95 lines
1.6 KiB
Go
95 lines
1.6 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 HeaderInBlock struct {
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Record int
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Block int
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Header string
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}
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func main() {
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file := flag.String("file", "test.tar", "Tar file to open")
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recordSize := flag.Int("recordSize", 20, "Amount of 512-bit blocks per record")
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checkpoint := flag.Int("checkpoint", 0, "Log current record after checkpoint kilobytes have been read")
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seek := flag.Int("seek", 0, "Record to seek too")
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flag.Parse()
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bytesToSeek := *recordSize * blockSize * *seek
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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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defer f.Close()
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record := 0
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for {
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// Seek to requested record
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if bytesToSeek > 0 && record < *seek {
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if _, err := f.Seek(int64(bytesToSeek), 0); err != nil {
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panic(err)
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}
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record = *seek
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continue
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}
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// Lock the current record if requested
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if *checkpoint > 0 && record%*checkpoint == 0 {
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log.Println("Checkpoint:", record)
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}
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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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headers := []HeaderInBlock{}
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for i := 0; i < *recordSize; i++ {
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tr := tar.NewReader(bytes.NewReader(bf[blockSize*i : blockSize*(i+1)]))
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hdr, err := tr.Next()
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if err != nil {
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continue
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}
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if hdr.Format == tar.FormatUnknown {
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// EOF
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break
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}
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headers = append(headers, HeaderInBlock{
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Record: record,
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Block: i,
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Header: fmt.Sprintf("%v", hdr),
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})
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}
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if len(headers) > 0 {
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fmt.Println(headers)
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}
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record++
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}
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}
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