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/*
* Copyright 2021 The WebRTC Project Authors. All rights reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "rtc_base/bitstream_reader.h"
#include <stddef.h>
#include <stdint.h>
#include <array>
#include <limits>
#include <optional>
#include "absl/numeric/bits.h"
#include "api/array_view.h"
#include "rtc_base/checks.h"
#include "test/gmock.h"
#include "test/gtest.h"
namespace webrtc {
namespace {
TEST(BitstreamReaderTest, InDebugModeRequiresToCheckOkStatusBeforeDestruction) {
const uint8_t bytes[32] = {};
std::optional<BitstreamReader> reader(std::in_place, bytes);
EXPECT_GE(reader->ReadBits(7), 0u);
#if RTC_DCHECK_IS_ON && GTEST_HAS_DEATH_TEST && !defined(OS_ANDROID)
EXPECT_DEATH(reader = std::nullopt, "");
#endif
EXPECT_TRUE(reader->Ok());
reader = std::nullopt;
}
TEST(BitstreamReaderTest, InDebugModeMayCheckRemainingBitsInsteadOfOkStatus) {
const uint8_t bytes[32] = {};
std::optional<BitstreamReader> reader(std::in_place, bytes);
EXPECT_GE(reader->ReadBit(), 0);
#if RTC_DCHECK_IS_ON && GTEST_HAS_DEATH_TEST && !defined(OS_ANDROID)
EXPECT_DEATH(reader = std::nullopt, "");
#endif
EXPECT_GE(reader->RemainingBitCount(), 0);
reader = std::nullopt;
}
TEST(BitstreamReaderTest, ConsumeBits) {
const uint8_t bytes[32] = {};
BitstreamReader reader(bytes);
int total_bits = 32 * 8;
EXPECT_EQ(reader.RemainingBitCount(), total_bits);
reader.ConsumeBits(3);
total_bits -= 3;
EXPECT_EQ(reader.RemainingBitCount(), total_bits);
reader.ConsumeBits(3);
total_bits -= 3;
EXPECT_EQ(reader.RemainingBitCount(), total_bits);
reader.ConsumeBits(15);
total_bits -= 15;
EXPECT_EQ(reader.RemainingBitCount(), total_bits);
reader.ConsumeBits(67);
total_bits -= 67;
EXPECT_EQ(reader.RemainingBitCount(), total_bits);
EXPECT_TRUE(reader.Ok());
reader.ConsumeBits(32 * 8);
EXPECT_FALSE(reader.Ok());
EXPECT_LT(reader.RemainingBitCount(), 0);
}
TEST(BitstreamReaderTest, ConsumeLotsOfBits) {
const uint8_t bytes[1] = {};
BitstreamReader reader(bytes);
reader.ConsumeBits(std::numeric_limits<int>::max());
reader.ConsumeBits(std::numeric_limits<int>::max());
EXPECT_GE(reader.ReadBit(), 0);
EXPECT_FALSE(reader.Ok());
}
TEST(BitstreamReaderTest, ReadBit) {
const uint8_t bytes[] = {0b0100'0001, 0b1011'0001};
BitstreamReader reader(bytes);
// First byte.
EXPECT_EQ(reader.ReadBit(), 0);
EXPECT_EQ(reader.ReadBit(), 1);
EXPECT_EQ(reader.ReadBit(), 0);
EXPECT_EQ(reader.ReadBit(), 0);
EXPECT_EQ(reader.ReadBit(), 0);
EXPECT_EQ(reader.ReadBit(), 0);
EXPECT_EQ(reader.ReadBit(), 0);
EXPECT_EQ(reader.ReadBit(), 1);
// Second byte.
EXPECT_EQ(reader.ReadBit(), 1);
EXPECT_EQ(reader.ReadBit(), 0);
EXPECT_EQ(reader.ReadBit(), 1);
EXPECT_EQ(reader.ReadBit(), 1);
EXPECT_EQ(reader.ReadBit(), 0);
EXPECT_EQ(reader.ReadBit(), 0);
EXPECT_EQ(reader.ReadBit(), 0);
EXPECT_EQ(reader.ReadBit(), 1);
EXPECT_TRUE(reader.Ok());
// Try to read beyound the buffer.
