Return bit-rot verified data instead of re-reading from disk (#5568)

- Data from disk was being read after bitrot verification to return
  data for GetObject. Strictly speaking this does not guarantee bitrot
  protection, as disks may return bad data even temporarily.

- This fix reads data from disk, verifies data for bitrot and then
  returns data to the client directly.

cmd/utils_test.go

@@ -409,3 +409,28 @@ func TestJSONSave(t *testing.T) {
 		t.Fatal("Size should not differ after jsonSave()", fi1.Size(), fi2.Size(), f.Name())
 	}
 }
+
+// Test ceilFrac
+func TestCeilFrac(t *testing.T) {
+	cases := []struct {
+		numerator, denominator, ceiling int64
+	}{
+		{0, 1, 0},
+		{-1, 2, 0},
+		{1, 2, 1},
+		{1, 1, 1},
+		{3, 2, 2},
+		{54, 11, 5},
+		{45, 11, 5},
+		{-4, 3, -1},
+		{4, -3, -1},
+		{-4, -3, 2},
+		{3, 0, 0},
+	}
+	for i, testCase := range cases {
+		ceiling := ceilFrac(testCase.numerator, testCase.denominator)
+		if ceiling != testCase.ceiling {
+			t.Errorf("Case %d: Unexpected result: %d", i, ceiling)
+		}
+	}
+}