1 files changed, 64 insertions, 0 deletions
diff --git a/src/encoding/json/stream_test.go b/src/encoding/json/stream_test.go
index 9e5d48d39d..0e937cfaa1 100644
--- a/src/encoding/json/stream_test.go
+++ b/src/encoding/json/stream_test.go
@@ -557,3 +557,67 @@ func TestTokenTruncation(t *testing.T) {
 		}
 	}
 }
+
+func TestDecoderInputOffset(t *testing.T) {
+	const input = ` [
+		[ ] , [ "one" ] , [ "one" , "two" ] ,
+		{ } , { "alpha" : "bravo" } , { "alpha" : "bravo" , "fizz" : "buzz" }
+	] `
+	wantOffsets := []int64{
+		0, 1, 2, 5, 6, 7, 8, 9, 12, 13, 18, 19, 20, 21, 24, 25, 30, 31,
+		38, 39, 40, 41, 46, 47, 48, 49, 52, 53, 60, 61, 70, 71, 72, 73,
+		76, 77, 84, 85, 94, 95, 103, 104, 112, 113, 114, 116, 117, 117,
+		117, 117,
+	}
+	wantMores := []bool{
+		true, true, false, true, true, false, true, true, true, false,
+		true, false, true, true, true, false, true, true, true, true,
+		true, false, false, false, false,
+	}
+
+	d := NewDecoder(strings.NewReader(input))
+	checkOffset := func() {
+		t.Helper()
+		got := d.InputOffset()
+		if len(wantOffsets) == 0 {
+			t.Fatalf("InputOffset = %d, want nil", got)
+		}
+		want := wantOffsets[0]
+		if got != want {
+			t.Fatalf("InputOffset = %d, want %d", got, want)
+		}
+		wantOffsets = wantOffsets[1:]
+	}
+	checkMore := func() {
+		t.Helper()
+		got := d.More()
+		if len(wantMores) == 0 {
+			t.Fatalf("More = %v, want nil", got)
+		}
+		want := wantMores[0]
+		if got != want {
+			t.Fatalf("More = %v, want %v", got, want)
+		}
+		wantMores = wantMores[1:]
+	}
+	checkOffset()
+	checkMore()
+	checkOffset()
+	for {
+		if _, err := d.Token(); err == io.EOF {
+			break
+		} else if err != nil {
+			t.Fatalf("Token error: %v", err)
+		}
+		checkOffset()
+		checkMore()
+		checkOffset()
+	}
+	checkOffset()
+	checkMore()
+	checkOffset()
+
+	if len(wantOffsets)+len(wantMores) > 0 {
+		t.Fatal("unconsumed testdata")
+	}
+}