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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
#include <cstddef>
#include <utility>
#include "mozilla/MulOverflowMask.h"
#include "mozilla/Assertions.h"
template <size_t N>
constexpr bool checkMulOverflowMask(size_t X) {
static_assert(N != 0);
size_t M = mozilla::MulOverflowMask<N>();
size_t cond = X & M;
size_t prod = N * X;
// That's the invariant specified in mozilla::MulOverflowMask documentation.
return cond || (prod >= X);
}
template <size_t... Ns>
constexpr bool check_all(size_t X, std::index_sequence<Ns...>) {
return (checkMulOverflowMask<Ns>(X) && ...);
}
static void TestMulOverflowMask() {
constexpr size_t highbit = (size_t)1
<< (std::numeric_limits<size_t>::digits - 1);
constexpr size_t allones = (size_t)-1;
constexpr std::index_sequence<1, 2, 3, 4, 5, 127, 128, 129, 1023, 1024,
113231, 3231323, highbit, highbit / 2,
highbit + 1, highbit - 1, allones, allones - 1,
allones / 2 + 1>
Ns;
static_assert(check_all(0, Ns));
static_assert(check_all(1, Ns));
static_assert(check_all(2, Ns));
static_assert(check_all(3, Ns));
static_assert(check_all(4, Ns));
static_assert(check_all(5, Ns));
static_assert(check_all(7, Ns));
static_assert(check_all(15, Ns));
static_assert(check_all(245, Ns));
static_assert(check_all(13279, Ns));
static_assert(check_all(highbit / 2, Ns));
static_assert(check_all(highbit - 1, Ns));
static_assert(check_all(highbit, Ns));
static_assert(check_all(highbit + 1, Ns));
static_assert(check_all(allones, Ns));
static_assert(check_all(allones - 1, Ns));
}
int main() {
TestMulOverflowMask();
return 0;
}