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main.go
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main.go
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// Copyright 2023 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// V6disk converts a Research Unix Sixth Edition disk image to the
// txtar disk format used by the v6unix package and related commands.
//
// Usage:
//
// v6disk [-o out.txtar] [-r root] [-x] diskfile
//
// The -r flag specifies the name of the root inode on the disk (default /).
//
// The -o flag specifies the name of the output file to write (default standard output).
//
// The -x flag inverts the operation: diskfile is now a txtar disk, and -o is the
// name of a directory to write the files into (default _fs).
package main
import (
"bytes"
"encoding/base64"
"flag"
"fmt"
"log"
"os"
"path"
"slices"
"strings"
"unicode/utf8"
"unsafe"
"golang.org/x/tools/txtar"
)
var (
outfile = flag.String("o", "", "write output txtar to `file` (default standard output)")
rootname = flag.String("r", "/", "use `name` for the root inode")
xflag = flag.Bool("x", false, "extract txtar disk")
)
func usage() {
fmt.Fprintf(os.Stderr, "usage: v6disk [-o out.txtar] [-r root] [-x] diskfile\n")
os.Exit(2)
}
type filsys struct {
isize uint16 /* size in blocks of I list */
fsize uint16 /* size in blocks of entire volume */
nfree uint16 /* number of in core free blocks (0-100) */
free [100]uint16 /* in core free blocks */
ninode uint16 /* number of in core I nodes (0-100) */
inode [100]uint16 /* in core free I nodes */
flock uint8 /* lock during free list manipulation */
ilock uint8 /* lock during I list manipulation */
fmod uint8 /* super block modified flag */
ronly uint8 /* mounted read-only flag */
time [2]uint16 /* current date of last update */
pad [50]uint16
}
type dirent struct {
ino uint16
nam [14]byte
}
func (de *dirent) name() string {
for i := 0; i < 14; i++ {
if de.nam[i] == 0 {
return string(de.nam[:i])
}
}
return string(de.nam[:])
}
type inode struct {
mode uint16
nlink int8
uid int8
gid int8
sizeHi uint8
sizeLo uint16
addr [8]uint16
atime utime
mtime utime
}
type utime struct {
hi uint16
lo uint16
}
func (t utime) unix() int64 {
return int64(t.hi)<<16 | int64(t.lo)
}
func (ip *inode) size() int {
return int(ip.sizeHi)<<16 | int(ip.sizeLo)
}
const (
_IALLOC uint16 = 0100000 /* file is used */
_IFMT uint16 = 060000 /* type of file */
_IFDIR uint16 = 040000 /* directory */
_IFCHR uint16 = 020000 /* character special */
_IFBLK uint16 = 060000 /* block special, 0 is regular */
_ILARG uint16 = 010000 /* large addressing algorithm */
_ISUID uint16 = 04000 /* set user id on execution */
_ISGID uint16 = 02000 /* set group id on execution */
_ISVTX uint16 = 01000 /* save swapped text even after use */
_IREAD uint16 = 0400 /* read, write, execute permissions */
_IWRITE uint16 = 0200
_IEXEC uint16 = 0100
)
type iname struct {
parent *iname
name string
*inode
content []byte
}
func (n *iname) path() string {
if n.parent == nil {
return *rootname
}
return path.Join(n.parent.path(), n.name)
}
func main() {
log.SetPrefix("v6disk: ")
log.SetFlags(0)
flag.Usage = usage
flag.Parse()
args := flag.Args()
if len(args) != 1 {
usage()
}
data, err := os.ReadFile(args[0])
if err != nil {
log.Fatal(err)
}
if *xflag {
if *outfile == "" {
*outfile = "_fs"
}
ar := txtar.Parse(data)
for _, f := range ar.Files {
name, _, _ := strings.Cut(f.Name, " ")
targ := path.Join(*outfile, name)
if strings.Contains(f.Name, "mode=0140") || strings.Contains(f.Name, "mode=015") {
if err := os.MkdirAll(targ, 0777); err != nil {
