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moby--moby/archive.go

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package docker
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import (
"errors"
"io"
"io/ioutil"
"os"
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"os/exec"
)
type Archive io.Reader
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type Compression uint32
const (
Uncompressed Compression = iota
Bzip2
Gzip
Xz
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)
func (compression *Compression) Flag() string {
switch *compression {
case Bzip2:
return "j"
case Gzip:
return "z"
case Xz:
return "J"
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}
return ""
}
func Tar(path string, compression Compression) (io.Reader, error) {
cmd := exec.Command("bsdtar", "-f", "-", "-C", path, "-c"+compression.Flag(), ".")
return CmdStream(cmd)
}
func Untar(archive io.Reader, path string) error {
cmd := exec.Command("bsdtar", "-f", "-", "-C", path, "-x")
cmd.Stdin = archive
output, err := cmd.CombinedOutput()
if err != nil {
return errors.New(err.Error() + ": " + string(output))
}
return nil
}
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// CmdStream executes a command, and returns its stdout as a stream.
// If the command fails to run or doesn't complete successfully, an error
// will be returned, including anything written on stderr.
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func CmdStream(cmd *exec.Cmd) (io.Reader, error) {
stdout, err := cmd.StdoutPipe()
if err != nil {
return nil, err
}
stderr, err := cmd.StderrPipe()
if err != nil {
return nil, err
}
pipeR, pipeW := io.Pipe()
errChan := make(chan []byte)
// Collect stderr, we will use it in case of an error
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go func() {
errText, e := ioutil.ReadAll(stderr)
if e != nil {
errText = []byte("(...couldn't fetch stderr: " + e.Error() + ")")
}
errChan <- errText
}()
// Copy stdout to the returned pipe
go func() {
_, err := io.Copy(pipeW, stdout)
if err != nil {
pipeW.CloseWithError(err)
}
errText := <-errChan
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if err := cmd.Wait(); err != nil {
pipeW.CloseWithError(errors.New(err.Error() + ": " + string(errText)))
} else {
pipeW.Close()
}
}()
// Run the command and return the pipe
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if err := cmd.Start(); err != nil {
return nil, err
}
return pipeR, nil
}
// NewTempArchive reads the content of src into a temporary file, and returns the contents
// of that file as an archive. The archive can only be read once - as soon as reading completes,
// the file will be deleted.
func NewTempArchive(src Archive, dir string) (*TempArchive, error) {
f, err := ioutil.TempFile(dir, "")
if err != nil {
return nil, err
}
if _, err := io.Copy(f, src); err != nil {
return nil, err
}
if _, err := f.Seek(0, 0); err != nil {
return nil, err
}
st, err := f.Stat()
if err != nil {
return nil, err
}
size := st.Size()
return &TempArchive{f, size}, nil
}
type TempArchive struct {
*os.File
Size int64 // Pre-computed from Stat().Size() as a convenience
}
func (archive *TempArchive) Read(data []byte) (int, error) {
n, err := archive.File.Read(data)
if err != nil {
os.Remove(archive.File.Name())
}
return n, err
}