SkFixed15

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=3981

Change-Id: I811b22004e8e2d5b7135f574caea296ffdff7011
Reviewed-on: https://skia-review.googlesource.com/3981
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>

1 files changed, 29 insertions, 0 deletions

diff --git a/tests/SkFixed15Test.cpp b/tests/SkFixed15Test.cpp
new file mode 100644
index 0000000000..e2108d5604
--- /dev/null
+++ b/tests/SkFixed15Test.cpp
@@ -0,0 +1,29 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "Test.h"
+#include "SkFixed15.h"
+
+DEF_TEST(SkFixed15, r) {
+    // For all v, v*0 == 0, v*1 == v.
+    for (uint16_t bits = 0; bits <= 32768; bits++) {
+        auto v = SkFixed15::Load(bits);
+        REPORTER_ASSERT(r, v * 0.0f == 0.0f);
+        REPORTER_ASSERT(r, v * 1.0f == v);
+    }
+
+    // Division and multiplication by powers of 2 is exact.
+    SkFixed15 v = 1.0f;
+    REPORTER_ASSERT(r, (v>>1)    == 0.50f);
+    REPORTER_ASSERT(r, (v>>2)    == 0.25f);
+    REPORTER_ASSERT(r, (v>>2<<1) == 0.50f);
+
+    // FromU8() should be just as good as going through float.
+    for (int x = 0; x < 256; x++) {
+        REPORTER_ASSERT(r, SkFixed15::FromU8(x) == SkFixed15(x * (1/255.0f)));
+    }
+}