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tarextractor.go
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/
tarextractor.go
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package tarextractor
import (
"encoding/gob"
"io"
"os"
humanize "github.com/dustin/go-humanize"
"github.com/go-errors/errors"
"github.com/itchio/arkive/tar"
"github.com/itchio/savior"
"github.com/itchio/wharf/state"
)
type tarExtractor struct {
source savior.Source
saveConsumer savior.SaveConsumer
consumer *state.Consumer
}
type TarExtractorState struct {
Result *savior.ExtractorResult
TarCheckpoint *tar.Checkpoint
}
var _ savior.Extractor = (*tarExtractor)(nil)
func New(source savior.Source) savior.Extractor {
return &tarExtractor{
source: source,
saveConsumer: savior.NopSaveConsumer(),
consumer: savior.NopConsumer(),
}
}
func (te *tarExtractor) SetSaveConsumer(saveConsumer savior.SaveConsumer) {
te.saveConsumer = saveConsumer
}
func (te *tarExtractor) SetConsumer(consumer *state.Consumer) {
te.consumer = consumer
}
func (te *tarExtractor) Resume(checkpoint *savior.ExtractorCheckpoint, sink savior.Sink) (*savior.ExtractorResult, error) {
var sr tar.SaverReader
var state *TarExtractorState
if checkpoint != nil {
if stateCheckpoint, ok := checkpoint.Data.(*TarExtractorState); ok {
if stateCheckpoint.Result != nil && stateCheckpoint.TarCheckpoint != nil {
te.consumer.Infof("↻ Resuming @ %.1f%%", checkpoint.Progress*100)
if checkpoint.SourceCheckpoint != nil {
savior.Debugf("tarextractor: resuming source from %d", checkpoint.SourceCheckpoint.Offset)
}
offset, err := te.source.Resume(checkpoint.SourceCheckpoint)
if err != nil {
return nil, errors.Wrap(err, 0)
}
tarCheckpoint := stateCheckpoint.TarCheckpoint
if offset < tarCheckpoint.Roffset {
delta := tarCheckpoint.Roffset - offset
savior.Debugf("tarextractor: discarding %d bytes to align source and tar checkpoint", delta)
savior.Debugf("tarextractor: source was at %d, tar checkpoint was at %d", offset, tarCheckpoint.Roffset)
err = savior.DiscardByRead(te.source, delta)
if err != nil {
return nil, errors.Wrap(err, 0)
}
}
sr, err = tarCheckpoint.Resume(te.source)
if err != nil {
return nil, errors.Wrap(err, 0)
}
state = stateCheckpoint
}
}
}
if sr == nil {
te.consumer.Infof("→ Starting fresh extraction")
state = &TarExtractorState{
Result: &savior.ExtractorResult{
Entries: []*savior.Entry{},
},
}
_, err := te.source.Resume(nil)
if err != nil {
return nil, errors.Wrap(err, 0)
}
checkpoint = &savior.ExtractorCheckpoint{
EntryIndex: 0,
}
sr, err = tar.NewSaverReader(te.source)
if err != nil {
return nil, errors.Wrap(err, 0)
}
}
var stopError error
// allocate a copy buffer once
copier := savior.NewCopier(te.saveConsumer)
var entry *savior.Entry
te.source.SetSourceSaveConsumer(&savior.CallbackSourceSaveConsumer{
OnSave: func(sourceCheckpoint *savior.SourceCheckpoint) error {
if entry == nil {
// if entry is nil here, then our source emitted a checkpoint
// during a call to `Next()`
return nil
}
savior.Debugf("tarextractor: making checkpoint at entry %d", checkpoint.EntryIndex)
tarCheckpoint, err := sr.Save()
if err != nil {
return errors.Wrap(err, 0)
}
savior.Debugf("tarextractor: at checkpoint, tar read offset is %s", humanize.IBytes(uint64(tarCheckpoint.Roffset)))
state.TarCheckpoint = tarCheckpoint
checkpoint.SourceCheckpoint = sourceCheckpoint
checkpoint.Data = state
checkpoint.Progress = te.source.Progress()
// FIXME: we're not syncing the writer here - but we should
action, err := te.saveConsumer.Save(checkpoint)
if err != nil {
return errors.Wrap(err, 0)
}
if action == savior.AfterSaveStop {
copier.Stop()
stopError = savior.ErrStop
}
return nil
},
})
entryIndex := checkpoint.EntryIndex
for stopError == nil {
err := func() error {
entry = nil
checkpoint.EntryIndex = entryIndex
entryIndex++
if checkpoint.Entry == nil {
hdr, err := sr.Next()
if err != nil {
if err == io.EOF {
// we done!
stopError = io.EOF
return nil
}
return errors.Wrap(err, 0)
}
entry := &savior.Entry{
CanonicalPath: hdr.Name,
UncompressedSize: hdr.Size,
Mode: os.FileMode(hdr.Mode),
}
switch hdr.Typeflag {
case tar.TypeDir:
entry.Kind = savior.EntryKindDir
case tar.TypeSymlink:
entry.Kind = savior.EntryKindSymlink
entry.Linkname = hdr.Linkname
case tar.TypeReg:
entry.Kind = savior.EntryKindFile
default:
// let's just ignore that one..
return nil
}
checkpoint.Entry = entry
}
entry = checkpoint.Entry
te.consumer.Debugf("→ %s", entry)
switch entry.Kind {
case savior.EntryKindDir:
savior.Debugf(`tar: extracting dir %s`, entry.CanonicalPath)
err := sink.Mkdir(entry)
if err != nil {
return errors.Wrap(err, 0)
}
case savior.EntryKindSymlink:
savior.Debugf(`tar: extracting symlink %s`, entry.CanonicalPath)
err := sink.Symlink(entry, entry.Linkname)
if err != nil {
return errors.Wrap(err, 0)
}
case savior.EntryKindFile:
savior.Debugf(`tar: extracting file %s`, entry.CanonicalPath)
w, err := sink.GetWriter(entry)
if err != nil {
return errors.Wrap(err, 0)
}
defer w.Close()
err = copier.Do(&savior.CopyParams{
Dst: w,
Src: sr,
Entry: entry,
Savable: te.source,
EmitProgress: func() {
te.consumer.Progress(te.source.Progress())
},
})
if err != nil {
return errors.Wrap(err, 0)
}
state.Result.Entries = append(state.Result.Entries, entry)
te.consumer.Progress(te.source.Progress())
}
checkpoint.Entry = nil
checkpoint.SourceCheckpoint = nil
checkpoint.Data = nil
return nil
}()
if err != nil {
return nil, errors.Wrap(err, 0)
}
}
if stopError != nil {
if stopError == io.EOF {
// success!
} else {
return nil, stopError
}
}
te.consumer.Statf("Extracted %s", state.Result.Stats())
return state.Result, nil
}
func (te *tarExtractor) Features() savior.ExtractorFeatures {
// tar has great resume support but cannot preallocate or grant random access.
return savior.ExtractorFeatures{
Name: "tar",
ResumeSupport: savior.ResumeSupportBlock,
Preallocate: false,
RandomAccess: false,
}
}
func init() {
gob.Register(&TarExtractorState{})
gob.Register(&tar.Checkpoint{})
}