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// Copyright 2011 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 packet
import (
"compress/bzip2"
"compress/flate"
"compress/zlib"
"golang.org/x/crypto/openpgp/errors"
"io"
"strconv"
)
// Compressed represents a compressed OpenPGP packet. The decompressed contents
// will contain more OpenPGP packets. See RFC 4880, section 5.6.
type Compressed struct {
Body io.Reader
}
const (
NoCompression = flate.NoCompression
BestSpeed = flate.BestSpeed
BestCompression = flate.BestCompression
DefaultCompression = flate.DefaultCompression
)
// CompressionConfig contains compressor configuration settings.
type CompressionConfig struct {
// Level is the compression level to use. It must be set to
// between -1 and 9, with -1 causing the compressor to use the
// default compression level, 0 causing the compressor to use
// no compression and 1 to 9 representing increasing (better,
// slower) compression levels. If Level is less than -1 or
// more then 9, a non-nil error will be returned during
// encryption. See the constants above for convenient common
// settings for Level.
Level int
}
func (c *Compressed) parse(r io.Reader) error {
var buf [1]byte
_, err := readFull(r, buf[:])
if err != nil {
return err
}
switch buf[0] {
case 1:
c.Body = flate.NewReader(r)
case 2:
c.Body, err = zlib.NewReader(r)
case 3:
c.Body = bzip2.NewReader(r)
default:
err = errors.UnsupportedError("unknown compression algorithm: " + strconv.Itoa(int(buf[0])))
}
return err
}
// compressedWriterCloser represents the serialized compression stream
// header and the compressor. Its Close() method ensures that both the
// compressor and serialized stream header are closed. Its Write()
// method writes to the compressor.
type compressedWriteCloser struct {
sh io.Closer // Stream Header
c io.WriteCloser // Compressor
}
func (cwc compressedWriteCloser) Write(p []byte) (int, error) {
return cwc.c.Write(p)
}
func (cwc compressedWriteCloser) Close() (err error) {
err = cwc.c.Close()
if err != nil {
return err
}
return cwc.sh.Close()
}
// SerializeCompressed serializes a compressed data packet to w and
// returns a WriteCloser to which the literal data packets themselves
// can be written and which MUST be closed on completion. If cc is
// nil, sensible defaults will be used to configure the compression
// algorithm.
func SerializeCompressed(w io.WriteCloser, algo CompressionAlgo, cc *CompressionConfig) (literaldata io.WriteCloser, err error) {
compressed, err := serializeStreamHeader(w, packetTypeCompressed)
if err != nil {
return
}
_, err = compressed.Write([]byte{uint8(algo)})
if err != nil {
return
}
level := DefaultCompression
if cc != nil {
level = cc.Level
}
var compressor io.WriteCloser
switch algo {
case CompressionZIP:
compressor, err = flate.NewWriter(compressed, level)
case CompressionZLIB:
compressor, err = zlib.NewWriterLevel(compressed, level)
default:
s := strconv.Itoa(int(algo))
err = errors.UnsupportedError("Unsupported compression algorithm: " + s)
}
if err != nil {
return
}
literaldata = compressedWriteCloser{compressed, compressor}
return
}
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