1 files changed, 36 insertions, 5 deletions

diff --git a/libgo/go/compress/flate/inflate.go b/libgo/go/compress/flate/inflate.go
index 3eb3b2b83e..76519bbf42 100644
--- a/libgo/go/compress/flate/inflate.go
+++ b/libgo/go/compress/flate/inflate.go
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:generate go run gen.go -output fixedhuff.go
+
 // Package flate implements the DEFLATE compressed data format, described in
 // RFC 1951.  The gzip and zlib packages implement access to DEFLATE-based file
 // formats.
@@ -54,7 +56,16 @@ func (e *WriteError) Error() string {
 	return "flate: write error at offset " + strconv.FormatInt(e.Offset, 10) + ": " + e.Err.Error()
 }
 
-// Note that much of the implemenation of huffmanDecoder is also copied
+// Resetter resets a ReadCloser returned by NewReader or NewReaderDict to
+// to switch to a new underlying Reader. This permits reusing a ReadCloser
+// instead of allocating a new one.
+type Resetter interface {
+	// Reset discards any buffered data and resets the Resetter as if it was
+	// newly initialized with the given reader.
+	Reset(r io.Reader, dict []byte) error
+}
+
+// Note that much of the implementation of huffmanDecoder is also copied
 // into gen.go (in package main) for the purpose of precomputing the
 // fixed huffman tables so they can be included statically.
 
@@ -180,7 +191,7 @@ func (h *huffmanDecoder) init(bits []int) bool {
 // the NewReader will introduce its own buffering.
 type Reader interface {
 	io.Reader
-	ReadByte() (c byte, err error)
+	io.ByteReader
 }
 
 // Decompress state.
@@ -677,10 +688,28 @@ func makeReader(r io.Reader) Reader {
 	return bufio.NewReader(r)
 }
 
+func (f *decompressor) Reset(r io.Reader, dict []byte) error {
+	*f = decompressor{
+		r:        makeReader(r),
+		bits:     f.bits,
+		codebits: f.codebits,
+		hist:     f.hist,
+		step:     (*decompressor).nextBlock,
+	}
+	if dict != nil {
+		f.setDict(dict)
+	}
+	return nil
+}
+
 // NewReader returns a new ReadCloser that can be used
-// to read the uncompressed version of r.  It is the caller's
-// responsibility to call Close on the ReadCloser when
-// finished reading.
+// to read the uncompressed version of r.
+// If r does not also implement io.ByteReader,
+// the decompressor may read more data than necessary from r.
+// It is the caller's responsibility to call Close on the ReadCloser
+// when finished reading.
+//
+// The ReadCloser returned by NewReader also implements Resetter.
 func NewReader(r io.Reader) io.ReadCloser {
 	var f decompressor
 	f.bits = new([maxLit + maxDist]int)
@@ -696,6 +725,8 @@ func NewReader(r io.Reader) io.ReadCloser {
 // the uncompressed data stream started with the given dictionary,
 // which has already been read.  NewReaderDict is typically used
 // to read data compressed by NewWriterDict.
+//
+// The ReadCloser returned by NewReader also implements Resetter.
 func NewReaderDict(r io.Reader, dict []byte) io.ReadCloser {
 	var f decompressor
 	f.r = makeReader(r)