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writer.go
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/
writer.go
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// Copyright 2015 The appc Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package aci
import (
"archive/tar"
"bytes"
"encoding/json"
"io"
"time"
"github.com/coreos/rkt/Godeps/_workspace/src/github.com/appc/spec/schema"
)
// ArchiveWriter writes App Container Images. Users wanting to create an ACI or
// should create an ArchiveWriter and add files to it; the ACI will be written
// to the underlying tar.Writer
type ArchiveWriter interface {
AddFile(hdr *tar.Header, r io.Reader) error
Close() error
}
type imageArchiveWriter struct {
*tar.Writer
am *schema.ImageManifest
}
// NewImageWriter creates a new ArchiveWriter which will generate an App
// Container Image based on the given manifest and write it to the given
// tar.Writer
func NewImageWriter(am schema.ImageManifest, w *tar.Writer) ArchiveWriter {
aw := &imageArchiveWriter{
w,
&am,
}
return aw
}
func (aw *imageArchiveWriter) AddFile(hdr *tar.Header, r io.Reader) error {
err := aw.Writer.WriteHeader(hdr)
if err != nil {
return err
}
if r != nil {
_, err := io.Copy(aw.Writer, r)
if err != nil {
return err
}
}
return nil
}
func (aw *imageArchiveWriter) addFileNow(path string, contents []byte) error {
buf := bytes.NewBuffer(contents)
now := time.Now()
hdr := tar.Header{
Name: path,
Mode: 0644,
Uid: 0,
Gid: 0,
Size: int64(buf.Len()),
ModTime: now,
Typeflag: tar.TypeReg,
Uname: "root",
Gname: "root",
ChangeTime: now,
}
return aw.AddFile(&hdr, buf)
}
func (aw *imageArchiveWriter) addManifest(name string, m json.Marshaler) error {
out, err := m.MarshalJSON()
if err != nil {
return err
}
return aw.addFileNow(name, out)
}
func (aw *imageArchiveWriter) Close() error {
if err := aw.addManifest(ManifestFile, aw.am); err != nil {
return err
}
return aw.Writer.Close()
}