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demultiplex.go
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/
demultiplex.go
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// Package demultiplex demultiplexes Docker attach streams
package demultiplex
import (
"bytes"
"encoding/binary"
"io"
)
func Streams(r io.Reader) (stdout, stderr io.Reader) {
outr, outw := io.Pipe()
errr, errw := io.Pipe()
go func() {
read := frameReader(r)
for {
typ, data, err := read()
if typ == frameTypeStderr {
if _, err := errw.Write(data); err != nil {
outw.Close()
return
}
} else {
if _, err := outw.Write(data); err != nil {
errw.Close()
return
}
}
if err != nil {
outw.CloseWithError(err)
errw.CloseWithError(err)
return
}
}
}()
return outr, errr
}
type frameType byte
const (
frameTypeStdin frameType = iota
frameTypeStdout
frameTypeStderr
)
func frameReader(r io.Reader) func() (frameType, []byte, error) {
var buf bytes.Buffer
var header [8]byte
return func() (frameType, []byte, error) {
buf.Reset()
if _, err := io.ReadFull(r, header[:]); err != nil {
return 0, nil, err
}
ft := frameType(header[0])
length := int(binary.BigEndian.Uint32(header[4:]))
buf.Grow(length)
data := buf.Bytes()[:length]
n, err := io.ReadFull(r, data)
return ft, data[:n], err
}
}
func Clean(r io.Reader) io.Reader {
pr, pw := io.Pipe()
go func() {
read := frameReader(r)
for {
_, data, err := read()
if _, err := pw.Write(data); err != nil {
return
}
if err != nil {
pw.CloseWithError(err)
return
}
}
}()
return pr
}
func Copy(stdout, stderr io.Writer, r io.Reader) error {
read := frameReader(r)
for {
t, data, err := read()
var ew error
if len(data) > 0 {
if stderr != nil && t == frameTypeStderr {
_, ew = stderr.Write(data)
} else {
_, ew = stdout.Write(data)
}
if ew != nil {
return ew
}
}
if err != nil {
if err == io.EOF {
err = nil
}
return err
}
}
}