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unpack.go
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unpack.go
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package main
import (
"compress/gzip"
"fmt"
"io"
"io/fs"
"os"
"path/filepath"
"github.com/cavaliergopher/cpio"
"github.com/klauspost/compress/zstd"
"github.com/ulikunitz/xz"
)
var errStop = fmt.Errorf("Stop Processing")
type processCpioEntryFn func(header *cpio.Header, reader *cpio.Reader) error
func processImage(file string, fn processCpioEntryFn) error {
input, err := os.Open(file)
if err != nil {
return err
}
var img *cpio.Reader
kind, err := filetype(input)
if err != nil {
return err
}
switch kind {
case "cpio":
img = cpio.NewReader(input)
case "zstd":
zst, err := zstd.NewReader(input)
if err != nil {
return err
}
defer zst.Close()
img = cpio.NewReader(zst)
case "gzip":
gz, err := gzip.NewReader(input)
if err != nil {
return err
}
defer gz.Close()
img = cpio.NewReader(gz)
case "xz":
conf := xz.ReaderConfig{}
if err := conf.Verify(); err != nil {
return err
}
x, err := conf.NewReader(input)
if err != nil {
return err
}
img = cpio.NewReader(x)
case "lz4":
lz, err := newLz4Reader(input)
if err != nil {
return err
}
defer lz.Close()
img = cpio.NewReader(lz)
}
for {
hdr, err := img.Next()
if err == io.EOF {
break
}
if err != nil {
return err
}
err = fn(hdr, img)
if err == errStop {
break
}
if err != nil {
return err
}
}
return nil
}
func runUnpack() error {
dir := opts.UnpackCommand.Args.OutputDir
fn := func(hdr *cpio.Header, r *cpio.Reader) error {
out := filepath.Join(dir, hdr.Name)
if err := os.MkdirAll(filepath.Dir(out), 0o755); err != nil {
return err
}
m := hdr.Mode & 0o770000
switch m {
case cpio.TypeDir:
if err := os.Mkdir(out, 0o755); err != nil {
return err
}
case cpio.TypeSymlink:
if err := os.Symlink(hdr.Linkname, out); err != nil {
return err
}
case cpio.TypeSocket:
fallthrough
case cpio.TypeBlock:
fallthrough
case cpio.TypeChar:
fallthrough
case cpio.TypeFifo:
// for device files create an empty regular file
f, err := os.Create(out)
if err != nil {
return err
}
f.Close()
case cpio.TypeReg:
fout, err := os.Create(out)
if err != nil {
return err
}
if _, err := io.Copy(fout, r); err != nil {
return err
}
default:
warning("Unknown type for file %s: %#o", hdr.Name, m)
}
return nil
}
return processImage(opts.UnpackCommand.Args.Image, fn)
}
func runCat() error {
var foundFile bool
fn := func(hdr *cpio.Header, r *cpio.Reader) error {
if hdr.Name == opts.CatCommand.Args.File {
if _, err := io.Copy(os.Stdout, r); err != nil {
return err
}
foundFile = true
return errStop
}
return nil
}
err := processImage(opts.CatCommand.Args.Image, fn)
if err != nil {
return err
} else if !foundFile {
return fs.ErrNotExist
}
return nil
}
func runLs() error {
fn := func(hdr *cpio.Header, r *cpio.Reader) error {
m := hdr.Mode & 0o770000
switch m {
case cpio.TypeDir:
fmt.Printf("%s/\n", hdr.Name)
case cpio.TypeSymlink:
fmt.Printf("%s -> %s\n", hdr.Name, hdr.Linkname)
case cpio.TypeSocket:
fallthrough
case cpio.TypeBlock:
fallthrough
case cpio.TypeChar:
fallthrough
case cpio.TypeFifo:
fmt.Println(hdr.Name)
case cpio.TypeReg:
fmt.Println(hdr.Name)
default:
warning("Unknown mode for file %s: %#o", hdr.Name, m)
}
return nil
}
return processImage(opts.LsCommand.Args.Image, fn)
}