// Copyright (c) 2017 Google Inc.
//
// 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 <limits>
#include <sstream>
#include <string>
#include <utility>
#include <vector>

#include "gmock/gmock.h"
#include "source/comp/bit_stream.h"

namespace spvtools {
namespace comp {
namespace {

// Converts |buffer| to a stream of '0' and '1'.
template <typename T>
std::string BufferToStream(const std::vector<T>& buffer) {
  std::stringstream ss;
  for (auto it = buffer.begin(); it != buffer.end(); ++it) {
    std::string str = std::bitset<sizeof(T) * 8>(*it).to_string();
    // Strings generated by std::bitset::to_string are read right to left.
    // Reversing to left to right.
    std::reverse(str.begin(), str.end());
    ss << str;
  }
  return ss.str();
}

// Converts a left-to-right input string of '0' and '1' to a buffer of |T|
// words.
template <typename T>
std::vector<T> StreamToBuffer(std::string str) {
  // The input string is left-to-right, the input argument of std::bitset needs
  // to right-to-left. Instead of reversing tokens, reverse the entire string
  // and iterate tokens from end to begin.
  std::reverse(str.begin(), str.end());
  const int word_size = static_cast<int>(sizeof(T) * 8);
  const int str_length = static_cast<int>(str.length());
  std::vector<T> buffer;
  buffer.reserve(NumBitsToNumWords<sizeof(T)>(str.length()));
  for (int index = str_length - word_size; index >= 0; index -= word_size) {
    buffer.push_back(static_cast<T>(
        std::bitset<sizeof(T) * 8>(str, index, word_size).to_ullong()));
  }
  const size_t suffix_length = str.length() % word_size;
  if (suffix_length != 0) {
    buffer.push_back(static_cast<T>(
        std::bitset<sizeof(T) * 8>(str, 0, suffix_length).to_ullong()));
  }
  return buffer;
}

// Adds '0' chars at the end of the string until the size is a multiple of N.
template <size_t N>
std::string PadToWord(std::string&& str) {
  const size_t tail_length = str.size() % N;
  if (tail_length != 0) str += std::string(N - tail_length, '0');
  return std::move(str);
}

// Adds '0' chars at the end of the string until the size is a multiple of N.
template <size_t N>
std::string PadToWord(const std::string& str) {
  return PadToWord<N>(std::string(str));
}

// Converts a left-to-right stream of bits to std::bitset.
template <size_t N>
std::bitset<N> StreamToBitset(std::string str) {
  std::reverse(str.begin(), str.end());
  return std::bitset<N>(str);
}

// Converts a left-to-right stream of bits to uint64.
uint64_t StreamToBits(std::string str) {
  std::reverse(str.begin(), str.end());
  return std::bitset<64>(str).to_ullong();
}

// A simple and inefficient implementatition of BitWriterInterface,
// using std::stringstream. Intended for tests only.
class BitWriterStringStream : public BitWriterInterface {
 public:
  void WriteBits(uint64_t bits, size_t num_bits) override {
    assert(num_bits <= 64);
    ss_ << BitsToStream(bits, num_bits);
  }

  size_t GetNumBits() const override { return ss_.str().size(); }

  std::vector<uint8_t> GetDataCopy() const override {
    return StreamToBuffer<uint8_t>(ss_.str());
  }

  std::string GetStreamRaw() const { return ss_.str(); }

 private:
  std::stringstream ss_;
};

// A simple and inefficient implementatition of BitReaderInterface.
// Intended for tests only.
class BitReaderFromString : public BitReaderInterface {
 public:
  explicit BitReaderFromString(std::string&& str)
      : str_(std::move(str)), pos_(0) {}

  explicit BitReaderFromString(const std::vector<uint64_t>& buffer)
      : str_(BufferToStream(buffer)), pos_(0) {}

  explicit BitReaderFromString(const std::vector<uint8_t>& buffer)
      : str_(PadToWord<64>(BufferToStream(buffer))), pos_(0) {}

  size_t ReadBits(uint64_t* bits, size_t num_bits) override {
    if (ReachedEnd()) return 0;
    std::string sub = str_.substr(pos_, num_bits);
    *bits = StreamToBits(sub);
    pos_ += sub.length();
    return sub.length();
  }

  size_t GetNumReadBits() const override { return pos_; }

  bool ReachedEnd() const override { return pos_ >= str_.length(); }

 private:
  std::string str_;
  size_t pos_;
};

TEST(NumBitsToNumWords, Word8) {
  EXPECT_EQ(0u, NumBitsToNumWords<8>(0));
  EXPECT_EQ(1u, NumBitsToNumWords<8>(1));
  EXPECT_EQ(1u, NumBitsToNumWords<8>(7));
  EXPECT_EQ(1u, NumBitsToNumWords<8>(8));
  EXPECT_EQ(2u, NumBitsToNumWords<8>(9));
  EXPECT_EQ(2u, NumBitsToNumWords<8>(16));
  EXPECT_EQ(3u, NumBitsToNumWords<8>(17));
  EXPECT_EQ(3u, NumBitsToNumWords<8>(23));
  EXPECT_EQ(3u, NumBitsToNumWords<8>(24));
  EXPECT_EQ(4u, NumBitsToNumWords<8>(25));
}

