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compression.go
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compression.go
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package compression
import (
"bytes"
"compress/bzip2"
"compress/flate"
"compress/gzip"
"compress/lzw"
"compress/zlib"
"github.com/ulikunitz/xz"
"io"
"io/ioutil"
"path/filepath"
)
const (
BZ2 = ".bz2"
GZ = ".gz"
TGZ = ".tgz"
LZW = ".Z"
INFL = ".infl"
Zlibe = ".xp3"
Xz = ".xz"
//Here comes the magic
gzipID1 = 0x1f
gzipID2 = 0x8b
bzip2ID1 = 0x42
bzip2ID2 = 0x5a
)
var LZMA_alone_magic = []byte{0x5d, 0x00, 0x00}
var XZ_magic = []byte{0xfd, 0x37, 0x7a}
type Compression interface {
GetReader(reader io.Reader) (io.ReadCloser, error)
}
func CreateCompression(fileName string) Compression {
ext := filepath.Ext(fileName)
switch ext {
case BZ2:
return new(Bzip2)
case GZ, TGZ:
return new(Gzip)
case LZW:
return new(Lzw)
case INFL:
return new(Flate)
case Zlibe:
return new(Zlib)
case Xz:
return new(XZ)
default:
return new(NoCompression)
}
}
func CreateCompressionFromBytes(magicBytes []byte) Compression {
//TODO: replace with switch
if magicBytes[0] == gzipID1 && magicBytes[1] == gzipID2 {
return new(Gzip)
}
if magicBytes[0] == bzip2ID1 && magicBytes[1] == bzip2ID2 {
return new(Bzip2)
}
if bytes.Equal(magicBytes[:3], XZ_magic) {
return new(XZ)
}
if bytes.Equal(magicBytes[:3], LZMA_alone_magic) {
}
return new(NoCompression)
}
type Bzip2 struct {
}
func (comp Bzip2) GetReader(reader io.Reader) (io.ReadCloser, error) {
fileReader := bzip2.NewReader(reader)
cReader := ioutil.NopCloser(fileReader)
return cReader, nil
}
type Flate struct {
}
func (comp Flate) GetReader(reader io.Reader) (io.ReadCloser, error) {
fileReader := flate.NewReader(reader)
return fileReader, nil
}
type Gzip struct {
}
func (comp Gzip) GetReader(reader io.Reader) (io.ReadCloser, error) {
fileReader, err := gzip.NewReader(reader)
if err != nil {
return nil, err
}
return fileReader, nil
}
type Lzw struct {
}
func (comp Lzw) GetReader(reader io.Reader) (io.ReadCloser, error) {
fileReader := lzw.NewReader(reader, lzw.LSB, 100)
return fileReader, nil
}
type Zlib struct {
}
func (comp Zlib) GetReader(reader io.Reader) (io.ReadCloser, error) {
fileReader, err := zlib.NewReader(reader)
if err != nil {
return nil, err
}
return fileReader, nil
}
type NoCompression struct {
}
func (comp NoCompression) GetReader(reader io.Reader) (io.ReadCloser, error) {
return nil, nil
}
type XZ struct {
}
func (comp XZ) GetReader(reader io.Reader) (io.ReadCloser, error) {
fileReader, err := xz.NewReader(reader)
if err != nil {
return nil, err
}
return XZReaderCloser{fileReader}, nil
}
type XZReaderCloser struct {
*xz.Reader
}
func (xzrc XZReaderCloser) Close() error {
return nil
}