feat: Merge tape and file tar tvf implementations
This commit is contained in:
Felicitas Pojtinger
@@ -1,137 +0,0 @@
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package main
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import (
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"archive/tar"
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"bufio"
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"flag"
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"io"
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"log"
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"os"
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"syscall"
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"unsafe"
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)
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// See https://github.com/benmcclelland/mtio
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const (
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MTIOCPOS = 0x80086d03 // Get tape position
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MTIOCTOP = 0x40086d01 // Do magnetic tape operation
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MTFSF = 1 // Forward space over FileMark, position at first record of next file
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blockSize = 512
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)
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// Position is struct for MTIOCPOS
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type Position struct {
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BlkNo int64 // Current block number
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}
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// Operation is struct for MTIOCTOP
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type Operation struct {
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Op int16 // Operation ID
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Pad int16 // Padding to match C structures
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Count int32 // Operation count
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}
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func main() {
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file := flag.String("file", "/dev/nst0", "File (tape drive or tar file) to open")
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recordSize := flag.Int("recordSize", 20, "Amount of 512-bit blocks per record")
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flag.Parse()
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fileDescription, err := os.Stat(*file)
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if err != nil {
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panic(err)
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}
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var f *os.File
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if fileDescription.Mode().IsRegular() {
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f, err = os.Open(*file)
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if err != nil {
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panic(err)
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}
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} else {
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f, err = os.OpenFile(*file, os.O_RDONLY, os.ModeCharDevice)
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if err != nil {
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panic(err)
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}
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}
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defer f.Close()
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var tr *tar.Reader
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if fileDescription.Mode().IsRegular() {
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tr = tar.NewReader(f)
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} else {
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br := bufio.NewReaderSize(f, blockSize**recordSize)
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tr = tar.NewReader(br)
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}
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record := int64(0)
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for {
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hdr, err := tr.Next()
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if err == io.EOF {
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if err := gotoNextFile(f); err != nil {
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panic(err)
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}
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if fileDescription.Mode().IsRegular() {
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tr = tar.NewReader(f)
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} else {
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br := bufio.NewReaderSize(f, blockSize**recordSize)
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tr = tar.NewReader(br)
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}
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hdr, err = tr.Next()
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if err != nil {
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if err == io.EOF {
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break
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}
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panic(err)
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}
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}
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if err != nil {
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panic(err)
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}
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log.Println("Record:", record, "Block:", 0, "Header:", hdr)
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record, err = getCurrentRecord(f)
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if err != nil {
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panic(err)
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}
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}
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}
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func gotoNextFile(f *os.File) error {
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if _, _, err := syscall.Syscall(
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syscall.SYS_IOCTL,
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f.Fd(),
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MTIOCTOP,
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uintptr(unsafe.Pointer(
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&Operation{
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Op: MTFSF,
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Count: 1,
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},
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)),
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); err != 0 {
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return err
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}
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return nil
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}
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func getCurrentRecord(f *os.File) (int64, error) {
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pos := &Position{}
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if _, _, err := syscall.Syscall(
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syscall.SYS_IOCTL,
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f.Fd(),
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MTIOCPOS,
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uintptr(unsafe.Pointer(pos)),
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); err != 0 {
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return 0, err
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}
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return pos.BlkNo, nil
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}
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@@ -2,16 +2,36 @@ package main
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import (
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"archive/tar"
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"bufio"
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"flag"
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"io"
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"log"
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"os"
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"syscall"
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"unsafe"
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)
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// See https://github.com/benmcclelland/mtio
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const (
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MTIOCPOS = 0x80086d03 // Get tape position
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MTIOCTOP = 0x40086d01 // Do magnetic tape operation
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MTFSF = 1 // Forward space over FileMark, position at first record of next file
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blockSize = 512
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)
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// Position is struct for MTIOCPOS
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type Position struct {
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BlkNo int64 // Current block number
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}
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// Operation is struct for MTIOCTOP
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type Operation struct {
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Op int16 // Operation ID
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Pad int16 // Padding to match C structures
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Count int32 // Operation count
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}
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func main() {
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file := flag.String("file", "/dev/nst0", "File (tape drive or tar file) to open")
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recordSize := flag.Int("recordSize", 20, "Amount of 512-bit blocks per record")
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@@ -37,18 +57,81 @@ func main() {
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}
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defer f.Close()
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tr := tar.NewReader(f)
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if fileDescription.Mode().IsRegular() {
