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// Copyright 2014-2017 Ulrich Kunitz. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package xz
import (
"errors"
"fmt"
"io"
"github.com/ulikunitz/xz/lzma"
)
// LZMA filter constants.
const (
lzmaFilterID = 0x21
lzmaFilterLen = 3
)
// lzmaFilter declares the LZMA2 filter information stored in an xz
// block header.
type lzmaFilter struct {
dictCap int64
}
// String returns a representation of the LZMA filter.
func (f lzmaFilter) String() string {
return fmt.Sprintf("LZMA dict cap %#x", f.dictCap)
}
// id returns the ID for the LZMA2 filter.
func (f lzmaFilter) id() uint64 { return lzmaFilterID }
// MarshalBinary converts the lzmaFilter in its encoded representation.
func (f lzmaFilter) MarshalBinary() (data []byte, err error) {
c := lzma.EncodeDictCap(f.dictCap)
return []byte{lzmaFilterID, 1, c}, nil
}
// UnmarshalBinary unmarshals the given data representation of the LZMA2
// filter.
func (f *lzmaFilter) UnmarshalBinary(data []byte) error {
if len(data) != lzmaFilterLen {
return errors.New("xz: data for LZMA2 filter has wrong length")
}
if data[0] != lzmaFilterID {
return errors.New("xz: wrong LZMA2 filter id")
}
if data[1] != 1 {
return errors.New("xz: wrong LZMA2 filter size")
}
dc, err := lzma.DecodeDictCap(data[2])
if err != nil {
return errors.New("xz: wrong LZMA2 dictionary size property")
}
f.dictCap = dc
return nil
}
// reader creates a new reader for the LZMA2 filter.
func (f lzmaFilter) reader(r io.Reader, c *ReaderConfig) (fr io.Reader,
err error) {
config := new(lzma.Reader2Config)
if c != nil {
config.DictCap = c.DictCap
}
dc := int(f.dictCap)
if dc < 1 {
return nil, errors.New("xz: LZMA2 filter parameter " +
"dictionary capacity overflow")
}
if dc > config.DictCap {
config.DictCap = dc
}
fr, err = config.NewReader2(r)
if err != nil {
return nil, err
}
return fr, nil
}
// writeCloser creates a io.WriteCloser for the LZMA2 filter.
func (f lzmaFilter) writeCloser(w io.WriteCloser, c *WriterConfig,
) (fw io.WriteCloser, err error) {
config := new(lzma.Writer2Config)
if c != nil {
*config = lzma.Writer2Config{
Properties: c.Properties,
DictCap: c.DictCap,
BufSize: c.BufSize,
Matcher: c.Matcher,
}
}
dc := int(f.dictCap)
if dc < 1 {
return nil, errors.New("xz: LZMA2 filter parameter " +
"dictionary capacity overflow")
}
if dc > config.DictCap {
config.DictCap = dc
}
fw, err = config.NewWriter2(w)
if err != nil {
return nil, err
}
return fw, nil
}
// last returns true, because an LZMA2 filter must be the last filter in
// the filter list.
func (f lzmaFilter) last() bool { return true }
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