package packfile import ( "bytes" "gopkg.in/src-d/go-git.v4/plumbing" "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 independand if the an // ObjectStorer was provided or not. type Decoder struct { s *Scanner o storer.EncodedObjectStorer tx storer.Transaction isDecoded bool offsetToHash map[int64]plumbing.Hash hashToOffset map[plumbing.Hash]int64 crcs map[plumbing.Hash]uint32 } // NewDecoder returns a new Decoder that decodes a Packfile using the given // s and store the objects in the provided o. ObjectStorer can be nil, in this // case the objects are not stored but objects offsets on the Packfile and the // CRCs are calculated. // // If ObjectStorer 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 something fails the Rollback is called func NewDecoder(s *Scanner, o storer.EncodedObjectStorer) (*Decoder, error) { if !canResolveDeltas(s, o) { return nil, ErrResolveDeltasNotSupported } return &Decoder{ s: s, o: o, offsetToHash: make(map[int64]plumbing.Hash, 0), hashToOffset: make(map[plumbing.Hash]int64, 0), crcs: make(map[plumbing.Hash]uint32, 0), }, 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 } _, 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 // interative way func (d *Decoder) DecodeObject() (plumbing.EncodedObject, error) { h, err := d.s.NextObjectHeader() if err != nil { return nil, err } obj := d.newObject() obj.SetSize(h.Length) obj.SetType(h.Type) var crc uint32 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 } hash := obj.Hash() d.setOffset(hash, h.Offset) d.setCRC(hash, 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, if Decode wasn't called // previously objects offset should provided using the SetOffsets method func (d *Decoder) DecodeObjectAt(offset int64) (plumbing.EncodedObject, error) { if !d.s.IsSeekable { return nil, ErrNonSeekable } beforeJump, err := d.s.Seek(offset) if err != nil { return nil, err } defer func() { _, seekErr := d.s.Seek(beforeJump) if err == nil { err = seekErr } }() return d.DecodeObject() } 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 := bytes.NewBuffer(nil) _, crc, err := d.s.NextObject(buf) if err != nil { return 0, err } base, err := d.recallByHash(ref) if err != nil { return 0, err } obj.SetType(base.Type()) return crc, ApplyDelta(obj, base, buf.Bytes()) } 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 } base, err := d.recallByOffset(offset) if err != nil { return 0, err } obj.SetType(base.Type()) return crc, ApplyDelta(obj, base, buf.Bytes()) } func (d *Decoder) setOffset(h plumbing.Hash, offset int64) { d.offsetToHash[offset] = h d.hashToOffset[h] = offset } func (d *Decoder) setCRC(h plumbing.Hash, crc uint32) { d.crcs[h] = crc } func (d *Decoder) recallByOffset(o int64) (plumbing.EncodedObject, error) { if d.s.IsSeekable { return d.DecodeObjectAt(o) } if h, ok := d.offsetToHash[o]; ok { return d.recallByHashNonSeekable(h) } return nil, plumbing.ErrObjectNotFound } func (d *Decoder) recallByHash(h plumbing.Hash) (plumbing.EncodedObject, error) { if d.s.IsSeekable { if o, ok := d.hashToOffset[h]; ok { return d.DecodeObjectAt(o) } } 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 } // SetOffsets sets the offsets, required when using the method DecodeObjectAt, // without decoding the full packfile func (d *Decoder) SetOffsets(offsets map[plumbing.Hash]int64) { d.hashToOffset = offsets } // Offsets returns the objects read offset, Decode method should be called // before to calculate the Offsets func (d *Decoder) Offsets() map[plumbing.Hash]int64 { return d.hashToOffset } // CRCs returns the CRC-32 for each objected read,Decode method should be called // before to calculate the CRCs func (d *Decoder) CRCs() map[plumbing.Hash]uint32 { return d.crcs } // Close close the Scanner, usually this mean that the whole reader is read and // discarded func (d *Decoder) Close() error { return d.s.Close() }