// Read reads actual data from the xz stream.
func (r *streamReader) Read(p []byte) (n int, err error) {
for n < len(p) {
if r.br == nil {
bh, hlen, err := readBlockHeader(r.xz)
if err != nil {
if err == errIndexIndicator {
if err = r.readTail(); err != nil {
return n, err
}
return n, io.EOF
}
return n, err
}
xlog.Debugf("block %v", *bh)
r.br, err = r.ReaderConfig.newBlockReader(r.xz, bh,
hlen, r.newHash())
if err != nil {
return n, err
}
}
k, err := r.br.Read(p[n:])
n += k
if err != nil {
if err == io.EOF {
r.index = append(r.index, r.br.record())
r.br = nil
} else {
return n, err
}
}
}
return n, nil
}
// newStreamReader creates a new xz stream reader using the given configuration
// parameters. NewReader reads and checks the header of the xz stream.
func (c ReaderConfig) newStreamReader(xz io.Reader) (r *streamReader, err error) {
if err = c.Verify(); err != nil {
return nil, err
}
data := make([]byte, HeaderLen)
if _, err := io.ReadFull(xz, data[:4]); err != nil {
return nil, err
}
if bytes.Equal(data[:4], []byte{0, 0, 0, 0}) {
return nil, errPadding
}
if _, err = io.ReadFull(xz, data[4:]); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return nil, err
}
r = &streamReader{
ReaderConfig: c,
xz: xz,
index: make([]record, 0, 4),
}
if err = r.h.UnmarshalBinary(data); err != nil {
return nil, err
}
xlog.Debugf("xz header %s", r.h)
if r.newHash, err = newHashFunc(r.h.flags); err != nil {
return nil, err
}
return r, nil
}
// readTail reads the index body and the xz footer.
func (r *streamReader) readTail() error {
index, n, err := readIndexBody(r.xz)
if err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return err
}
if len(index) != len(r.index) {
return fmt.Errorf("xz: index length is %d; want %d",
len(index), len(r.index))
}
for i, rec := range r.index {
if rec != index[i] {
return fmt.Errorf("xz: record %d is %v; want %v",
i, rec, index[i])
}
}
p := make([]byte, footerLen)
if _, err = io.ReadFull(r.xz, p); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return err
}
var f footer
if err = f.UnmarshalBinary(p); err != nil {
return err
}
xlog.Debugf("xz footer %s", f)
if f.flags != r.h.flags {
return errors.New("xz: footer flags incorrect")
}
if f.indexSize != int64(n)+1 {
return errors.New("xz: index size in footer wrong")
}
return nil
}