folly/lang/test/BitsTest.cpp

   1 /*
   2  * Copyright 2017 Facebook, Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *   http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 // @author Tudor Bosman (tudorb@fb.com)
  18
  19 #include <folly/lang/Bits.h>
  20
  21 #include <folly/Random.h>
  22 #include <random>
  23
  24 #include <folly/portability/GTest.h>
  25
  26 using namespace folly;
  27
  28 // Test constexpr-ness.
  29 #if !defined(__clang__) && !defined(_MSC_VER)
  30 static_assert(findFirstSet(2u) == 2, "findFirstSet");
  31 static_assert(findLastSet(2u) == 2, "findLastSet");
  32 static_assert(nextPowTwo(2u) == 2, "nextPowTwo");
  33 #endif
  34
  35 #ifndef __clang__
  36 static_assert(isPowTwo(2u), "isPowTwo");
  37 #endif
  38
  39 namespace {
  40
  41 template <class INT>
  42 void testFFS() {
  43   EXPECT_EQ(0, findFirstSet(static_cast<INT>(0)));
  44   size_t bits = std::numeric_limits<
  45     typename std::make_unsigned<INT>::type>::digits;
  46   for (size_t i = 0; i < bits; i++) {
  47     INT v = (static_cast<INT>(1) << (bits - 1)) |
  48             (static_cast<INT>(1) << i);
  49     EXPECT_EQ(i+1, findFirstSet(v));
  50   }
  51 }
  52
  53 template <class INT>
  54 void testFLS() {
  55   typedef typename std::make_unsigned<INT>::type UINT_T;
  56   EXPECT_EQ(0, findLastSet(static_cast<INT>(0)));
  57   size_t bits = std::numeric_limits<UINT_T>::digits;
  58   for (size_t i = 0; i < bits; i++) {
  59     INT v1 = static_cast<UINT_T>(1) << i;
  60     EXPECT_EQ(i + 1, findLastSet(v1));
  61
  62     INT v2 = (static_cast<UINT_T>(1) << i) - 1;
  63     EXPECT_EQ(i, findLastSet(v2));
  64   }
  65 }
  66
  67 } // namespace
  68
  69 TEST(Bits, FindFirstSet) {
  70   testFFS<char>();
  71   testFFS<signed char>();
  72   testFFS<unsigned char>();
  73   testFFS<short>();
  74   testFFS<unsigned short>();
  75   testFFS<int>();
  76   testFFS<unsigned int>();
  77   testFFS<long>();
  78   testFFS<unsigned long>();
  79   testFFS<long long>();
  80   testFFS<unsigned long long>();
  81 }
  82
  83 TEST(Bits, FindLastSet) {
  84   testFLS<char>();
  85   testFLS<signed char>();
  86   testFLS<unsigned char>();
  87   testFLS<short>();
  88   testFLS<unsigned short>();
  89   testFLS<int>();
  90   testFLS<unsigned int>();
  91   testFLS<long>();
  92   testFLS<unsigned long>();
  93   testFLS<long long>();
  94   testFLS<unsigned long long>();
  95 }
  96
  97 TEST(Bits, nextPowTwoClz) {
  98   EXPECT_EQ(1, nextPowTwo(0u));
  99   EXPECT_EQ(1, nextPowTwo(1u));
 100   EXPECT_EQ(2, nextPowTwo(2u));
 101   EXPECT_EQ(4, nextPowTwo(3u));
 102   EXPECT_EQ(4, nextPowTwo(4u));
 103   EXPECT_EQ(8, nextPowTwo(5u));
 104   EXPECT_EQ(8, nextPowTwo(6u));
 105   EXPECT_EQ(8, nextPowTwo(7u));
 106   EXPECT_EQ(8, nextPowTwo(8u));
 107   EXPECT_EQ(16, nextPowTwo(9u));
 108   EXPECT_EQ(16, nextPowTwo(13u));
 109   EXPECT_EQ(16, nextPowTwo(16u));
 110   EXPECT_EQ(512, nextPowTwo(510u));
 111   EXPECT_EQ(512, nextPowTwo(511u));
 112   EXPECT_EQ(512, nextPowTwo(512u));
 113   EXPECT_EQ(1024, nextPowTwo(513u));
 114   EXPECT_EQ(1024, nextPowTwo(777u));
 115   EXPECT_EQ(1ul << 31, nextPowTwo((1ul << 31) - 1));
 116   EXPECT_EQ(1ull << 32, nextPowTwo((1ull << 32) - 1));