TEST(NumBitsToNumWords, Word64) {
  EXPECT_EQ(0u, NumBitsToNumWords<64>(0));
  EXPECT_EQ(1u, NumBitsToNumWords<64>(1));
  EXPECT_EQ(1u, NumBitsToNumWords<64>(64));
  EXPECT_EQ(2u, NumBitsToNumWords<64>(65));
  EXPECT_EQ(2u, NumBitsToNumWords<64>(128));
  EXPECT_EQ(3u, NumBitsToNumWords<64>(129));
}

TEST(ZigZagCoding, Encode0) {
  EXPECT_EQ(0u, EncodeZigZag(0, 0));
  EXPECT_EQ(1u, EncodeZigZag(-1, 0));
  EXPECT_EQ(2u, EncodeZigZag(1, 0));
  EXPECT_EQ(3u, EncodeZigZag(-2, 0));
  EXPECT_EQ(std::numeric_limits<uint64_t>::max() - 1,
            EncodeZigZag(std::numeric_limits<int64_t>::max(), 0));
  EXPECT_EQ(std::numeric_limits<uint64_t>::max(),
            EncodeZigZag(std::numeric_limits<int64_t>::min(), 0));
}

TEST(ZigZagCoding, Decode0) {
  EXPECT_EQ(0, DecodeZigZag(0, 0));
  EXPECT_EQ(-1, DecodeZigZag(1, 0));
  EXPECT_EQ(1, DecodeZigZag(2, 0));
  EXPECT_EQ(-2, DecodeZigZag(3, 0));
  EXPECT_EQ(std::numeric_limits<int64_t>::min(),
            DecodeZigZag(std::numeric_limits<uint64_t>::max(), 0));
  EXPECT_EQ(std::numeric_limits<int64_t>::max(),
            DecodeZigZag(std::numeric_limits<uint64_t>::max() - 1, 0));
}

TEST(ZigZagCoding, Encode1) {
  EXPECT_EQ(0u, EncodeZigZag(0, 1));
  EXPECT_EQ(1u, EncodeZigZag(1, 1));
  EXPECT_EQ(2u, EncodeZigZag(-1, 1));
  EXPECT_EQ(3u, EncodeZigZag(-2, 1));
  EXPECT_EQ(4u, EncodeZigZag(2, 1));
  EXPECT_EQ(5u, EncodeZigZag(3, 1));
  EXPECT_EQ(6u, EncodeZigZag(-3, 1));
  EXPECT_EQ(7u, EncodeZigZag(-4, 1));
  EXPECT_EQ(std::numeric_limits<uint64_t>::max() - 2,
            EncodeZigZag(std::numeric_limits<int64_t>::max(), 1));
  EXPECT_EQ(std::numeric_limits<uint64_t>::max() - 1,
            EncodeZigZag(std::numeric_limits<int64_t>::min() + 1, 1));
  EXPECT_EQ(std::numeric_limits<uint64_t>::max(),
            EncodeZigZag(std::numeric_limits<int64_t>::min(), 1));
}

TEST(ZigZagCoding, Decode1) {
  EXPECT_EQ(0, DecodeZigZag(0, 1));
  EXPECT_EQ(1, DecodeZigZag(1, 1));
  EXPECT_EQ(-1, DecodeZigZag(2, 1));
  EXPECT_EQ(-2, DecodeZigZag(3, 1));
  EXPECT_EQ(2, DecodeZigZag(4, 1));
  EXPECT_EQ(3, DecodeZigZag(5, 1));
  EXPECT_EQ(-3, DecodeZigZag(6, 1));
  EXPECT_EQ(-4, DecodeZigZag(7, 1));
  EXPECT_EQ(std::numeric_limits<int64_t>::min(),
            DecodeZigZag(std::numeric_limits<uint64_t>::max(), 1));
  EXPECT_EQ(std::numeric_limits<int64_t>::min() + 1,
            DecodeZigZag(std::numeric_limits<uint64_t>::max() - 1, 1));
  EXPECT_EQ(std::numeric_limits<int64_t>::max(),
            DecodeZigZag(std::numeric_limits<uint64_t>::max() - 2, 1));
}

TEST(ZigZagCoding, Encode2) {
  EXPECT_EQ(0u, EncodeZigZag(0, 2));
  EXPECT_EQ(1u, EncodeZigZag(1, 2));
  EXPECT_EQ(2u, EncodeZigZag(2, 2));
  EXPECT_EQ(3u, EncodeZigZag(3, 2));
  EXPECT_EQ(4u, EncodeZigZag(-1, 2));
  EXPECT_EQ(5u, EncodeZigZag(-2, 2));
  EXPECT_EQ(6u, EncodeZigZag(-3, 2));
  EXPECT_EQ(7u, EncodeZigZag(-4, 2));
  EXPECT_EQ(8u, EncodeZigZag(4, 2));
  EXPECT_EQ(9u, EncodeZigZag(5, 2));
  EXPECT_EQ(10u, EncodeZigZag(6, 2));
  EXPECT_EQ(11u, EncodeZigZag(7, 2));
  EXPECT_EQ(12u, EncodeZigZag(-5, 2));
  EXPECT_EQ(13u, EncodeZigZag(-6, 2));
  EXPECT_EQ(14u, EncodeZigZag(-7, 2));
  EXPECT_EQ(15u, EncodeZigZag(-8, 2));
  EXPECT_EQ(std::numeric_limits<uint64_t>::max() - 4,
            EncodeZigZag(std::numeric_limits<int64_t>::max(), 2));
  EXPECT_EQ(std::numeric_limits<uint64_t>::max() - 3,
            EncodeZigZag(std::numeric_limits<int64_t>::min() + 3, 2));
  EXPECT_EQ(std::numeric_limits<uint64_t>::max() - 2,
            EncodeZigZag(std::numeric_limits<int64_t>::min() + 2, 2));
  EXPECT_EQ(std::numeric_limits<uint64_t>::max() - 1,
            EncodeZigZag(std::numeric_limits<int64_t>::min() + 1, 2));
  EXPECT_EQ(std::numeric_limits<uint64_t>::max(),
            EncodeZigZag(std::numeric_limits<int64_t>::min(), 2));
}

