package packfile
import (
"bytes"
"gopkg.in/src-d/go-git.v4/plumbing"
"gopkg.in/src-d/go-git.v4/plumbing/cache"
"gopkg.in/src-d/go-git.v4/plumbing/storer"
)
// Format specifies if the packfile uses ref-deltas or ofs-deltas.
type Format int
// Possible values of the Format type.
const (
UnknownFormat Format = iota
OFSDeltaFormat
REFDeltaFormat
)
var (
// ErrMaxObjectsLimitReached is returned by Decode when the number
// of objects in the packfile is higher than
// Decoder.MaxObjectsLimit.
ErrMaxObjectsLimitReached = NewError("max. objects limit reached")
// ErrInvalidObject is returned by Decode when an invalid object is
// found in the packfile.
ErrInvalidObject = NewError("invalid git object")
// ErrPackEntryNotFound is returned by Decode when a reference in
// the packfile references and unknown object.
ErrPackEntryNotFound = NewError("can't find a pack entry")
// ErrZLib is returned by Decode when there was an error unzipping
// the packfile contents.
ErrZLib = NewError("zlib reading error")
// ErrCannotRecall is returned by RecallByOffset or RecallByHash if the object
// to recall cannot be returned.
ErrCannotRecall = NewError("cannot recall object")
// ErrResolveDeltasNotSupported is returned if a NewDecoder is used with a
// non-seekable scanner and without a plumbing.ObjectStorage
ErrResolveDeltasNotSupported = NewError("resolve delta is not supported")
// ErrNonSeekable is returned if a ReadObjectAt method is called without a
// seekable scanner
ErrNonSeekable = NewError("non-seekable scanner")
// ErrRollback error making Rollback over a transaction after an error
ErrRollback = NewError("rollback error, during set error")
// ErrAlreadyDecoded is returned if NewDecoder is called for a second time
ErrAlreadyDecoded = NewError("packfile was already decoded")
)
// Decoder reads and decodes packfiles from an input Scanner, if an ObjectStorer
// was provided the decoded objects are store there. If not the decode object
// is destroyed. The Offsets and CRCs are calculated whether an
// ObjectStorer was provided or not.
type Decoder struct {
deltaBaseCache cache.Object
s *Scanner
o storer.EncodedObjectStorer
tx storer.Transaction
isDecoded bool
// hasBuiltIndex indicates if the index is fully built or not. If it is not,
// will be built incrementally while decoding.
hasBuiltIndex bool
idx *Index
offsetToType map[int64]plumbing.ObjectType
decoderType plumbing.ObjectType
}
// NewDecoder returns a new Decoder that decodes a Packfile using the given
// Scanner and stores the objects in the provided EncodedObjectStorer. ObjectStorer can be nil, in this
// If the passed EncodedObjectStorer is nil, objects are not stored, but
// offsets on the Packfile and CRCs are calculated.
//
// If EncodedObjectStorer is nil and the Scanner is not Seekable, ErrNonSeekable is
// returned.
//
// If the ObjectStorer implements storer.Transactioner, a transaction is created
// during the Decode execution. If anything fails, Rollback is called
func NewDecoder(s *Scanner, o storer.EncodedObjectStorer) (*Decoder, error) {
return NewDecoderForType(s, o, plumbing.AnyObject,
cache.NewObjectLRUDefault())
}
// NewDecoderWithCache is a version of NewDecoder where cache can be specified.
func NewDecoderWithCache(s *Scanner, o storer.EncodedObjectStorer,
cacheObject cache.Object) (*Decoder, error) {
return NewDecoderForType(s, o, plumbing.AnyObject, cacheObject)
}
// NewDecoderForType returns a new Decoder but in this case for a specific object type.
// When an object is read using this Decoder instance and it is not of the same type of
// the specified one, nil will be returned. This is intended to avoid the content
// deserialization of all the objects.
//
// cacheObject is a cache.Object implementation that is used to speed up the
// process. If cache is not needed you can pass nil. To create an LRU cache
// object with the default size you can use the helper cache.ObjectLRUDefault().
