bit_stream.cpp

// 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 <sstream>
#include <string>
#include <vector>

#include "gmock/gmock.h"
#include "util/bit_stream.h"

namespace {

using spvutils::BitReaderInterface;
using spvutils::BitReaderWord64;
using spvutils::BitsetToStream;
using spvutils::BitsToStream;
using spvutils::BitWriterInterface;
using spvutils::BitWriterWord64;
using spvutils::BufferToStream;
using spvutils::DecodeZigZag;
using spvutils::EncodeZigZag;
using spvutils::GetLowerBits;
using spvutils::Log2U64;
using spvutils::NumBitsToNumWords;
using spvutils::PadToWord;
using spvutils::StreamToBits;
using spvutils::StreamToBitset;
using spvutils::StreamToBuffer;

// A simple and inefficient implementatition of BitWriterInterface,
// using std::stringstream. Intended for tests only.
class BitWriterStringStream : public BitWriterInterface {
 public:
  void WriteStream(const std::string& bits) override { ss_ << bits; }

  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(); }

  const std::string& GetStreamPadded64() const { return str_; }

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

TEST(Log2U16, Test) {
  EXPECT_EQ(0u, Log2U64(0));
  EXPECT_EQ(0u, Log2U64(1));
  EXPECT_EQ(1u, Log2U64(2));
  EXPECT_EQ(1u, Log2U64(3));
  EXPECT_EQ(2u, Log2U64(4));
  EXPECT_EQ(2u, Log2U64(5));
  EXPECT_EQ(2u, Log2U64(6));
  EXPECT_EQ(2u, Log2U64(7));
  EXPECT_EQ(3u, Log2U64(8));
  EXPECT_EQ(3u, Log2U64(9));
  EXPECT_EQ(3u, Log2U64(10));
  EXPECT_EQ(3u, Log2U64(11));
  EXPECT_EQ(3u, Log2U64(12));
  EXPECT_EQ(3u, Log2U64(13));
  EXPECT_EQ(3u, Log2U64(14));
  EXPECT_EQ(3u, Log2U64(15));
  EXPECT_EQ(4u, Log2U64(16));
  EXPECT_EQ(4u, Log2U64(17));
  EXPECT_EQ(5u, Log2U64(35));
  EXPECT_EQ(6u, Log2U64(72));
  EXPECT_EQ(7u, Log2U64(255));
  EXPECT_EQ(8u, Log2U64(256));
  EXPECT_EQ(15u, Log2U64(65535));
  EXPECT_EQ(16u, Log2U64(65536));
  EXPECT_EQ(19u, Log2U64(0xFFFFF));
  EXPECT_EQ(23u, Log2U64(0xFFFFFF));
  EXPECT_EQ(27u, Log2U64(0xFFFFFFF));
  EXPECT_EQ(31u, Log2U64(0xFFFFFFFF));
  EXPECT_EQ(35u, Log2U64(0xFFFFFFFFF));
  EXPECT_EQ(39u, Log2U64(0xFFFFFFFFFF));
  EXPECT_EQ(43u, Log2U64(0xFFFFFFFFFFF));
  EXPECT_EQ(47u, Log2U64(0xFFFFFFFFFFFF));
  EXPECT_EQ(51u, Log2U64(0xFFFFFFFFFFFFF));
  EXPECT_EQ(55u, Log2U64(0xFFFFFFFFFFFFFF));
  EXPECT_EQ(59u, Log2U64(0xFFFFFFFFFFFFFFF));
  EXPECT_EQ(63u, Log2U64(0xFFFFFFFFFFFFFFFF));
}

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

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

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, Decode0SameAsNormalZigZag) {
  for (int32_t i = -10000; i < 10000; i += 123) {
    ASSERT_EQ(DecodeZigZag(i), DecodeZigZag(i, 0));
  }
}

TEST(ZigZagCoding, Encode0SameAsNormalZigZag) {
  for (uint32_t i = 0; i < 10000; i += 123) {
    ASSERT_EQ(EncodeZigZag(i), EncodeZigZag(i, 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, WriteStream) {
  BitWriterStringStream writer;
  const std::string bits1 = "1011111111111111111";
  writer.WriteStream(bits1);
  EXPECT_EQ(19u, writer.GetNumBits());
  EXPECT_EQ(3u, writer.GetDataSizeBytes());
  EXPECT_EQ(bits1, writer.GetStreamRaw());

  const std::string bits2 = "10100001010101010000111111111111111111111111111";
  writer.WriteStream(bits2);
  EXPECT_EQ(66u, writer.GetNumBits());
  EXPECT_EQ(9u, writer.GetDataSizeBytes());
  EXPECT_EQ(bits1 + bits2, writer.GetStreamRaw());
}

