diff options
| -rw-r--r-- | plumbing/format/idxfile/idxfile.go | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/plumbing/format/idxfile/idxfile.go b/plumbing/format/idxfile/idxfile.go index adeba44..f8debb1 100644 --- a/plumbing/format/idxfile/idxfile.go +++ b/plumbing/format/idxfile/idxfile.go @@ -28,6 +28,8 @@ type Index interface { FindOffset(h plumbing.Hash) (int64, error) // FindCRC32 finds the CRC32 of the object with the given hash. FindCRC32(h plumbing.Hash) (uint32, error) + // FindHash finds the hash for the object with the given offset. + FindHash(o int64) (plumbing.Hash, error) // Count returns the number of entries in the index. Count() (int64, error) // Entries returns an iterator to retrieve all index entries. @@ -48,6 +50,8 @@ type MemoryIndex struct { Offset64 []byte PackfileChecksum [20]byte IdxChecksum [20]byte + + offsetHash map[int64]plumbing.Hash } var _ Index = (*MemoryIndex)(nil) @@ -149,6 +153,53 @@ func (idx *MemoryIndex) getCrc32(firstLevel, secondLevel int) (uint32, error) { return binary.ReadUint32(buf) } +// FindHash implements the Index interface. +func (idx *MemoryIndex) FindHash(o int64) (plumbing.Hash, error) { + // Lazily generate the reverse offset/hash map if required. + if idx.offsetHash == nil { + err := idx.genOffsetHash() + if err != nil { + return plumbing.ZeroHash, nil + } + } + + hash, ok := idx.offsetHash[o] + if !ok { + return plumbing.ZeroHash, plumbing.ErrObjectNotFound + } + + return hash, nil +} + +// genOffsetHash generates the offset/hash mapping for reverse search. +func (idx *MemoryIndex) genOffsetHash() error { + count, err := idx.Count() + if err != nil { + return err + } + + idx.offsetHash = make(map[int64]plumbing.Hash, count) + + iter, err := idx.Entries() + if err != nil { + return err + } + + var entry *Entry + for err != nil { + entry, err = iter.Next() + if err == nil { + idx.offsetHash[int64(entry.Offset)] = entry.Hash + } + } + + if err == io.EOF { + return nil + } + + return err +} + // Count implements the Index interface. func (idx *MemoryIndex) Count() (int64, error) { return int64(idx.Fanout[fanout-1]), nil |