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
|
package pipe
import (
"context"
"fmt"
"io"
)
// StageFunc is a function that can be used to power a `goStage`. It
// should read its input from `stdin` and write its output to
// `stdout`. `stdin` and `stdout` will be closed automatically (if
// necessary) once the function returns.
//
// Neither `stdin` nor `stdout` are necessarily buffered. If the
// `StageFunc` requires buffering, it needs to arrange that itself.
//
// A `StageFunc` is run in a separate goroutine, so it must be careful
// to synchronize any data access aside from reading and writing.
type StageFunc func(ctx context.Context, env Env, stdin io.Reader, stdout io.Writer) error
// Function returns a pipeline `Stage` that will run a `StageFunc` in
// a separate goroutine to process the data. See `StageFunc` for more
// information.
func Function(name string, f StageFunc) Stage {
return &goStage{
name: name,
f: f,
done: make(chan struct{}),
}
}
// goStage is a `Stage` that does its work by running an arbitrary
// `stageFunc` in a goroutine.
type goStage struct {
name string
f StageFunc
done chan struct{}
err error
}
func (s *goStage) Name() string {
return s.name
}
func (s *goStage) Start(ctx context.Context, env Env, stdin io.ReadCloser) (io.ReadCloser, error) {
r, w := io.Pipe()
go func() {
s.err = s.f(ctx, env, stdin, w)
if err := w.Close(); err != nil && s.err == nil {
s.err = fmt.Errorf("error closing output pipe for stage %q: %w", s.Name(), err)
}
if stdin != nil {
if err := stdin.Close(); err != nil && s.err == nil {
s.err = fmt.Errorf("error closing stdin for stage %q: %w", s.Name(), err)
}
}
close(s.done)
}()
return r, nil
}
func (s *goStage) Wait() error {
<-s.done
return s.err
}
|