EXPECT_EQ(reader.ReadBit(), 0);
EXPECT_FALSE(reader.Ok());
}
TEST(BitstreamReaderTest, ReadBoolConsumesSingleBit) {
const uint8_t bytes[] = {0b1010'1010};
BitstreamReader reader(bytes);
ASSERT_EQ(reader.RemainingBitCount(), 8);
EXPECT_TRUE(reader.Read<bool>());
EXPECT_EQ(reader.RemainingBitCount(), 7);
}
TEST(BitstreamReaderTest, ReadBytesAligned) {
const uint8_t bytes[] = {0x0A, //
0xBC, //
0xDE, 0xF1, //
0x23, 0x45, 0x67, 0x89};
BitstreamReader reader(bytes);
EXPECT_EQ(reader.Read<uint8_t>(), 0x0Au);
EXPECT_EQ(reader.Read<uint8_t>(), 0xBCu);
EXPECT_EQ(reader.Read<uint16_t>(), 0xDEF1u);
EXPECT_EQ(reader.Read<uint32_t>(), 0x23456789u);
EXPECT_TRUE(reader.Ok());
}
TEST(BitstreamReaderTest, ReadBytesOffset4) {
const uint8_t bytes[] = {0x0A, 0xBC, 0xDE, 0xF1, 0x23,
0x45, 0x67, 0x89, 0x0A};
BitstreamReader reader(bytes);
reader.ConsumeBits(4);
EXPECT_EQ(reader.Read<uint8_t>(), 0xABu);
EXPECT_EQ(reader.Read<uint8_t>(), 0xCDu);
EXPECT_EQ(reader.Read<uint16_t>(), 0xEF12u);
EXPECT_EQ(reader.Read<uint32_t>(), 0x34567890u);
EXPECT_TRUE(reader.Ok());
}
TEST(BitstreamReaderTest, ReadBytesOffset3) {
// The pattern we'll check against is counting down from 0b1111. It looks
// weird here because it's all offset by 3.
// Byte pattern is:
// 56701234
// 0b00011111,
// 0b11011011,
// 0b10010111,
// 0b01010011,
// 0b00001110,
// 0b11001010,
// 0b10000110,
// 0b01000010
// xxxxx <-- last 5 bits unused.
// The bytes. It almost looks like counting down by two at a time, except the
// jump at 5->3->0, since that's when the high bit is turned off.
const uint8_t bytes[] = {0x1F, 0xDB, 0x97, 0x53, 0x0E, 0xCA, 0x86, 0x42};
BitstreamReader reader(bytes);
reader.ConsumeBits(3);
EXPECT_EQ(reader.Read<uint8_t>(), 0xFEu);
EXPECT_EQ(reader.Read<uint16_t>(), 0xDCBAu);
EXPECT_EQ(reader.Read<uint32_t>(), 0x98765432u);
EXPECT_TRUE(reader.Ok());
// 5 bits left unread. Not enough to read a uint8_t.
EXPECT_EQ(reader.RemainingBitCount(), 5);
EXPECT_EQ(reader.Read<uint8_t>(), 0);
EXPECT_FALSE(reader.Ok());
}
TEST(BitstreamReaderTest, ReadBits) {
const uint8_t bytes[] = {0b010'01'101, 0b0011'00'1'0};
BitstreamReader reader(bytes);
EXPECT_EQ(reader.ReadBits(3), 0b010u);
EXPECT_EQ(reader.ReadBits(2), 0b01u);
EXPECT_EQ(reader.ReadBits(7), 0b101'0011u);
EXPECT_EQ(reader.ReadBits(2), 0b00u);
EXPECT_EQ(reader.ReadBits(1), 0b1u);
EXPECT_EQ(reader.ReadBits(1), 0b0u);
EXPECT_TRUE(reader.Ok());
EXPECT_EQ(reader.ReadBits(1), 0u);
EXPECT_FALSE(reader.Ok());
}
TEST(BitstreamReaderTest, ReadZeroBits) {
BitstreamReader reader(rtc::ArrayView<const uint8_t>(nullptr, 0));
EXPECT_EQ(reader.ReadBits(0), 0u);
EXPECT_TRUE(reader.Ok());
}
TEST(BitstreamReaderTest, ReadBitFromEmptyArray) {
BitstreamReader reader(rtc::ArrayView<const uint8_t>(nullptr, 0));
// Trying to read from the empty array shouldn't dereference the pointer,
// i.e. shouldn't crash.
