Add marshaling for Entry

entry.go

@@ -15,7 +15,11 @@
 // Package tessera provides an implementation of a tile-based logging framework.
 package tessera
 
-import "github.com/transparency-dev/merkle/rfc6962"
+import (
+	"encoding/binary"
+
+	"github.com/transparency-dev/merkle/rfc6962"
+)
 
 // Entry represents an entry in a log.
 type Entry struct {
@@ -43,6 +47,30 @@ func NewEntry(data []byte, opts ...EntryOpt) Entry {
 	return e
 }
 
+func (e *Entry) MarshalBinary() ([]byte, error) {
+	buf := make([]byte, 0, len(e.data)+len(e.identity)+len(e.leafHash)+12)
+	buf = binary.AppendVarint(buf, int64(len(e.data)))
+	buf = append(buf, e.data...)
+	buf = binary.AppendVarint(buf, int64(len(e.identity)))
+	buf = append(buf, e.identity...)
+	buf = binary.AppendVarint(buf, int64(len(e.leafHash)))
+	buf = append(buf, e.leafHash...)
+	return buf, nil
+}
+
+func (e *Entry) UnmarshalBinary(buf []byte) error {
+	l, n := binary.Varint(buf)
+	buf = buf[n:]
+	e.data, buf = buf[:l], buf[l:]
+	l, n = binary.Varint(buf)
+	buf = buf[n:]
+	e.identity, buf = buf[:l], buf[l:]
+	l, n = binary.Varint(buf)
+	buf = buf[n:]
+	e.leafHash, buf = buf[:l], buf[l:]
+	return nil
+}
+
 // EntryOpt is the signature of options for creating new Entry instances.
 type EntryOpt func(e *Entry)
 

entry_test.go

@@ -0,0 +1,42 @@
+// Copyright 2024 The Tessera authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tessera
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestEntryMarshalRoundTrip(t *testing.T) {
+	e := &Entry{
+		data:     []byte("this is data"),
+		identity: []byte("I am who I am"),
+		leafHash: []byte("lettuce"),
+	}
+
+	raw, err := e.MarshalBinary()
+	if err != nil {
+		t.Fatalf("MarshalBinary: %v", err)
+	}
+
+	e2 := &Entry{}
+	if err := e2.UnmarshalBinary(raw); err != nil {
+		t.Fatalf("UnmarshalBinary: %v", err)
+	}
+
+	if !reflect.DeepEqual(e, e2) {
+		t.Fatalf("got %#v, want %#v", e2, e)
+	}
+}