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main.go
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main.go
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package main
import (
"encoding/json"
"errors"
"flag"
"fmt"
"io"
"os"
"github.com/klauspost/compress/zstd"
"github.com/lima-vm/go-qcow2reader"
"github.com/lima-vm/go-qcow2reader/image"
"github.com/lima-vm/go-qcow2reader/image/qcow2"
"github.com/lima-vm/go-qcow2reader/log"
)
func warn(s string) {
fmt.Fprintln(os.Stderr, "WARNING: "+s)
}
func debugPrint(s string) {
fmt.Fprintln(os.Stderr, "DEBUG: "+s)
}
type zstdDecompressor struct {
*zstd.Decoder
}
func (x *zstdDecompressor) Close() error {
x.Decoder.Close()
return nil
}
func newZstdDecompressor(r io.Reader) (io.ReadCloser, error) {
dec, err := zstd.NewReader(r)
if err != nil {
return nil, err
}
return &zstdDecompressor{dec}, nil
}
func main() {
log.SetWarnFunc(warn)
// zlib (deflate) decompressor is registered by default, but zstd is not.
qcow2.SetDecompressor(qcow2.CompressionTypeZstd, newZstdDecompressor)
if err := xmain(); err != nil {
fmt.Fprintln(os.Stderr, "ERROR: "+err.Error())
os.Exit(1)
}
}
func xmain() error {
flag.Usage = func() {
fmt.Fprintf(flag.CommandLine.Output(), "Usage: %s [OPTIONS...] FILE\n", os.Args[0])
flag.PrintDefaults()
}
var (
debug bool
info bool
bufferSize int
offset int64
length int64
)
flag.BoolVar(&debug, "debug", false, "enable printing debug messages")
flag.BoolVar(&info, "info", false, "print the image info and exit")
flag.IntVar(&bufferSize, "buffer", 65536, "buffer size")
flag.Int64Var(&offset, "offset", 0, "offset to read")
flag.Int64Var(&length, "length", -1, "length to read")
flag.Parse()
if debug {
log.SetDebugFunc(debugPrint)
}
args := flag.Args()
switch len(args) {
case 0:
return errors.New("no file was specified")
case 1:
// NOP
default:
return errors.New("too many files were specified")
}
fName := args[0]
f, err := os.Open(fName)
if err != nil {
return err
}
defer f.Close()
img, err := qcow2reader.Open(f)
if err != nil {
return err
}
if info {
imgInfo := image.NewImageInfo(img)
j, err := json.MarshalIndent(imgInfo, "", " ")
if err != nil {
return err
}
if _, err = fmt.Println(string(j)); err != nil {
return err
}
if err = img.Readable(); err != nil {
warn(err.Error())
}
return nil
}
if length < 0 {
length = img.Size()
}
buf := make([]byte, bufferSize)
sr := io.NewSectionReader(img, offset, length)
_, err = io.CopyBuffer(os.Stdout, sr, buf)
return err
}