add size for inmem

inmem.go

@@ -119,7 +119,12 @@ func (b *InMemBucket) Get(_ context.Context, name string) (io.ReadCloser, error)
 		return nil, errNotFound
 	}
 
-	return io.NopCloser(bytes.NewReader(file)), nil
+	return ObjectSizerReadCloser{
+		ReadCloser: io.NopCloser(bytes.NewReader(file)),
+		Size: func() (int64, error) {
+			return int64(len(file)), nil
+		},
+	}, nil
 }
 
 // GetRange returns a new range reader for the given object name and range.
@@ -136,23 +141,40 @@ func (b *InMemBucket) GetRange(_ context.Context, name string, off, length int64
 	}
 
 	if int64(len(file)) < off {
-		return io.NopCloser(bytes.NewReader(nil)), nil
+		return ObjectSizerReadCloser{
+			ReadCloser: io.NopCloser(bytes.NewReader(nil)),
+			Size:       func() (int64, error) { return 0, nil },
+		}, nil
 	}
 
 	if length == -1 {
-		return io.NopCloser(bytes.NewReader(file[off:])), nil
+		return ObjectSizerReadCloser{
+			ReadCloser: io.NopCloser(bytes.NewReader(file[off:])),
+			Size: func() (int64, error) {
+				return int64(len(file[off:])), nil
+			},
+		}, nil
 	}
 
 	if length <= 0 {
-		return io.NopCloser(bytes.NewReader(nil)), errors.New("length cannot be smaller or equal 0")
+		// wrap with ObjectSizerReadCloser to return 0 size.
+		return ObjectSizerReadCloser{
+			ReadCloser: io.NopCloser(bytes.NewReader(nil)),
+			Size:       func() (int64, error) { return 0, nil },
+		}, errors.New("length cannot be smaller or equal 0")
 	}
 
 	if int64(len(file)) <= off+length {
 		// Just return maximum of what we have.
 		length = int64(len(file)) - off
 	}
 
-	return io.NopCloser(bytes.NewReader(file[off : off+length])), nil
+	return ObjectSizerReadCloser{
+		ReadCloser: io.NopCloser(bytes.NewReader(file[off : off+length])),
+		Size: func() (int64, error) {
+			return length, nil
+		},
+	}, nil
 }
 
 // Exists checks if the given directory exists in memory.