local-server/vendor/github.com/cavaliercoder/go-cpio/reader.go

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2018-06-17 07:32:44 +00:00
package cpio
import (
"io"
"io/ioutil"
)
// A Reader provides sequential access to the contents of a CPIO archive. A CPIO
// archive consists of a sequence of files. The Next method advances to the next
// file in the archive (including the first), and then it can be treated as an
// io.Reader to access the file's data.
type Reader struct {
r io.Reader // underlying file reader
hdr *Header // current Header
eof int64 // bytes until the end of the current file
}
// NewReader creates a new Reader reading from r.
func NewReader(r io.Reader) *Reader {
return &Reader{
r: r,
}
}
// Read reads from the current entry in the CPIO archive. It returns 0, io.EOF
// when it reaches the end of that entry, until Next is called to advance to the
// next entry.
func (r *Reader) Read(p []byte) (n int, err error) {
if r.hdr == nil || r.eof == 0 {
return 0, io.EOF
}
rn := len(p)
if r.eof < int64(rn) {
rn = int(r.eof)
}
n, err = r.r.Read(p[0:rn])
r.eof -= int64(n)
return
}
// Next advances to the next entry in the CPIO archive.
// io.EOF is returned at the end of the input.
func (r *Reader) Next() (*Header, error) {
if r.hdr == nil {
return r.next()
}
skp := r.eof + r.hdr.pad
if skp > 0 {
_, err := io.CopyN(ioutil.Discard, r.r, skp)
if err != nil {
return nil, err
}
}
return r.next()
}
func (r *Reader) next() (*Header, error) {
r.eof = 0
hdr, err := readHeader(r.r)
if err != nil {
return nil, err
}
r.hdr = hdr
r.eof = hdr.Size
return hdr, nil
}
// ReadHeader creates a new Header, reading from r.
func readHeader(r io.Reader) (*Header, error) {
// currently only SVR4 format is supported
return readSVR4Header(r)
}