fix for out of range reads

weed/filer2/reader_at.go

@@ -108,12 +108,10 @@ func (c *ChunkReadAt) doReadAt(p []byte, offset int64) (n int, err error) {
 
 	glog.V(4).Infof("doReadAt [%d,%d), n:%v, err:%v", offset, offset+int64(len(p)), n, err)
 
-	if remaining > 0 {
-		glog.V(4).Infof("zero2 [%d,%d)", n, n+int(remaining))
-		n += int(remaining)
-		if n > int(c.fileSize - offset){
-			n = int(c.fileSize - offset)
-		}
+	if remaining > 0 && c.fileSize > startOffset {
+		delta := int(min(remaining, c.fileSize - startOffset))
+		glog.V(4).Infof("zero2 [%d,%d)", n, n+delta)
+		n += delta
 	}
 
 	if offset+int64(n) >= c.fileSize {

weed/filer2/reader_at_test.go

@@ -77,6 +77,11 @@ func testReadAt(t *testing.T, readerAt *ChunkReadAt, offset int64, size int, exp
 	data := make([]byte, size)
 	n, err := readerAt.ReadAt(data, offset)
 
+	for _, d := range data {
+		fmt.Printf("%x", d)
+	}
+	fmt.Println()
+
 	if expected != n {
 		t.Errorf("unexpected read size: %d, expect: %d", n, expected)
 	}
@@ -84,10 +89,6 @@ func testReadAt(t *testing.T, readerAt *ChunkReadAt, offset int64, size int, exp
 		t.Errorf("unexpected read error: %v, expect: %v", err, expectedErr)
 	}
 
-	for _, d := range data {
-		fmt.Printf("%x", d)
-	}
-	fmt.Println()
 }
 
 func TestReaderAt0(t *testing.T) {
@@ -119,4 +120,6 @@ func TestReaderAt0(t *testing.T) {
 	testReadAt(t, readerAt, 3, 16, 7, io.EOF)
 	testReadAt(t, readerAt, 3, 5, 5, nil)
 
+	testReadAt(t, readerAt, 11, 5, 0, io.EOF)
+
 }