func skipToArMember(arReader *ar.Reader, memberPrefix string) (io.Reader, error) {
var err error
// find the right ar member
var header *ar.Header
for {
header, err = arReader.Next()
if err != nil {
return nil, err
}
if strings.HasPrefix(header.Name, memberPrefix) {
break
}
}
// figure out what compression to use
var dataReader io.Reader
switch {
case strings.HasSuffix(header.Name, ".gz"):
dataReader, err = gzip.NewReader(arReader)
if err != nil {
return nil, err
}
case strings.HasSuffix(header.Name, ".bz2"):
dataReader = bzip2.NewReader(arReader)
case strings.HasSuffix(header.Name, ".xz"):
dataReader = xzPipeReader(arReader)
default:
return nil, fmt.Errorf("Can not handle %s", header.Name)
}
return dataReader, nil
}
// extract 'control' file from 'reader'. the contents of a 'control' file
// is a set of key-value pairs as described in
// https://www.debian.org/doc/debian-policy/ch-controlfields.html
func extractControlFromIpk(reader io.Reader) (string, error) {
var (
arReader *ar.Reader
tarReader *tar.Reader
gzReader *gzip.Reader
)
arReader = ar.NewReader(reader)
for {
header, err := arReader.Next()
if err != nil && err != io.EOF {
return "", fmt.Errorf("extracting contents: %v", err)
} else if header == nil {
break
}
// NOTE: strangeley the name of the files end with a "/" ... content error?
if header.Name == "control.tar.gz/" || header.Name == "control.tar.gz" {
gzReader, err = gzip.NewReader(arReader)
if err != nil {
return "", fmt.Errorf("analyzing control.tar.gz: %v", err)
}
break
}
}
if gzReader == nil {
return "", fmt.Errorf("missing control.tar.gz entry")
}
defer gzReader.Close()
buffer := bytes.NewBuffer(nil)
tarReader = tar.NewReader(gzReader)
for {
header, err := tarReader.Next()
if err != nil && err != io.EOF {
return "", fmt.Errorf("extracting control.tar.gz: %v", err)
} else if header == nil {
break
}
if header.Name != "./control" {
continue
}
io.Copy(buffer, tarReader)
break
}
if buffer.Len() == 0 {
return "", fmt.Errorf("missing or empty 'control' file inside 'control.tar.gz'")
}
return buffer.String(), nil
}