TEST(BitWriterStringStream, WriteBitSet) {
  BitWriterStringStream writer;
  const std::string bits1 = "10101";
  writer.WriteBitset(StreamToBitset<16>(bits1));
  EXPECT_EQ(16u, writer.GetNumBits());
  EXPECT_EQ(2u, writer.GetDataSizeBytes());
  EXPECT_EQ(PadToWord<16>(bits1), 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 std::string bits1 = "101001111111001100010000001110001111111100";
  writer.WriteStream(bits1);

  const std::string bits2 = "10100011000010010101";
  writer.WriteBitset(StreamToBitset<20>(bits2));

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

  const std::string expected = bits1 + bits2 + bits3;

  EXPECT_EQ(expected.length(), writer.GetNumBits());
  EXPECT_EQ(9u, 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());
  EXPECT_EQ("", writer.GetStreamPadded64());
}

TEST(BitWriterWord64, WriteStream) {
  BitWriterWord64 writer;
  std::string expected;

  {
    const std::string bits = "101";
    expected += bits;
    writer.WriteStream(bits);
    EXPECT_EQ(expected.length(), writer.GetNumBits());
    EXPECT_EQ(1u, writer.GetDataSizeBytes());
    EXPECT_EQ(PadToWord<64>(expected), writer.GetStreamPadded64());
  }

  {
    const std::string bits = "10000111111111110000000";
    expected += bits;
    writer.WriteStream(bits);
    EXPECT_EQ(expected.length(), writer.GetNumBits());
    EXPECT_EQ(PadToWord<64>(expected), writer.GetStreamPadded64());
  }

  {
    const std::string bits = "101001111111111100000111111111111100";
    expected += bits;
    writer.WriteStream(bits);
    EXPECT_EQ(expected.length(), writer.GetNumBits());
    EXPECT_EQ(PadToWord<64>(expected), writer.GetStreamPadded64());
  }
}

TEST(BitWriterWord64, WriteBitset) {
  BitWriterWord64 writer;
  const std::string bits1 = "10101";
  writer.WriteBitset(StreamToBitset<16>(bits1), 12);
  EXPECT_EQ(12u, writer.GetNumBits());
  EXPECT_EQ(2u, writer.GetDataSizeBytes());
  EXPECT_EQ(PadToWord<64>(bits1), writer.GetStreamPadded64());
}

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());
  EXPECT_EQ(PadToWord<64>("110011100111001"), writer.GetStreamPadded64());
}

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);
  EXPECT_EQ(PadToWord<64>("1"), writer.GetStreamPadded64());
  writer.WriteBits(0, 63);
  EXPECT_EQ(64u, writer.GetNumBits());
  writer.WriteBits(0, 0);
  writer.WriteBits(7, 3);
  writer.WriteBits(0, 0);
  EXPECT_EQ(
      PadToWord<64>(
          "1"
          "000000000000000000000000000000000000000000000000000000000000000"
          "111"),
      writer.GetStreamPadded64());
}

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());
  }

  EXPECT_EQ(PadToWord<64>(writer1.GetStreamRaw()), writer2.GetStreamPadded64());
}

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

  for (int i = 0; i < 1000; ++i) {
    std::string bits = "1111100000";
    if (i % 2) bits += "101010";
    if (i % 3) bits += "1110100";
    if (i % 5) bits += "1110100111111111111";
    writer1.WriteStream(bits);
    writer2.WriteStream(bits);
    ASSERT_EQ(writer1.GetNumBits(), writer2.GetNumBits());
  }

  EXPECT_EQ(PadToWord<64>(writer1.GetStreamRaw()), writer2.GetStreamPadded64());
}

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

  for (uint64_t i = 0; i < 65000; i += 25) {
    std::bitset<16> bits1(i);
    std::bitset<24> bits2(i);
    writer1.WriteBitset(bits1);
    writer1.WriteBitset(bits2);
    writer2.WriteBitset(bits1);
    writer2.WriteBitset(bits2);
    ASSERT_EQ(writer1.GetNumBits(), writer2.GetNumBits());
  }

  EXPECT_EQ(PadToWord<64>(writer1.GetStreamRaw()), writer2.GetStreamPadded64());
}

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);
  EXPECT_EQ(PadToWord<64>(total_stream), reader.GetStreamPadded64());