func NewDecoderForType(s *Scanner, o storer.EncodedObjectStorer,
t plumbing.ObjectType, cacheObject cache.Object) (*Decoder, error) {
if t == plumbing.OFSDeltaObject ||
t == plumbing.REFDeltaObject ||
t == plumbing.InvalidObject {
return nil, plumbing.ErrInvalidType
}
if !canResolveDeltas(s, o) {
return nil, ErrResolveDeltasNotSupported
}
return &Decoder{
s: s,
o: o,
deltaBaseCache: cacheObject,
idx: NewIndex(0),
offsetToType: make(map[int64]plumbing.ObjectType),
decoderType: t,
}, nil
}
func canResolveDeltas(s *Scanner, o storer.EncodedObjectStorer) bool {
return s.IsSeekable || o != nil
}
// Decode reads a packfile and stores it in the value pointed to by s. The
// offsets and the CRCs are calculated by this method
func (d *Decoder) Decode() (checksum plumbing.Hash, err error) {
defer func() { d.isDecoded = true }()
if d.isDecoded {
return plumbing.ZeroHash, ErrAlreadyDecoded
}
if err := d.doDecode(); err != nil {
return plumbing.ZeroHash, err
}
return d.s.Checksum()
}
func (d *Decoder) doDecode() error {
_, count, err := d.s.Header()
if err != nil {
return err
}
if !d.hasBuiltIndex {
d.idx = NewIndex(int(count))
}
defer func() { d.hasBuiltIndex = true }()
_, isTxStorer := d.o.(storer.Transactioner)
switch {
case d.o == nil:
return d.decodeObjects(int(count))
case isTxStorer:
return d.decodeObjectsWithObjectStorerTx(int(count))
default:
return d.decodeObjectsWithObjectStorer(int(count))
}
}
func (d *Decoder) decodeObjects(count int) error {
for i := 0; i < count; i++ {
if _, err := d.DecodeObject(); err != nil {
return err
}
}
return nil
}
func (d *Decoder) decodeObjectsWithObjectStorer(count int) error {
for i := 0; i < count; i++ {
obj, err := d.DecodeObject()
if err != nil {
return err
}
if _, err := d.o.SetEncodedObject(obj); err != nil {
return err
}
}
return nil
}
func (d *Decoder) decodeObjectsWithObjectStorerTx(count int) error {
d.tx = d.o.(storer.Transactioner).Begin()
for i := 0; i < count; i++ {
obj, err := d.DecodeObject()
if err != nil {
return err
}
if _, err := d.tx.SetEncodedObject(obj); err != nil {
if rerr := d.tx.Rollback(); rerr != nil {
return ErrRollback.AddDetails(
"error: %s, during tx.Set error: %s", rerr, err,
)
}
return err
}
}
return d.tx.Commit()
}
// DecodeObject reads the next object from the scanner and returns it. This
// method can be used in replacement of the Decode method, to work in a
// interactive way. If you created a new decoder instance using NewDecoderForType
// constructor, if the object decoded is not equals to the specified one, nil will
// be returned
func (d *Decoder) DecodeObject() (plumbing.EncodedObject, error) {
return d.doDecodeObject(d.decoderType)
}
func (d *Decoder) doDecodeObject(t plumbing.ObjectType) (plumbing.EncodedObject, error) {
h, err := d.s.NextObjectHeader()
if err != nil {
return nil, err
}
if t == plumbing.AnyObject {
return d.decodeByHeader(h)
}
return d.decodeIfSpecificType(h)
}
func (d *Decoder) decodeIfSpecificType(h *ObjectHeader) (plumbing.EncodedObject, error) {
var (
obj plumbing.EncodedObject
realType plumbing.ObjectType
err error
)
switch h.Type {
case plumbing.OFSDeltaObject:
realType, err = d.ofsDeltaType(h.OffsetReference)
case plumbing.REFDeltaObject:
realType, err = d.refDeltaType(h.Reference)
if err == plumbing.ErrObjectNotFound {
obj, err = d.decodeByHeader(h)
if err != nil {
realType = obj.Type()
}
}
default:
realType = h.Type
}
if err != nil {
return nil, err
}
d.offsetToType[h.Offset] = realType
if d.decoderType == realType {
if obj != nil {
return obj, nil
}
return d.decodeByHeader(h)
}
return nil, nil
}
func (d *Decoder) ofsDeltaType(offset int64) (plumbing.ObjectType, error) {
t, ok := d.offsetToType[offset]
if !ok {
return plumbing.InvalidObject, plumbing.ErrObjectNotFound
}
return t, nil
}
func (d *Decoder) refDeltaType(ref plumbing.Hash) (plumbing.ObjectType, error) {
e, ok := d.idx.LookupHash(ref)
if !ok {
return plumbing.InvalidObject, plumbing.ErrObjectNotFound
}
return d.ofsDeltaType(int64(e.Offset))
}
func (d *Decoder) decodeByHeader(h *ObjectHeader) (plumbing.EncodedObject, error) {
obj := d.newObject()
obj.SetSize(h.Length)
obj.SetType(h.Type)
var crc uint32
var err error
switch h.Type {
case plumbing.CommitObject, plumbing.TreeObject, plumbing.BlobObject, plumbing.TagObject:
crc, err = d.fillRegularObjectContent(obj)
case plumbing.REFDeltaObject:
crc, err = d.fillREFDeltaObjectContent(obj, h.Reference)
case plumbing.OFSDeltaObject:
crc, err = d.fillOFSDeltaObjectContent(obj, h.OffsetReference)
default:
err = ErrInvalidObject.AddDetails("type %q", h.Type)
}
if err != nil {
return obj, err
}
if !d.hasBuiltIndex {
d.idx.Add(obj.Hash(), uint64(h.Offset), crc)
}
return obj, nil
}
func (d *Decoder) newObject() plumbing.EncodedObject {
if d.o == nil {
return &plumbing.MemoryObject{}
}
return d.o.NewEncodedObject()
}
// DecodeObjectAt reads an object at the given location. Every EncodedObject
// returned is added into a internal index. This is intended to be able to regenerate
// objects from deltas (offset deltas or reference deltas) without an package index
// (.idx file). If Decode wasn't called previously objects offset should provided
// using the SetOffsets method. It decodes the object regardless of the Decoder
// type.
