// reads are running.
type syncReadCloser struct {
	rc io.ReadCloser
	mu sync.Mutex
}

func (pr *syncReadCloser) Read(p []byte) (n int, err error) {
	// This ensures that Close will block until Read has completed.
	// This allows another goroutine to close the reader.
	pr.mu.Lock()
	defer pr.mu.Unlock()
	if pr.rc == nil {
		return 0, io.EOF
	}
	return pr.rc.Read(p)
}

	uuid []byte
}

// Write -  implement hash.Hash Write
func (u UUIDHash) Write(p []byte) (n int, err error) {
	return len(p), nil
}

// Sum -  implement md5.Sum
func (u UUIDHash) Sum(b []byte) []byte {
	return u.uuid
}

// Reset -  implement hash.Hash Reset
func (u UUIDHash) Reset() {
	return
}

// Size -  implement hash.Hash Size
func (u UUIDHash) Size() int {
	return len(u.uuid)

)

// Reader - JSON record reader for S3Select.
type Reader struct {
	args    *json.ReaderArgs
	input   chan simdjson.Stream
	decoded chan simdjson.Object

	// err will only be returned after decoded has been closed.
	err          *error
	readCloser   io.ReadCloser
	onReaderExit func()

	exitReader chan struct{}
	readerWg   sync.WaitGroup
}

// Read - reads single record.