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dcsctp: UnwrappedSequenceNumber use StrongAlias

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As this library will only use StrongAlias types for all its
sequence numbers, the UnwrappedSequenceNumber class should use those
types and not the primitive underlying types (e.g. uint32_t).

This makes e.g. Unwrap() return a strong type, which is preferred.

Bug: webrtc:12614
Change-Id: Icd0900c643a1988d1a3bbf49d87b4d4d1bbfbf1f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/213663
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33651}
This commit is contained in:
Victor Boivie 2021-04-02 00:18:48 +02:00 committed by Commit Bot
parent 471fc8c329
commit 83c726f3e5
3 changed files with 52 additions and 41 deletions
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33
net/dcsctp/common/sequence_numbers.h
View File

@ -14,6 +14,8 @@
#include <limits>
#include <utility>
#include "net/dcsctp/common/internal_types.h"
namespace dcsctp {
// UnwrappedSequenceNumber handles wrapping sequence numbers and unwraps them to
@ -23,14 +25,18 @@ namespace dcsctp {
// Sequence numbers are expected to be monotonically increasing, but they do not
// need to be unwrapped in order, as long as the difference to the previous one
// is not larger than half the range of the wrapped sequence number.
//
// The WrappedType must be a StrongAlias type.
template <typename WrappedType>
class UnwrappedSequenceNumber {
public:
static_assert(!std::numeric_limits<WrappedType>::is_signed,
"The wrapped type must be unsigned");
static_assert(std::numeric_limits<WrappedType>::max() <
std::numeric_limits<int64_t>::max(),
"The wrapped type must be less than the int64_t value space");
static_assert(
!std::numeric_limits<typename WrappedType::UnderlyingType>::is_signed,
"The wrapped type must be unsigned");
static_assert(
std::numeric_limits<typename WrappedType::UnderlyingType>::max() <
std::numeric_limits<int64_t>::max(),
"The wrapped type must be less than the int64_t value space");
// The unwrapper is a sort of factory and converts wrapped sequence numbers to
// unwrapped ones.
@ -70,8 +76,9 @@ class UnwrappedSequenceNumber {
private:
static int64_t Delta(WrappedType value, WrappedType prev_value) {
static constexpr WrappedType kBreakpoint = kValueLimit / 2;
WrappedType diff = value - prev_value;
static constexpr typename WrappedType::UnderlyingType kBreakpoint =
kValueLimit / 2;
typename WrappedType::UnderlyingType diff = *value - *prev_value;
diff %= kValueLimit;
if (diff < kBreakpoint) {
return static_cast<int64_t>(diff);
@ -124,26 +131,28 @@ class UnwrappedSequenceNumber {
}
// Compares the difference between two sequence numbers.
WrappedType Difference(UnwrappedSequenceNumber<WrappedType> other) const {
typename WrappedType::UnderlyingType Difference(
UnwrappedSequenceNumber<WrappedType> other) const {
return value_ - other.value_;
}
private:
explicit UnwrappedSequenceNumber(int64_t value) : value_(value) {}
static constexpr int64_t kValueLimit =
static_cast<int64_t>(1) << std::numeric_limits<WrappedType>::digits;
static_cast<int64_t>(1)
<< std::numeric_limits<typename WrappedType::UnderlyingType>::digits;
int64_t value_;
};
// Unwrapped Transmission Sequence Numbers (TSN)
using UnwrappedTSN = UnwrappedSequenceNumber<uint32_t>;
using UnwrappedTSN = UnwrappedSequenceNumber<TSN>;
// Unwrapped Stream Sequence Numbers (SSN)
using UnwrappedSSN = UnwrappedSequenceNumber<uint16_t>;
using UnwrappedSSN = UnwrappedSequenceNumber<SSN>;
// Unwrapped Message Identifier (MID)
using UnwrappedMID = UnwrappedSequenceNumber<uint32_t>;
using UnwrappedMID = UnwrappedSequenceNumber<MID>;
} // namespace dcsctp

