Add envelope test for partial prefix read failures

envelope_test.go

@@ -0,0 +1,74 @@
+// Copyright 2021-2023 The Connect Authors
+//
+// 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 connect
+
+import (
+	"bytes"
+	"encoding/binary"
+	"io"
+	"testing"
+
+	"connectrpc.com/connect/internal/assert"
+)
+
+func TestEnvelope_read(t *testing.T) {
+	t.Parallel()
+
+	head := [5]byte{}
+	payload := []byte(`{"number": 42}`)
+	binary.BigEndian.PutUint32(head[1:], uint32(len(payload)))
+
+	buf := &bytes.Buffer{}
+	buf.Write(head[:])
+	buf.Write(payload)
+
+	t.Run("full", func(t *testing.T) {
+		t.Parallel()
+		env := &envelope{Data: &bytes.Buffer{}}
+		rdr := envelopeReader{
+			reader: bytes.NewReader(buf.Bytes()),
+		}
+		assert.Nil(t, rdr.Read(env))
+		assert.Equal(t, payload, env.Data.Bytes())
+	})
+	t.Run("byteByByte", func(t *testing.T) {
+		t.Parallel()
+		env := &envelope{Data: &bytes.Buffer{}}
+		rdr := envelopeReader{
+			reader: byteByByteReader{
+				reader: bytes.NewReader(buf.Bytes()),
+			},
+		}
+		assert.Nil(t, rdr.Read(env))
+		assert.Equal(t, payload, env.Data.Bytes())
+	})
+}
+
+// byteByByteReader is test reader that reads a single byte at a time.
+type byteByByteReader struct {
+	reader io.ByteReader
+}
+
+func (b byteByByteReader) Read(data []byte) (int, error) {
+	if len(data) == 0 {
+		return 0, nil
+	}
+	next, err := b.reader.ReadByte()
+	if err != nil {
+		return 0, err
+	}
+	data[0] = next
+	return 1, nil
+}