Add a math::round_up_to_multiple_of<N>() utility

Diffs=
bb7d5ac4c Add a math::round_up_to_multiple_of<N>() utility (#6061)

Co-authored-by: Chris Dalton <99840794+csmartdalton@users.noreply.github.com>

.rive_head

diff --git a/.rive_head b/.rive_head
index e292a4a..5f1cbb1 100644
--- a/.rive_head
+++ b/.rive_head
@@ -1 +1 @@
-6ee7cea9edb3efb81318bc5a8a1db2c6a28c011a
+bb7d5ac4ccbe04a80c8469b56da55b9b92a70ef6

include/rive/math/math_types.hpp

diff --git a/include/rive/math/math_types.hpp b/include/rive/math/math_types.hpp
index a830408..3dd14bf 100644
--- a/include/rive/math/math_types.hpp
+++ b/include/rive/math/math_types.hpp
@@ -81,6 +81,15 @@
     return (doubleBits >> 52) - 1022;
 #endif
 }
+
+// Returns x rounded up to the next multiple of N.
+// If x is already a multiple of N, returns x.
+template <size_t N> RIVE_ALWAYS_INLINE constexpr size_t round_up_to_multiple_of(size_t x)
+{
+    static_assert(N != 0 && (N & (N - 1)) == 0,
+                  "math::round_up_to_multiple_of<> only supports powers of 2.");
+    return (x + (N - 1)) & ~(N - 1);
+}
 } // namespace math
 
 template <typename T> T lerp(const T& a, const T& b, float t) { return a + (b - a) * t; }

test/math_test.cpp

diff --git a/test/math_test.cpp b/test/math_test.cpp
index 63bfabf..4bf0006 100644
--- a/test/math_test.cpp
+++ b/test/math_test.cpp
@@ -61,8 +61,8 @@
     CHECK(std::isnan(math::bit_cast<float>(0x7fc00000)));
 }
 
-// Check math::nextlog2.
-TEST_CASE("nextlog2", "[math]")
+// Check math::msb.
+TEST_CASE("msb", "[math]")
 {
     CHECK(math::msb(0) == 0);
     CHECK(math::msb(1) == 1);
@@ -80,3 +80,20 @@
     }
     CHECK(math::msb(0xffffffff) == 32);
 }
+
+// Check math::round_up_to_multiple_of.
+TEST_CASE("round_up_to_multiple_of", "[math]")
+{
+    CHECK(math::round_up_to_multiple_of<4>(0) == 0);
+    CHECK(math::round_up_to_multiple_of<4>(3) == 4);
+    CHECK(math::round_up_to_multiple_of<8>(16) == 16);
+    CHECK(math::round_up_to_multiple_of<8>(24) == 24);
+    CHECK(math::round_up_to_multiple_of<8>(25) == 32);
+    CHECK(math::round_up_to_multiple_of<8>(31) == 32);
+    CHECK(math::round_up_to_multiple_of<8>(32) == 32);
+    for (size_t i = 0; i < 10; ++i)
+    {
+        CHECK(math::round_up_to_multiple_of<1>(i) == i);
+    }
+    CHECK(math::round_up_to_multiple_of<2>(~size_t(0)) == 0);
+}