  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);
  EXPECT_EQ(total_stream, reader.GetStreamPadded64());

  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, ReadBitsetSingleByte) {
  BitReaderWord64 reader(std::vector<uint8_t>({uint8_t(0xCC)}));
  std::bitset<4> bits;
  EXPECT_EQ(2u, reader.ReadBitset(&bits, 2));
  EXPECT_EQ(0u, bits.to_ullong());
  EXPECT_EQ(2u, reader.ReadBitset(&bits, 2));
  EXPECT_EQ(3u, bits.to_ullong());
  EXPECT_FALSE(reader.OnlyZeroesLeft());
  EXPECT_EQ(4u, reader.ReadBitset(&bits, 4));
  EXPECT_EQ(12u, bits.to_ullong());
  EXPECT_TRUE(reader.OnlyZeroesLeft());
}

TEST(BitReaderWord64, ReadStreamSingleByte) {
  BitReaderWord64 reader(std::vector<uint8_t>({uint8_t(0xAA)}));
  EXPECT_EQ("", reader.ReadStream(0));
  EXPECT_EQ("0", reader.ReadStream(1));
  EXPECT_EQ("101", reader.ReadStream(3));
  EXPECT_EQ("01010000", reader.ReadStream(8));
  EXPECT_TRUE(reader.OnlyZeroesLeft());
  EXPECT_EQ("0000000000000000000000000000000000000000000000000000",
            reader.ReadStream(64));
  EXPECT_TRUE(reader.ReachedEnd());
}

TEST(BitReaderWord64, ReadStreamEmpty) {
  std::vector<uint64_t> buffer;
  BitReaderWord64 reader(std::move(buffer));
  EXPECT_TRUE(reader.OnlyZeroesLeft());
  EXPECT_TRUE(reader.ReachedEnd());
  EXPECT_EQ("", reader.ReadStream(10));
  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());
  writer.WriteVariableWidthU8(0, 2);
  EXPECT_EQ(
      "000"
      "000"
      "000"
      "000",
      writer.GetStreamRaw());
}

TEST(VariableWidthWrite, Write0S) {
  BitWriterStringStream writer;
  writer.WriteVariableWidthS64(0, 2, 0);
  EXPECT_EQ("000", writer.GetStreamRaw());
  writer.WriteVariableWidthS32(0, 2, 0);
  EXPECT_EQ(
      "000"
      "000",
      writer.GetStreamRaw());
  writer.WriteVariableWidthS16(0, 2, 0);
  EXPECT_EQ(
      "000"
      "000"
      "000",
      writer.GetStreamRaw());
  writer.WriteVariableWidthS8(0, 2, 0);
  EXPECT_EQ(
      "000"
      "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());
  writer.WriteVariableWidthU8(4, 2);
  EXPECT_EQ(
      "100"
      "010"
      "110"
      "001100",
      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());
  writer.WriteVariableWidthS16(3, 2, 0);
  EXPECT_EQ(
      "010"
      "100"
      "011100",
      writer.GetStreamRaw());
  writer.WriteVariableWidthS8(-4, 2, 0);
  EXPECT_EQ(
      "010"
      "100"
      "011100"
      "111100",
      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, U8Val128ChunkLength7) {
  BitWriterStringStream writer;
  writer.WriteVariableWidthU8(128, 7);
  EXPECT_EQ(
      "0000000"
      "1"
      "1",
      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(VariableWidthWrite, S8ValM128ChunkLength7) {
  BitWriterStringStream writer;
  writer.WriteVariableWidthS8(-128, 7, 0);
  EXPECT_EQ(
      "1111111"
      "1"
      "1",
      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, U8Val128ChunkLength7) {
  BitReaderFromString reader(
      "0000000"
      "1"
      "1");
  uint8_t val = 0;
  ASSERT_TRUE(reader.ReadVariableWidthU8(&val, 7));
  EXPECT_EQ(128u, 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, S8ValM128ChunkLength7) {
  BitReaderFromString reader(
      "1111111"
      "1"
      "1");
  int8_t val = 0;
  ASSERT_TRUE(reader.ReadVariableWidthS8(&val, 7, 0));
  EXPECT_EQ(-128, 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, SingleWriteReadS32) {
  for (int32_t i = 0; i < 100000; i += 123) {
    const int32_t val = i * (i % 2 ? -i : i);
    const size_t chunk_length = i % 16 + 1;
    const size_t zigzag_exponent = i % 11;

