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package archive
import (
"bytes"
"fmt"
"io"
"os"
)
// DetectCompression detects compression from a file name.
func DetectCompression(fname string) ([]string, string, []string, error) {
f, err := os.Open(fname)
if err != nil {
return nil, "", nil, err
}
defer func() { _ = f.Close() }()
return DetectCompressionFile(f)
}
// DetectCompressionFile detects the compression type of a file and returns the tar arguments needed
// to unpack the file, compression type (in the form of a file extension), and the command needed
// to decompress the file to an uncompressed tarball.
func DetectCompressionFile(f io.Reader) ([]string, string, []string, error) {
// read header parts to detect compression method
// bz2 - 2 bytes, 'BZ' signature/magic number
// gz - 2 bytes, 0x1f 0x8b
// lzma - 6 bytes, { [0x000, 0xE0], '7', 'z', 'X', 'Z', 0x00 } -
// xz - 6 bytes, header format { 0xFD, '7', 'z', 'X', 'Z', 0x00 }
// tar - 263 bytes, trying to get ustar from 257 - 262
// lz4 - 4 bytes 0x04 0x22 0x4d 0x18, magic number
header := make([]byte, 263)
_, err := f.Read(header)
if err != nil {
return nil, "", nil, err
}
switch {
case bytes.Equal(header[0:2], []byte{'B', 'Z'}):
return []string{"-jxf"}, ".tar.bz2", []string{"bzip2", "-d"}, nil
case bytes.Equal(header[0:2], []byte{0x1f, 0x8b}):
return []string{"-zxf"}, ".tar.gz", []string{"gzip", "-d"}, nil
case (bytes.Equal(header[1:5], []byte{'7', 'z', 'X', 'Z'}) && header[0] == 0xFD):
return []string{"-Jxf"}, ".tar.xz", []string{"xz", "-d"}, nil
case (bytes.Equal(header[1:5], []byte{'7', 'z', 'X', 'Z'}) && header[0] != 0xFD):
return []string{"--lzma", "-xf"}, ".tar.lzma", []string{"lzma", "-d"}, nil
case bytes.Equal(header[0:3], []byte{0x5d, 0x00, 0x00}):
return []string{"--lzma", "-xf"}, ".tar.lzma", []string{"lzma", "-d"}, nil
case bytes.Equal(header[257:262], []byte{'u', 's', 't', 'a', 'r'}):
return []string{"-xf"}, ".tar", []string{}, nil
case bytes.Equal(header[0:4], []byte{'h', 's', 'q', 's'}):
return []string{"-xf"}, ".squashfs", []string{"sqfs2tar", "--no-skip"}, nil
case bytes.Equal(header[0:3], []byte{'Q', 'F', 'I'}):
return []string{""}, ".qcow2", []string{"qemu-img", "convert", "-O", "raw"}, nil
case bytes.Equal(header[0:4], []byte{'K', 'D', 'M', 'V'}):
return []string{""}, ".vmdk", []string{"qemu-img", "convert", "-O", "raw"}, nil
case bytes.Equal(header[0:4], []byte{0x28, 0xb5, 0x2f, 0xfd}):
return []string{"--zstd", "-xf"}, ".tar.zst", []string{"zstd", "-d"}, nil
case bytes.Equal(header[0:4], []byte{0x04, 0x22, 0x4d, 0x18}):
return []string{"-Ilz4", "-xf"}, ".tar.lz4", []string{"lz4", "-d"}, nil
default:
return nil, "", nil, fmt.Errorf("Unsupported compression")
}
}
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