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tr := tar.NewReader(f)
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record := int64(0)
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block := int64(0)
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firstRecordOfArchive := int64(0)
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record := int64(0)
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block := int64(0)
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firstRecordOfArchive := int64(0)
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for {
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hdr, err := tr.Next()
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if err != nil {
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// Seek right after the next two blocks to skip the trailer
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if _, err := f.Seek((int64(*recordSize)*blockSize*record)+(block+1)*blockSize, io.SeekStart); err == nil {
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tr = tar.NewReader(f)
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for {
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hdr, err := tr.Next()
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if err != nil {
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// Seek right after the next two blocks to skip the trailer
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if _, err := f.Seek((int64(*recordSize)*blockSize*record)+(block+1)*blockSize, io.SeekStart); err == nil {
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tr = tar.NewReader(f)
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hdr, err = tr.Next()
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if err != nil {
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if err == io.EOF {
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break
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}
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panic(err)
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}
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block++
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if block > int64(*recordSize) {
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record++
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block = 0
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}
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firstRecordOfArchive = record
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} else {
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panic(err)
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}
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}
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if record == 0 && block == 0 {
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log.Println("Record:", 0, "Block:", 0, "Header:", hdr)
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} else {
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log.Println("Record:", record, "Block:", block, "Header:", hdr)
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}
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curr, err := f.Seek(0, io.SeekCurrent)
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if err != nil {
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panic(err)
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}
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nextTotalBlocks := (curr + hdr.Size) / blockSize
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record = nextTotalBlocks / int64(*recordSize)
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if record == 0 && block == 0 || record == firstRecordOfArchive {
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block = nextTotalBlocks - (record * int64(*recordSize)) // For the first record of the file or archive, the offset of one is not needed
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} else {
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block = nextTotalBlocks - (record * int64(*recordSize)) + 1 // +1 because we need to start reading right after the last block
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}
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if block > int64(*recordSize) {
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record++
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block = 0
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}
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}
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} else {
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br := bufio.NewReaderSize(f, blockSize**recordSize)
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tr := tar.NewReader(br)
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record := int64(0)
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for {
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hdr, err := tr.Next()
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if err == io.EOF {
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if err := gotoNextFileOnTape(f); err != nil {
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panic(err)
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}
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br = bufio.NewReaderSize(f, blockSize**recordSize)
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tr = tar.NewReader(br)
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hdr, err = tr.Next()
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if err != nil {
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@@ -58,45 +141,50 @@ func main() {
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panic(err)
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}
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}
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block++
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if block > int64(*recordSize) {
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record++
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block = 0
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}
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firstRecordOfArchive = record
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} else {
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if err != nil {
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panic(err)
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}
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// TODO: Seek with matching syscall (`mt seek (int64(*recordSize)*record)+1`)
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}
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log.Println("Record:", record, "Block:", 0, "Header:", hdr)
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// TODO: Do `tell` on tape drive instead, which returns the block - but how do we get the current block? Maybe we have to use the old, iterating method and call.Next after we found the correct record & block.
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curr, err := f.Seek(0, io.SeekCurrent)
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if err != nil {
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panic(err)
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}
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if record == 0 && block == 0 {
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log.Println("Record:", 0, "Block:", 0, "Header:", hdr)
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} else {
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log.Println("Record:", record, "Block:", block, "Header:", hdr)
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}
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nextTotalBlocks := (curr + hdr.Size) / blockSize
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record = nextTotalBlocks / int64(*recordSize)
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if record == 0 && block == 0 || record == firstRecordOfArchive {
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block = nextTotalBlocks - (record * int64(*recordSize)) // For the first record of the file or archive, the offset of one is not needed
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} else {
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block = nextTotalBlocks - (record * int64(*recordSize)) + 1 // +1 because we need to start reading right after the last block
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}
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if block > int64(*recordSize) {
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record++
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block = 0
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record, err = getCurrentRecordFromTape(f)
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if err != nil {
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panic(err)
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}
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}
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}
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}
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func gotoNextFileOnTape(f *os.File) error {
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if _, _, err := syscall.Syscall(
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syscall.SYS_IOCTL,
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f.Fd(),
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MTIOCTOP,
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uintptr(unsafe.Pointer(
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&Operation{
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Op: MTFSF,
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Count: 1,
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},
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)),
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); err != 0 {
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return err
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}
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return nil
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}
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func getCurrentRecordFromTape(f *os.File) (int64, error) {
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pos := &Position{}
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if _, _, err := syscall.Syscall(
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syscall.SYS_IOCTL,
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f.Fd(),
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MTIOCPOS,
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uintptr(unsafe.Pointer(pos)),
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); err != 0 {
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return 0, err
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}
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return pos.BlkNo, nil
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}
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