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.gitignore

@@ -23,3 +23,4 @@ cmd/xb/xb
 
 # default compression test file
 enwik8*
+/fox

format.go

@@ -101,8 +101,8 @@ func newHashFunc(flags byte) (newHash func() hash.Hash, err error) {
 	return
 }
 
-// header provides the actual content of the xz file header: the flags.
-type header struct {
+// streamHeader provides the actual content of the xz stream: the flags.
+type streamHeader struct {
 	flags byte
 }
 
@@ -112,18 +112,36 @@ var errHeaderMagic = errors.New("xz: invalid header magic bytes")
 // ValidHeader checks whether data is a correct xz file header. The
 // length of data must be HeaderLen.
 func ValidHeader(data []byte) bool {
-	var h header
+	var h streamHeader
 	err := h.UnmarshalBinary(data)
 	return err == nil
 }
 
 // String returns a string representation of the flags.
-func (h header) String() string {
+func (h streamHeader) String() string {
 	return flagString(h.flags)
 }
 
+func (h *streamHeader) UnmarshalReader(xz io.Reader) error {
+	data := make([]byte, HeaderLen)
+	if _, err := io.ReadFull(xz, data[:4]); err != nil {
+		return err
+	}
+	if bytes.Equal(data[:4], []byte{0, 0, 0, 0}) {
+		return errPadding
+	}
+	if _, err := io.ReadFull(xz, data[4:]); err != nil {
+		if err == io.EOF {
+			err = io.ErrUnexpectedEOF
+		}
+		return err
+	}
+
+	return h.UnmarshalBinary(data)
+}
+
 // UnmarshalBinary reads header from the provided data slice.
-func (h *header) UnmarshalBinary(data []byte) error {
+func (h *streamHeader) UnmarshalBinary(data []byte) error {
 	// header length
 	if len(data) != HeaderLen {
 		return errors.New("xz: wrong file header length")
@@ -155,7 +173,7 @@ func (h *header) UnmarshalBinary(data []byte) error {
 }
 
 // MarshalBinary generates the xz file header.
-func (h *header) MarshalBinary() (data []byte, err error) {
+func (h *streamHeader) MarshalBinary() (data []byte, err error) {
 	if err = verifyFlags(h.flags); err != nil {
 		return nil, err
 	}
@@ -193,7 +211,7 @@ func (f footer) String() string {
 // Minimum and maximum for the size of the index (backward size).
 const (
 	minIndexSize = 4
-	maxIndexSize = (1 << 32) * 4
+	maxIndexSize = 1 << 32 * 4
 )
 
 // MarshalBinary converts footer values into an xz file footer. Note
@@ -213,7 +231,7 @@ func (f *footer) MarshalBinary() (data []byte, err error) {
 	data = make([]byte, footerLen)
 
 	// backward size (index size)
-	s := (f.indexSize / 4) - 1
+	s := f.indexSize/4 - 1
 	putUint32LE(data[4:], uint32(s))
 	// flags
 	data[9] = f.flags
@@ -228,8 +246,7 @@ func (f *footer) MarshalBinary() (data []byte, err error) {
 	return data, nil
 }
 
-// UnmarshalBinary sets the footer value by unmarshalling an xz file
-// footer.
+// UnmarshalBinary sets the footer value by unmarshalling an xz file footer.
 func (f *footer) UnmarshalBinary(data []byte) error {
 	if len(data) != footerLen {
 		return errors.New("xz: wrong footer length")
@@ -627,6 +644,11 @@ func (rec *record) MarshalBinary() (data []byte, err error) {
 	return p[:n], nil
 }
 
+// paddedLen returns the padded length of the compressed record.
+func (rec *record) paddedLen() int64 {
+	return int64(padLen(rec.unpaddedSize)) + rec.unpaddedSize
+}
+
 // writeIndex writes the index, a sequence of records.
 func writeIndex(w io.Writer, index []record) (n int64, err error) {
 	crc := crc32.NewIEEE()

format_test.go

@@ -10,12 +10,12 @@ import (
 )
 
 func TestHeader(t *testing.T) {
-	h := header{flags: CRC32}
+	h := streamHeader{flags: CRC32}
 	data, err := h.MarshalBinary()
 	if err != nil {
 		t.Fatalf("MarshalBinary error %s", err)
 	}
-	var g header
+	var g streamHeader
 	if err = g.UnmarshalBinary(data); err != nil {
 		t.Fatalf("UnmarshalBinary error %s", err)
 	}

reader.go

@@ -61,7 +61,7 @@ type streamReader struct {
 	xz      io.Reader
 	br      *blockReader
 	newHash func() hash.Hash
-	h       header
+	h       streamHeader
 	index   []record
 }
 
@@ -137,27 +137,17 @@ 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 {
+
+	if err := r.h.UnmarshalReader(xz); 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
@@ -188,15 +178,8 @@ func (r *streamReader) readTail() error {
 		}
 	}
 
-	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 {
+	f, err := readFooter(r.xz)
+	if err != nil {
 		return err
 	}
 	xlog.Debugf("xz footer %s", f)
@@ -209,6 +192,22 @@ func (r *streamReader) readTail() error {
 	return nil
 }
 
+func readFooter(r io.Reader) (*footer, error) {
+	p := make([]byte, footerLen)
+	if _, err := io.ReadFull(r, p); err != nil {
+		if err == io.EOF {
+			err = io.ErrUnexpectedEOF
+		}
+		return nil, err
+	}
+	var f footer
+	if err := f.UnmarshalBinary(p); err != nil {
+		return nil, err
+	}
+
+	return &f, nil
+}
+
 // Read reads actual data from the xz stream.
 func (r *streamReader) Read(p []byte) (n int, err error) {
 	for n < len(p) {