/*
* Copyright (c) Meta Platforms, Inc. and affiliates.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <folly/lang/Bits.h>
#include <algorithm>
#include <random>
#include <vector>
#include <folly/Random.h>
#include <folly/portability/GTest.h>
namespace folly {
// Test constexpr-ness.
#if !defined(__clang__) && !defined(_MSC_VER)
static_assert(findFirstSet(2u) == 2, "findFirstSet");
static_assert(findLastSet(2u) == 2, "findLastSet");
static_assert(nextPowTwo(2u) == 2, "nextPowTwo");
#endif
#ifndef __clang__
static_assert(isPowTwo(2u), "isPowTwo");
#endif
namespace {
template <class INT>
void testFFS() {
EXPECT_EQ(0, findFirstSet(static_cast<INT>(0)));
size_t bits =
std::numeric_limits<typename std::make_unsigned<INT>::type>::digits;
for (size_t i = 0; i < bits; i++) {
INT v = (static_cast<INT>(1) << (bits - 1)) | (static_cast<INT>(1) << i);
EXPECT_EQ(i + 1, findFirstSet(v));
}
}
template <class INT>
void testFLS() {
typedef typename std::make_unsigned<INT>::type UINT_T;
EXPECT_EQ(0, findLastSet(static_cast<INT>(0)));
size_t bits = std::numeric_limits<UINT_T>::digits;
for (size_t i = 0; i < bits; i++) {
INT v1 = static_cast<UINT_T>(1) << i;
EXPECT_EQ(i + 1, findLastSet(v1));
INT v2 = (static_cast<UINT_T>(1) << i) - 1;
EXPECT_EQ(i, findLastSet(v2));
}
}
template <class UINT>
void testEFS() {
EXPECT_EQ(0, extractFirstSet(static_cast<UINT>(0)));
size_t bits = std::numeric_limits<UINT>::digits;
for (size_t i = 0; i < bits; i++) {
UINT lsb = static_cast<UINT>(1) << i;
UINT v = (static_cast<UINT>(1) << (bits - 1)) | lsb;
EXPECT_EQ(lsb, extractFirstSet(v));
}
}
} // namespace
TEST(Bits, FindFirstSet) {
testFFS<char>();
testFFS<signed char>();
testFFS<unsigned char>();
testFFS<short>();
testFFS<unsigned short>();
testFFS<int>();
testFFS<unsigned int>();
testFFS<long>();
testFFS<unsigned long>();
testFFS<long long>();
testFFS<unsigned long long>();
}
TEST(Bits, FindLastSet) {
testFLS<char>();
testFLS<signed char>();
testFLS<unsigned char>();
testFLS<short>();
testFLS<unsigned short>();
testFLS<int>();
testFLS<unsigned int>();
testFLS<long>();
testFLS<unsigned long>();
testFLS<long long>();
testFLS<unsigned long long>();
}
TEST(Bits, ExtractFirstSet) {
testEFS<unsigned char>();
testEFS<unsigned short>();
testEFS<unsigned int>();
testEFS<unsigned long>();
testEFS<unsigned long long>();
}
TEST(Bits, nextPowTwoClz) {
EXPECT_EQ(1, nextPowTwo(0u));
EXPECT_EQ(1, nextPowTwo(1u));
EXPECT_EQ(2, nextPowTwo(2u));
EXPECT_EQ(4, nextPowTwo(3u));
EXPECT_EQ(4, nextPowTwo(4u));
EXPECT_EQ(8, nextPowTwo(5u));
EXPECT_EQ(8, nextPowTwo(6u));
EXPECT_EQ(8, nextPowTwo(7u));
EXPECT_EQ(8, nextPowTwo(8u));
EXPECT_EQ(16, nextPowTwo(9u));
EXPECT_EQ(16, nextPowTwo(13u));
EXPECT_EQ(16, nextPowTwo(16u));
EXPECT_EQ(512, nextPowTwo(510u));
EXPECT_EQ(512, nextPowTwo(511u));
EXPECT_EQ(512, nextPowTwo(512u));
EXPECT_EQ(1024, nextPowTwo(513u));
EXPECT_EQ(1024, nextPowTwo(777u));
EXPECT_EQ(1ul << 31, nextPowTwo((1ul << 31) - 1));
EXPECT_EQ(1ull << 32, nextPowTwo((1ull << 32) - 1));
EXPECT_EQ(1ull << 63, nextPowTwo((1ull << 62) + 1));
}
TEST(Bits, strictNextPowTwoClz) {
EXPECT_EQ(1, strictNextPowTwo(0u));
EXPECT_EQ(2, strictNextPowTwo(1u));
EXPECT_EQ(4, strictNextPowTwo(2u));
