/*
 * 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/hash/Checksum.h>

#include <boost/crc.hpp>

#include <folly/Benchmark.h>
#include <folly/Random.h>
#include <folly/hash/Hash.h>
#include <folly/hash/detail/ChecksumDetail.h>
#include <folly/portability/GFlags.h>
#include <folly/portability/GTest.h>

namespace {
const unsigned int BUFFER_SIZE = 512 * 1024 * sizeof(uint64_t);
uint8_t buffer[BUFFER_SIZE];

struct ExpectedResult {
  size_t offset;
  size_t length;
  uint32_t crc32c;
};

ExpectedResult expectedResults[] = {
    // Zero-byte input
    {0, 0, ~0U},
    // Small aligned inputs to test special cases in SIMD implementations
    {8, 1, 1543413366},
    {8, 2, 523493126},
    {8, 3, 1560427360},
    {8, 4, 3422504776},
    {8, 5, 447841138},
    {8, 6, 3910050499},
    {8, 7, 3346241981},
    // Small unaligned inputs
    {9, 1, 3855826643},
    {10, 2, 560880875},
    {11, 3, 1479707779},
    {12, 4, 2237687071},
    {13, 5, 4063855784},
    {14, 6, 2553454047},
    {15, 7, 1349220140},
    // Larger inputs to test leftover chunks at the end of aligned blocks
    {8, 8, 627613930},
    {8, 9, 2105929409},
    {8, 10, 2447068514},
    {8, 11, 863807079},
    {8, 12, 292050879},
    {8, 13, 1411837737},
    {8, 14, 2614515001},
    {8, 15, 3579076296},
    {8, 16, 2897079161},
    {8, 17, 675168386},
    // Much larger inputs
    {0, BUFFER_SIZE, 2096790750},
    {1, BUFFER_SIZE / 2, 3854797577},
};

void testCRC32C(
    std::function<uint32_t(const uint8_t*, size_t, uint32_t)> impl) {
  for (auto expected : expectedResults) {
    uint32_t result = impl(buffer + expected.offset, expected.length, ~0U);
    EXPECT_EQ(expected.crc32c, result);
  }
}

void testCRC32CContinuation(
    std::function<uint32_t(const uint8_t*, size_t, uint32_t)> impl) {
  for (auto expected : expectedResults) {
    size_t partialLength = expected.length / 2;
    uint32_t partialChecksum =
        impl(buffer + expected.offset, partialLength, ~0U);
    uint32_t result = impl(
        buffer + expected.offset + partialLength,
        expected.length - partialLength,
        partialChecksum);
    EXPECT_EQ(expected.crc32c, result);
  }
}

void testMatchesBoost32Type() {
  for (auto expected : expectedResults) {
    boost::crc_32_type result;
    result.process_bytes(buffer + expected.offset, expected.length);
    const uint32_t boostResult = result.checksum();
    const uint32_t follyResult =
        folly::crc32_type(buffer + expected.offset, expected.length);
    EXPECT_EQ(follyResult, boostResult);
  }
}

} // namespace

TEST(Checksum, crc32c_software) {
  testCRC32C(folly::detail::crc32c_sw);
}

TEST(Checksum, crc32c_continuation_software) {
  testCRC32CContinuation(folly::detail::crc32c_sw);
}

TEST(Checksum, crc32c_hardware) {
  if (folly::detail::crc32c_hw_supported()) {
    testCRC32C(folly::detail::crc32c_hw);
  } else {
    LOG(WARNING) << "skipping hardware-accelerated CRC-32C tests"
                 << " (not supported on this CPU)";
  }
}

TEST(Checksum, crc32c_hardware_eq) {
  if (folly::detail::crc32c_hw_supported()) {
    for (int i = 0; i < 1000; i++) {
      auto sw = folly::detail::crc32c_sw(buffer, i, 0);
      auto hw = folly::detail::crc32c_hw(buffer, i, 0);
      EXPECT_EQ(sw, hw);
    }
  } else {
    LOG(WARNING) << "skipping hardware-accelerated CRC-32C tests"
                 << " (not supported on this CPU)";
  }
}

TEST(Checksum, crc32c_continuation_hardware) {
  if (folly::detail::crc32c_hw_supported()) {
    testCRC32CContinuation(folly::detail::crc32c_hw);
  } else {
    LOG(WARNING) << "skipping hardware-accelerated CRC-32C tests"
                 << " (not supported on this CPU)";
  }
}

TEST(Checksum, crc32c_autodetect) {
  testCRC32C(folly::crc32c);
}

TEST(Checksum, crc32c_continuation_autodetect) {
  testCRC32CContinuation(folly::crc32c);
}

