objectid: Add RawBytes

2 files changed, 34 insertions, 0 deletions

diff --git a/objectid/objectid.go b/objectid/objectid.go
index 4058bc20..a2fa28c4 100644
--- a/objectid/objectid.go
+++ b/objectid/objectid.go
@@ -159,6 +159,17 @@ func (id ObjectID) Bytes() []byte {
 	return append([]byte(nil), id.data[:size]...)
 }
 
+// RawBytes returns a direct byte slice view of the object ID bytes.
+//
+// The returned slice aliases the object ID's internal storage. Callers MUST
+// treat it as read-only and MUST NOT modify its contents.
+//
+// Use Bytes when an independent copy is required.
+func (id *ObjectID) RawBytes() []byte {
+	size := id.Size()
+	return id.data[:size:size]
+}
+
 // ParseHex parses an object ID from hex for the specified algorithm.
 func ParseHex(algo Algorithm, s string) (ObjectID, error) {
 	var id ObjectID
diff --git a/objectid/objectid_test.go b/objectid/objectid_test.go
index ea4e9f44..7abeb963 100644
--- a/objectid/objectid_test.go
+++ b/objectid/objectid_test.go
@@ -127,6 +127,29 @@ func TestBytesReturnsCopy(t *testing.T) {
 	}
 }
 
+func TestRawBytesAliasesStorage(t *testing.T) {
+	t.Parallel()
+
+	id, err := objectid.ParseHex(objectid.AlgorithmSHA1, "0123456789abcdef0123456789abcdef01234567")
+	if err != nil {
+		t.Fatalf("ParseHex failed: %v", err)
+	}
+
+	b := id.RawBytes()
+	if len(b) != id.Size() {
+		t.Fatalf("RawBytes len = %d, want %d", len(b), id.Size())
+	}
+	if cap(b) != len(b) {
+		t.Fatalf("RawBytes cap = %d, want %d", cap(b), len(b))
+	}
+
+	orig := id.String()
+	b[0] ^= 0xff
+	if id.String() == orig {
+		t.Fatalf("RawBytes should alias object ID storage")
+	}
+}
+
 func TestAlgorithmSum(t *testing.T) {
 	t.Parallel()