EXPECT_EQ(4, strictNextPowTwo(3u));
EXPECT_EQ(8, strictNextPowTwo(4u));
EXPECT_EQ(8, strictNextPowTwo(5u));
EXPECT_EQ(8, strictNextPowTwo(6u));
EXPECT_EQ(8, strictNextPowTwo(7u));
EXPECT_EQ(16, strictNextPowTwo(8u));
EXPECT_EQ(16, strictNextPowTwo(9u));
EXPECT_EQ(16, strictNextPowTwo(13u));
EXPECT_EQ(32, strictNextPowTwo(16u));
EXPECT_EQ(512, strictNextPowTwo(510u));
EXPECT_EQ(512, strictNextPowTwo(511u));
EXPECT_EQ(1024, strictNextPowTwo(512u));
EXPECT_EQ(1024, strictNextPowTwo(513u));
EXPECT_EQ(1024, strictNextPowTwo(777u));
EXPECT_EQ(1ul << 31, strictNextPowTwo((1ul << 31) - 1));
EXPECT_EQ(1ull << 32, strictNextPowTwo((1ull << 32) - 1));
EXPECT_EQ(1ull << 63, strictNextPowTwo((1ull << 62) + 1));
}
TEST(Bits, prevPowTwoClz) {
EXPECT_EQ(0, prevPowTwo(0u));
EXPECT_EQ(1, prevPowTwo(1u));
EXPECT_EQ(2, prevPowTwo(2u));
EXPECT_EQ(2, prevPowTwo(3u));
EXPECT_EQ(4, prevPowTwo(4u));
EXPECT_EQ(4, prevPowTwo(5u));
EXPECT_EQ(4, prevPowTwo(6u));
EXPECT_EQ(4, prevPowTwo(7u));
EXPECT_EQ(8, prevPowTwo(8u));
EXPECT_EQ(8, prevPowTwo(9u));
EXPECT_EQ(8, prevPowTwo(13u));
EXPECT_EQ(16, prevPowTwo(16u));
EXPECT_EQ(256, prevPowTwo(510u));
EXPECT_EQ(256, prevPowTwo(511u));
EXPECT_EQ(512, prevPowTwo(512u));
EXPECT_EQ(512, prevPowTwo(513u));
EXPECT_EQ(512, prevPowTwo(777u));
EXPECT_EQ(1ul << 30, prevPowTwo((1ul << 31) - 1));
EXPECT_EQ(1ull << 31, prevPowTwo((1ull << 32) - 1));
EXPECT_EQ(1ull << 62, prevPowTwo((1ull << 62) + 1));
}
TEST(Bits, strictPrevPowTwoClz) {
EXPECT_EQ(0, strictPrevPowTwo(0u));
EXPECT_EQ(0, strictPrevPowTwo(1u));
EXPECT_EQ(1, strictPrevPowTwo(2u));
EXPECT_EQ(2, strictPrevPowTwo(3u));
EXPECT_EQ(2, strictPrevPowTwo(4u));
EXPECT_EQ(4, strictPrevPowTwo(5u));
EXPECT_EQ(4, strictPrevPowTwo(6u));
EXPECT_EQ(4, strictPrevPowTwo(7u));
EXPECT_EQ(4, strictPrevPowTwo(8u));
EXPECT_EQ(8, strictPrevPowTwo(9u));
EXPECT_EQ(8, strictPrevPowTwo(13u));
EXPECT_EQ(8, strictPrevPowTwo(16u));
EXPECT_EQ(256, strictPrevPowTwo(510u));
EXPECT_EQ(256, strictPrevPowTwo(511u));
EXPECT_EQ(256, strictPrevPowTwo(512u));
EXPECT_EQ(512, strictPrevPowTwo(513u));
EXPECT_EQ(512, strictPrevPowTwo(777u));
EXPECT_EQ(1ul << 30, strictPrevPowTwo((1ul << 31) - 1));
EXPECT_EQ(1ull << 31, strictPrevPowTwo((1ull << 32) - 1));
EXPECT_EQ(1ull << 62, strictPrevPowTwo((1ull << 62) + 1));
}
TEST(Bits, isPowTwo) {
EXPECT_FALSE(isPowTwo(0u));
EXPECT_TRUE(isPowTwo(1ul));
EXPECT_TRUE(isPowTwo(2ull));
EXPECT_FALSE(isPowTwo(3ul));
EXPECT_TRUE(isPowTwo(4ul));
EXPECT_FALSE(isPowTwo(5ul));
EXPECT_TRUE(isPowTwo(8ul));
EXPECT_FALSE(isPowTwo(15u));
EXPECT_TRUE(isPowTwo(16u));
EXPECT_FALSE(isPowTwo(17u));
EXPECT_FALSE(isPowTwo(511ul));
EXPECT_TRUE(isPowTwo(512ul));
EXPECT_FALSE(isPowTwo(513ul));
EXPECT_FALSE(isPowTwo((1ul << 31) - 1));
EXPECT_TRUE(isPowTwo(1ul << 31));
EXPECT_FALSE(isPowTwo((1ul << 31) + 1));
EXPECT_FALSE(isPowTwo((1ull << 63) - 1));
EXPECT_TRUE(isPowTwo(1ull << 63));
EXPECT_FALSE(isPowTwo((1ull << 63) + 1));
}
TEST(Bits, popcount) {
EXPECT_EQ(0, popcount(0U));
EXPECT_EQ(1, popcount(1U));
EXPECT_EQ(32, popcount(uint32_t(-1)));
EXPECT_EQ(64, popcount(uint64_t(-1)));
}
TEST(Bits, EndianSwapUint) {
EXPECT_EQ(uint8_t(0xda), Endian::swap(uint8_t(0xda)));
EXPECT_EQ(uint16_t(0x4175), Endian::swap(uint16_t(0x7541)));
