api/client: New and Improved `docker cp` behavior

Supports copying things INTO a container from a local file or from a tar
archive read from stdin.

Docker-DCO-1.1-Signed-off-by: Josh Hawn <josh.hawn@docker.com> (github: jlhawn)

api/client/cp.go

@@ -1,8 +1,14 @@
 package client
 
 import (
+	"encoding/base64"
+	"encoding/json"
 	"fmt"
 	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"path/filepath"
 	"strings"
 
 	"github.com/docker/docker/api/types"
@@ -10,48 +16,289 @@ import (
 	flag "github.com/docker/docker/pkg/mflag"
 )
 
-// CmdCp copies files/folders from a path on the container to a directory on the host running the command.
+type copyDirection int
+
+const (
+	fromContainer copyDirection = (1 << iota)
+	toContainer
+	acrossContainers = fromContainer | toContainer
+)
+
+// CmdCp copies files/folders to or from a path in a container.
 //
-// If HOSTDIR is '-', the data is written as a tar file to STDOUT.
+// When copying from a container, if LOCALPATH is '-' the data is written as a
+// tar archive file to STDOUT.
 //
-// Usage: docker cp CONTAINER:PATH HOSTDIR
+// When copying to a container, if LOCALPATH is '-' the data is read as a tar
+// archive file from STDIN, and the destination CONTAINER:PATH, must specify
+// a directory.
+//
+// Usage:
+// 	docker cp CONTAINER:PATH LOCALPATH|-
+// 	docker cp LOCALPATH|- CONTAINER:PATH
 func (cli *DockerCli) CmdCp(args ...string) error {
-	cmd := cli.Subcmd("cp", []string{"CONTAINER:PATH HOSTDIR|-"}, "Copy files/folders from a container's PATH to a HOSTDIR on the host\nrunning the command. Use '-' to write the data as a tar file to STDOUT.", true)
-	cmd.Require(flag.Exact, 2)
+	cmd := cli.Subcmd(
+		"cp",
+		[]string{"CONTAINER:PATH LOCALPATH|-", "LOCALPATH|- CONTAINER:PATH"},
+		strings.Join([]string{
+			"Copy files/folders between a container and your host.\n",
+			"Use '-' as the source to read a tar archive from stdin\n",
+			"and extract it to a directory destination in a container.\n",
+			"Use '-' as the destination to stream a tar archive of a\n",
+			"container source to stdout.",
+		}, ""),
+		true,
+	)
 
+	cmd.Require(flag.Exact, 2)
 	cmd.ParseFlags(args, true)
 
-	// deal with path name with `:`
-	info := strings.SplitN(cmd.Arg(0), ":", 2)
+	if cmd.Arg(0) == "" {
+		return fmt.Errorf("source can not be empty")
+	}
+	if cmd.Arg(1) == "" {
+		return fmt.Errorf("destination can not be empty")
+	}
+
+	srcContainer, srcPath := splitCpArg(cmd.Arg(0))
+	dstContainer, dstPath := splitCpArg(cmd.Arg(1))
+
+	var direction copyDirection
+	if srcContainer != "" {
+		direction |= fromContainer
+	}
+	if dstContainer != "" {
+		direction |= toContainer
+	}
+
+	switch direction {
+	case fromContainer:
+		return cli.copyFromContainer(srcContainer, srcPath, dstPath)
+	case toContainer:
+		return cli.copyToContainer(srcPath, dstContainer, dstPath)
+	case acrossContainers:
+		// Copying between containers isn't supported.
+		return fmt.Errorf("copying between containers is not supported")
+	default:
+		// User didn't specify any container.
+		return fmt.Errorf("must specify at least one container source")
+	}
+}
 