func (d *Decoder) DecodeObjectAt(offset int64) (plumbing.EncodedObject, error) {
if !d.s.IsSeekable {
return nil, ErrNonSeekable
}
beforeJump, err := d.s.SeekFromStart(offset)
if err != nil {
return nil, err
}
defer func() {
_, seekErr := d.s.SeekFromStart(beforeJump)
if err == nil {
err = seekErr
}
}()
return d.doDecodeObject(plumbing.AnyObject)
}
func (d *Decoder) fillRegularObjectContent(obj plumbing.EncodedObject) (uint32, error) {
w, err := obj.Writer()
if err != nil {
return 0, err
}
_, crc, err := d.s.NextObject(w)
return crc, err
}
func (d *Decoder) fillREFDeltaObjectContent(obj plumbing.EncodedObject, ref plumbing.Hash) (uint32, error) {
buf := bufPool.Get().(*bytes.Buffer)
buf.Reset()
_, crc, err := d.s.NextObject(buf)
if err != nil {
return 0, err
}
base, ok := d.cacheGet(ref)
if !ok {
base, err = d.recallByHash(ref)
if err != nil {
return 0, err
}
}
obj.SetType(base.Type())
err = ApplyDelta(obj, base, buf.Bytes())
d.cachePut(obj)
bufPool.Put(buf)
return crc, err
}
func (d *Decoder) fillOFSDeltaObjectContent(obj plumbing.EncodedObject, offset int64) (uint32, error) {
buf := bytes.NewBuffer(nil)
_, crc, err := d.s.NextObject(buf)
if err != nil {
return 0, err
}
e, ok := d.idx.LookupOffset(uint64(offset))
var base plumbing.EncodedObject
if ok {
base, ok = d.cacheGet(e.Hash)
}
if !ok {
base, err = d.recallByOffset(offset)
if err != nil {
return 0, err
}
}
obj.SetType(base.Type())
err = ApplyDelta(obj, base, buf.Bytes())
d.cachePut(obj)
return crc, err
}
func (d *Decoder) cacheGet(h plumbing.Hash) (plumbing.EncodedObject, bool) {
if d.deltaBaseCache == nil {
return nil, false
}
return d.deltaBaseCache.Get(h)
}
func (d *Decoder) cachePut(obj plumbing.EncodedObject) {
if d.deltaBaseCache == nil {
return
}
d.deltaBaseCache.Put(obj)
}
func (d *Decoder) recallByOffset(o int64) (plumbing.EncodedObject, error) {
if d.s.IsSeekable {
return d.DecodeObjectAt(o)
}
if e, ok := d.idx.LookupOffset(uint64(o)); ok {
return d.recallByHashNonSeekable(e.Hash)
}
return nil, plumbing.ErrObjectNotFound
}
func (d *Decoder) recallByHash(h plumbing.Hash) (plumbing.EncodedObject, error) {
if d.s.IsSeekable {
if e, ok := d.idx.LookupHash(h); ok {
return d.DecodeObjectAt(int64(e.Offset))
}
}
return d.recallByHashNonSeekable(h)
}
// recallByHashNonSeekable if we are in a transaction the objects are read from
// the transaction, if not are directly read from the ObjectStorer
func (d *Decoder) recallByHashNonSeekable(h plumbing.Hash) (obj plumbing.EncodedObject, err error) {
if d.tx != nil {
obj, err = d.tx.EncodedObject(plumbing.AnyObject, h)
} else {
obj, err = d.o.EncodedObject(plumbing.AnyObject, h)
}
if err != plumbing.ErrObjectNotFound {
return obj, err
}
return nil, plumbing.ErrObjectNotFound
}
// SetIndex sets an index for the packfile. It is recommended to set this.
// The index might be read from a file or reused from a previous Decoder usage
// (see Index function).
func (d *Decoder) SetIndex(idx *Index) {
d.hasBuiltIndex = true
d.idx = idx
}
// Index returns the index for the packfile. If index was set with SetIndex,
// Index will return it. Otherwise, it will return an index that is built while
// decoding. If neither SetIndex was called with a full index or Decode called
// for the whole packfile, then the returned index will be incomplete.
func (d *Decoder) Index() *Index {
return d.idx
}
// Close closes the Scanner. usually this mean that the whole reader is read and
// discarded
func (d *Decoder) Close() error {
return d.s.Close()
}