TEST(Checksum, crc32) {
  if (folly::detail::crc32c_hw_supported()) {
    // Just check that sw and hw match
    for (auto expected : expectedResults) {
      uint32_t sw_res =
          folly::detail::crc32_sw(buffer + expected.offset, expected.length, 0);
      uint32_t hw_res =
          folly::detail::crc32_hw(buffer + expected.offset, expected.length, 0);
      EXPECT_EQ(sw_res, hw_res);
    }
  } else {
    LOG(WARNING) << "skipping hardware-accelerated CRC-32 tests"
                 << " (not supported on this CPU)";
  }
}

TEST(Checksum, crc32_continuation) {
  if (folly::detail::crc32c_hw_supported()) {
    // Just check that sw and hw match
    for (auto expected : expectedResults) {
      auto halflen = expected.length / 2;
      uint32_t sw_res =
          folly::detail::crc32_sw(buffer + expected.offset, halflen, 0);
      sw_res = folly::detail::crc32_sw(
          buffer + expected.offset + halflen, halflen, sw_res);
      uint32_t hw_res =
          folly::detail::crc32_hw(buffer + expected.offset, halflen, 0);
      hw_res = folly::detail::crc32_hw(
          buffer + expected.offset + halflen, halflen, hw_res);
      EXPECT_EQ(sw_res, hw_res);
      uint32_t sw_res2 =
          folly::detail::crc32_sw(buffer + expected.offset, halflen * 2, 0);
      EXPECT_EQ(sw_res, sw_res2);
      uint32_t hw_res2 =
          folly::detail::crc32_hw(buffer + expected.offset, halflen * 2, 0);
      EXPECT_EQ(hw_res, hw_res2);
    }
  } else {
    LOG(WARNING) << "skipping hardware-accelerated CRC-32 tests"
                 << " (not supported on this CPU)";
  }
}

TEST(Checksum, crc32_type) {
  // Test that crc32_type matches boost::crc_32_type
  testMatchesBoost32Type();
}

TEST(Checksum, crc32_combine) {
  for (size_t totlen = 1024; totlen < BUFFER_SIZE; totlen += BUFFER_SIZE / 8) {
    auto mid = folly::Random::rand64(0, totlen);
    auto crc1 = folly::crc32(&buffer[0], mid, 0);
    auto crc2 = folly::crc32(&buffer[mid], totlen - mid, 0);
    auto crcfull = folly::crc32(&buffer[0], totlen, 0);
    auto combined = folly::crc32_combine(crc1, crc2, totlen - mid);
    EXPECT_EQ(combined, crcfull);
  }
}

TEST(Checksum, crc32c_combine) {
  for (size_t totlen = 1024; totlen < BUFFER_SIZE; totlen += BUFFER_SIZE / 8) {
    auto mid = folly::Random::rand64(0, totlen);
    auto crc1 = folly::crc32c(&buffer[0], mid, 0);
    auto crc2 = folly::crc32c(&buffer[mid], totlen - mid, 0);
    auto crcfull = folly::crc32c(&buffer[0], totlen, 0);
    auto combined = folly::crc32c_combine(crc1, crc2, totlen - mid);
    EXPECT_EQ(combined, crcfull);
  }
}

void benchmarkHardwareCRC32C(unsigned long iters, size_t blockSize) {
  if (folly::detail::crc32c_hw_supported()) {
    uint32_t checksum;
    for (unsigned long i = 0; i < iters; i++) {
      checksum = folly::detail::crc32c_hw(buffer, blockSize);
      folly::doNotOptimizeAway(checksum);
    }
  } else {
    LOG(WARNING) << "skipping hardware-accelerated CRC-32C benchmarks"
                 << " (not supported on this CPU)";
  }
}

void benchmarkSoftwareCRC32C(unsigned long iters, size_t blockSize) {
  uint32_t checksum;
  for (unsigned long i = 0; i < iters; i++) {
    checksum = folly::detail::crc32c_sw(buffer, blockSize);
    folly::doNotOptimizeAway(checksum);
  }
}

void benchmarkHardwareCRC32(unsigned long iters, size_t blockSize) {
  if (folly::detail::crc32_hw_supported()) {
    uint32_t checksum;
    for (unsigned long i = 0; i < iters; i++) {
      checksum = folly::detail::crc32_hw(buffer, blockSize);
      folly::doNotOptimizeAway(checksum);
    }
  } else {
    LOG(WARNING) << "skipping hardware-accelerated CRC-32 benchmarks"
                 << " (not supported on this CPU)";
  }
}

void benchmarkSoftwareCRC32(unsigned long iters, size_t blockSize) {
  uint32_t checksum;
  for (unsigned long i = 0; i < iters; i++) {
    checksum = folly::detail::crc32_sw(buffer, blockSize);
    folly::doNotOptimizeAway(checksum);
  }
}

