base/big_endian_unittest.cc

// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/big_endian.h"

#include <stdint.h>

#include <limits>
#include <string_view>

#include "testing/gtest/include/gtest/gtest.h"

namespace base {

TEST(BigEndianReaderTest, ReadsValues) {
  std::array<uint8_t, 21u> data = {0,   1,   2,    3,    4,    5,    6,
                                   7,   8,   9,    0xA,  0xB,  0xC,  0xD,
                                   0xE, 0xF, 0x1A, 0x2B, 0x3C, 0x4D, 0x5E};
  uint8_t buf[2];
  uint8_t u8;
  uint16_t u16;
  uint32_t u32;
  uint64_t u64;
  std::string_view piece;

  {
    BigEndianReader reader(data);
    EXPECT_TRUE(reader.Skip(4u));
    EXPECT_EQ(reader.remaining_bytes().data(), &data[4u]);
    EXPECT_EQ(reader.remaining(), sizeof(data) - 4);
    EXPECT_TRUE(reader.ReadU8(&u8));
    EXPECT_EQ(0x4, u8);
    EXPECT_TRUE(reader.ReadU16(&u16));
    EXPECT_EQ(0x0506, u16);
    EXPECT_TRUE(reader.ReadU32(&u32));
    EXPECT_EQ(0x0708090Au, u32);
    EXPECT_TRUE(reader.ReadU64(&u64));
    EXPECT_EQ(0x0B0C0D0E0F1A2B3Cllu, u64);
    std::string_view expected(reinterpret_cast<const char*>(reader.ptr()), 2);
    EXPECT_TRUE(reader.ReadPiece(&piece, 2));
    EXPECT_EQ(2u, piece.size());
    EXPECT_EQ(expected.data(), piece.data());
  }

  // Signed integer reads.
  {
    std::array<uint8_t, 21u> sdata = {
        0,    1,    2,    3,                            //
        0x84,                                           //
        0x85, 0x06,                                     //
        0x87, 0x08, 0x09, 0x0A,                         //
        0x8B, 0x0C, 0x0D, 0x0E, 0x0F, 0x1A, 0x2B, 0x3C  //
    };
    int8_t i8;
    int16_t i16;
    int32_t i32;
    int64_t i64;

    BigEndianReader reader(sdata);
    EXPECT_TRUE(reader.Skip(4u));
    EXPECT_TRUE(reader.ReadI8(&i8));
    EXPECT_EQ(-124, i8);
    EXPECT_EQ(static_cast<int8_t>(0x84u), i8);
    EXPECT_TRUE(reader.ReadI16(&i16));
    EXPECT_EQ(-31482, i16);
    EXPECT_EQ(static_cast<int16_t>(0x8506u), i16);
    EXPECT_TRUE(reader.ReadI32(&i32));
    EXPECT_EQ(-2029516534, i32);
    EXPECT_EQ(static_cast<int32_t>(0x8708090Au), i32);
    EXPECT_TRUE(reader.ReadI64(&i64));
    EXPECT_EQ(-8427346448682964164, i64);
    EXPECT_EQ(static_cast<int64_t>(0x8B0C0D0E0F1A2B3Cllu), i64);
  }

  {
    BigEndianReader reader(data);
    // Fixed size span.
    auto s1 = reader.ReadSpan<2u>().value();
    static_assert(std::same_as<decltype(s1), base::span<const uint8_t, 2u>>);
    EXPECT_EQ(s1.data(), &data[0u]);
    EXPECT_EQ(s1.size(), 2u);

    // Dynamic size span.
    auto s2 = reader.ReadSpan(2u).value();
    static_assert(std::same_as<decltype(s2), base::span<const uint8_t>>);
    EXPECT_EQ(s2.data(), &data[2u]);
    EXPECT_EQ(s2.size(), 2u);

    buf[0] = buf[1] = uint8_t{0};

    // Fixed size span.
    EXPECT_TRUE(reader.ReadBytes(buf));
    EXPECT_EQ(buf[0], 4u);
    EXPECT_EQ(buf[1], 5u);

    // Dynamic size span.
    EXPECT_TRUE(reader.ReadBytes(span<uint8_t>(buf)));
    EXPECT_EQ(buf[0], 6u);
    EXPECT_EQ(buf[1], 7u);

    EXPECT_EQ(reader.remaining_bytes().data(), &data[8u]);
  }
}

TEST(BigEndianReaderTest, ReadsLengthPrefixedValues) {
  {
    uint8_t u8_prefixed_data[] = {8,   8,   9,    0xA,  0xB,  0xC,  0xD,
                                  0xE, 0xF, 0x1A, 0x2B, 0x3C, 0x4D, 0x5E};
    BigEndianReader reader(u8_prefixed_data, sizeof(u8_prefixed_data));

    std::string_view piece;
    ASSERT_TRUE(reader.ReadU8LengthPrefixed(&piece));
    // |reader| should skip both a u8 and the length-8 length-prefixed field.
    EXPECT_EQ(reader.ptr(), u8_prefixed_data + 9);
    EXPECT_EQ(piece.size(), 8u);
    EXPECT_EQ(reinterpret_cast<const uint8_t*>(piece.data()),
              u8_prefixed_data + 1);
  }

