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