EXPECT_EQ(reader.ReadBit(), 0);
EXPECT_FALSE(reader.Ok());
}
TEST(BitstreamReaderTest, ReadBitsFromEmptyArray) {
BitstreamReader reader(rtc::ArrayView<const uint8_t>(nullptr, 0));
// Trying to read from the empty array shouldn't dereference the pointer,
// i.e. shouldn't crash.
EXPECT_EQ(reader.ReadBits(1), 0u);
EXPECT_FALSE(reader.Ok());
}
TEST(BitstreamReaderTest, ReadBits64) {
const uint8_t bytes[] = {0x4D, 0x32, 0xAB, 0x54, 0x00, 0xFF, 0xFE, 0x01,
0xAB, 0xCD, 0xEF, 0x01, 0x23, 0x45, 0x67, 0x89};
BitstreamReader reader(bytes);
EXPECT_EQ(reader.ReadBits(33), 0x4D32AB5400FFFE01u >> (64 - 33));
constexpr uint64_t kMask31Bits = (1ull << 32) - 1;
EXPECT_EQ(reader.ReadBits(31), 0x4D32AB5400FFFE01ull & kMask31Bits);
EXPECT_EQ(reader.ReadBits(64), 0xABCDEF0123456789ull);
EXPECT_TRUE(reader.Ok());
// Nothing more to read.
EXPECT_EQ(reader.ReadBit(), 0);
EXPECT_FALSE(reader.Ok());
}
TEST(BitstreamReaderTest, CanPeekBitsUsingCopyConstructor) {
// BitstreamReader doesn't have peek function. To simulate it, user may use
// cheap BitstreamReader copy constructor.
const uint8_t bytes[] = {0x0A, 0xBC};
BitstreamReader reader(bytes);
reader.ConsumeBits(4);
ASSERT_EQ(reader.RemainingBitCount(), 12);
BitstreamReader peeker = reader;
EXPECT_EQ(peeker.ReadBits(8), 0xABu);
EXPECT_EQ(peeker.RemainingBitCount(), 4);
EXPECT_EQ(reader.RemainingBitCount(), 12);
// Can resume reading from before peeker was created.
EXPECT_EQ(reader.ReadBits(4), 0xAu);
EXPECT_EQ(reader.RemainingBitCount(), 8);
}
TEST(BitstreamReaderTest,
ReadNonSymmetricSameNumberOfBitsWhenNumValuesPowerOf2) {
const uint8_t bytes[2] = {0xf3, 0xa0};
BitstreamReader reader(bytes);
ASSERT_EQ(reader.RemainingBitCount(), 16);
EXPECT_EQ(reader.ReadNonSymmetric(/*num_values=*/1 << 4), 0xfu);
EXPECT_EQ(reader.ReadNonSymmetric(/*num_values=*/1 << 4), 0x3u);
EXPECT_EQ(reader.ReadNonSymmetric(/*num_values=*/1 << 4), 0xau);
EXPECT_EQ(reader.ReadNonSymmetric(/*num_values=*/1 << 4), 0x0u);
EXPECT_EQ(reader.RemainingBitCount(), 0);
EXPECT_TRUE(reader.Ok());
}
TEST(BitstreamReaderTest, ReadNonSymmetricOnlyValueConsumesZeroBits) {
const uint8_t bytes[2] = {};
BitstreamReader reader(bytes);
ASSERT_EQ(reader.RemainingBitCount(), 16);
EXPECT_EQ(reader.ReadNonSymmetric(/*num_values=*/1), 0u);
EXPECT_EQ(reader.RemainingBitCount(), 16);
}
std::array<uint8_t, 8> GolombEncoded(uint32_t val) {
int val_width = absl::bit_width(val + 1);
int total_width = 2 * val_width - 1;
uint64_t representation = (uint64_t{val} + 1) << (64 - total_width);
std::array<uint8_t, 8> result;
for (int i = 0; i < 8; ++i) {
result[i] = representation >> (7 - i) * 8;
}
return result;
}
TEST(BitstreamReaderTest, GolombUint32Values) {
// Test over the uint32_t range with a large enough step that the test doesn't
// take forever. Around 20,000 iterations should do.