TEST(ZigZagCoding, Decode2) {
  EXPECT_EQ(0, DecodeZigZag(0, 2));
  EXPECT_EQ(1, DecodeZigZag(1, 2));
  EXPECT_EQ(2, DecodeZigZag(2, 2));
  EXPECT_EQ(3, DecodeZigZag(3, 2));
  EXPECT_EQ(-1, DecodeZigZag(4, 2));
  EXPECT_EQ(-2, DecodeZigZag(5, 2));
  EXPECT_EQ(-3, DecodeZigZag(6, 2));
  EXPECT_EQ(-4, DecodeZigZag(7, 2));
  EXPECT_EQ(4, DecodeZigZag(8, 2));
  EXPECT_EQ(5, DecodeZigZag(9, 2));
  EXPECT_EQ(6, DecodeZigZag(10, 2));
  EXPECT_EQ(7, DecodeZigZag(11, 2));
  EXPECT_EQ(-5, DecodeZigZag(12, 2));
  EXPECT_EQ(-6, DecodeZigZag(13, 2));
  EXPECT_EQ(-7, DecodeZigZag(14, 2));
  EXPECT_EQ(-8, DecodeZigZag(15, 2));
  EXPECT_EQ(std::numeric_limits<int64_t>::min(),
            DecodeZigZag(std::numeric_limits<uint64_t>::max(), 2));
  EXPECT_EQ(std::numeric_limits<int64_t>::min() + 1,
            DecodeZigZag(std::numeric_limits<uint64_t>::max() - 1, 2));
  EXPECT_EQ(std::numeric_limits<int64_t>::min() + 2,
            DecodeZigZag(std::numeric_limits<uint64_t>::max() - 2, 2));
  EXPECT_EQ(std::numeric_limits<int64_t>::min() + 3,
            DecodeZigZag(std::numeric_limits<uint64_t>::max() - 3, 2));
  EXPECT_EQ(std::numeric_limits<int64_t>::max(),
            DecodeZigZag(std::numeric_limits<uint64_t>::max() - 4, 2));
}

TEST(ZigZagCoding, Encode63) {
  EXPECT_EQ(0u, EncodeZigZag(0, 63));

  for (int64_t i = 0; i < 0xFFFFFFFF; i += 1234567) {
    const int64_t positive_val = GetLowerBits(i * i * i + i * i, 63) | 1UL;
    ASSERT_EQ(static_cast<uint64_t>(positive_val),
              EncodeZigZag(positive_val, 63));
    ASSERT_EQ((1ULL << 63) - 1 + positive_val, EncodeZigZag(-positive_val, 63));
  }

  EXPECT_EQ((1ULL << 63) - 1,
            EncodeZigZag(std::numeric_limits<int64_t>::max(), 63));
  EXPECT_EQ(std::numeric_limits<uint64_t>::max() - 1,
            EncodeZigZag(std::numeric_limits<int64_t>::min() + 1, 63));
  EXPECT_EQ(std::numeric_limits<uint64_t>::max(),
            EncodeZigZag(std::numeric_limits<int64_t>::min(), 63));
}

TEST(BufToStream, UInt8_Empty) {
  const std::string expected_bits = "";
  std::vector<uint8_t> buffer = StreamToBuffer<uint8_t>(expected_bits);
  EXPECT_TRUE(buffer.empty());
  const std::string result_bits = BufferToStream(buffer);
  EXPECT_EQ(expected_bits, result_bits);
}

TEST(BufToStream, UInt8_OneWord) {
  const std::string expected_bits = "00101100";
  std::vector<uint8_t> buffer = StreamToBuffer<uint8_t>(expected_bits);
  EXPECT_EQ(std::vector<uint8_t>({static_cast<uint8_t>(
                StreamToBitset<8>(expected_bits).to_ulong())}),
            buffer);
  const std::string result_bits = BufferToStream(buffer);
  EXPECT_EQ(expected_bits, result_bits);
}

TEST(BufToStream, UInt8_MultipleWords) {
  const std::string expected_bits =
      "00100010"
      "01101010"
      "01111101"
      "00100010";
  std::vector<uint8_t> buffer = StreamToBuffer<uint8_t>(expected_bits);
  EXPECT_EQ(std::vector<uint8_t>({
                static_cast<uint8_t>(StreamToBitset<8>("00100010").to_ulong()),
                static_cast<uint8_t>(StreamToBitset<8>("01101010").to_ulong()),
                static_cast<uint8_t>(StreamToBitset<8>("01111101").to_ulong()),
                static_cast<uint8_t>(StreamToBitset<8>("00100010").to_ulong()),
            }),
            buffer);
  const std::string result_bits = BufferToStream(buffer);
  EXPECT_EQ(expected_bits, result_bits);
}

