107 lines
2.2 KiB
Go
107 lines
2.2 KiB
Go
// Package holes finds and pretty-prints holes & data sections of a file.
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// Used by TestFileHoleCopy in the gocryptfs test suite.
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package holes
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import (
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"fmt"
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"syscall"
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)
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const (
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SEEK_DATA = 3
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SEEK_HOLE = 4
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SegmentHole = SegmentType(100)
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SegmentData = SegmentType(101)
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SegmentEOF = SegmentType(102)
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)
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type Segment struct {
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Offset int64
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Type SegmentType
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}
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func (s Segment) String() string {
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return fmt.Sprintf("%10d %v", s.Offset, s.Type)
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}
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type SegmentType int
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func (s SegmentType) String() string {
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switch s {
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case SegmentHole:
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return "hole"
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case SegmentData:
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return "data"
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case SegmentEOF:
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return "eof"
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default:
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return "???"
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}
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}
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// PrettyPrint pretty-prints the Segments.
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func PrettyPrint(segments []Segment) (out string) {
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for _, s := range segments {
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out += "\n" + s.String()
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}
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return out
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}
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// Find examines the file passed via file descriptor and returns the found holes
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// and data sections.
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func Find(fd int) (segments []Segment, err error) {
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var st syscall.Stat_t
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err = syscall.Fstat(fd, &st)
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if err != nil {
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return nil, err
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}
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totalSize := st.Size
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var cursor int64
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// find out if file starts with data or hole
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off, err := syscall.Seek(fd, 0, SEEK_DATA)
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if err == syscall.ENXIO {
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segments = append(segments,
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Segment{0, SegmentHole},
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Segment{totalSize, SegmentEOF})
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return segments, nil
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}
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if err != nil {
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return nil, err
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}
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if off == cursor {
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segments = append(segments, Segment{0, SegmentData})
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} else {
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segments = append(segments,
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Segment{0, SegmentHole},
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Segment{totalSize, SegmentData})
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cursor = off
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}
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// now we are at the start of data.
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// find next hole, then next data, then next hole, then next data...
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for {
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cursor, err = syscall.Seek(fd, cursor, SEEK_HOLE)
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if err != nil {
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return nil, err
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}
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if cursor == totalSize {
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segments = append(segments, Segment{cursor, SegmentEOF})
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break
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}
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segments = append(segments, Segment{cursor, SegmentHole})
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cursor, err = syscall.Seek(fd, cursor, SEEK_DATA)
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if err != nil {
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return nil, err
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}
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if cursor == totalSize {
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segments = append(segments, Segment{cursor, SegmentEOF})
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break
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}
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segments = append(segments, Segment{cursor, SegmentData})
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}
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return segments, nil
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}
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