WIP: adding randommessage package for generating test data

testlib/randommessage/randommessage.go

@@ -0,0 +1,100 @@
+package randommessage
+
+/*
+   Copyright 2025 Suyono <suyono3484@gmail.com>
+
+   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.
+*/
+
+import (
+	"crypto/rand"
+	"encoding/binary"
+	"errors"
+	"hash"
+	"io"
+
+	"golang.org/x/crypto/blake2s"
+)
+
+type StreamReader struct {
+	pos        int64
+	size       int64
+	hashEngine hash.Hash
+}
+
+var (
+	ErrInvalidBufSize = errors.New("invalid buffer size")
+)
+
+func NewStreamReader(size int64) (*StreamReader, error) {
+	var (
+		h   hash.Hash
+		err error
+	)
+
+	if h, err = blake2s.New256(nil); err != nil {
+		return nil, err
+	}
+	return &StreamReader{
+		pos:        0,
+		size:       size,
+		hashEngine: h,
+	}, nil
+}
+
+func (s *StreamReader) Read(buf []byte) (int, error) {
+	var (
+		n   int
+		err error
+	)
+
+	if s.pos == 0 {
+		if len(buf) < 4 {
+			return 0, ErrInvalidBufSize
+		}
+		binary.BigEndian.PutUint32(buf, uint32(s.size))
+
+		n, err = s.read(buf[4:])
+		n += 4
+	} else {
+		n, err = s.read(buf)
+	}
+
+	return n, err
+}
+
+func (s *StreamReader) read(buf []byte) (int, error) {
+	var (
+		n     int
+		limit int
+		err   error
+	)
+
+	limit = len(buf)
+	err = nil
+	if s.size-s.pos < int64(len(buf)) {
+		err = io.EOF
+		limit = int(s.size - s.pos)
+		if limit < 0 {
+			panic("unexpected limit")
+		}
+	}
+
+	if limit > 0 {
+		n, _ = rand.Read(buf[:limit])
+		s.pos += int64(limit)
+		s.hashEngine.Write(buf[:limit])
+	}
+
+	return n, err
+}