Pad snapshot filenames with 0s

[otoolep]

Allowing up to 24 0s is sufficient for a 64-bit unsigned int.

[otoolep]

OK, what about this trivial change to address issue 235? This will not fix busted systems, but systems going forward should be better.

[otoolep]

I ran the unit test suite with this change in place. It passed.

[otoolep]

I guess to be fully functional, the patch would need to pad last index too.

[otoolep]

http://play.golang.org/p/B5dVjbT37o

[otoolep]

This is, of course, not backwards compatible with snapshots that already exist.

[bcwaldon]

Handling backwards-compatibility could look like so:

func NewSnapshotFileNames(names []string) ([]SnapshotFileName, error) {
    s := make([]SnapshotFileName, 0)
    for _, n := range names {
        trimmed := strings.TrimSuffix(n, ".ss")
        if trimmed == n {
            return nil, fmt.Errorf("file %q does not have .ss extension", n)
        }

        parts := strings.SplitN(trimmed, "_", 2)
        if len(parts) != 2 {
            return nil, fmt.Errorf("unrecognized file name format %q", n)
        }

        fn := SnapshotFileName{FileName: n}

        var err error
        fn.Term, err = strconv.ParseUint(parts[0], 10, 64)
        if err != nil {
            return nil, fmt.Errorf("unable to parse term from filename %q: %v", err)
        }

        fn.Index, err = strconv.ParseUint(parts[1], 10, 64)
        if err != nil {
            return nil, fmt.Errorf("unable to parse index from filename %q: %v", err)
        }

        s = append(s, fn)
    }

    sortable := SnapshotFileNames(s)
    sort.Sort(&sortable)
    return s, nil
}

type SnapshotFileNames []SnapshotFileName
type SnapshotFileName struct {
    FileName string
    Term     uint64
    Index    uint64
}

func (n *SnapshotFileNames) Less(i, j int) bool {
    iTerm, iIndex := (*n)[i].Term, (*n)[i].Index
    jTerm, jIndex := (*n)[j].Term, (*n)[j].Index
    return iTerm < jTerm || (iTerm == jTerm && iIndex < jIndex)
}

func (n *SnapshotFileNames) Swap(i, j int) {
    (*n)[i], (*n)[j] = (*n)[j], (*n)[i]
}

func (n *SnapshotFileNames) Len() int {
    return len([]SnapshotFileName(*n))
}

[bcwaldon]

And if we've already established one filename format out there, I question why we want to change that if we still need to deal with backwards-compatibility.

[otoolep]

Cute. :-)