return "flate: write error at offset " + strconv.FormatInt(e.Offset, 10) + ": " + e.Err.Error()
}
+// 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.
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.
// 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)
// 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)
--- /dev/null
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package flate
+
+import (
+ "bytes"
+ "io"
+ "testing"
+)
+
+func TestReset(t *testing.T) {
+ ss := []string{
+ "lorem ipsum izzle fo rizzle",
+ "the quick brown fox jumped over",
+ }
+
+ deflated := make([]bytes.Buffer, 2)
+ for i, s := range ss {
+ w, _ := NewWriter(&deflated[i], 1)
+ w.Write([]byte(s))
+ w.Close()
+ }
+
+ inflated := make([]bytes.Buffer, 2)
+
+ f := NewReader(&deflated[0])
+ io.Copy(&inflated[0], f)
+ f.(Resetter).Reset(&deflated[1], nil)
+ io.Copy(&inflated[1], f)
+ f.Close()
+
+ for i, s := range ss {
+ if s != inflated[i].String() {
+ t.Errorf("inflated[%d]:\ngot %q\nwant %q", i, inflated[i], s)
+ }
+ }
+}
scratch [4]byte
}
-// NewReader creates a new io.ReadCloser.
-// Reads from the returned io.ReadCloser read and decompress data from r.
+// 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
+}
+
+// NewReader creates a new ReadCloser.
+// Reads from the returned ReadCloser read and decompress data from r.
// The implementation buffers input and may read more data than necessary from r.
// It is the caller's responsibility to call Close on the ReadCloser when done.
+//
+// The ReadCloser returned by NewReader also implements Resetter.
func NewReader(r io.Reader) (io.ReadCloser, error) {
return NewReaderDict(r, nil)
}
// NewReaderDict is like NewReader but uses a preset dictionary.
// NewReaderDict ignores the dictionary if the compressed data does not refer to it.
// If the compressed data refers to a different dictionary, NewReaderDict returns ErrDictionary.
+//
+// The ReadCloser returned by NewReaderDict also implements Resetter.
func NewReaderDict(r io.Reader, dict []byte) (io.ReadCloser, error) {
z := new(reader)
- if fr, ok := r.(flate.Reader); ok {
- z.r = fr
- } else {
- z.r = bufio.NewReader(r)
- }
- _, err := io.ReadFull(z.r, z.scratch[0:2])
+ err := z.Reset(r, dict)
if err != nil {
return nil, err
}
- h := uint(z.scratch[0])<<8 | uint(z.scratch[1])
- if (z.scratch[0]&0x0f != zlibDeflate) || (h%31 != 0) {
- return nil, ErrHeader
- }
- if z.scratch[1]&0x20 != 0 {
- _, err = io.ReadFull(z.r, z.scratch[0:4])
- if err != nil {
- return nil, err
- }
- checksum := uint32(z.scratch[0])<<24 | uint32(z.scratch[1])<<16 | uint32(z.scratch[2])<<8 | uint32(z.scratch[3])
- if checksum != adler32.Checksum(dict) {
- return nil, ErrDictionary
- }
- z.decompressor = flate.NewReaderDict(z.r, dict)
- } else {
- z.decompressor = flate.NewReader(z.r)
- }
- z.digest = adler32.New()
return z, nil
}
z.err = z.decompressor.Close()
return z.err
}
+
+func (z *reader) Reset(r io.Reader, dict []byte) error {
+ if fr, ok := r.(flate.Reader); ok {
+ z.r = fr
+ } else {
+ z.r = bufio.NewReader(r)
+ }
+ _, err := io.ReadFull(z.r, z.scratch[0:2])
+ if err != nil {
+ return err
+ }
+ h := uint(z.scratch[0])<<8 | uint(z.scratch[1])
+ if (z.scratch[0]&0x0f != zlibDeflate) || (h%31 != 0) {
+ return ErrHeader
+ }
+ haveDict := z.scratch[1]&0x20 != 0
+ if haveDict {
+ _, err = io.ReadFull(z.r, z.scratch[0:4])
+ if err != nil {
+ return err
+ }
+ checksum := uint32(z.scratch[0])<<24 | uint32(z.scratch[1])<<16 | uint32(z.scratch[2])<<8 | uint32(z.scratch[3])
+ if checksum != adler32.Checksum(dict) {
+ return ErrDictionary
+ }
+ }
+ if z.decompressor == nil {
+ if haveDict {
+ z.decompressor = flate.NewReaderDict(z.r, dict)
+ } else {
+ z.decompressor = flate.NewReader(z.r)
+ }
+ } else {
+ z.decompressor.(flate.Resetter).Reset(z.r, dict)
+ }
+ z.digest = adler32.New()
+ return nil
+}