...)
if err != nil || len(b) == 0 {
break
}
}
tot := s.pos + n
if len(s.b) < tot {
tot = len(s.b)
}
b = s.b[s.pos:tot]
s.pos = tot
return
}
var errSeekable = errors.New("cannot seek this file")
// Seek sets the offset for the next Read to offset, relative to the origin
// of the file.
func (s *Seek) Seek(offset time.Duration) error {
if s.b == nil {
return errSeekable
}
pos := int(offset / s.sr)
if pos < len(s.b) {
s.pos = pos
return nil
}
_, err := s.Read(pos - len(s.b))
if err != nil {
return err
}
s.pos = pos
return nil
}
func (s *Seek) Pos() time.Duration {
return s.sr * time.Duration(s.pos)
}