    BitWriterWord64 writer;
    writer.WriteVariableWidthS32(val, chunk_length, zigzag_exponent);

    BitReaderWord64 reader(writer.GetDataCopy());
    int32_t read_val = 0;
    ASSERT_TRUE(
        reader.ReadVariableWidthS32(&read_val, chunk_length, zigzag_exponent));

    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, SingleWriteReadS16) {
  for (int i = -32768; i < 32768; i += 123) {
    const int16_t val = static_cast<int16_t>(i);
    const size_t chunk_length = std::abs(i) % 10 + 1;
    const size_t zigzag_exponent = std::abs(i) % 7;

    BitWriterWord64 writer;
    writer.WriteVariableWidthS16(val, chunk_length, zigzag_exponent);

    BitReaderWord64 reader(writer.GetDataCopy());
    int16_t read_val = 0;
    ASSERT_TRUE(
        reader.ReadVariableWidthS16(&read_val, chunk_length, zigzag_exponent));

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

TEST(VariableWidthWriteRead, SingleWriteReadU8) {
  for (int i = 0; i < 256; ++i) {
    const uint8_t val = static_cast<uint8_t>(i);
    const size_t chunk_length = val % 5 + 1;

    BitWriterWord64 writer;
    writer.WriteVariableWidthU8(val, chunk_length);

    BitReaderWord64 reader(writer.GetDataCopy());
    uint8_t read_val = 0;
    ASSERT_TRUE(reader.ReadVariableWidthU8(&read_val, chunk_length));

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

TEST(VariableWidthWriteRead, SingleWriteReadS8) {
  for (int i = -128; i < 128; ++i) {
    const int8_t val = static_cast<int8_t>(i);
    const size_t chunk_length = std::abs(i) % 5 + 1;
    const size_t zigzag_exponent = std::abs(i) % 3;

    BitWriterWord64 writer;
    writer.WriteVariableWidthS8(val, chunk_length, zigzag_exponent);

    BitReaderWord64 reader(writer.GetDataCopy());
    int8_t read_val = 0;
    ASSERT_TRUE(
        reader.ReadVariableWidthS8(&read_val, chunk_length, zigzag_exponent));

    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);
}

TEST(FixedWidthWrite, Val0Max3) {
  BitWriterStringStream writer;
  writer.WriteFixedWidth(0, 3);
  EXPECT_EQ("00", writer.GetStreamRaw());
}

TEST(FixedWidthWrite, Val0Max5) {
  BitWriterStringStream writer;
  writer.WriteFixedWidth(0, 5);
  EXPECT_EQ("000", writer.GetStreamRaw());
}

TEST(FixedWidthWrite, Val0Max255) {
  BitWriterStringStream writer;
  writer.WriteFixedWidth(0, 255);
  EXPECT_EQ("00000000", writer.GetStreamRaw());
}

TEST(FixedWidthWrite, Val3Max8) {
  BitWriterStringStream writer;
  writer.WriteFixedWidth(3, 8);
  EXPECT_EQ("1100", writer.GetStreamRaw());
}

TEST(FixedWidthWrite, Val15Max127) {
  BitWriterStringStream writer;
  writer.WriteFixedWidth(15, 127);
  EXPECT_EQ("1111000", writer.GetStreamRaw());
}

TEST(FixedWidthRead, Val0Max3) {
  BitReaderFromString reader("0011111");
  uint64_t val = 0;
  ASSERT_TRUE(reader.ReadFixedWidth(&val, 3));
  EXPECT_EQ(0u, val);
}

TEST(FixedWidthRead, Val0Max5) {
  BitReaderFromString reader("0001010101");
  uint64_t val = 0;
  ASSERT_TRUE(reader.ReadFixedWidth(&val, 5));
  EXPECT_EQ(0u, val);
}

TEST(FixedWidthRead, Val3Max8) {
  BitReaderFromString reader("11001010101");
  uint64_t val = 0;
  ASSERT_TRUE(reader.ReadFixedWidth(&val, 8));
  EXPECT_EQ(3u, val);
}

TEST(FixedWidthRead, Val15Max127) {
  BitReaderFromString reader("111100010101");
  uint64_t val = 0;
  ASSERT_TRUE(reader.ReadFixedWidth(&val, 127));
  EXPECT_EQ(15u, val);
}

TEST(FixedWidthRead, Fail) {
  BitReaderFromString reader("111100");
  uint64_t val = 0;
  ASSERT_FALSE(reader.ReadFixedWidth(&val, 127));
}

}  // anonymous namespace