-
-
Notifications
You must be signed in to change notification settings - Fork 0
/
sizedwriter.go
72 lines (64 loc) · 1.43 KB
/
sizedwriter.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
72
package sizedwriter
import (
"errors"
"io"
"os"
)
type cb func(*Writer) error
// Writer is a size-limited writer with specified size. When writer return
// error when file size over the limited size.
type Writer struct {
Filename string
Size int64
Perm os.FileMode
Cb cb
file *os.File
}
// NewWriter create new writer with specified filename, size, permission,
// and callback. when file size reach the size, writer close the file
// descriptor and call callback.
func NewWriter(filename string, size int64, perm os.FileMode, over cb) io.WriteCloser {
return &Writer{filename, size, perm, over, nil}
}
// Write write bytes into the file.
func (sw *Writer) Write(b []byte) (int, error) {
fi, err := os.Lstat(sw.Filename)
var size int64
if err == nil {
size = fi.Size() + int64(len(b))
} else if os.IsNotExist(err) {
size = int64(len(b))
}
if size > sw.Size {
if sw.Cb != nil {
sw.file.Close()
sw.file = nil
err = sw.Cb(sw)
if err != nil {
return 0, err
}
} else {
return 0, errors.New("Can't write more")
}
}
if sw.file == nil {
sw.file, err = os.OpenFile(sw.Filename, os.O_RDWR|os.O_APPEND|os.O_CREATE, sw.Perm)
if err != nil {
return 0, err
}
}
n, err := sw.file.Write(b)
sw.file.Sync()
return n, err
}
// Close closes the file.
func (sw *Writer) Close() error {
var err error
if sw.file != nil {
err = sw.file.Close()
if err == nil {
sw.file = nil
}
}
return err
}