TEST(BufToStream, UInt64_Empty) {
  const std::string expected_bits = "";
  std::vector<uint64_t> buffer = StreamToBuffer<uint64_t>(expected_bits);
  EXPECT_TRUE(buffer.empty());
  const std::string result_bits = BufferToStream(buffer);
  EXPECT_EQ(expected_bits, result_bits);
}

TEST(BufToStream, UInt64_OneWord) {
  const std::string expected_bits =
      "0001000111101110011001101010101000100010110011000100010010001000";
  std::vector<uint64_t> buffer = StreamToBuffer<uint64_t>(expected_bits);
  ASSERT_EQ(1u, buffer.size());
  EXPECT_EQ(0x1122334455667788u, buffer[0]);
  const std::string result_bits = BufferToStream(buffer);
  EXPECT_EQ(expected_bits, result_bits);
}

TEST(BufToStream, UInt64_Unaligned) {
  const std::string expected_bits =
      "0010001001101010011111010010001001001010000111110010010010010101"
      "0010001001101010011111111111111111111111";
  std::vector<uint64_t> buffer = StreamToBuffer<uint64_t>(expected_bits);
  EXPECT_EQ(std::vector<uint64_t>({
                StreamToBits(expected_bits.substr(0, 64)),
                StreamToBits(expected_bits.substr(64, 64)),
            }),
            buffer);
  const std::string result_bits = BufferToStream(buffer);
  EXPECT_EQ(PadToWord<64>(expected_bits), result_bits);
}

TEST(BufToStream, UInt64_MultipleWords) {
  const std::string expected_bits =
      "0010001001101010011111010010001001001010000111110010010010010101"
      "0010001001101010011111111111111111111111000111110010010010010111"
      "0000000000000000000000000000000000000000000000000010010011111111";
  std::vector<uint64_t> buffer = StreamToBuffer<uint64_t>(expected_bits);
  EXPECT_EQ(std::vector<uint64_t>({
                StreamToBits(expected_bits.substr(0, 64)),
                StreamToBits(expected_bits.substr(64, 64)),
                StreamToBits(expected_bits.substr(128, 64)),
            }),
            buffer);
  const std::string result_bits = BufferToStream(buffer);
  EXPECT_EQ(expected_bits, result_bits);
}

TEST(PadToWord, Test) {
  EXPECT_EQ("10100000", PadToWord<8>("101"));
  EXPECT_EQ(
      "10100000"
      "00000000",
      PadToWord<16>("101"));
  EXPECT_EQ(
      "10100000"
      "00000000"
      "00000000"
      "00000000",
      PadToWord<32>("101"));
  EXPECT_EQ(
      "10100000"
      "00000000"
      "00000000"
      "00000000"
      "00000000"
      "00000000"
      "00000000"
      "00000000",
      PadToWord<64>("101"));
}

TEST(BitWriterStringStream, Empty) {
  BitWriterStringStream writer;
  EXPECT_EQ(0u, writer.GetNumBits());
  EXPECT_EQ(0u, writer.GetDataSizeBytes());
  EXPECT_EQ("", writer.GetStreamRaw());
}

TEST(BitWriterStringStream, WriteBits) {
  BitWriterStringStream writer;
  const uint64_t bits1 = 0x1 | 0x2 | 0x10;
  writer.WriteBits(bits1, 5);
  EXPECT_EQ(5u, writer.GetNumBits());
  EXPECT_EQ(1u, writer.GetDataSizeBytes());
  EXPECT_EQ("11001", writer.GetStreamRaw());
}

TEST(BitWriterStringStream, WriteUnencodedU8) {
  BitWriterStringStream writer;
  const uint8_t bits = 127;
  writer.WriteUnencoded(bits);
  EXPECT_EQ(8u, writer.GetNumBits());
  EXPECT_EQ("11111110", writer.GetStreamRaw());
}

TEST(BitWriterStringStream, WriteUnencodedS64) {
  BitWriterStringStream writer;
  const int64_t bits = std::numeric_limits<int64_t>::min() + 7;
  writer.WriteUnencoded(bits);
  EXPECT_EQ(64u, writer.GetNumBits());
  EXPECT_EQ("1110000000000000000000000000000000000000000000000000000000000001",
            writer.GetStreamRaw());
}

TEST(BitWriterStringStream, WriteMultiple) {
  BitWriterStringStream writer;

  std::string expected_result;

  const uint64_t b2_val = 0x4 | 0x2 | 0x40;
  const std::string bits2 = BitsToStream(b2_val, 8);
  writer.WriteBits(b2_val, 8);

  const uint64_t val = 0x1 | 0x2 | 0x10;
  const std::string bits3 = BitsToStream(val, 8);
  writer.WriteBits(val, 8);

  const std::string expected = bits2 + bits3;

  EXPECT_EQ(expected.length(), writer.GetNumBits());
  EXPECT_EQ(2u, writer.GetDataSizeBytes());
  EXPECT_EQ(expected, writer.GetStreamRaw());

  EXPECT_EQ(PadToWord<8>(expected), BufferToStream(writer.GetDataCopy()));
}

TEST(BitWriterWord64, Empty) {
  BitWriterWord64 writer;
  EXPECT_EQ(0u, writer.GetNumBits());
  EXPECT_EQ(0u, writer.GetDataSizeBytes());
}