EXPECT_EQ(uint32_t(0x42efb918), Endian::swap(uint32_t(0x18b9ef42)));
EXPECT_EQ(
uint64_t(0xa244f5e862c71d8a), Endian::swap(uint64_t(0x8a1dc762e8f544a2)));
}
TEST(Bits, EndianSwapReal) {
std::mt19937_64 rng;
auto f = std::uniform_real_distribution<float>()(rng);
EXPECT_NE(f, Endian::swap(f));
EXPECT_EQ(f, Endian::swap(Endian::swap(f)));
auto d = std::uniform_real_distribution<double>()(rng);
EXPECT_NE(d, Endian::swap(d));
EXPECT_EQ(d, Endian::swap(Endian::swap(d)));
}
uint64_t reverse_simple(uint64_t v) {
uint64_t r = 0;
for (int i = 0; i < 64; i++) {
r <<= 1;
r |= v & 1;
v >>= 1;
}
return r;
}
TEST(Bits, BitReverse) {
EXPECT_EQ(folly::bitReverse<uint8_t>(0), 0);
EXPECT_EQ(folly::bitReverse<uint8_t>(1), 128);
for (int i = 0; i < 100; i++) {
uint64_t v = folly::Random::rand64();
EXPECT_EQ(folly::bitReverse(v), reverse_simple(v));
uint32_t b = folly::Random::rand32();
EXPECT_EQ(folly::bitReverse(b), reverse_simple(b) >> 32);
}
}
static_assert(std::is_trivial_v<Unaligned<uint64_t>>);
static_assert(std::is_trivially_copy_assignable_v<Unaligned<uint64_t>>);
static_assert(std::is_nothrow_constructible_v<Unaligned<uint64_t>, uint64_t>);
static_assert(std::is_nothrow_assignable_v<Unaligned<uint64_t>, uint64_t>);
static_assert(sizeof(Unaligned<uint64_t>) == sizeof(uint64_t));
static_assert(alignof(Unaligned<uint64_t>) == 1);
TEST(Bits, PartialLoadUnaligned) {
std::vector<char> buf(128);
std::generate(
buf.begin(), buf.end(), [] { return folly::Random::rand32(255); });
for (size_t l = 0; l < 8; ++l) {
for (size_t pos = 0; pos <= buf.size() - l; ++pos) {
auto p = buf.data() + pos;
auto x = folly::partialLoadUnaligned<uint64_t>(p, l);
uint64_t expected = 0;
memcpy(&expected, p, l);
EXPECT_EQ(x, expected);
if (l < 4) {
auto x32 = folly::partialLoadUnaligned<uint32_t>(p, l);
EXPECT_EQ(x32, static_cast<uint32_t>(expected));
}
}
}
}
TEST(Bits, BitCastBasic) {
auto one = std::make_unique<int>();
auto two = folly::bit_cast<std::uintptr_t>(one.get());
EXPECT_EQ(folly::bit_cast<int*>(two), one.get());
struct FancyInt {
FancyInt() {
ADD_FAILURE() << "Default constructor should not be called by bit_cast";
}
int value;
};
int x = 5;
auto bi = folly::bit_cast<FancyInt>(x);
EXPECT_EQ(x, bi.value);
}
TEST(Bits, BitCastCompatibilityTest) {
static_assert(sizeof(double) == sizeof(std::uint64_t));
auto one = folly::Random::rand64();
auto dbl = folly::bit_cast<double>(one);
auto two = folly::bit_cast<std::uint64_t>(dbl);
EXPECT_EQ(one, two);
}
TEST(Bits, LoadUnalignedUB) {
// test case from: https://github.com/facebook/folly/issues/2150
auto func = [](uint8_t a, uint8_t b, uint64_t c, uint64_t d) -> uint32_t {
char buffer[1 + 1 + 8 + 8];
folly::storeUnaligned<uint8_t>(buffer + 0, a);
folly::storeUnaligned<uint8_t>(buffer + 1, b);
folly::storeUnaligned<uint64_t>(buffer + 2, c);
folly::storeUnaligned<uint64_t>(buffer + 2 + 8, d);
uint16_t ret = 0;
for (std::size_t i = 0; i < sizeof(buffer); i += 2) {
ret += folly::loadUnaligned<uint16_t>(buffer + i);
}
return ret;
};
uint8_t a = 0, b = 0;
uint64_t c = 0, d = 0;
uint16_t x = func(a, b, c, d);
EXPECT_EQ(0, x);
}
} // namespace folly
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