-	if len(info) != 2 {
-		return fmt.Errorf("Error: Path not specified")
+// We use `:` as a delimiter between CONTAINER and PATH, but `:` could also be
+// in a valid LOCALPATH, like `file:name.txt`. We can resolve this ambiguity by
+// requiring a LOCALPATH with a `:` to be made explicit with a relative or
+// absolute path:
+// 	`/path/to/file:name.txt` or `./file:name.txt`
+//
+// This is apparently how `scp` handles this as well:
+// 	http://www.cyberciti.biz/faq/rsync-scp-file-name-with-colon-punctuation-in-it/
+//
+// We can't simply check for a filepath separator because container names may
+// have a separator, e.g., "host0/cname1" if container is in a Docker cluster,
+// so we have to check for a `/` or `.` prefix. Also, in the case of a Windows
+// client, a `:` could be part of an absolute Windows path, in which case it
+// is immediately proceeded by a backslash.
+func splitCpArg(arg string) (container, path string) {
+	if filepath.IsAbs(arg) {
+		// Explicit local absolute path, e.g., `C:\foo` or `/foo`.
+		return "", arg
 	}
 
-	cfg := &types.CopyConfig{
-		Resource: info[1],
+	parts := strings.SplitN(arg, ":", 2)
+
+	if len(parts) == 1 || strings.HasPrefix(parts[0], ".") {
+		// Either there's no `:` in the arg
+		// OR it's an explicit local relative path like `./file:name.txt`.
+		return "", arg
 	}
-	serverResp, err := cli.call("POST", "/containers/"+info[0]+"/copy", cfg, nil)
-	if serverResp.body != nil {
-		defer serverResp.body.Close()
+
+	return parts[0], parts[1]
+}
+
+func (cli *DockerCli) statContainerPath(containerName, path string) (types.ContainerPathStat, error) {
+	var stat types.ContainerPathStat
+
+	query := make(url.Values, 1)
+	query.Set("path", filepath.ToSlash(path)) // Normalize the paths used in the API.
+
+	urlStr := fmt.Sprintf("/containers/%s/archive?%s", containerName, query.Encode())
+
+	response, err := cli.call("HEAD", urlStr, nil, nil)
+	if err != nil {
+		return stat, err
 	}
-	if serverResp.statusCode == 404 {
-		return fmt.Errorf("No such container: %v", info[0])
+	defer response.body.Close()
+
+	if response.statusCode != http.StatusOK {
+		return stat, fmt.Errorf("unexpected status code from daemon: %d", response.statusCode)
 	}
+
+	return getContainerPathStatFromHeader(response.header)
+}
+
+func getContainerPathStatFromHeader(header http.Header) (types.ContainerPathStat, error) {
+	var stat types.ContainerPathStat
+
+	encodedStat := header.Get("X-Docker-Container-Path-Stat")
+	statDecoder := base64.NewDecoder(base64.StdEncoding, strings.NewReader(encodedStat))
+
+	err := json.NewDecoder(statDecoder).Decode(&stat)
+	if err != nil {
+		err = fmt.Errorf("unable to decode container path stat header: %s", err)
+	}
+
+	return stat, err
+}
+
+func resolveLocalPath(localPath string) (absPath string, err error) {
+	if absPath, err = filepath.Abs(localPath); err != nil {
+		return
+	}
+
+	return archive.PreserveTrailingDotOrSeparator(absPath, localPath), nil
+}
+
+func (cli *DockerCli) copyFromContainer(srcContainer, srcPath, dstPath string) (err error) {
+	if dstPath != "-" {
+		// Get an absolute destination path.
+		dstPath, err = resolveLocalPath(dstPath)
+		if err != nil {
+			return err
+		}
+	}
+
+	query := make(url.Values, 1)
+	query.Set("path", filepath.ToSlash(srcPath)) // Normalize the paths used in the API.
+
+	urlStr := fmt.Sprintf("/containers/%s/archive?%s", srcContainer, query.Encode())
+
+	response, err := cli.call("GET", urlStr, nil, nil)
 	if err != nil {
 		return err
 	}
+	defer response.body.Close()
+
+	if response.statusCode != http.StatusOK {
+		return fmt.Errorf("unexpected status code from daemon: %d", response.statusCode)
+	}
+
+	if dstPath == "-" {
+		// Send the response to STDOUT.
+		_, err = io.Copy(os.Stdout, response.body)
+
+		return err
+	}
+
+	// In order to get the copy behavior right, we need to know information
+	// about both the source and the destination. The response headers include
+	// stat info about the source that we can use in deciding exactly how to
+	// copy it locally. Along with the stat info about the local destination,
+	// we have everything we need to handle the multiple possibilities there
+	// can be when copying a file/dir from one location to another file/dir.
+	stat, err := getContainerPathStatFromHeader(response.header)
+	if err != nil {
+		return fmt.Errorf("unable to get resource stat from response: %s", err)
+	}
+
+	// Prepare source copy info.
+	srcInfo := archive.CopyInfo{
+		Path:   srcPath,
+		Exists: true,
+		IsDir:  stat.Mode.IsDir(),
+	}
 
