package commitgraph import ( "crypto/sha1" "hash" "io" "github.com/go-git/go-git/v5/plumbing" "github.com/go-git/go-git/v5/utils/binary" ) // Encoder writes MemoryIndex structs to an output stream. type Encoder struct { io.Writer hash hash.Hash } // NewEncoder returns a new stream encoder that writes to w. func NewEncoder(w io.Writer) *Encoder { h := sha1.New() mw := io.MultiWriter(w, h) return &Encoder{mw, h} } // Encode writes an index into the commit-graph file func (e *Encoder) Encode(idx Index) error { // Get all the hashes in the input index hashes := idx.Hashes() // Sort the inout and prepare helper structures we'll need for encoding hashToIndex, fanout, extraEdgesCount := e.prepare(idx, hashes) chunkSignatures := [][]byte{oidFanoutSignature, oidLookupSignature, commitDataSignature} chunkSizes := []uint64{4 * 256, uint64(len(hashes)) * 20, uint64(len(hashes)) * 36} if extraEdgesCount > 0 { chunkSignatures = append(chunkSignatures, extraEdgeListSignature) chunkSizes = append(chunkSizes, uint64(extraEdgesCount)*4) } if err := e.encodeFileHeader(len(chunkSignatures)); err != nil { return err } if err := e.encodeChunkHeaders(chunkSignatures, chunkSizes); err != nil { return err } if err := e.encodeFanout(fanout); err != nil { return err } if err := e.encodeOidLookup(hashes); err != nil { return err } if extraEdges, err := e.encodeCommitData(hashes, hashToIndex, idx); err == nil { if err = e.encodeExtraEdges(extraEdges); err != nil { return err } } else { return err } return e.encodeChecksum() } func (e *Encoder) prepare(idx Index, hashes []plumbing.Hash) (hashToIndex map[plumbing.Hash]uint32, fanout []uint32, extraEdgesCount uint32) { // Sort the hashes and build our index plumbing.HashesSort(hashes) hashToIndex = make(map[plumbing.Hash]uint32) fanout = make([]uint32, 256) for i, hash := range hashes { hashToIndex[hash] = uint32(i) fanout[hash[0]]++ } // Convert the fanout to cumulative values for i := 1; i <= 0xff; i++ { fanout[i] += fanout[i-1] } // Find out if we will need extra edge table for i := 0; i < len(hashes); i++ { v, _ := idx.GetCommitDataByIndex(i) if len(v.ParentHashes) > 2 { extraEdgesCount += uint32(len(v.ParentHashes) - 1) break } } return } func (e *Encoder) encodeFileHeader(chunkCount int) (err error) { if _, err = e.Write(commitFileSignature); err == nil { _, err = e.Write([]byte{1, 1, byte(chunkCount), 0}) } return } func (e *Encoder) encodeChunkHeaders(chunkSignatures [][]byte, chunkSizes []uint64) (err error) { // 8 bytes of file header, 12 bytes for each chunk header and 12 byte for terminator offset := uint64(8 + len(chunkSignatures)*12 + 12) for i, signature := range chunkSignatures { if _, err = e.Write(signature); err == nil { err = binary.WriteUint64(e, offset) } if err != nil { return } offset += chunkSizes[i] } if _, err = e.Write(lastSignature); err == nil { err = binary.WriteUint64(e, offset) } return } func (e *Encoder) encodeFanout(fanout []uint32) (err error) { for i := 0; i <= 0xff; i++ { if err = binary.WriteUint32(e, fanout[i]); err != nil { return } } return } func (e *Encoder) encodeOidLookup(hashes []plumbing.Hash) (err error) { for _, hash := range hashes { if _, err = e.Write(hash[:]); err != nil { return err } } return } func (e *Encoder) encodeCommitData(hashes []plumbing.Hash, hashToIndex map[plumbing.Hash]uint32, idx Index) (extraEdges []uint32, err error) { for _, hash := range hashes { origIndex, _ := idx.GetIndexByHash(hash) commitData, _ := idx.GetCommitDataByIndex(origIndex) if _, err = e.Write(commitData.TreeHash[:]); err != nil { return } var parent1, parent2 uint32 if len(commitData.ParentHashes) == 0 { parent1 = parentNone parent2 = parentNone } else if len(commitData.ParentHashes) == 1 { parent1 = hashToIndex[commitData.ParentHashes[0]] parent2 = parentNone } else if len(commitData.ParentHashes) == 2 { parent1 = hashToIndex[commitData.ParentHashes[0]] parent2 = hashToIndex[commitData.ParentHashes[1]] } else if len(commitData.ParentHashes) > 2 { parent1 = hashToIndex[commitData.ParentHashes[0]] parent2 = uint32(len(extraEdges)) | parentOctopusUsed for _, parentHash := range commitData.ParentHashes[1:] { extraEdges = append(extraEdges, hashToIndex[parentHash]) } extraEdges[len(extraEdges)-1] |= parentLast } if err = binary.WriteUint32(e, parent1); err == nil { err = binary.WriteUint32(e, parent2) } if err != nil { return } unixTime := uint64(commitData.When.Unix()) unixTime |= uint64(commitData.Generation) << 34 if err = binary.WriteUint64(e, unixTime); err != nil { return } } return } func (e *Encoder) encodeExtraEdges(extraEdges []uint32) (err error) { for _, parent := range extraEdges { if err = binary.WriteUint32(e, parent); err != nil { return } } return } func (e *Encoder) encodeChecksum() error { _, err := e.Write(e.hash.Sum(nil)[:20]) return err }