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memory: all of a sudden I remembered what greater than or equal to means :)

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This commit is contained in:
Michele Caini
2021-10-10 00:42:25 +02:00
parent acb2d332ea
commit ff41faa3fe
2 changed files with 14 additions and 19 deletions
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14
src/entt/core/memory.hpp
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@@ -2,6 +2,7 @@
#define ENTT_CORE_MEMORY_HPP
#include <cstddef>
#include <limits>
#include <memory>
#include <type_traits>
#include <utility>
@@ -81,16 +82,11 @@ constexpr void propagate_on_container_swap([[maybe_unused]] Allocator &lhs, [[ma
* @return The smallest power of two greater than or equal to the given value.
*/
[[nodiscard]] inline constexpr std::size_t next_power_of_two(const std::size_t value) ENTT_NOEXCEPT {
std::size_t curr = value;
ENTT_ASSERT(value < (std::size_t{1u} << (std::numeric_limits<std::size_t>::digits - 1)), "Numeric limits exceeded");
std::size_t curr = value - (value != 0u);
curr |= curr >> 1;
curr |= curr >> 2;
curr |= curr >> 4;
curr |= curr >> 8;
curr |= curr >> 16;
if constexpr(sizeof(value) > sizeof(std::uint32_t)) {
curr |= curr >> 32;
for(int next = 1; next < std::numeric_limits<std::size_t>::digits; next = next * 2) {
curr |= curr >> next;
}
return ++curr;

19
test/entt/core/memory.cpp
View File

@@ -1,4 +1,5 @@
#include <cmath>
#include <limits>
#include <memory>
#include <gtest/gtest.h>
#include <entt/core/memory.hpp>
@@ -51,17 +52,15 @@ TEST(Memory, NextPowerOfTwo) {
constexpr auto next_power_of_two_of_zero = entt::next_power_of_two(0u);
ASSERT_EQ(next_power_of_two_of_zero, 1u);
ASSERT_EQ(entt::next_power_of_two(1u), 2u);
ASSERT_EQ(entt::next_power_of_two(1u), 1u);
ASSERT_EQ(entt::next_power_of_two(2u), 2u);
ASSERT_EQ(entt::next_power_of_two(3u), 4u);
ASSERT_EQ(entt::next_power_of_two(17u), 32u);
ASSERT_EQ(entt::next_power_of_two(32u), 64u);
ASSERT_EQ(entt::next_power_of_two(32u), 64u);
if constexpr(sizeof(std::size_t) > sizeof(std::uint32_t)) {
ASSERT_EQ(entt::next_power_of_two(std::pow(2, 32)), std::pow(2, 33));
ASSERT_EQ(entt::next_power_of_two(std::pow(2, 64)), 0u);
} else {
ASSERT_EQ(entt::next_power_of_two(std::pow(2, 32)), 0u);
}
ASSERT_EQ(entt::next_power_of_two(32u), 32u);
ASSERT_EQ(entt::next_power_of_two(33u), 64u);
ASSERT_EQ(entt::next_power_of_two(std::pow(2, 16)), std::pow(2, 16));
ASSERT_EQ(entt::next_power_of_two(std::pow(2, 16) + 1u), std::pow(2, 17));
ASSERT_DEATH(static_cast<void>(entt::next_power_of_two((std::size_t{1u} << (std::numeric_limits<std::size_t>::digits - 1)) + 1)), "");
}
TEST(Memory, FastMod) {