archive: move stat-header handling into copy package

Move handling the stat header into `pkg/copy`.  All copy-related should
ideally be located in this package to increase locality and reduce
scattering where possible.

Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

pkg/api/handlers/compat/containers_archive.go

@@ -1,13 +1,8 @@
 package compat
 
 import (
-	"bytes"
-	"encoding/base64"
-	"encoding/json"
 	"fmt"
 	"net/http"
-	"os"
-	"time"
 
 	"github.com/containers/podman/v2/libpod"
 	"github.com/containers/podman/v2/libpod/define"
@@ -71,12 +66,12 @@ func handleHeadAndGet(w http.ResponseWriter, r *http.Request, decoder *schema.De
 		utils.Error(w, "Not found.", http.StatusNotFound, errors.Wrapf(err, "error stating container path %q", query.Path))
 		return
 	}
-	statHeader, err := fileInfoToDockerStats(info)
+	statHeader, err := copy.EncodeFileInfo(info)
 	if err != nil {
 		utils.Error(w, "Something went wrong", http.StatusInternalServerError, err)
 		return
 	}
-	w.Header().Add("X-Docker-Container-Path-Stat", statHeader)
+	w.Header().Add(copy.XDockerContainerPathStatHeader, statHeader)
 
 	// Our work is done when the user is interested in the header only.
 	if r.Method == http.MethodHead {
@@ -98,42 +93,6 @@ func handleHeadAndGet(w http.ResponseWriter, r *http.Request, decoder *schema.De
 	}
 }
 
-func fileInfoToDockerStats(info *copy.FileInfo) (string, error) {
-	dockerStats := struct {
-		Name       string      `json:"name"`
-		Size       int64       `json:"size"`
-		Mode       os.FileMode `json:"mode"`
-		ModTime    time.Time   `json:"mtime"`
-		LinkTarget string      `json:"linkTarget"`
-	}{
-		Name:       info.Name,
-		Size:       info.Size,
-		Mode:       info.Mode,
-		ModTime:    info.ModTime,
-		LinkTarget: info.LinkTarget,
-	}
-
-	jsonBytes, err := json.Marshal(&dockerStats)
-	if err != nil {
-		return "", errors.Wrap(err, "failed to serialize file stats")
-	}
-
-	buff := bytes.NewBuffer(make([]byte, 0, 128))
-	base64encoder := base64.NewEncoder(base64.StdEncoding, buff)
-
-	_, err = base64encoder.Write(jsonBytes)
-	if err != nil {
-		return "", err
-	}
-
-	err = base64encoder.Close()
-	if err != nil {
-		return "", err
-	}
-
-	return buff.String(), nil
-}
-
 func handlePut(w http.ResponseWriter, r *http.Request, decoder *schema.Decoder, runtime *libpod.Runtime) {
 	query := struct {
 		Path string `schema:"path"`

pkg/copy/copy.go

@@ -114,7 +114,6 @@ func enforceCopyRules(source, destination *CopyItem) error {
 		return nil
 	}
 
-	// Source is a *stream*.
 	if source.info.IsStream {
 		if !(destination.info.IsDir || destination.info.IsStream) {
 			return errors.New("destination must be a directory or stream when copying from a stream")

pkg/copy/fileinfo.go

@@ -0,0 +1,56 @@
+package copy
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"net/http"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/pkg/errors"
+)
+
+// XDockerContainerPathStatHeader is the *key* in http headers pointing to the
+// base64 encoded JSON payload of stating a path in a container.
+const XDockerContainerPathStatHeader = "X-Docker-Container-Path-Stat"
+
+// FileInfo describes a file or directory and is returned by
+// (*CopyItem).Stat().
+type FileInfo struct {
+	Name       string      `json:"name"`
+	Size       int64       `json:"size"`
+	Mode       os.FileMode `json:"mode"`
+	ModTime    time.Time   `json:"mtime"`
+	IsDir      bool        `json:"isDir"`
+	IsStream   bool        `json:"isStream"`
+	LinkTarget string      `json:"linkTarget"`
+}
+
+// EncodeFileInfo serializes the specified FileInfo as a base64 encoded JSON
+// payload.  Intended for Docker compat.
+func EncodeFileInfo(info *FileInfo) (string, error) {
+	buf, err := json.Marshal(&info)
+	if err != nil {
+		return "", errors.Wrap(err, "failed to serialize file stats")
+	}
+	return base64.URLEncoding.EncodeToString(buf), nil
+}
+
+// ExtractFileInfoFromHeader extracts a base64 encoded JSON payload of a
+// FileInfo in the http header.  If no such header entry is found, nil is
+// returned.  Intended for Docker compat.
+func ExtractFileInfoFromHeader(header *http.Header) (*FileInfo, error) {
+	rawData := header.Get(XDockerContainerPathStatHeader)
+	if len(rawData) == 0 {
+		return nil, nil
+	}
+
+	info := FileInfo{}
+	base64Decoder := base64.NewDecoder(base64.URLEncoding, strings.NewReader(rawData))
+	if err := json.NewDecoder(base64Decoder).Decode(&info); err != nil {
+		return nil, err
+	}
+
+	return &info, nil
+}

pkg/copy/item.go

@@ -5,7 +5,6 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
-	"time"
 
 	buildahCopiah "github.com/containers/buildah/copier"
 	"github.com/containers/buildah/pkg/chrootuser"
@@ -75,18 +74,6 @@ type CopyItem struct {
 // deferFunc allows for returning functions that must be deferred at call sites.
 type deferFunc func()
 
-// FileInfo describes a file or directory and is returned by
-// (*CopyItem).Stat().
-type FileInfo struct {
-	Name       string      `json:"name"`
-	Size       int64       `json:"size"`
-	Mode       os.FileMode `json:"mode"`
-	ModTime    time.Time   `json:"mtime"`
-	IsDir      bool        `json:"isDir"`
-	IsStream   bool        `json:"isStream"`
-	LinkTarget string      `json:"linkTarget"`
-}
-
 // Stat returns the FileInfo.
 func (item *CopyItem) Stat() (*FileInfo, error) {
 	return &item.info, item.statError