readers: add NewPatternReader

lib/readers/pattern_reader_test.go

@@ -0,0 +1,30 @@
+package readers
+
+import (
+	"io"
+	"io/ioutil"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestPatternReader(t *testing.T) {
+	b2 := make([]byte, 1)
+
+	r := NewPatternReader(0)
+	b, err := ioutil.ReadAll(r)
+	require.NoError(t, err)
+	assert.Equal(t, []byte{}, b)
+	n, err := r.Read(b2)
+	require.Equal(t, io.EOF, err)
+	require.Equal(t, 0, n)
+
+	r = NewPatternReader(10)
+	b, err = ioutil.ReadAll(r)
+	require.NoError(t, err)
+	assert.Equal(t, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}, b)
+	n, err = r.Read(b2)
+	require.Equal(t, io.EOF, err)
+	require.Equal(t, 0, n)
+}