net/quic/quic_data_writer_test.cc

// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "net/quic/quic_data_writer.h"

#include <stdint.h>

#include <memory>

#include "net/quic/quic_data_reader.h"
#include "net/test/gtest_util.h"
#include "testing/gtest/include/gtest/gtest.h"

namespace net {
namespace test {
namespace {

TEST(QuicDataWriterTest, SanityCheckUFloat16Consts) {
  // Check the arithmetic on the constants - otherwise the values below make
  // no sense.
  EXPECT_EQ(30, kUFloat16MaxExponent);
  EXPECT_EQ(11, kUFloat16MantissaBits);
  EXPECT_EQ(12, kUFloat16MantissaEffectiveBits);
  EXPECT_EQ(UINT64_C(0x3FFC0000000), kUFloat16MaxValue);
}

TEST(QuicDataWriterTest, WriteUFloat16) {
  struct TestCase {
    uint64_t decoded;
    uint16_t encoded;
  };
  TestCase test_cases[] = {
      // Small numbers represent themselves.
      {0, 0},
      {1, 1},
      {2, 2},
      {3, 3},
      {4, 4},
      {5, 5},
      {6, 6},
      {7, 7},
      {15, 15},
      {31, 31},
      {42, 42},
      {123, 123},
      {1234, 1234},
      // Check transition through 2^11.
      {2046, 2046},
      {2047, 2047},
      {2048, 2048},
      {2049, 2049},
      // Running out of mantissa at 2^12.
      {4094, 4094},
      {4095, 4095},
      {4096, 4096},
      {4097, 4096},
      {4098, 4097},
      {4099, 4097},
      {4100, 4098},
      {4101, 4098},
      // Check transition through 2^13.
      {8190, 6143},
      {8191, 6143},
      {8192, 6144},
      {8193, 6144},
      {8194, 6144},
      {8195, 6144},
      {8196, 6145},
      {8197, 6145},
      // Half-way through the exponents.
      {0x7FF8000, 0x87FF},
      {0x7FFFFFF, 0x87FF},
      {0x8000000, 0x8800},
      {0xFFF0000, 0x8FFF},
      {0xFFFFFFF, 0x8FFF},
      {0x10000000, 0x9000},
      // Transition into the largest exponent.
      {0x1FFFFFFFFFE, 0xF7FF},
      {0x1FFFFFFFFFF, 0xF7FF},
      {0x20000000000, 0xF800},
      {0x20000000001, 0xF800},
      {0x2003FFFFFFE, 0xF800},
      {0x2003FFFFFFF, 0xF800},
      {0x20040000000, 0xF801},
      {0x20040000001, 0xF801},
      // Transition into the max value and clamping.
      {0x3FF80000000, 0xFFFE},
      {0x3FFBFFFFFFF, 0xFFFE},
      {0x3FFC0000000, 0xFFFF},
      {0x3FFC0000001, 0xFFFF},
      {0x3FFFFFFFFFF, 0xFFFF},
      {0x40000000000, 0xFFFF},
      {0xFFFFFFFFFFFFFFFF, 0xFFFF},
  };
  int num_test_cases = sizeof(test_cases) / sizeof(test_cases[0]);

  for (int i = 0; i < num_test_cases; ++i) {
    char buffer[2];
    QuicDataWriter writer(2, buffer);
    EXPECT_TRUE(writer.WriteUFloat16(test_cases[i].decoded));
    EXPECT_EQ(test_cases[i].encoded,
              *reinterpret_cast<uint16_t*>(writer.data()));
  }
}

TEST(QuicDataWriterTest, ReadUFloat16) {
  struct TestCase {
    uint64_t decoded;
    uint16_t encoded;
  };
  TestCase test_cases[] = {
      // There are fewer decoding test cases because encoding truncates, and
      // decoding returns the smallest expansion.
      // Small numbers represent themselves.
      {0, 0},
      {1, 1},
      {2, 2},
      {3, 3},
      {4, 4},
      {5, 5},
      {6, 6},
      {7, 7},
      {15, 15},
      {31, 31},
      {42, 42},
      {123, 123},
      {1234, 1234},
      // Check transition through 2^11.
      {2046, 2046},
      {2047, 2047},
      {2048, 2048},
      {2049, 2049},
      // Running out of mantissa at 2^12.
      {4094, 4094},
      {4095, 4095},
      {4096, 4096},
      {4098, 4097},
      {4100, 4098},
      // Check transition through 2^13.
      {8190, 6143},
      {8192, 6144},
      {8196, 6145},
      // Half-way through the exponents.
      {0x7FF8000, 0x87FF},
      {0x8000000, 0x8800},
      {0xFFF0000, 0x8FFF},
      {0x10000000, 0x9000},
      // Transition into the largest exponent.
      {0x1FFE0000000, 0xF7FF},
      {0x20000000000, 0xF800},
      {0x20040000000, 0xF801},
      // Transition into the max value.
      {0x3FF80000000, 0xFFFE},
      {0x3FFC0000000, 0xFFFF},
  };
  int num_test_cases = sizeof(test_cases) / sizeof(test_cases[0]);

  for (int i = 0; i < num_test_cases; ++i) {
    QuicDataReader reader(reinterpret_cast<char*>(&test_cases[i].encoded), 2);
    uint64_t value;
    EXPECT_TRUE(reader.ReadUFloat16(&value));
    EXPECT_EQ(test_cases[i].decoded, value);
  }
}

TEST(QuicDataWriterTest, RoundTripUFloat16) {
  // Just test all 16-bit encoded values. 0 and max already tested above.
  uint64_t previous_value = 0;
  for (uint16_t i = 1; i < 0xFFFF; ++i) {
    // Read the two bytes.
    QuicDataReader reader(reinterpret_cast<char*>(&i), 2);
    uint64_t value;
    // All values must be decodable.
    EXPECT_TRUE(reader.ReadUFloat16(&value));
    // Check that small numbers represent themselves
    if (i < 4097)
      EXPECT_EQ(i, value);
    // Check there's monotonic growth.
    EXPECT_LT(previous_value, value);
    // Check that precision is within 0.5% away from the denormals.
    if (i > 2000)
      EXPECT_GT(previous_value * 1005, value * 1000);
    // Check we're always within the promised range.
    EXPECT_LT(value, UINT64_C(0x3FFC0000000));
    previous_value = value;
    char buffer[6];
    QuicDataWriter writer(6, buffer);
    EXPECT_TRUE(writer.WriteUFloat16(value - 1));
    EXPECT_TRUE(writer.WriteUFloat16(value));
    EXPECT_TRUE(writer.WriteUFloat16(value + 1));
    // Check minimal decoding (previous decoding has previous encoding).
    EXPECT_EQ(i - 1, *reinterpret_cast<uint16_t*>(writer.data()));
    // Check roundtrip.
    EXPECT_EQ(i, *reinterpret_cast<uint16_t*>(writer.data() + 2));
    // Check next decoding.
    EXPECT_EQ(i < 4096 ? i + 1 : i,
              *reinterpret_cast<uint16_t*>(writer.data() + 4));
  }
}

}  // namespace
}  // namespace test
}  // namespace net