92 lines
1.7 KiB
Go
92 lines
1.7 KiB
Go
package main
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import (
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"archive/tar"
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"bytes"
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"flag"
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"fmt"
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"io"
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"log"
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"os"
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)
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const (
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blockSize = 512
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)
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type Wrapper struct {
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Record int64
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Block int64
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Header string
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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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record := int64(0)
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block := int64(0)
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for {
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// Read exactly one record
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bf := make([]byte, *recordSize*blockSize)
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if _, err := io.ReadFull(f, bf); 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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// Get the headers from the record
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for currentBlock := 0; currentBlock < *recordSize; currentBlock++ {
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tr := tar.NewReader(bytes.NewReader(bf[blockSize*currentBlock : blockSize*(currentBlock+1)]))
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hdr, err := tr.Next() // TODO: Read PAX header info by a plain `tar tvf` before; reads should still be efficient even when seeking back as reads are cached
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if err != nil {
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continue
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}
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wrapper := &Wrapper{
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Record: record,
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Block: block,
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Header: fmt.Sprintf("%v", hdr),
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}
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log.Println(wrapper)
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curr := (record * int64(*recordSize) * blockSize) + int64(currentBlock)*blockSize
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nextTotalBlocks := (curr + hdr.Size) / blockSize
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record := nextTotalBlocks / int64(*recordSize)
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block = nextTotalBlocks - (record * int64(*recordSize)) + 1
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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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record++
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}
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}
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