void benchmarkCombineHardwareCrc32(unsigned long iters, size_t blockSize) {
  // Arbitrarily chosen checksums
  uint32_t checksum1 = 0xEDB88320;
  uint32_t checksum2 = 0x82F63B78;
  uint32_t result;
  for (unsigned long i = 0; i < iters; i++) {
    result = folly::crc32_combine(checksum1, checksum2, blockSize);
    folly::doNotOptimizeAway(result);
  }
}

void benchmarkCombineSoftwareLinear(unsigned long iters, size_t blockSize) {
  // Arbitrarily chosen checksums
  std::vector<uint8_t> zbuffer;
  zbuffer.reserve(blockSize);
  memset(zbuffer.data(), 0, blockSize);
  uint32_t checksum1 = 0xEDB88320;
  uint32_t checksum2 = 0x82F63B78;
  uint32_t result;
  for (unsigned long i = 0; i < iters; i++) {
    result = folly::crc32c(zbuffer.data(), blockSize, checksum1);
    result ^= checksum2;
    folly::doNotOptimizeAway(result);
  }
}

void benchmarkCombineHardwareCrc32c(unsigned long iters, size_t blockSize) {
  // Arbitrarily chosen checksums
  uint32_t checksum1 = 0xEDB88320;
  uint32_t checksum2 = 0x82F63B78;
  uint32_t result;
  for (unsigned long i = 0; i < iters; i++) {
    result = folly::crc32c_combine(checksum1, checksum2, blockSize);
    folly::doNotOptimizeAway(result);
  }
}

// This test fits easily in the L1 cache on modern server processors,
// and thus it mainly measures the speed of the checksum computation.
BENCHMARK(crc32c_hardware_1KB_block, iters) {
  benchmarkHardwareCRC32C(iters, 1024);
}

BENCHMARK(crc32c_software_1KB_block, iters) {
  benchmarkSoftwareCRC32C(iters, 1024);
}

BENCHMARK(crc32_hardware_1KB_block, iters) {
  benchmarkHardwareCRC32(iters, 1024);
}

BENCHMARK(crc32_software_1KB_block, iters) {
  benchmarkSoftwareCRC32(iters, 1024);
}

BENCHMARK_DRAW_LINE();

// This test is too big for the L1 cache but fits in L2
BENCHMARK(crc32c_hardware_64KB_block, iters) {
  benchmarkHardwareCRC32C(iters, 64 * 1024);
}

BENCHMARK(crc32c_software_64KB_block, iters) {
  benchmarkSoftwareCRC32C(iters, 64 * 1024);
}

BENCHMARK(crc32_hardware_64KB_block, iters) {
  benchmarkHardwareCRC32(iters, 64 * 1024);
}

BENCHMARK(crc32_software_64KB_block, iters) {
  benchmarkSoftwareCRC32(iters, 64 * 1024);
}

BENCHMARK_DRAW_LINE();

// This test is too big for the L2 cache but fits in L3
BENCHMARK(crc32c_hardware_512KB_block, iters) {
  benchmarkHardwareCRC32C(iters, 512 * 1024);
}

BENCHMARK(crc32c_software_512KB_block, iters) {
  benchmarkSoftwareCRC32C(iters, 512 * 1024);
}

BENCHMARK(crc32_hardware_512KB_block, iters) {
  benchmarkHardwareCRC32(iters, 512 * 1024);
}

BENCHMARK(crc32_software_512KB_block, iters) {
  benchmarkSoftwareCRC32(iters, 512 * 1024);
}

BENCHMARK_DRAW_LINE();

BENCHMARK(crc32_combine_linear_512KB_block, iters) {
  benchmarkCombineSoftwareLinear(iters, 512 * 1024);
}

BENCHMARK(crc32_combine_512KB_block, iters) {
  benchmarkCombineHardwareCrc32(iters, 512 * 1024);
}

BENCHMARK(crc32c_combine_512KB_block, iters) {
  benchmarkCombineHardwareCrc32c(iters, 512 * 1024);
}

int main(int argc, char** argv) {
  testing::InitGoogleTest(&argc, argv);
  gflags::ParseCommandLineFlags(&argc, &argv, true);

  // Populate a buffer with a deterministic pattern
  // on which to compute checksums
  const uint8_t* src = buffer;
  uint64_t* dst = (uint64_t*)buffer;
  const uint64_t* end = (const uint64_t*)(buffer + BUFFER_SIZE);
  *dst++ = 0;
  while (dst < end) {
    *dst++ = folly::hash::fnv64_buf((const char*)src, sizeof(uint64_t));
    src += sizeof(uint64_t);
  }

  auto ret = RUN_ALL_TESTS();
  if (!ret && FLAGS_benchmark) {
    folly::runBenchmarks();
  }
  return ret;
}
