forked from mvo5/godd
/
godd.go
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/
godd.go
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package main
import (
"bufio"
"fmt"
"io"
"os"
"path/filepath"
"strconv"
"strings"
"github.com/cheggaaa/pb"
"github.com/mvo5/godd/udev"
)
// var to allow tests to change it
var defaultBufSize = 4 * 1024 * 1024
// go does not offer support to customize the buffer size for
// io.Copy directly, so we need to implement a custom type with:
// ReadFrom and Write
type FixedBuffer struct {
w io.Writer
buf []byte
}
func NewFixedBuffer(w io.Writer, size int) *FixedBuffer {
return &FixedBuffer{
w: w,
buf: make([]byte, size),
}
}
func (f *FixedBuffer) ReadFrom(r io.Reader) (int, error) {
return r.Read(f.buf)
}
func (f *FixedBuffer) Write(data []byte) (int, error) {
return f.w.Write(data)
}
// the dd releated stuff
type ddOpts struct {
src string
dst string
bs int
}
func ddAtoi(s string) (int, error) {
if len(s) < 2 {
return strconv.Atoi(s)
}
// dd supports suffixes via two chars like "kB"
fac := 1
switch s[len(s)-2:] {
case "kB":
fac = 1000
case "MB":
fac = 1000 * 1000
case "GB":
fac = 1000 * 1000 * 1000
case "TB":
fac = 1000 * 1000 * 1000 * 1000
}
// adjust string if its from xB group
if fac%10 == 0 {
s = s[:len(s)-2]
}
// check for single char digests
switch s[len(s)-1] {
case 'b':
fac = 512
case 'K':
fac = 1024
case 'M':
fac = 1024 * 1024
case 'G':
fac = 1024 * 1024 * 1024
case 'T':
fac = 1024 * 1024 * 1024 * 1024
}
// ajust string if its from the X group
if fac%512 == 0 {
s = s[:len(s)-1]
}
n, err := strconv.Atoi(s)
n *= fac
return n, err
}
func findNonCdromRemovableDeviceFiles() (res []string) {
c := udev.New(nil)
for _, d := range c.QueryBySubsystem("block") {
if d.GetSysfsAttr("removable") == "1" && d.GetProperty("ID_CDROM") != "1" {
res = append(res, d.GetDeviceFile())
}
}
return res
}
func parseArgs(args []string) (*ddOpts, error) {
// support: auto-detect removable devices
if len(args) == 1 {
fmt.Printf(`
No target selected, detected the following removable device:
%s
`, strings.Join(findNonCdromRemovableDeviceFiles(), "\n "))
return nil, fmt.Errorf("please select target device")
}
// support:
// # godd in-file out-file
// for the lazy people
if len(args) == 2 &&
!strings.Contains(args[0], "=") &&
!strings.Contains(args[1], "=") {
return &ddOpts{src: args[0], dst: args[1]}, nil
}
// ok, real work
opts := ddOpts{
bs: defaultBufSize,
}
for _, arg := range args {
l := strings.SplitN(arg, "=", 2)
switch l[0] {
case "if":
opts.src = l[1]
case "of":
opts.dst = l[1]
case "bs":
bs, err := ddAtoi(l[1])
if err != nil {
return nil, err
}
opts.bs = bs
default:
return nil, fmt.Errorf("unknown argument %q", arg)
}
}
return &opts, nil
}
var mountinfoPath = "/proc/self/mountinfo"
func sanityCheckDst(dstPath string) error {
// see https://www.kernel.org/doc/Documentation/filesystems/proc.txt,
// sec. 3.5
f, err := os.Open(mountinfoPath)
if os.IsNotExist(err) {
return nil
}
if err != nil {
return err
}
defer f.Close()
// resolve any symlink to the target
resolvedDstPath, err := filepath.EvalSymlinks(dstPath)
if err == nil {
dstPath = resolvedDstPath
}
scanner := bufio.NewScanner(f)
for scanner.Scan() {
l := strings.Fields(scanner.Text())
if len(l) == 0 {
continue
}
mountPoint := l[4]
mountSrc := l[9]
// resolve any symlinks in mountSrc
resolvedMountSrc, err := filepath.EvalSymlinks(mountSrc)
if err == nil {
mountSrc = resolvedMountSrc
}
if strings.HasPrefix(mountSrc, dstPath) {
return fmt.Errorf("%s is mounted on %s", mountSrc, mountPoint)
}
}
return scanner.Err()
}
func dd(srcPath, dstPath string, bs int) error {
if bs == 0 {
bs = defaultBufSize
}
src, err := os.Open(srcPath)
if err != nil {
return err
}
defer src.Close()
if err := sanityCheckDst(dstPath); err != nil {
return err
}
dst, err := os.Create(dstPath)
if err != nil {
return err
}
defer func() {
dst.Sync()
dst.Close()
}()
// huge default bufsize
w := NewFixedBuffer(dst, bs)
stat, err := src.Stat()
if err != nil {
return err
}
pbar := pb.New64(stat.Size()).SetUnits(pb.U_BYTES)
pbar.Start()
mw := io.MultiWriter(w, pbar)
_, err = io.Copy(mw, src)
return err
}
func main() {
opts, err := parseArgs(os.Args[1:])
if err != nil {
fmt.Println(fmt.Errorf("failed to parse args: %v", err))
os.Exit(1)
}
if err := dd(opts.src, opts.dst, opts.bs); err != nil {
fmt.Println(fmt.Errorf("failed to dd: %v", err))
os.Exit(1)
}
}