plumbing/format/idxfile: add new Index and MemoryIndex

Signed-off-by: Miguel Molina <miguel@erizocosmi.co>

2 files changed, 17 insertions, 135 deletions

diff --git a/plumbing/format/packfile/decoder.go b/plumbing/format/packfile/decoder.go
index f706e5d..765401f 100644
--- a/plumbing/format/packfile/decoder.go
+++ b/plumbing/format/packfile/decoder.go
@@ -5,6 +5,7 @@ import (
 
 	"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/format/idxfile"
 	"gopkg.in/src-d/go-git.v4/plumbing/storer"
 )
 
@@ -63,7 +64,7 @@ type Decoder struct {
 	// hasBuiltIndex indicates if the index is fully built or not. If it is not,
 	// will be built incrementally while decoding.
 	hasBuiltIndex bool
-	idx           *Index
+	idx           idxfile.Index
 
 	offsetToType map[int64]plumbing.ObjectType
 	decoderType  plumbing.ObjectType
@@ -117,7 +118,7 @@ func NewDecoderForType(s *Scanner, o storer.EncodedObjectStorer,
 		o:              o,
 		deltaBaseCache: cacheObject,
 
-		idx:          NewIndex(0),
+		idx:          idxfile.NewMemoryIndex(),
 		offsetToType: make(map[int64]plumbing.ObjectType),
 		decoderType:  t,
 	}, nil
@@ -150,7 +151,8 @@ func (d *Decoder) doDecode() error {
 	}
 
 	if !d.hasBuiltIndex {
-		d.idx = NewIndex(int(count))
+		// TODO: MemoryIndex is not writable, change to something else
+		d.idx = idxfile.NewMemoryIndex()
 	}
 	defer func() { d.hasBuiltIndex = true }()
 
@@ -284,12 +286,12 @@ func (d *Decoder) ofsDeltaType(offset int64) (plumbing.ObjectType, error) {
 }
 
 func (d *Decoder) refDeltaType(ref plumbing.Hash) (plumbing.ObjectType, error) {
-	e, ok := d.idx.LookupHash(ref)
-	if !ok {
+	offset, err := d.idx.FindOffset(ref)
+	if err != nil {
 		return plumbing.InvalidObject, plumbing.ErrObjectNotFound
 	}
 
-	return d.ofsDeltaType(int64(e.Offset))
+	return d.ofsDeltaType(offset)
 }
 
 func (d *Decoder) decodeByHeader(h *ObjectHeader) (plumbing.EncodedObject, error) {
@@ -314,9 +316,14 @@ func (d *Decoder) decodeByHeader(h *ObjectHeader) (plumbing.EncodedObject, error
 		return obj, err
 	}
 
+	// TODO: remove this
+	_ = crc
+
+	/* Add is no longer available
 	if !d.hasBuiltIndex {
 		d.idx.Add(obj.Hash(), uint64(h.Offset), crc)
 	}
+	*/
 
 	return obj, nil
 }
@@ -448,8 +455,8 @@ func (d *Decoder) recallByOffset(o int64) (plumbing.EncodedObject, error) {
 
 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))
+		if offset, err := d.idx.FindOffset(h); err != nil {
+			return d.DecodeObjectAt(offset)
 		}
 	}
 
@@ -475,7 +482,7 @@ func (d *Decoder) recallByHashNonSeekable(h plumbing.Hash) (obj plumbing.Encoded
 // 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) {
+func (d *Decoder) SetIndex(idx idxfile.Index) {
 	d.hasBuiltIndex = true
 	d.idx = idx
 }
@@ -484,7 +491,7 @@ func (d *Decoder) SetIndex(idx *Index) {
 // 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 {
+func (d *Decoder) Index() idxfile.Index {
 	return d.idx
 }
 
