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package objfile
import (
"compress/zlib"
"errors"
"io"
"strconv"
"gopkg.in/src-d/go-git.v4/plumbing"
"gopkg.in/src-d/go-git.v4/plumbing/format/packfile"
)
var (
ErrClosed = errors.New("objfile: already closed")
ErrHeader = errors.New("objfile: invalid header")
ErrNegativeSize = errors.New("objfile: negative object size")
)
// Reader reads and decodes compressed objfile data from a provided io.Reader.
// Reader implements io.ReadCloser. Close should be called when finished with
// the Reader. Close will not close the underlying io.Reader.
type Reader struct {
multi io.Reader
zlib io.ReadCloser
hasher plumbing.Hasher
}
// NewReader returns a new Reader reading from r.
func NewReader(r io.Reader) (*Reader, error) {
zlib, err := zlib.NewReader(r)
if err != nil {
return nil, packfile.ErrZLib.AddDetails(err.Error())
}
return &Reader{
zlib: zlib,
}, nil
}
// Header reads the type and the size of object, and prepares the reader for read
func (r *Reader) Header() (t plumbing.ObjectType, size int64, err error) {
var raw []byte
raw, err = r.readUntil(' ')
if err != nil {
return
}
t, err = plumbing.ParseObjectType(string(raw))
if err != nil {
return
}
raw, err = r.readUntil(0)
if err != nil {
return
}
size, err = strconv.ParseInt(string(raw), 10, 64)
if err != nil {
err = ErrHeader
return
}
defer r.prepareForRead(t, size)
return
}
// readSlice reads one byte at a time from r until it encounters delim or an
// error.
func (r *Reader) readUntil(delim byte) ([]byte, error) {
var buf [1]byte
value := make([]byte, 0, 16)
for {
if n, err := r.zlib.Read(buf[:]); err != nil && (err != io.EOF || n == 0) {
if err == io.EOF {
return nil, ErrHeader
}
return nil, err
}
if buf[0] == delim {
return value, nil
}
value = append(value, buf[0])
}
}
func (r *Reader) prepareForRead(t plumbing.ObjectType, size int64) {
r.hasher = plumbing.NewHasher(t, size)
r.multi = io.TeeReader(r.zlib, r.hasher)
}
// Read reads len(p) bytes into p from the object data stream. It returns
// the number of bytes read (0 <= n <= len(p)) and any error encountered. Even
// if Read returns n < len(p), it may use all of p as scratch space during the
// call.
//
// If Read encounters the end of the data stream it will return err == io.EOF,
// either in the current call if n > 0 or in a subsequent call.
func (r *Reader) Read(p []byte) (n int, err error) {
return r.multi.Read(p)
}
// Hash returns the hash of the object data stream that has been read so far.
func (r *Reader) Hash() plumbing.Hash {
return r.hasher.Sum()
}
// Close releases any resources consumed by the Reader. Calling Close does not
// close the wrapped io.Reader originally passed to NewReader.
func (r *Reader) Close() error {
if err := r.zlib.Close(); err != nil {
return err
}
return nil
}
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