TEST(BitWriterWord64, WriteBits) {
  BitWriterWord64 writer;
  const uint64_t bits1 = 0x1 | 0x2 | 0x10;
  writer.WriteBits(bits1, 5);
  writer.WriteBits(bits1, 5);
  writer.WriteBits(bits1, 5);
  EXPECT_EQ(15u, writer.GetNumBits());
  EXPECT_EQ(2u, writer.GetDataSizeBytes());
}

TEST(BitWriterWord64, WriteZeroBits) {
  BitWriterWord64 writer;
  writer.WriteBits(0, 0);
  writer.WriteBits(1, 0);
  EXPECT_EQ(0u, writer.GetNumBits());
  writer.WriteBits(1, 1);
  writer.WriteBits(0, 0);
  writer.WriteBits(0, 63);
  EXPECT_EQ(64u, writer.GetNumBits());
  writer.WriteBits(0, 0);
  writer.WriteBits(7, 3);
  writer.WriteBits(0, 0);
}

TEST(BitWriterWord64, ComparisonTestWriteLotsOfBits) {
  BitWriterStringStream writer1;
  BitWriterWord64 writer2(16384);

  for (uint64_t i = 0; i < 65000; i += 25) {
    writer1.WriteBits(i, 16);
    writer2.WriteBits(i, 16);
    ASSERT_EQ(writer1.GetNumBits(), writer2.GetNumBits());
  }
}

TEST(GetLowerBits, Test) {
  EXPECT_EQ(0u, GetLowerBits<uint8_t>(255, 0));
  EXPECT_EQ(1u, GetLowerBits<uint8_t>(255, 1));
  EXPECT_EQ(3u, GetLowerBits<uint8_t>(255, 2));
  EXPECT_EQ(7u, GetLowerBits<uint8_t>(255, 3));
  EXPECT_EQ(15u, GetLowerBits<uint8_t>(255, 4));
  EXPECT_EQ(31u, GetLowerBits<uint8_t>(255, 5));
  EXPECT_EQ(63u, GetLowerBits<uint8_t>(255, 6));
  EXPECT_EQ(127u, GetLowerBits<uint8_t>(255, 7));
  EXPECT_EQ(255u, GetLowerBits<uint8_t>(255, 8));
  EXPECT_EQ(0xFFu, GetLowerBits<uint32_t>(0xFFFFFFFF, 8));
  EXPECT_EQ(0xFFFFu, GetLowerBits<uint32_t>(0xFFFFFFFF, 16));
  EXPECT_EQ(0xFFFFFFu, GetLowerBits<uint32_t>(0xFFFFFFFF, 24));
  EXPECT_EQ(0xFFFFFFu, GetLowerBits<uint64_t>(0xFFFFFFFFFFFF, 24));
  EXPECT_EQ(0xFFFFFFFFFFFFFFFFu,
            GetLowerBits<uint64_t>(0xFFFFFFFFFFFFFFFFu, 64));
  EXPECT_EQ(StreamToBits("1010001110"),
            GetLowerBits<uint64_t>(StreamToBits("1010001110111101111111"), 10));
}

TEST(BitReaderFromString, FromU8) {
  std::vector<uint8_t> buffer = {
      0xAA,
      0xBB,
      0xCC,
      0xDD,
  };

  const std::string total_stream =
      "01010101"
      "11011101"
      "00110011"
      "10111011";

  BitReaderFromString reader(buffer);

  uint64_t bits = 0;
  EXPECT_EQ(2u, reader.ReadBits(&bits, 2));
  EXPECT_EQ(PadToWord<64>("01"), BitsToStream(bits));
  EXPECT_EQ(20u, reader.ReadBits(&bits, 20));
  EXPECT_EQ(PadToWord<64>("01010111011101001100"), BitsToStream(bits));
  EXPECT_EQ(20u, reader.ReadBits(&bits, 20));
  EXPECT_EQ(PadToWord<64>("11101110110000000000"), BitsToStream(bits));
  EXPECT_EQ(22u, reader.ReadBits(&bits, 30));
  EXPECT_EQ(PadToWord<64>("0000000000000000000000"), BitsToStream(bits));
  EXPECT_TRUE(reader.ReachedEnd());
}

TEST(BitReaderFromString, FromU64) {
  std::vector<uint64_t> buffer = {
      0xAAAAAAAAAAAAAAAA,
      0xBBBBBBBBBBBBBBBB,
      0xCCCCCCCCCCCCCCCC,
      0xDDDDDDDDDDDDDDDD,
  };

  const std::string total_stream =
      "0101010101010101010101010101010101010101010101010101010101010101"
      "1101110111011101110111011101110111011101110111011101110111011101"
      "0011001100110011001100110011001100110011001100110011001100110011"
      "1011101110111011101110111011101110111011101110111011101110111011";

  BitReaderFromString reader(buffer);

  uint64_t bits = 0;
  size_t pos = 0;
  size_t to_read = 5;
  while (reader.ReadBits(&bits, to_read) > 0) {
    EXPECT_EQ(BitsToStream(bits),
              PadToWord<64>(total_stream.substr(pos, to_read)));
    pos += to_read;
    to_read = (to_read + 35) % 64 + 1;
  }
  EXPECT_TRUE(reader.ReachedEnd());
}