log.Fatal(err)
}
} else if strings.Contains(f.Name, "mode=0100") || strings.Contains(f.Name, "mode=011") {
data := f.Data
if strings.Contains(f.Name, "base64=1") {
dec, err := base64.StdEncoding.DecodeString(string(data))
if err != nil {
log.Fatalf("decoding %s: %v", name, err)
}
data = dec
}
if err := os.WriteFile(targ, data, 0666); err != nil {
log.Fatal(err)
}
}
}
return
}
if len(data) < 512 {
log.Fatalf("disk too small")
}
fsys := (*filsys)(unsafe.Pointer(&data[0]))
if int(fsys.fsize)*512 != len(data) {
log.Fatalf("corrupt disk: invalid size: %d != %d", int(fsys.fsize)*512, len(data))
}
if 2*512+int(fsys.isize)*512 > len(data) {
log.Fatalf("corrupt disk: too many inodes")
}
inodes := unsafe.Slice((*inode)(unsafe.Pointer(&data[2*512])), int(fsys.isize)*512/32)
inames := make([]iname, len(inodes))
var list []*iname
for i := range inodes {
ip := &inodes[i]
if ip.mode == 0 {
continue
}
var content []byte
if m := ip.mode & _IFMT; m != _IFCHR && m != _IFBLK {
size := ip.size()
content = make([]byte, size)
for j := 0; j < size; j += 512 {
copy(content[j:], getblk(data, ip, j/512))
}
}
inam := &inames[i]
list = append(list, inam)
inam.content = content
inam.inode = ip
if ip.mode&_IFMT == _IFDIR {
if len(content) == 0 {
fmt.Printf("#%d NO CONTENT\n", i+1)
continue
}
dirs := unsafe.Slice((*dirent)(unsafe.Pointer(&content[0])), len(content)/16)
for j := range dirs {
de := &dirs[j]
name := de.name()
if de.ino == 0 || name == "." || name == ".." {
continue
}
cnam := &inames[de.ino-1]
cnam.parent = inam
cnam.name = name
}
}
}
w := os.Stdout
if *outfile != "" {
f, err := os.Create(*outfile)
if err != nil {
log.Fatal(err)
}
w = f
}
slices.SortFunc(list, func(x, y *iname) int { return pathCompare(x.path(), y.path()) })
for _, inam := range list {
dev := ""
if m := inam.mode & _IFMT; m == _IFCHR || m == _IFBLK {
dev = fmt.Sprintf(" major=%d minor=%d", uint8(inam.addr[0]>>8), uint8(inam.addr[0]))
}
b64 := ""
var c []byte
if inam.mode&_IFMT == 0 {
c = inam.content
if !utf8.Valid(c) || bytes.HasPrefix(c, []byte("-- ")) || bytes.Contains(c, []byte("\n-- ")) || !bytes.HasSuffix(c, []byte("\n")) {
// base64 encode
b64 = " base64=1"
c = []byte(wrap(base64.StdEncoding.EncodeToString(c)))
}
}
fmt.Fprintf(w, "-- %s mode=%07o uid=%d gid=%d atime=%d mtime=%d%s%s --\n%s",
inam.path(), inam.mode, inam.uid, inam.gid, inam.atime.unix(), inam.mtime.unix(), dev, b64, c)
}
}
func wrap(text string) string {
if len(text) < 70 {
return text + "\n"
}
return text[:70] + "\n" + wrap(text[70:])
}
func pathCompare(x, y string) int {
return strings.Compare(strings.ReplaceAll(x, "/", "\x01"), strings.ReplaceAll(y, "/", "\x01"))
}
func getblk(disk []byte, ip *inode, bn int) []byte {
if bn&^0o77777 != 0 {
panic("block too big")
}
var addr uint16
if ip.mode&_ILARG == 0 {
addr = ip.addr[bn]
} else {
i := bn >> 8
if i > 7 {
i = 7
}
addr = ip.addr[i]
if addr == 0 {
// zero addresses could be handled by using a block of zeros,
// but more likely it is a problem. If we find a disk that needs it,
// we can add support.
log.Fatalf("corrupt disk: zero address")
}
ptrs := (*[256]uint16)(diskblk(disk, addr))
if i == 7 {
addr = ptrs[(bn>>8)&0o377-7]
if addr == 0 {
log.Fatalf("corrupt disk: zero address")
}
ptrs = (*[256]uint16)(diskblk(disk, addr))
}
addr = ptrs[bn&0o377]
if addr == 0 {
log.Fatalf("corrupt disk: zero address")
}
}
return (*[512]byte)(diskblk(disk, addr))[:]
}
func diskblk(disk []byte, addr uint16) unsafe.Pointer {
off := int(addr) * 512
if off < 0 || off+512 > len(disk) {
log.Fatalf("corrupt disk: address out of bounds")
}
return unsafe.Pointer(&disk[off])
}