const int kStep = std::numeric_limits<uint32_t>::max() / 20000;
for (uint32_t i = 0; i < std::numeric_limits<uint32_t>::max() - kStep;
i += kStep) {
std::array<uint8_t, 8> buffer = GolombEncoded(i);
BitstreamReader reader(buffer);
// Use assert instead of EXPECT to avoid spamming thousands of failed
// expectation when this test fails.
ASSERT_EQ(reader.ReadExponentialGolomb(), i);
EXPECT_TRUE(reader.Ok());
}
}
TEST(BitstreamReaderTest, SignedGolombValues) {
uint8_t golomb_bits[][1] = {
{0b1'0000000}, {0b010'00000}, {0b011'00000}, {0b00100'000}, {0b00111'000},
};
int expected[] = {0, 1, -1, 2, -3};
for (size_t i = 0; i < sizeof(golomb_bits); ++i) {
BitstreamReader reader(golomb_bits[i]);
EXPECT_EQ(reader.ReadSignedExponentialGolomb(), expected[i])
<< "Mismatch in expected/decoded value for golomb_bits[" << i
<< "]: " << static_cast<int>(golomb_bits[i][0]);
EXPECT_TRUE(reader.Ok());
}
}
TEST(BitstreamReaderTest, NoGolombOverread) {
const uint8_t bytes[] = {0x00, 0xFF, 0xFF};
// Make sure the bit buffer correctly enforces byte length on golomb reads.
// If it didn't, the above buffer would be valid at 3 bytes.
BitstreamReader reader1(rtc::MakeArrayView(bytes, 1));
// When parse fails, `ReadExponentialGolomb` may return any number.
reader1.ReadExponentialGolomb();
EXPECT_FALSE(reader1.Ok());
BitstreamReader reader2(rtc::MakeArrayView(bytes, 2));
reader2.ReadExponentialGolomb();
EXPECT_FALSE(reader2.Ok());
BitstreamReader reader3(bytes);
// Golomb should have read 9 bits, so 0x01FF, and since it is golomb, the
// result is 0x01FF - 1 = 0x01FE.
EXPECT_EQ(reader3.ReadExponentialGolomb(), 0x01FEu);
EXPECT_TRUE(reader3.Ok());
}
TEST(BitstreamReaderTest, ReadLeb128) {
const uint8_t bytes[] = {0xFF, 0x7F};
BitstreamReader reader(bytes);
EXPECT_EQ(reader.ReadLeb128(), 0x3FFFu);
EXPECT_TRUE(reader.Ok());
}
TEST(BitstreamReaderTest, ReadLeb128Large) {
const uint8_t max_uint64[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0x1};
BitstreamReader max_reader(max_uint64);
EXPECT_EQ(max_reader.ReadLeb128(), std::numeric_limits<uint64_t>::max());
EXPECT_TRUE(max_reader.Ok());
const uint8_t overflow_unit64_t[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0x2};
BitstreamReader overflow_reader(overflow_unit64_t);
EXPECT_EQ(overflow_reader.ReadLeb128(), uint64_t{0});
EXPECT_FALSE(overflow_reader.Ok());
}
TEST(BitstreamReaderTest, ReadLeb128NoEndByte) {
const uint8_t bytes[] = {0xFF, 0xFF};
BitstreamReader reader(bytes);
EXPECT_EQ(reader.ReadLeb128(), uint64_t{0});
EXPECT_FALSE(reader.Ok());
}
} // namespace
} // namespace webrtc