// +build !windows
 

 package chrootarchive // import "github.com/docker/docker/pkg/chrootarchive"

 
 import (

 	"bytes"
 	"encoding/json"
 	"flag"
 	"fmt"
 	"io"

 	"io/ioutil"

 	"os"

 	"path/filepath"

 	"runtime"

 	"strings"

 
 	"github.com/docker/docker/pkg/archive"
 	"github.com/docker/docker/pkg/reexec"

 	"github.com/pkg/errors"

 )
 

 // untar is the entry-point for docker-untar on re-exec. This is not used on
 // Windows as it does not support chroot, hence no point sandboxing through
 // chroot and rexec.
 func untar() {
 	runtime.LockOSThread()
 	flag.Parse()
 

 	var options archive.TarOptions

 	// read the options from the pipe "ExtraFiles"

 	if err := json.NewDecoder(os.NewFile(3, "options")).Decode(&options); err != nil {
 		fatal(err)
 	}
 

 	dst := flag.Arg(0)
 	var root string
 	if len(flag.Args()) > 1 {
 		root = flag.Arg(1)
 	}
 
 	if root == "" {
 		root = dst
 	}
 
 	if err := chroot(root); err != nil {

 		fatal(err)
 	}
 

 	if err := archive.Unpack(os.Stdin, dst, &options); err != nil {

 		fatal(err)
 	}
 	// fully consume stdin in case it is zero padded

 	if _, err := flush(os.Stdin); err != nil {
 		fatal(err)
 	}
 

 	os.Exit(0)
 }
 

 func invokeUnpack(decompressedArchive io.Reader, dest string, options *archive.TarOptions, root string) error {

 	if root == "" {
 		return errors.New("must specify a root to chroot to")
 	}

 
 	// We can't pass a potentially large exclude list directly via cmd line
 	// because we easily overrun the kernel's max argument/environment size
 	// when the full image list is passed (e.g. when this is used by
 	// `docker load`). We will marshall the options via a pipe to the
 	// child
 	r, w, err := os.Pipe()
 	if err != nil {
 		return fmt.Errorf("Untar pipe failure: %v", err)
 	}
 

 	if root != "" {
 		relDest, err := filepath.Rel(root, dest)
 		if err != nil {
 			return err
 		}
 		if relDest == "." {
 			relDest = "/"
 		}
 		if relDest[0] != '/' {
 			relDest = "/" + relDest
 		}
 		dest = relDest
 	}
 
 	cmd := reexec.Command("docker-untar", dest, root)

 	cmd.Stdin = decompressedArchive
 
 	cmd.ExtraFiles = append(cmd.ExtraFiles, r)
 	output := bytes.NewBuffer(nil)
 	cmd.Stdout = output
 	cmd.Stderr = output
 
 	if err := cmd.Start(); err != nil {

 		w.Close()

 		return fmt.Errorf("Untar error on re-exec cmd: %v", err)
 	}

 	// write the options to the pipe for the untar exec to read

 	if err := json.NewEncoder(w).Encode(options); err != nil {

 		w.Close()

 		return fmt.Errorf("Untar json encode to pipe failed: %v", err)
 	}
 	w.Close()
 
 	if err := cmd.Wait(); err != nil {

 		// when `xz -d -c -q | docker-untar ...` failed on docker-untar side,
 		// we need to exhaust `xz`'s output, otherwise the `xz` side will be
 		// pending on write pipe forever
 		io.Copy(ioutil.Discard, decompressedArchive)
 

 		return fmt.Errorf("Error processing tar file(%v): %s", err, output)

 	}
 	return nil
 }

 
 func tar() {
 	runtime.LockOSThread()
 	flag.Parse()
 
 	src := flag.Arg(0)
 	var root string
 	if len(flag.Args()) > 1 {
 		root = flag.Arg(1)
 	}
 
 	if root == "" {
 		root = src
 	}
 
 	if err := realChroot(root); err != nil {
 		fatal(err)
 	}
 
 	var options archive.TarOptions
 	if err := json.NewDecoder(os.Stdin).Decode(&options); err != nil {
 		fatal(err)
 	}
 
 	rdr, err := archive.TarWithOptions(src, &options)
 	if err != nil {
 		fatal(err)
 	}
 	defer rdr.Close()
 
 	if _, err := io.Copy(os.Stdout, rdr); err != nil {
 		fatal(err)
 	}
 
 	os.Exit(0)
 }
 
 func invokePack(srcPath string, options *archive.TarOptions, root string) (io.ReadCloser, error) {
 	if root == "" {
 		return nil, errors.New("root path must not be empty")
 	}
 
 	relSrc, err := filepath.Rel(root, srcPath)
 	if err != nil {
 		return nil, err
 	}
 	if relSrc == "." {
 		relSrc = "/"
 	}
 	if relSrc[0] != '/' {
 		relSrc = "/" + relSrc
 	}
 
 	// make sure we didn't trim a trailing slash with the call to `Rel`
 	if strings.HasSuffix(srcPath, "/") && !strings.HasSuffix(relSrc, "/") {
 		relSrc += "/"
 	}
 
 	cmd := reexec.Command("docker-tar", relSrc, root)
 
 	errBuff := bytes.NewBuffer(nil)
 	cmd.Stderr = errBuff
 
 	tarR, tarW := io.Pipe()
 	cmd.Stdout = tarW
 
 	stdin, err := cmd.StdinPipe()
 	if err != nil {
 		return nil, errors.Wrap(err, "error getting options pipe for tar process")
 	}
 
 	if err := cmd.Start(); err != nil {
 		return nil, errors.Wrap(err, "tar error on re-exec cmd")
 	}
 
 	go func() {
 		err := cmd.Wait()
 		err = errors.Wrapf(err, "error processing tar file: %s", errBuff)
 		tarW.CloseWithError(err)
 	}()
 
 	if err := json.NewEncoder(stdin).Encode(options); err != nil {
 		stdin.Close()
 		return nil, errors.Wrap(err, "tar json encode to pipe failed")
 	}
 	stdin.Close()
 
 	return tarR, nil
 }