TEST(BitReaderWord64, ReadBitsSingleByte) {
  BitReaderWord64 reader(std::vector<uint8_t>({uint8_t(0xF0)}));
  EXPECT_FALSE(reader.ReachedEnd());

  uint64_t bits = 0;
  EXPECT_EQ(1u, reader.ReadBits(&bits, 1));
  EXPECT_EQ(0u, bits);
  EXPECT_EQ(2u, reader.ReadBits(&bits, 2));
  EXPECT_EQ(0u, bits);
  EXPECT_EQ(2u, reader.ReadBits(&bits, 2));
  EXPECT_EQ(2u, bits);
  EXPECT_EQ(2u, reader.ReadBits(&bits, 2));
  EXPECT_EQ(3u, bits);
  EXPECT_FALSE(reader.OnlyZeroesLeft());
  EXPECT_FALSE(reader.ReachedEnd());
  EXPECT_EQ(2u, reader.ReadBits(&bits, 2));
  EXPECT_EQ(1u, bits);
  EXPECT_TRUE(reader.OnlyZeroesLeft());
  EXPECT_FALSE(reader.ReachedEnd());
  EXPECT_EQ(55u, reader.ReadBits(&bits, 64));
  EXPECT_EQ(0u, bits);
  EXPECT_TRUE(reader.ReachedEnd());
}

TEST(BitReaderWord64, ReadBitsTwoWords) {
  std::vector<uint64_t> buffer = {0x0000000000000001, 0x0000000000FFFFFF};

  BitReaderWord64 reader(std::move(buffer));

  uint64_t bits = 0;
  EXPECT_EQ(1u, reader.ReadBits(&bits, 1));
  EXPECT_EQ(1u, bits);
  EXPECT_EQ(62u, reader.ReadBits(&bits, 62));
  EXPECT_EQ(0u, bits);
  EXPECT_EQ(2u, reader.ReadBits(&bits, 2));
  EXPECT_EQ(2u, bits);
  EXPECT_EQ(3u, reader.ReadBits(&bits, 3));
  EXPECT_EQ(7u, bits);
  EXPECT_FALSE(reader.OnlyZeroesLeft());
  EXPECT_EQ(32u, reader.ReadBits(&bits, 32));
  EXPECT_EQ(0xFFFFFu, bits);
  EXPECT_TRUE(reader.OnlyZeroesLeft());
  EXPECT_FALSE(reader.ReachedEnd());
  EXPECT_EQ(28u, reader.ReadBits(&bits, 32));
  EXPECT_EQ(0u, bits);
  EXPECT_TRUE(reader.ReachedEnd());
}

TEST(BitReaderFromString, ReadUnencodedU8) {
  BitReaderFromString reader("11111110");
  uint8_t val = 0;
  ASSERT_TRUE(reader.ReadUnencoded(&val));
  EXPECT_EQ(8u, reader.GetNumReadBits());
  EXPECT_EQ(127, val);
}

TEST(BitReaderFromString, ReadUnencodedU16Fail) {
  BitReaderFromString reader("11111110");
  uint16_t val = 0;
  ASSERT_FALSE(reader.ReadUnencoded(&val));
}

TEST(BitReaderFromString, ReadUnencodedS64) {
  BitReaderFromString reader(
      "1110000000000000000000000000000000000000000000000000000000000001");
  int64_t val = 0;
  ASSERT_TRUE(reader.ReadUnencoded(&val));
  EXPECT_EQ(64u, reader.GetNumReadBits());
  EXPECT_EQ(std::numeric_limits<int64_t>::min() + 7, val);
}

TEST(BitReaderWord64, FromU8) {
  std::vector<uint8_t> buffer = {
      0xAA,
      0xBB,
      0xCC,
      0xDD,
  };

  BitReaderWord64 reader(std::move(buffer));

  uint64_t bits = 0;
  EXPECT_EQ(2u, reader.ReadBits(&bits, 2));
  EXPECT_EQ(PadToWord<64>("01"), BitsToStream(bits));
  EXPECT_EQ(20u, reader.ReadBits(&bits, 20));
  EXPECT_EQ(PadToWord<64>("01010111011101001100"), BitsToStream(bits));
  EXPECT_EQ(20u, reader.ReadBits(&bits, 20));
  EXPECT_EQ(PadToWord<64>("11101110110000000000"), BitsToStream(bits));
  EXPECT_EQ(22u, reader.ReadBits(&bits, 30));
  EXPECT_EQ(PadToWord<64>("0000000000000000000000"), BitsToStream(bits));
  EXPECT_TRUE(reader.ReachedEnd());
}

TEST(BitReaderWord64, FromU64) {
  std::vector<uint64_t> buffer = {
      0xAAAAAAAAAAAAAAAA,
      0xBBBBBBBBBBBBBBBB,
      0xCCCCCCCCCCCCCCCC,
      0xDDDDDDDDDDDDDDDD,
  };

  const std::string total_stream =
      "0101010101010101010101010101010101010101010101010101010101010101"
      "1101110111011101110111011101110111011101110111011101110111011101"
      "0011001100110011001100110011001100110011001100110011001100110011"
      "1011101110111011101110111011101110111011101110111011101110111011";

  BitReaderWord64 reader(std::move(buffer));

  uint64_t bits = 0;
  size_t pos = 0;
  size_t to_read = 5;
  while (reader.ReadBits(&bits, to_read) > 0) {
    EXPECT_EQ(BitsToStream(bits),
              PadToWord<64>(total_stream.substr(pos, to_read)));
    pos += to_read;
    to_read = (to_read + 35) % 64 + 1;
  }
  EXPECT_TRUE(reader.ReachedEnd());
}

