1 files changed, 39 insertions, 0 deletions
diff --git a/formats/packfile/read_recaller.go b/formats/packfile/read_recaller.go
new file mode 100644
index 0000000..92ab1b2
--- /dev/null
+++ b/formats/packfile/read_recaller.go
@@ -0,0 +1,39 @@
+package packfile
+
+import "gopkg.in/src-d/go-git.v3/core"
+
+var (
+	// ErrDuplicatedObject is returned by Remember if an object appears several
+	// times in a packfile.
+	ErrDuplicatedObject = NewError("duplicated object")
+	// ErrCannotRecall is returned by RecallByOffset or RecallByHash if the object
+	// to recall cannot be returned.
+	ErrCannotRecall = NewError("cannot recall object")
+)
+
+// The ReadRecaller interface has all the functions needed by a packfile
+// Parser to operate. We provide two very different implementations:
+// Seekable and Stream.
+type ReadRecaller interface {
+	// Read reads up to len(p) bytes into p.
+	Read(p []byte) (int, error)
+	// ReadByte is needed because of these:
+	// - https://github.com/golang/go/commit/7ba54d45732219af86bde9a5b73c145db82b70c6
+	// - https://groups.google.com/forum/#!topic/golang-nuts/fWTRdHpt0QI
+	// - https://gowalker.org/compress/zlib#NewReader
+	ReadByte() (byte, error)
+	// Offset returns the number of bytes parsed so far from the
+	// packfile.
+	Offset() (int64, error)
+	// Remember ask the ReadRecaller to remember the offset and hash for
+	// an object, so you can later call RecallByOffset and RecallByHash.
+	Remember(int64, core.Object) error
+	// ForgetAll forgets all previously remembered objects.
+	ForgetAll()
+	// RecallByOffset returns the previously processed object found at a
+	// given offset.
+	RecallByOffset(int64) (core.Object, error)
+	// RecallByHash returns the previously processed object with the
+	// given hash.
+	RecallByHash(core.Hash) (core.Object, error)
+}