5 files changed, 47 insertions, 0 deletions
diff --git a/plumbing/format/packfile/packfile.go b/plumbing/format/packfile/packfile.go
index 852a834..0d13066 100644
--- a/plumbing/format/packfile/packfile.go
+++ b/plumbing/format/packfile/packfile.go
@@ -90,6 +90,24 @@ func (p *Packfile) GetByOffset(o int64) (plumbing.EncodedObject, error) {
 	return p.nextObject()
 }
 
+// GetSizeByOffset retrieves the size of the encoded object from the
+// packfile with the given offset.
+func (p *Packfile) GetSizeByOffset(o int64) (size int64, err error) {
+	if _, err := p.s.SeekFromStart(o); err != nil {
+		if err == io.EOF || isInvalid(err) {
+			return 0, plumbing.ErrObjectNotFound
+		}
+
+		return 0, err
+	}
+
+	h, err := p.nextObjectHeader()
+	if err != nil {
+		return 0, err
+	}
+	return h.Length, nil
+}
+
 func (p *Packfile) nextObjectHeader() (*ObjectHeader, error) {
 	h, err := p.s.NextObjectHeader()
 	p.s.pendingObject = nil
diff --git a/plumbing/object/tree.go b/plumbing/object/tree.go
index c36a137..78d61a1 100644
--- a/plumbing/object/tree.go
+++ b/plumbing/object/tree.go
@@ -87,6 +87,17 @@ func (t *Tree) File(path string) (*File, error) {
 	return NewFile(path, e.Mode, blob), nil
 }
 
+// Size returns the plaintext size of an object, without reading it
+// into memory.
+func (t *Tree) Size(path string) (int64, error) {
+	e, err := t.FindEntry(path)
+	if err != nil {
+		return 0, ErrEntryNotFound
+	}
+
+	return t.s.EncodedObjectSize(e.Hash)
+}
+
 // Tree returns the tree identified by the `path` argument.
 // The path is interpreted as relative to the tree receiver.
 func (t *Tree) Tree(path string) (*Tree, error) {
diff --git a/plumbing/object/tree_test.go b/plumbing/object/tree_test.go
index 7366421..889c63a 100644
--- a/plumbing/object/tree_test.go
+++ b/plumbing/object/tree_test.go
@@ -98,6 +98,12 @@ func (s *TreeSuite) TestFileFailsWithExistingTrees(c *C) {
 	c.Assert(err, Equals, ErrFileNotFound)
 }
 
+func (s *TreeSuite) TestSize(c *C) {
+	size, err := s.Tree.Size("LICENSE")
+	c.Assert(err, IsNil)
+	c.Assert(size, Equals, int64(1072))
+}
+
 func (s *TreeSuite) TestFiles(c *C) {
 	var count int
 	err := s.Tree.Files().ForEach(func(f *File) error {
diff --git a/plumbing/storer/object.go b/plumbing/storer/object.go
index 92aa629..2ac9b09 100644
--- a/plumbing/storer/object.go
+++ b/plumbing/storer/object.go
@@ -40,6 +40,8 @@ type EncodedObjectStorer interface {
 	// HasEncodedObject returns ErrObjNotFound if the object doesn't
 	// exist.  If the object does exist, it returns nil.
 	HasEncodedObject(plumbing.Hash) error
+	// EncodedObjectSize returns the plaintext size of the encoded object.
+	EncodedObjectSize(plumbing.Hash) (int64, error)
 }
 
 // DeltaObjectStorer is an EncodedObjectStorer that can return delta
diff --git a/plumbing/storer/object_test.go b/plumbing/storer/object_test.go
index 6b4fe0f..bc22f7b 100644
--- a/plumbing/storer/object_test.go
+++ b/plumbing/storer/object_test.go
@@ -141,6 +141,16 @@ func (o *MockObjectStorage) HasEncodedObject(h plumbing.Hash) error {
 	return plumbing.ErrObjectNotFound
 }
 
+func (o *MockObjectStorage) EncodedObjectSize(h plumbing.Hash) (
+	size int64, err error) {
+	for _, o := range o.db {
+		if o.Hash() == h {
+			return o.Size(), nil
+		}
+	}
+	return 0, plumbing.ErrObjectNotFound
+}
+
 func (o *MockObjectStorage) EncodedObject(t plumbing.ObjectType, h plumbing.Hash) (plumbing.EncodedObject, error) {
 	for _, o := range o.db {
 		if o.Hash() == h {