move implementation to internal/ directory (#828)

internal/util/limitio/limitio.go

@@ -0,0 +1,36 @@
+package limitio
+
+import "io"
+
+type readCloser struct {
+	read  int64
+	limit int64
+	r     io.ReadCloser
+}
+
+func ReadCloser(rc io.ReadCloser, limit int64) io.ReadCloser {
+	return &readCloser{0, limit, rc}
+}
+
+var _ io.ReadCloser = (*readCloser)(nil)
+
+func (r *readCloser) Read(b []byte) (int, error) {
+
+	if len(b) == 0 {
+		return 0, nil
+	}
+
+	if r.read == r.limit {
+		return 0, io.EOF
+	}
+
+	if r.read+int64(len(b)) >= r.limit {
+		b = b[:int(r.limit-r.read)]
+	}
+
+	readN, err := r.r.Read(b)
+	r.read += int64(readN)
+	return readN, err
+}
+
+func (r *readCloser) Close() error { return r.r.Close() }

internal/util/limitio/limitio_readcloser_test.go

@@ -0,0 +1,44 @@
+package limitio
+
+import (
+	"bytes"
+	"io"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type mockRC struct {
+	r      io.Reader
+	closed bool
+}
+
+func newMockRC(r io.Reader) *mockRC { return &mockRC{r, false} }
+
+func (m mockRC) Read(b []byte) (int, error) {
+	if m.closed {
+		return 0, io.ErrClosedPipe
+	}
+	return m.r.Read(b)
+}
+
+func (m *mockRC) Close() error {
+	m.closed = true
+	return nil
+}
+
+func TestReadCloser(t *testing.T) {
+	foobarReader := bytes.NewReader([]byte("foobar2342"))
+	mock := newMockRC(foobarReader)
+	limited := ReadCloser(mock, 6)
+	var buf [20]byte
+	n, err := limited.Read(buf[:])
+	assert.NoError(t, err)
+	assert.Equal(t, 6, n)
+	assert.Equal(t, buf[:n], []byte("foobar"))
+	n, err = limited.Read(buf[:])
+	assert.Equal(t, 0, n)
+	assert.Equal(t, io.EOF, err)
+	limited.Close()
+	assert.True(t, mock.closed)
+}