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capture.go
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package capture | |
import ( | |
"bufio" | |
"fmt" | |
"io" | |
"os" | |
"syscall" | |
"testing" | |
) | |
type Capture struct { | |
done chan struct{} | |
fd int | |
oldfile *os.File | |
io.Reader | |
} | |
func (c *Capture) Close() error { | |
// fd -> closefd | |
closefd, err := syscall.Dup(c.fd) | |
if err != nil { | |
return err | |
} | |
// oldfile.fd -> fd | |
err = syscall.Dup2(int(c.oldfile.Fd()), c.fd) | |
if err != nil { | |
return err | |
} | |
err = syscall.Close(closefd) | |
if err != nil { | |
return err | |
} | |
<-c.done | |
return nil | |
} | |
func NewCapture(fd int) (*Capture, error) { | |
c := &Capture{ | |
done: make(chan struct{}), | |
fd: fd, | |
} | |
// fd -> oldfd | |
oldfd, err := syscall.Dup(c.fd) | |
if err != nil { | |
return nil, err | |
} | |
c.oldfile = os.NewFile(uintptr(oldfd), "") | |
ospr, ospw, err := os.Pipe() | |
if err != nil { | |
c.oldfile.Close() | |
return nil, err | |
} | |
defer ospw.Close() | |
// ospw -> fd | |
err = syscall.Dup2(int(ospw.Fd()), c.fd) | |
if err != nil { | |
c.oldfile.Close() | |
ospr.Close() | |
return nil, err | |
} | |
iopr, iopw := io.Pipe() | |
go func() { | |
// copy from ospr -> c.oldfile and iopw (read by c.Reader) | |
_, err = io.Copy(io.MultiWriter(c.oldfile, iopw), ospr) | |
iopw.CloseWithError(err) | |
close(c.done) | |
}() | |
c.Reader = iopr | |
return c, nil | |
} | |
func TestCapture(t *testing.T) { | |
c, err := NewCapture(1) | |
if err != nil { | |
t.Fatal(err) | |
} | |
done := make(chan struct{}) | |
go func() { | |
br := bufio.NewReader(c) | |
for { | |
s, err := br.ReadString('\n') | |
if err != nil { | |
break | |
} | |
fmt.Fprint(os.Stderr, s) // TODO: write to insights | |
} | |
close(done) | |
}() | |
fmt.Println("Hello!") | |
err = c.Close() | |
if err != nil { | |
t.Fatal(err) | |
} | |
<-done | |
fmt.Println("Message 2") | |
} |
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