diff --git a/plumbing/format/packfile/index.go b/plumbing/format/packfile/index.go
deleted file mode 100644
index 021b2d1..0000000
--- a/plumbing/format/packfile/index.go
+++ /dev/null
@@ -1,125 +0,0 @@
-package packfile
-
-import (
-	"sort"
-
-	"gopkg.in/src-d/go-git.v4/plumbing"
-	"gopkg.in/src-d/go-git.v4/plumbing/format/idxfile"
-)
-
-// Index is an in-memory representation of a packfile index.
-// This uses idxfile.Idxfile under the hood to obtain indexes from .idx files
-// or to store them.
-type Index struct {
-	byHash   map[plumbing.Hash]*idxfile.Entry
-	byOffset []*idxfile.Entry // sorted by their offset
-}
-
-// NewIndex creates a new empty index with the given size. Size is a hint and
-// can be 0. It is recommended to set it to the number of objects to be indexed
-// if it is known beforehand (e.g. reading from a packfile).
-func NewIndex(size int) *Index {
-	return &Index{
-		byHash:   make(map[plumbing.Hash]*idxfile.Entry, size),
-		byOffset: make([]*idxfile.Entry, 0, size),
-	}
-}
-
-// NewIndexFromIdxFile creates a new Index from an idxfile.IdxFile.
-func NewIndexFromIdxFile(idxf *idxfile.Idxfile) *Index {
-	idx := &Index{
-		byHash:   make(map[plumbing.Hash]*idxfile.Entry, idxf.ObjectCount),
-		byOffset: make([]*idxfile.Entry, 0, idxf.ObjectCount),
-	}
-	sorted := true
-	for i, e := range idxf.Entries {
-		idx.addUnsorted(e)
-		if i > 0 && idx.byOffset[i-1].Offset >= e.Offset {
-			sorted = false
-		}
-	}
-
-	// If the idxfile was loaded from a regular packfile index
-	// then it will already be in offset order, in which case we
-	// can avoid doing a relatively expensive idempotent sort.
-	if !sorted {
-		sort.Sort(orderByOffset(idx.byOffset))
-	}
-
-	return idx
-}
-
-// orderByOffset is a sort.Interface adapter that arranges
-// a slice of entries by their offset.
-type orderByOffset []*idxfile.Entry
-
-func (o orderByOffset) Len() int           { return len(o) }
-func (o orderByOffset) Less(i, j int) bool { return o[i].Offset < o[j].Offset }
-func (o orderByOffset) Swap(i, j int)      { o[i], o[j] = o[j], o[i] }
-
-// Add adds a new Entry with the given values to the index.
-func (idx *Index) Add(h plumbing.Hash, offset uint64, crc32 uint32) {
-	e := &idxfile.Entry{
-		Hash:   h,
-		Offset: offset,
-		CRC32:  crc32,
-	}
-	idx.byHash[e.Hash] = e
-
-	// Find the right position in byOffset.
-	// Look for the first position whose offset is *greater* than e.Offset.
-	i := sort.Search(len(idx.byOffset), func(i int) bool {
-		return idx.byOffset[i].Offset > offset
-	})
-	if i == len(idx.byOffset) {
-		// Simple case: add it to the end.
-		idx.byOffset = append(idx.byOffset, e)
-		return
-	}
-	// Harder case: shift existing entries down by one to make room.
-	// Append a nil entry first so we can use existing capacity in case
-	// the index was carefully preallocated.
-	idx.byOffset = append(idx.byOffset, nil)
-	copy(idx.byOffset[i+1:], idx.byOffset[i:len(idx.byOffset)-1])
-	idx.byOffset[i] = e
-}
-
-func (idx *Index) addUnsorted(e *idxfile.Entry) {
-	idx.byHash[e.Hash] = e
-	idx.byOffset = append(idx.byOffset, e)
-}
-
-// LookupHash looks an entry up by its hash. An idxfile.Entry is returned and
-// a bool, which is true if it was found or false if it wasn't.
-func (idx *Index) LookupHash(h plumbing.Hash) (*idxfile.Entry, bool) {
-	e, ok := idx.byHash[h]
-	return e, ok
-}
-
-// LookupHash looks an entry up by its offset in the packfile. An idxfile.Entry
-// is returned and a bool, which is true if it was found or false if it wasn't.
-func (idx *Index) LookupOffset(offset uint64) (*idxfile.Entry, bool) {
-	i := sort.Search(len(idx.byOffset), func(i int) bool {
-		return idx.byOffset[i].Offset >= offset
-	})
-	if i >= len(idx.byOffset) || idx.byOffset[i].Offset != offset {
-		return nil, false // not present
-	}
-	return idx.byOffset[i], true
-}
-
-// Size returns the number of entries in the index.
-func (idx *Index) Size() int {
-	return len(idx.byHash)
-}
-
-// ToIdxFile converts the index to an idxfile.Idxfile, which can then be used
-// to serialize.
-func (idx *Index) ToIdxFile() *idxfile.Idxfile {
-	idxf := idxfile.NewIdxfile()
-	for _, e := range idx.byHash {
-		idxf.Entries = append(idxf.Entries, e)
-	}
-
-	return idxf
-}