TEST(BitReaderWord64, ComparisonLotsOfU8) {
  std::vector<uint8_t> buffer;
  for (uint32_t i = 0; i < 10003; ++i) {
    buffer.push_back(static_cast<uint8_t>(i % 255));
  }

  BitReaderFromString reader1(buffer);
  BitReaderWord64 reader2(std::move(buffer));

  uint64_t bits1 = 0, bits2 = 0;
  size_t to_read = 5;
  while (reader1.ReadBits(&bits1, to_read) > 0) {
    reader2.ReadBits(&bits2, to_read);
    EXPECT_EQ(bits1, bits2);
    to_read = (to_read + 35) % 64 + 1;
  }

  EXPECT_EQ(0u, reader2.ReadBits(&bits2, 1));
}

TEST(BitReaderWord64, ComparisonLotsOfU64) {
  std::vector<uint64_t> buffer;
  for (uint64_t i = 0; i < 1000; ++i) {
    buffer.push_back(i);
  }

  BitReaderFromString reader1(buffer);
  BitReaderWord64 reader2(std::move(buffer));

  uint64_t bits1 = 0, bits2 = 0;
  size_t to_read = 5;
  while (reader1.ReadBits(&bits1, to_read) > 0) {
    reader2.ReadBits(&bits2, to_read);
    EXPECT_EQ(bits1, bits2);
    to_read = (to_read + 35) % 64 + 1;
  }

  EXPECT_EQ(0u, reader2.ReadBits(&bits2, 1));
}

TEST(ReadWriteWord64, ReadWriteLotsOfBits) {
  BitWriterWord64 writer(16384);
  for (uint64_t i = 0; i < 65000; i += 25) {
    const uint64_t num_bits = i % 64 + 1;
    const uint64_t bits = i >> (64 - num_bits);
    writer.WriteBits(bits, size_t(num_bits));
  }

  BitReaderWord64 reader(writer.GetDataCopy());
  for (uint64_t i = 0; i < 65000; i += 25) {
    const uint64_t num_bits = i % 64 + 1;
    const uint64_t expected_bits = i >> (64 - num_bits);
    uint64_t bits = 0;
    reader.ReadBits(&bits, size_t(num_bits));
    EXPECT_EQ(expected_bits, bits);
  }

  EXPECT_TRUE(reader.OnlyZeroesLeft());
}

TEST(VariableWidthWrite, Write0U) {
  BitWriterStringStream writer;
  writer.WriteVariableWidthU64(0, 2);
  EXPECT_EQ("000", writer.GetStreamRaw());
  writer.WriteVariableWidthU32(0, 2);
  EXPECT_EQ(
      "000"
      "000",
      writer.GetStreamRaw());
  writer.WriteVariableWidthU16(0, 2);
  EXPECT_EQ(
      "000"
      "000"
      "000",
      writer.GetStreamRaw());
}

TEST(VariableWidthWrite, WriteSmallUnsigned) {
  BitWriterStringStream writer;
  writer.WriteVariableWidthU64(1, 2);
  EXPECT_EQ("100", writer.GetStreamRaw());
  writer.WriteVariableWidthU32(2, 2);
  EXPECT_EQ(
      "100"
      "010",
      writer.GetStreamRaw());
  writer.WriteVariableWidthU16(3, 2);
  EXPECT_EQ(
      "100"
      "010"
      "110",
      writer.GetStreamRaw());
}

TEST(VariableWidthWrite, WriteSmallSigned) {
  BitWriterStringStream writer;
  writer.WriteVariableWidthS64(1, 2, 0);
  EXPECT_EQ("010", writer.GetStreamRaw());
  writer.WriteVariableWidthS64(-1, 2, 0);
  EXPECT_EQ(
      "010"
      "100",
      writer.GetStreamRaw());
}

TEST(VariableWidthWrite, U64Val127ChunkLength7) {
  BitWriterStringStream writer;
  writer.WriteVariableWidthU64(127, 7);
  EXPECT_EQ(
      "1111111"
      "0",
      writer.GetStreamRaw());
}

TEST(VariableWidthWrite, U32Val255ChunkLength7) {
  BitWriterStringStream writer;
  writer.WriteVariableWidthU32(255, 7);
  EXPECT_EQ(
      "1111111"
      "1"
      "1000000"
      "0",
      writer.GetStreamRaw());
}

TEST(VariableWidthWrite, U16Val2ChunkLength4) {
  BitWriterStringStream writer;
  writer.WriteVariableWidthU16(2, 4);
  EXPECT_EQ(
      "0100"
      "0",
      writer.GetStreamRaw());
}

TEST(VariableWidthWrite, U64ValAAAAChunkLength2) {
  BitWriterStringStream writer;
  writer.WriteVariableWidthU64(0xAAAA, 2);
  EXPECT_EQ(
      "01"
      "1"
      "01"
      "1"
      "01"
      "1"
      "01"
      "1"
      "01"
      "1"
      "01"
      "1"
      "01"
      "1"
      "01"
      "0",
      writer.GetStreamRaw());
}

TEST(VariableWidthRead, U64Val127ChunkLength7) {
  BitReaderFromString reader(
      "1111111"
      "0");
  uint64_t val = 0;
  ASSERT_TRUE(reader.ReadVariableWidthU64(&val, 7));
  EXPECT_EQ(127u, val);
}

TEST(VariableWidthRead, U32Val255ChunkLength7) {
  BitReaderFromString reader(
      "1111111"
      "1"
      "1000000"
      "0");
  uint32_t val = 0;
  ASSERT_TRUE(reader.ReadVariableWidthU32(&val, 7));
  EXPECT_EQ(255u, val);
}

