[x/serialize] Fix off-by-one error in encoder (#3815)

src/x/serialize/encode_decode_test.go

@@ -0,0 +1,41 @@
+// Copyright (c) 2021 Uber Technologies, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+package serialize
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/m3db/m3/src/x/ident"
+)
+
+func TestRoundTripLiteralsOfMaximumLength(t *testing.T) {
+	name := strings.Repeat("n", int(DefaultMaxTagLiteralLength))
+	value := strings.Repeat("v", int(DefaultMaxTagLiteralLength))
+	tags := ident.NewTagsIterator(ident.NewTags(ident.StringTag(name, value)))
+	newTags, err := encodeAndDecode(tags)
+	require.NoError(t, err)
+	ok, err := tagItersAreEqual(tags, newTags)
+	require.NoError(t, err)
+	require.True(t, ok)
+}

src/x/serialize/encoder.go

@@ -182,7 +182,7 @@ func (e *encoder) encodeID(i ident.ID) error {
 	d := i.Bytes()
 
 	max := int(e.opts.TagSerializationLimits().MaxTagLiteralLength())
-	if len(d) >= max {
+	if len(d) > max {
 		return errTagLiteralTooLong
 	}
 

src/x/serialize/encoder_test.go

@@ -21,7 +21,7 @@
 package serialize
 
 import (
-	"bytes"
+	"strings"
 	"testing"
 
 	"github.com/m3db/m3/src/x/checked"
@@ -122,10 +122,10 @@ func TestSimpleEncode(t *testing.T) {
 func TestTagEncoderErrorEncoding(t *testing.T) {
 	opts := NewTagEncoderOptions()
 	e := newTagEncoder(defaultNewCheckedBytesFn, opts, nil)
-	maxLiteralLen := opts.TagSerializationLimits().MaxTagLiteralLength()
+	maxLiteralLen := int(opts.TagSerializationLimits().MaxTagLiteralLength())
 	tags := ident.NewTagsIterator(ident.NewTags(
 		ident.StringTag("abc", "defg"),
-		ident.StringTag("x", nstring(1+int(maxLiteralLen))),
+		ident.StringTag("x", strings.Repeat("x", 1+maxLiteralLen)),
 	))
 
 	require.Error(t, e.Encode(tags))
@@ -134,7 +134,10 @@ func TestTagEncoderErrorEncoding(t *testing.T) {
 	require.False(t, ok)
 
 	e.Reset()
-	tags = ident.NewTagsIterator(ident.NewTags(ident.StringTag("abc", "defg")))
+	tags = ident.NewTagsIterator(ident.NewTags(
+		ident.StringTag("abc", "defg"),
+		ident.StringTag("x", strings.Repeat("x", maxLiteralLen)),
+	))
 	require.NoError(t, e.Encode(tags))
 }
 
@@ -219,11 +222,3 @@ func TestSingleValueTagIterEncode(t *testing.T) {
 	mockBytes.EXPECT().DecRef()
 	enc.Reset()
 }
-
-func nstring(n int) string {
-	var buf bytes.Buffer
-	for i := 0; i < n; i++ {
-		buf.WriteByte(byte('a'))
-	}
-	return buf.String()
-}