methods_test.go: Fix Gap calculation

1 files changed, 16 insertions, 6 deletions

diff --git a/methods_test.go b/methods_test.go
index f5d5a9a..64af28c 100644
--- a/methods_test.go
+++ b/methods_test.go
@@ -30,6 +30,10 @@ type SumRun struct {
 	Sums         ShortSum
 }
 
+func (run SumRun) Size() int64 {
+	return int64(len(run.Sums)/(2*run.ChecksumSize)) * (4 * 1024)
+}
+
 type SumRunWithGaps struct {
 	Addr int64
 	Size int64
@@ -47,13 +51,19 @@ func (sg SumRunWithGaps) EncodeJSON(w io.Writer) error {
 				return err
 			}
 		}
-		if run.Addr > cur {
+		switch {
+		case run.Addr < cur:
+			return fmt.Errorf("invalid %T: addr went backwards: %v < %v", sg, run.Addr, cur)
+		case run.Addr > cur:
 			if _, err := fmt.Fprintf(w, `{"Gap":%d},`, run.Addr-cur); err != nil {
 				return err
 			}
-		}
-		if err := lowmemjson.NewEncoder(w).Encode(run); err != nil {
-			return err
+			fallthrough
+		default:
+			if err := lowmemjson.NewEncoder(w).Encode(run); err != nil {
+				return err
+			}
+			cur = run.Addr + run.Size()
 		}
 	}
 	end := sg.Addr + sg.Size
@@ -110,14 +120,14 @@ func TestMethods(t *testing.T) {
 			{
 				ChecksumSize: 4,
 				Addr:         1095761920,
-				Sums:         "c160817cb5c72bbbe",
+				Sums:         "c160817cb5c72bbb",
 			},
 		},
 	}
 	var buf bytes.Buffer
 	assert.NoError(t, lowmemjson.NewEncoder(&buf).Encode(in))
 	assert.Equal(t,
-		`{"Addr":13631488,"Size":416033783808,"Runs":[{"Gap":1082130432},{"ChecksumSize":4,"Addr":1095761920,"Sums":"c160817cb5c72bbbe"},{"Gap":416033783808}]}`,
+		`{"Addr":13631488,"Size":416033783808,"Runs":[{"Gap":1082130432},{"ChecksumSize":4,"Addr":1095761920,"Sums":"c160817cb5c72bbb"},{"Gap":414951645184}]}`,
 		buf.String())
 	var out SumRunWithGaps
 	assert.NoError(t, lowmemjson.NewDecoder(&buf).Decode(&out))