-
Notifications
You must be signed in to change notification settings - Fork 1.7k
/
deferable_write_closer.go
61 lines (55 loc) · 1.5 KB
/
deferable_write_closer.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
package utils
import (
"io"
"sync"
)
// DeferableWriteCloser is to be used in leiu of defer'ing
// Close on an [io.WriteCloser] (// For more background see https://www.joeshaw.org/dont-defer-close-on-writable-files/)
// Callers should *both*
// explicitly call Close and check for errors when done with the underlying writerclose
// *and* defer the Close() to handle returns before the explicit close
//
// For example rather than
//
// import "os"
// f, err := os.Create("./foo")
// if err != nil { return err}
// defer f.Close()
// return f.Write([]bytes("hi"))
//
// do
//
// import "os"
// f, err := os.Create("./foo")
// if err != nil {return nil}
// wc := NewDeferableWriteCloser(f)
// defer wc.Close()
// err = wc.Write([]bytes("hi"))
// if err != nil {return err}
// return wc.Close()
type DeferableWriteCloser struct {
mu sync.Mutex
closed bool
closeErr error
io.WriteCloser
}
// NewDeferableWriteCloser creates a deferable writercloser. Callers
// should explicit call and defer Close. See DeferabelWriterCloser for details.
func NewDeferableWriteCloser(wc io.WriteCloser) *DeferableWriteCloser {
return &DeferableWriteCloser{
WriteCloser: wc,
}
}
// Close closes the WriterCloser. The underlying Closer
// is Closed exactly once and resulting error is cached.
// Should be called explicitly AND defered
// Thread safe
func (wc *DeferableWriteCloser) Close() error {
wc.mu.Lock()
defer wc.mu.Unlock()
if !wc.closed {
wc.closeErr = wc.WriteCloser.Close()
wc.closed = true
}
return wc.closeErr
}