fix(cidlink): check for byte buffer

linking/cid/cidLink.go

@@ -30,8 +30,15 @@ func (lnk Link) Load(ctx context.Context, lnkCtx ipld.LinkContext, na ipld.NodeA
 	if !exists {
 		return fmt.Errorf("no decoder registered for multicodec %d", lnk.Prefix().Codec)
 	}
+	var hasherBytes []byte
+	var decodeErr error
+	byteBuf, ok := r.(*bytes.Buffer)
+	if ok {
+		hasherBytes = byteBuf.Bytes()
+		decodeErr = mcDecoder(na, r)
+	} else {
 		var hasher bytes.Buffer // multihash only exports bulk use, which is... really inefficient and should be fixed.
-	decodeErr := mcDecoder(na, io.TeeReader(r, &hasher))
+		decodeErr = mcDecoder(na, io.TeeReader(r, &hasher))
 		// Error checking order here is tricky.
 		//  If decoding errored out, we should still run the reader to the end, to check the hash.
 		//  (We still don't implement this by running the hash to the end first, because that would increase the high-water memory requirement.)
@@ -43,7 +50,10 @@ func (lnk Link) Load(ctx context.Context, lnkCtx ipld.LinkContext, na ipld.NodeA
 				return err
 			}
 		}
-	cid, err := lnk.Prefix().Sum(hasher.Bytes())
+		hasherBytes = hasher.Bytes()
+	}
+
+	cid, err := lnk.Prefix().Sum(hasherBytes)
 	if err != nil {
 		return err
 	}