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extract.go
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extract.go
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package extract
import (
"archive/tar"
"bufio"
"compress/gzip"
"errors"
"io"
"os"
"path"
"strings"
"time"
perrors "github.com/pkg/errors"
)
type Options struct {
StripLevels int
Perm *os.FileMode
UID *int
GID *int
}
type Option func(o *Options)
func StripLevels(levels int) Option {
return func(o *Options) {
o.StripLevels = levels
}
}
func Extract(origReader io.Reader, destFolder string, options ...Option) error {
extractOptions := &Options{}
for _, o := range options {
o(extractOptions)
}
// read ahead
bufioReader := bufio.NewReader(origReader)
testBytes, err := bufioReader.Peek(2) // read 2 bytes
if err != nil {
return err
}
// is gzipped?
var reader io.Reader
if testBytes[0] == 31 && testBytes[1] == 139 {
gzipReader, err := gzip.NewReader(bufioReader)
if err != nil {
return perrors.Errorf("error decompressing: %v", err)
}
defer gzipReader.Close()
reader = gzipReader
} else {
reader = bufioReader
}
tarReader := tar.NewReader(reader)
for {
shouldContinue, err := extractNext(tarReader, destFolder, extractOptions)
if err != nil {
return perrors.Wrap(err, "decompress")
} else if !shouldContinue {
return nil
}
}
}
func extractNext(tarReader *tar.Reader, destFolder string, options *Options) (bool, error) {
header, err := tarReader.Next()
if err != nil {
if !errors.Is(err, io.EOF) {
return false, perrors.Wrap(err, "tar reader next")
}
return false, nil
}
relativePath := getRelativeFromFullPath("/"+header.Name, "")
if options.StripLevels > 0 {
for i := 0; i < options.StripLevels; i++ {
relativePath = strings.TrimPrefix(relativePath, "/")
index := strings.Index(relativePath, "/")
if index == -1 {
break
}
relativePath = relativePath[index+1:]
}
relativePath = "/" + relativePath
}
outFileName := path.Join(destFolder, relativePath)
baseName := path.Dir(outFileName)
dirPerm := os.ModePerm
if options.Perm != nil {
dirPerm = *options.Perm
}
// Check if newer file is there and then don't override?
if err := os.MkdirAll(baseName, dirPerm); err != nil {
return false, err
}
// whats the file perm?
filePerm := os.FileMode(0644)
if options.Perm != nil {
filePerm = *options.Perm
}
// Is dir?
if header.Typeflag == tar.TypeDir {
if err := os.MkdirAll(outFileName, dirPerm); err != nil {
return false, err
}
return true, nil
} else if header.Typeflag == tar.TypeSymlink {
err := os.Symlink(header.Linkname, outFileName)
if err != nil {
return false, err
}
return true, nil
} else if header.Typeflag == tar.TypeLink {
err := os.Link(header.Linkname, outFileName)
if err != nil {
return false, err
}
return true, nil
}
// Create / Override file
outFile, err := os.OpenFile(outFileName, os.O_RDWR|os.O_CREATE|os.O_TRUNC, filePerm)
if err != nil {
// Try again after 5 seconds
time.Sleep(time.Second * 5)
outFile, err = os.OpenFile(outFileName, os.O_RDWR|os.O_CREATE|os.O_TRUNC, filePerm)
if err != nil {
return false, perrors.Wrapf(err, "create %s", outFileName)
}
}
defer outFile.Close()
if _, err := io.Copy(outFile, tarReader); err != nil {
return false, perrors.Wrapf(err, "io copy tar reader %s", outFileName)
}
if err := outFile.Close(); err != nil {
return false, perrors.Wrapf(err, "out file close %s", outFileName)
}
// Set permissions
if options.Perm == nil {
_ = os.Chmod(outFileName, header.FileInfo().Mode()|0600)
}
// Set mod time from tar header
_ = os.Chtimes(outFileName, time.Now(), header.FileInfo().ModTime())
return true, nil
}
func getRelativeFromFullPath(fullpath string, prefix string) string {
return strings.TrimPrefix(strings.ReplaceAll(strings.ReplaceAll(fullpath[len(prefix):], "\\", "/"), "//", "/"), ".")
}