68 lines
2.6 KiB
C++
68 lines
2.6 KiB
C++
// Copyright 2022 Memgraph Ltd.
|
|
//
|
|
// Use of this software is governed by the Business Source License
|
|
// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
|
|
// License, and you may not use this file except in compliance with the Business Source License.
|
|
//
|
|
// As of the Change Date specified in that file, in accordance with
|
|
// the Business Source License, use of this software will be governed
|
|
// by the Apache License, Version 2.0, included in the file
|
|
// licenses/APL.txt.
|
|
|
|
#pragma once
|
|
|
|
#include <cstdint>
|
|
#include <limits>
|
|
#include <optional>
|
|
#include <type_traits>
|
|
|
|
namespace memgraph::utils {
|
|
|
|
static_assert(std::is_same_v<uint64_t, unsigned long>,
|
|
"utils::Log requires uint64_t to be implemented as unsigned long.");
|
|
|
|
/// This function computes the log2 function on integer types. It is faster than
|
|
/// the cmath `log2` function because it doesn't use floating point values for
|
|
/// calculation.
|
|
constexpr inline uint64_t Log2(uint64_t val) {
|
|
// The `clz` function is undefined when the passed value is 0 and the value of
|
|
// `log` is `-inf` so we special case it here.
|
|
if (val == 0) return 0;
|
|
// clzl = count leading zeros from long
|
|
// ^ ^ ^ ^
|
|
int ret = __builtin_clzl(val);
|
|
return 64UL - static_cast<uint64_t>(ret) - 1UL;
|
|
}
|
|
|
|
/// Return `true` if `val` is a power of 2.
|
|
constexpr inline bool IsPow2(uint64_t val) noexcept { return val != 0ULL && (val & (val - 1ULL)) == 0ULL; }
|
|
|
|
/// Return `val` if it is power of 2, otherwise get the next power of 2 value.
|
|
/// If `val` is sufficiently large, the next power of 2 value may not fit into
|
|
/// the result type and you will get a wrapped value to 1ULL.
|
|
constexpr inline uint64_t Ceil2(uint64_t val) noexcept {
|
|
if (val == 0ULL || val == 1ULL) return 1ULL;
|
|
return 1ULL << (Log2(val - 1ULL) + 1ULL);
|
|
}
|
|
|
|
/// Round `val` to the next `multiple` value, if needed.
|
|
/// `std::nullopt` is returned in case of an overflow or if `multiple` is 0.
|
|
///
|
|
/// Examples:
|
|
///
|
|
/// RoundUint64ToMultiple(5, 8) == 8
|
|
/// RoundUint64ToMultiple(8, 8) == 8
|
|
/// RoundUint64ToMultiple(9, 8) == 16
|
|
constexpr inline std::optional<uint64_t> RoundUint64ToMultiple(uint64_t val, uint64_t multiple) noexcept {
|
|
if (multiple == 0) return std::nullopt;
|
|
uint64_t numerator = val + multiple - 1;
|
|
// Check for overflow.
|
|
if (numerator < val) return std::nullopt;
|
|
// Rely on integer division to get the rounded multiple.
|
|
// No overflow is possible as the final, rounded value can only be less than
|
|
// or equal to `numerator`.
|
|
return (numerator / multiple) * multiple;
|
|
}
|
|
|
|
} // namespace memgraph::utils
|