-	hostPath := cmd.Arg(1)
-	if serverResp.statusCode == 200 {
-		if hostPath == "-" {
-			_, err = io.Copy(cli.out, serverResp.body)
-		} else {
-			err = archive.Untar(serverResp.body, hostPath, &archive.TarOptions{NoLchown: true})
+	// See comments in the implementation of `archive.CopyTo` for exactly what
+	// goes into deciding how and whether the source archive needs to be
+	// altered for the correct copy behavior.
+	return archive.CopyTo(response.body, srcInfo, dstPath)
+}
+
+func (cli *DockerCli) copyToContainer(srcPath, dstContainer, dstPath string) (err error) {
+	if srcPath != "-" {
+		// Get an absolute source path.
+		srcPath, err = resolveLocalPath(srcPath)
+		if err != nil {
+			return err
 		}
+	}
+
+	// In order to get the copy behavior right, we need to know information
+	// about both the source and destination. The API is a simple tar
+	// archive/extract API but we can use the stat info header about the
+	// destination to be more informed about exactly what the destination is.
+
+	// Prepare destination copy info by stat-ing the container path.
+	dstInfo := archive.CopyInfo{Path: dstPath}
+	dstStat, err := cli.statContainerPath(dstContainer, dstPath)
+	// Ignore any error and assume that the parent directory of the destination
+	// path exists, in which case the copy may still succeed. If there is any
+	// type of conflict (e.g., non-directory overwriting an existing directory
+	// or vice versia) the extraction will fail. If the destination simply did
+	// not exist, but the parent directory does, the extraction will still
+	// succeed.
+	if err == nil {
+		dstInfo.Exists, dstInfo.IsDir = true, dstStat.Mode.IsDir()
+	}
+
+	var content io.Reader
+	if srcPath == "-" {
+		// Use STDIN.
+		content = os.Stdin
+		if !dstInfo.IsDir {
+			return fmt.Errorf("destination %q must be a directory", fmt.Sprintf("%s:%s", dstContainer, dstPath))
+		}
+	} else {
+		srcArchive, err := archive.TarResource(srcPath)
+		if err != nil {
+			return err
+		}
+		defer srcArchive.Close()
+
+		// With the stat info about the local source as well as the
+		// destination, we have enough information to know whether we need to
+		// alter the archive that we upload so that when the server extracts
+		// it to the specified directory in the container we get the disired
+		// copy behavior.
+
+		// Prepare source copy info.
+		srcInfo, err := archive.CopyInfoStatPath(srcPath, true)
+		if err != nil {
+			return err
+		}
+
+		// See comments in the implementation of `archive.PrepareArchiveCopy`
+		// for exactly what goes into deciding how and whether the source
+		// archive needs to be altered for the correct copy behavior when it is
+		// extracted. This function also infers from the source and destination
+		// info which directory to extract to, which may be the parent of the
+		// destination that the user specified.
+		dstDir, preparedArchive, err := archive.PrepareArchiveCopy(srcArchive, srcInfo, dstInfo)
 		if err != nil {
 			return err
 		}
+		defer preparedArchive.Close()
+
+		dstPath = dstDir
+		content = preparedArchive
+	}
+
+	query := make(url.Values, 2)
+	query.Set("path", filepath.ToSlash(dstPath)) // Normalize the paths used in the API.
+	// Do not allow for an existing directory to be overwritten by a non-directory and vice versa.
+	query.Set("noOverwriteDirNonDir", "true")
+
+	urlStr := fmt.Sprintf("/containers/%s/archive?%s", dstContainer, query.Encode())
+
+	response, err := cli.stream("PUT", urlStr, &streamOpts{in: content})
+	if err != nil {
+		return err
 	}
+	defer response.body.Close()
+
+	if response.statusCode != http.StatusOK {
+		return fmt.Errorf("unexpected status code from daemon: %d", response.statusCode)
+	}
+
 	return nil
 }