 117   EXPECT_EQ(1ull << 63, nextPowTwo((1ull << 62) + 1));
 118 }
 119
 120 TEST(Bits, prevPowTwoClz) {
 121   EXPECT_EQ(0, prevPowTwo(0u));
 122   EXPECT_EQ(1, prevPowTwo(1u));
 123   EXPECT_EQ(2, prevPowTwo(2u));
 124   EXPECT_EQ(2, prevPowTwo(3u));
 125   EXPECT_EQ(4, prevPowTwo(4u));
 126   EXPECT_EQ(4, prevPowTwo(5u));
 127   EXPECT_EQ(4, prevPowTwo(6u));
 128   EXPECT_EQ(4, prevPowTwo(7u));
 129   EXPECT_EQ(8, prevPowTwo(8u));
 130   EXPECT_EQ(8, prevPowTwo(9u));
 131   EXPECT_EQ(8, prevPowTwo(13u));
 132   EXPECT_EQ(16, prevPowTwo(16u));
 133   EXPECT_EQ(256, prevPowTwo(510u));
 134   EXPECT_EQ(256, prevPowTwo(511u));
 135   EXPECT_EQ(512, prevPowTwo(512u));
 136   EXPECT_EQ(512, prevPowTwo(513u));
 137   EXPECT_EQ(512, prevPowTwo(777u));
 138   EXPECT_EQ(1ul << 30, prevPowTwo((1ul << 31) - 1));
 139   EXPECT_EQ(1ull << 31, prevPowTwo((1ull << 32) - 1));
 140   EXPECT_EQ(1ull << 62, prevPowTwo((1ull << 62) + 1));
 141 }
 142
 143 TEST(Bits, isPowTwo) {
 144   EXPECT_FALSE(isPowTwo(0u));
 145   EXPECT_TRUE(isPowTwo(1ul));
 146   EXPECT_TRUE(isPowTwo(2ull));
 147   EXPECT_FALSE(isPowTwo(3ul));
 148   EXPECT_TRUE(isPowTwo(4ul));
 149   EXPECT_FALSE(isPowTwo(5ul));
 150   EXPECT_TRUE(isPowTwo(8ul));
 151   EXPECT_FALSE(isPowTwo(15u));
 152   EXPECT_TRUE(isPowTwo(16u));
 153   EXPECT_FALSE(isPowTwo(17u));
 154   EXPECT_FALSE(isPowTwo(511ul));
 155   EXPECT_TRUE(isPowTwo(512ul));
 156   EXPECT_FALSE(isPowTwo(513ul));
 157   EXPECT_FALSE(isPowTwo((1ul<<31) - 1));
 158   EXPECT_TRUE(isPowTwo(1ul<<31));
 159   EXPECT_FALSE(isPowTwo((1ul<<31) + 1));
 160   EXPECT_FALSE(isPowTwo((1ull<<63) - 1));
 161   EXPECT_TRUE(isPowTwo(1ull<<63));
 162   EXPECT_FALSE(isPowTwo((1ull<<63) + 1));
 163 }
 164
 165 TEST(Bits, popcount) {
 166   EXPECT_EQ(0, popcount(0U));
 167   EXPECT_EQ(1, popcount(1U));
 168   EXPECT_EQ(32, popcount(uint32_t(-1)));
 169   EXPECT_EQ(64, popcount(uint64_t(-1)));
 170 }
 171
 172 TEST(Bits, Endian_swap_uint) {
 173   EXPECT_EQ(uint8_t(0xda), Endian::swap(uint8_t(0xda)));
 174   EXPECT_EQ(uint16_t(0x4175), Endian::swap(uint16_t(0x7541)));
 175   EXPECT_EQ(uint32_t(0x42efb918), Endian::swap(uint32_t(0x18b9ef42)));
 176   EXPECT_EQ(
 177       uint64_t(0xa244f5e862c71d8a), Endian::swap(uint64_t(0x8a1dc762e8f544a2)));
 178 }
 179
 180 TEST(Bits, Endian_swap_real) {
 181   std::mt19937_64 rng;
 182   auto f = std::uniform_real_distribution<float>()(rng);
 183   EXPECT_NE(f, Endian::swap(f));
 184   EXPECT_EQ(f, Endian::swap(Endian::swap(f)));
 185   auto d = std::uniform_real_distribution<double>()(rng);
 186   EXPECT_NE(d, Endian::swap(d));
 187   EXPECT_EQ(d, Endian::swap(Endian::swap(d)));
 188 }
 189
 190 uint64_t reverse_simple(uint64_t v) {
 191   uint64_t r = 0;
 192
 193   for (int i = 0; i < 64; i++) {
 194     r <<= 1;
 195     r |= v & 1;
 196     v >>= 1;
 197   }
 198   return r;
 199 }
 200
 201 TEST(Bits, BitReverse) {
 202   EXPECT_EQ(folly::bitReverse<uint8_t>(0), 0);
 203   EXPECT_EQ(folly::bitReverse<uint8_t>(1), 128);
 204   for (int i = 0; i < 100; i++) {
 205     uint64_t v = folly::Random::rand64();
 206     EXPECT_EQ(folly::bitReverse(v), reverse_simple(v));
 207     uint32_t b = folly::Random::rand32();
 208     EXPECT_EQ(folly::bitReverse(b), reverse_simple(b) >> 32);
 209   }
 210 }