/
tarzip.go
117 lines (109 loc) · 2.78 KB
/
tarzip.go
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//
// Copyright (c) SAS Institute Inc.
//
// 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 zipslicer
import (
"archive/tar"
"errors"
"fmt"
"io"
"io/ioutil"
"os"
)
const (
TarMemberCD = "zipdir.bin"
TarMemberZip = "contents.zip"
)
// Make a tar archive with two members:
// - the central directory of the zip file
// - the complete zip file
// This lets us process the zip in one pass, which normally isn't possible with
// the directory at the end.
func ZipToTar(r *os.File, w io.Writer) error {
size, err := r.Seek(0, io.SeekEnd)
if err != nil {
return err
}
dirLoc, err := FindDirectory(r, size)
if err != nil {
return err
}
tw := tar.NewWriter(w)
if _, err := r.Seek(dirLoc, 0); err != nil {
return err
}
if err := tarAddStream(tw, r, TarMemberCD, size-dirLoc); err != nil {
return err
}
if _, err := r.Seek(0, 0); err != nil {
return err
}
if err := tarAddStream(tw, r, TarMemberZip, size); err != nil {
return err
}
return tw.Close()
}
func tarAddStream(tw *tar.Writer, r io.Reader, name string, size int64) error {
hdr := &tar.Header{Name: name, Mode: 0644, Size: size}
if err := tw.WriteHeader(hdr); err != nil {
return err
}
if _, err := io.CopyN(tw, r, size); err != nil {
return err
}
return nil
}
// Read a tar stream produced by ZipToTar and return the zip directory. Files
// must be read from the zip in order or an error will be raised.
func ReadZipTar(r io.Reader) (*Directory, error) {
tr := tar.NewReader(r)
hdr, err := tr.Next()
if err != nil {
return nil, fmt.Errorf("error reading tar: %w", err)
} else if hdr.Name != TarMemberCD {
return nil, errors.New("invalid tarzip")
}
zipdir, err := ioutil.ReadAll(tr)
if err != nil {
return nil, fmt.Errorf("error reading tar: %w", err)
}
hdr, err = tr.Next()
if err != nil {
return nil, err
} else if hdr.Name != TarMemberZip {
return nil, errors.New("invalid tarzip")
}
zr := &zipTarReader{tr: tr}
return ReadStream(zr, hdr.Size, zipdir)
}
type zipTarReader struct {
tr *tar.Reader
}
func (z *zipTarReader) Read(d []byte) (int, error) {
if z.tr == nil {
return 0, io.EOF
}
n, err := z.tr.Read(d)
if err == io.EOF {
_, err2 := z.tr.Next()
if err2 == nil {
err = errors.New("invalid tarzip")
} else if err2 != io.EOF {
err = err2
}
z.tr = nil
}
return n, err
}