readers: add NewPatternReader

backend/jottacloud/jottacloud_internal_test.go

@@ -4,50 +4,25 @@ import (
 	"crypto/md5"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"testing"
 
+	"github.com/ncw/rclone/lib/readers"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
-// A test reader to return a test pattern of size
-type testReader struct {
-	size int64
-	c    byte
-}
-
-// Reader is the interface that wraps the basic Read method.
-func (r *testReader) Read(p []byte) (n int, err error) {
-	for i := range p {
-		if r.size <= 0 {
-			return n, io.EOF
-		}
-		p[i] = r.c
-		r.c = (r.c + 1) % 253
-		r.size--
-		n++
-	}
-	return
-}
-
 func TestReadMD5(t *testing.T) {
-	// smoke test the reader
-	b, err := ioutil.ReadAll(&testReader{size: 10})
-	require.NoError(t, err)
-	assert.Equal(t, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}, b)
-
 	// Check readMD5 for different size and threshold
 	for _, size := range []int64{0, 1024, 10 * 1024, 100 * 1024} {
 		t.Run(fmt.Sprintf("%d", size), func(t *testing.T) {
 			hasher := md5.New()
-			n, err := io.Copy(hasher, &testReader{size: size})
+			n, err := io.Copy(hasher, readers.NewPatternReader(size))
 			require.NoError(t, err)
 			assert.Equal(t, n, size)
 			wantMD5 := fmt.Sprintf("%x", hasher.Sum(nil))
 			for _, threshold := range []int64{512, 1024, 10 * 1024, 20 * 1024} {
 				t.Run(fmt.Sprintf("%d", threshold), func(t *testing.T) {
-					in := &testReader{size: size}
+					in := readers.NewPatternReader(size)
 					gotMD5, out, cleanup, err := readMD5(in, size, threshold)
 					defer cleanup()
 					require.NoError(t, err)

lib/readers/pattern_reader.go

@@ -0,0 +1,29 @@
+package readers
+
+import "io"
+
+// NewPatternReader creates a reader, that returns a deterministic byte pattern.
+// After length bytes are read
+func NewPatternReader(length int64) io.Reader {
+	return &patternReader{
+		length: length,
+	}
+}
+
+type patternReader struct {
+	length int64
+	c      byte
+}
+
+func (r *patternReader) Read(p []byte) (n int, err error) {
+	for i := range p {
+		if r.length <= 0 {
+			return n, io.EOF
+		}
+		p[i] = r.c
+		r.c = (r.c + 1) % 253
+		r.length--
+		n++
+	}
+	return
+}

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)
+}