  {
    uint8_t u16_prefixed_data[] = {0,    8,    0xD,  0xE,  0xF,
                                   0x1A, 0x2B, 0x3C, 0x4D, 0x5E};
    BigEndianReader reader(u16_prefixed_data, sizeof(u16_prefixed_data));
    std::string_view piece;
    ASSERT_TRUE(reader.ReadU16LengthPrefixed(&piece));
    // |reader| should skip both a u16 and the length-8 length-prefixed field.
    EXPECT_EQ(reader.ptr(), u16_prefixed_data + 10);
    EXPECT_EQ(piece.size(), 8u);
    EXPECT_EQ(reinterpret_cast<const uint8_t*>(piece.data()),
              u16_prefixed_data + 2);

    // With no data left, we shouldn't be able to
    // read another u8 length prefix (or a u16 length prefix,
    // for that matter).
    EXPECT_FALSE(reader.ReadU8LengthPrefixed(&piece));
    EXPECT_FALSE(reader.ReadU16LengthPrefixed(&piece));
  }

  {
    // Make sure there's no issue reading a zero-value length prefix.
    uint8_t u16_prefixed_data[3] = {};
    BigEndianReader reader(u16_prefixed_data, sizeof(u16_prefixed_data));
    std::string_view piece;
    ASSERT_TRUE(reader.ReadU16LengthPrefixed(&piece));
    EXPECT_EQ(reader.ptr(), u16_prefixed_data + 2);
    EXPECT_EQ(reinterpret_cast<const uint8_t*>(piece.data()),
              u16_prefixed_data + 2);
    EXPECT_EQ(piece.size(), 0u);
  }
}

TEST(BigEndianReaderTest, LengthPrefixedReadsFailGracefully) {
  // We can't read 0xF (or, for that matter, 0xF8) bytes after the length
  // prefix: there isn't enough data.
  uint8_t data[] = {0xF, 8,   9,    0xA,  0xB,  0xC,  0xD,
                    0xE, 0xF, 0x1A, 0x2B, 0x3C, 0x4D, 0x5E};
  BigEndianReader reader(data, sizeof(data));
  std::string_view piece;
  EXPECT_FALSE(reader.ReadU8LengthPrefixed(&piece));
  EXPECT_EQ(data, reader.ptr());

  EXPECT_FALSE(reader.ReadU16LengthPrefixed(&piece));
  EXPECT_EQ(data, reader.ptr());
}

TEST(BigEndianReaderTest, RespectsLength) {
  uint8_t data[8];
  uint8_t buf[2];
  uint8_t u8;
  uint16_t u16;
  uint32_t u32;
  uint64_t u64;
  std::string_view piece;
  BigEndianReader reader(data, sizeof(data));
  // 8 left
  EXPECT_FALSE(reader.Skip(9));
  EXPECT_TRUE(reader.Skip(1));
  // 7 left
  EXPECT_FALSE(reader.ReadU64(&u64));
  EXPECT_TRUE(reader.Skip(4));
  // 3 left
  EXPECT_FALSE(reader.ReadU32(&u32));
  EXPECT_FALSE(reader.ReadPiece(&piece, 4));
  EXPECT_TRUE(reader.Skip(2));
  // 1 left
  EXPECT_FALSE(reader.ReadU16(&u16));
  EXPECT_FALSE(reader.ReadBytes(span<uint8_t>(buf)));
  EXPECT_FALSE(reader.ReadBytes(span<uint8_t, 2u>(buf)));
  EXPECT_TRUE(reader.Skip(1));
  // 0 left
  EXPECT_FALSE(reader.ReadU8(&u8));
  EXPECT_EQ(0u, reader.remaining());
}

TEST(BigEndianReaderTest, SafePointerMath) {
  uint8_t data[3];
  BigEndianReader reader(data);
  // The test should fail without ever dereferencing the |dummy_buf| pointer.
  uint8_t* dummy_buf = reinterpret_cast<uint8_t*>(0xdeadbeef);
  // Craft an extreme length value that would cause |reader.data() + len| to
  // overflow.
  size_t extreme_length = std::numeric_limits<size_t>::max() - 1;
  std::string_view piece;
  EXPECT_FALSE(reader.Skip(extreme_length));
  EXPECT_FALSE(reader.ReadBytes(
      // SAFETY: This will create Undefined Behaviour if the invalid length is
      // ever added to the pointer. However span() constructor does not do so,
      // and ReadBytes() checks the size before using the pointer and returns
      // false.
      UNSAFE_BUFFERS(span(dummy_buf, extreme_length))));
  EXPECT_FALSE(reader.ReadPiece(&piece, extreme_length));
}

}  // namespace base