Add GrNextSizePow2

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4069

BUG=skia:5882

Change-Id: Ib9af5918716be594c3c07239eca179dbb4eb8566
Reviewed-on: https://skia-review.googlesource.com/4069
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/tests/MathTest.cpp b/tests/MathTest.cpp
index 41a4104bd4..35b4136b44 100644
--- a/tests/MathTest.cpp
+++ b/tests/MathTest.cpp
@@ -685,3 +685,41 @@ DEF_TEST(divmod_s32, r) {
 DEF_TEST(divmod_s64, r) {
     test_divmod<int64_t>(r);
 }
+
+static void test_nextsizepow2(skiatest::Reporter* r, size_t test, size_t expectedAns) {
+    size_t ans = GrNextSizePow2(test);
+
+    REPORTER_ASSERT(r, ans == expectedAns);
+    //SkDebugf("0x%zx -> 0x%zx (0x%zx)\n", test, ans, expectedAns);
+}
+
+DEF_TEST(GrNextSizePow2, reporter) {
+    constexpr int kNumSizeTBits = 8 * sizeof(size_t);
+
+    size_t test = 0, expectedAns = 1;
+
+    test_nextsizepow2(reporter, test, expectedAns);
+
+    test = 1; expectedAns = 1;
+
+    for (int i = 1; i < kNumSizeTBits; ++i) {
+        test_nextsizepow2(reporter, test, expectedAns);
+
+        test++;
+        expectedAns <<= 1;
+
+        test_nextsizepow2(reporter, test, expectedAns);
+
+        test = expectedAns;
+    }
+
+    // For the remaining three tests there is no higher power (of 2)
+    test = 0x1;
+    test <<= kNumSizeTBits-1;
+    test_nextsizepow2(reporter, test, test);
+
+    test++;
+    test_nextsizepow2(reporter, test, test);
+
+    test_nextsizepow2(reporter, SIZE_MAX, SIZE_MAX);
+}