TEST(VariableWidthRead, U16Val2ChunkLength4) {
  BitReaderFromString reader(
      "0100"
      "0");
  uint16_t val = 0;
  ASSERT_TRUE(reader.ReadVariableWidthU16(&val, 4));
  EXPECT_EQ(2u, val);
}

TEST(VariableWidthRead, U64ValAAAAChunkLength2) {
  BitReaderFromString reader(
      "01"
      "1"
      "01"
      "1"
      "01"
      "1"
      "01"
      "1"
      "01"
      "1"
      "01"
      "1"
      "01"
      "1"
      "01"
      "0");
  uint64_t val = 0;
  ASSERT_TRUE(reader.ReadVariableWidthU64(&val, 2));
  EXPECT_EQ(0xAAAAu, val);
}

TEST(VariableWidthRead, FailTooShort) {
  BitReaderFromString reader("00000001100000");
  uint64_t val = 0;
  ASSERT_FALSE(reader.ReadVariableWidthU64(&val, 7));
}

TEST(VariableWidthWriteRead, SingleWriteReadU64) {
  for (uint64_t i = 0; i < 1000000; i += 1234) {
    const uint64_t val = i * i * i;
    const size_t chunk_length = size_t(i % 16 + 1);

    BitWriterWord64 writer;
    writer.WriteVariableWidthU64(val, chunk_length);

    BitReaderWord64 reader(writer.GetDataCopy());
    uint64_t read_val = 0;
    ASSERT_TRUE(reader.ReadVariableWidthU64(&read_val, chunk_length));

    ASSERT_EQ(val, read_val) << "Chunk length " << chunk_length;
  }
}

TEST(VariableWidthWriteRead, SingleWriteReadS64) {
  for (int64_t i = 0; i < 1000000; i += 4321) {
    const int64_t val = i * i * (i % 2 ? -i : i);
    const size_t chunk_length = size_t(i % 16 + 1);
    const size_t zigzag_exponent = size_t(i % 13);

    BitWriterWord64 writer;
    writer.WriteVariableWidthS64(val, chunk_length, zigzag_exponent);

    BitReaderWord64 reader(writer.GetDataCopy());
    int64_t read_val = 0;
    ASSERT_TRUE(
        reader.ReadVariableWidthS64(&read_val, chunk_length, zigzag_exponent));

    ASSERT_EQ(val, read_val) << "Chunk length " << chunk_length;
  }
}

TEST(VariableWidthWriteRead, SingleWriteReadU32) {
  for (uint32_t i = 0; i < 100000; i += 123) {
    const uint32_t val = i * i;
    const size_t chunk_length = i % 16 + 1;

    BitWriterWord64 writer;
    writer.WriteVariableWidthU32(val, chunk_length);

    BitReaderWord64 reader(writer.GetDataCopy());
    uint32_t read_val = 0;
    ASSERT_TRUE(reader.ReadVariableWidthU32(&read_val, chunk_length));

    ASSERT_EQ(val, read_val) << "Chunk length " << chunk_length;
  }
}

TEST(VariableWidthWriteRead, SingleWriteReadU16) {
  for (int i = 0; i < 65536; i += 123) {
    const uint16_t val = static_cast<int16_t>(i);
    const size_t chunk_length = val % 10 + 1;

    BitWriterWord64 writer;
    writer.WriteVariableWidthU16(val, chunk_length);

    BitReaderWord64 reader(writer.GetDataCopy());
    uint16_t read_val = 0;
    ASSERT_TRUE(reader.ReadVariableWidthU16(&read_val, chunk_length));

    ASSERT_EQ(val, read_val) << "Chunk length " << chunk_length;
  }
}

TEST(VariableWidthWriteRead, SmallNumbersChunkLength4) {
  const std::vector<uint64_t> expected_values = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};

  BitWriterWord64 writer;
  for (uint64_t val : expected_values) {
    writer.WriteVariableWidthU64(val, 4);
  }

  EXPECT_EQ(50u, writer.GetNumBits());

  std::vector<uint64_t> actual_values;
  BitReaderWord64 reader(writer.GetDataCopy());
  while (!reader.OnlyZeroesLeft()) {
    uint64_t val = 0;
    ASSERT_TRUE(reader.ReadVariableWidthU64(&val, 4));
    actual_values.push_back(val);
  }

  EXPECT_EQ(expected_values, actual_values);
}

TEST(VariableWidthWriteRead, VariedNumbersChunkLength8) {
  const std::vector<uint64_t> expected_values = {1000, 0, 255, 4294967296};
  const size_t kExpectedNumBits = 9 * (2 + 1 + 1 + 5);

  BitWriterWord64 writer;
  for (uint64_t val : expected_values) {
    writer.WriteVariableWidthU64(val, 8);
  }

  EXPECT_EQ(kExpectedNumBits, writer.GetNumBits());

  std::vector<uint64_t> actual_values;
  BitReaderWord64 reader(writer.GetDataCopy());
  while (!reader.OnlyZeroesLeft()) {
    uint64_t val = 0;
    ASSERT_TRUE(reader.ReadVariableWidthU64(&val, 8));
    actual_values.push_back(val);
  }

  EXPECT_EQ(expected_values, actual_values);
}

}  // namespace
}  // namespace comp
}  // namespace spvtools