55
net/dcsctp/common/sequence_numbers_test.cc
View File

@ -14,15 +14,16 @@
namespace dcsctp {
namespace {
using TestSequence = UnwrappedSequenceNumber<uint16_t>;
using Wrapped = StrongAlias<class WrappedTag, uint16_t>;
using TestSequence = UnwrappedSequenceNumber<Wrapped>;
TEST(SequenceNumbersTest, SimpleUnwrapping) {
TestSequence::Unwrapper unwrapper;
TestSequence s0 = unwrapper.Unwrap(0);
TestSequence s1 = unwrapper.Unwrap(1);
TestSequence s2 = unwrapper.Unwrap(2);
TestSequence s3 = unwrapper.Unwrap(3);
TestSequence s0 = unwrapper.Unwrap(Wrapped(0));
TestSequence s1 = unwrapper.Unwrap(Wrapped(1));
TestSequence s2 = unwrapper.Unwrap(Wrapped(2));
TestSequence s3 = unwrapper.Unwrap(Wrapped(3));
EXPECT_LT(s0, s1);
EXPECT_LT(s0, s2);
@ -55,10 +56,10 @@ TEST(SequenceNumbersTest, SimpleUnwrapping) {
TEST(SequenceNumbersTest, MidValueUnwrapping) {
TestSequence::Unwrapper unwrapper;
TestSequence s0 = unwrapper.Unwrap(0x7FFE);
TestSequence s1 = unwrapper.Unwrap(0x7FFF);
TestSequence s2 = unwrapper.Unwrap(0x8000);
TestSequence s3 = unwrapper.Unwrap(0x8001);
TestSequence s0 = unwrapper.Unwrap(Wrapped(0x7FFE));
TestSequence s1 = unwrapper.Unwrap(Wrapped(0x7FFF));
TestSequence s2 = unwrapper.Unwrap(Wrapped(0x8000));
TestSequence s3 = unwrapper.Unwrap(Wrapped(0x8001));
EXPECT_LT(s0, s1);
EXPECT_LT(s0, s2);
@ -91,10 +92,10 @@ TEST(SequenceNumbersTest, MidValueUnwrapping) {
TEST(SequenceNumbersTest, WrappedUnwrapping) {
TestSequence::Unwrapper unwrapper;
TestSequence s0 = unwrapper.Unwrap(0xFFFE);
TestSequence s1 = unwrapper.Unwrap(0xFFFF);
TestSequence s2 = unwrapper.Unwrap(0x0000);
TestSequence s3 = unwrapper.Unwrap(0x0001);
TestSequence s0 = unwrapper.Unwrap(Wrapped(0xFFFE));
TestSequence s1 = unwrapper.Unwrap(Wrapped(0xFFFF));
TestSequence s2 = unwrapper.Unwrap(Wrapped(0x0000));
TestSequence s3 = unwrapper.Unwrap(Wrapped(0x0001));
EXPECT_LT(s0, s1);
EXPECT_LT(s0, s2);
@ -127,12 +128,12 @@ TEST(SequenceNumbersTest, WrappedUnwrapping) {
TEST(SequenceNumbersTest, WrapAroundAFewTimes) {
TestSequence::Unwrapper unwrapper;
TestSequence s0 = unwrapper.Unwrap(0);
TestSequence s0 = unwrapper.Unwrap(Wrapped(0));
TestSequence prev = s0;
for (uint32_t i = 1; i < 65536 * 3; i++) {
uint16_t wrapped = static_cast<uint16_t>(i);
TestSequence si = unwrapper.Unwrap(wrapped);
TestSequence si = unwrapper.Unwrap(Wrapped(wrapped));
EXPECT_LT(s0, si);
EXPECT_LT(prev, si);
@ -143,11 +144,11 @@ TEST(SequenceNumbersTest, WrapAroundAFewTimes) {
TEST(SequenceNumbersTest, IncrementIsSameAsWrapped) {
TestSequence::Unwrapper unwrapper;
TestSequence s0 = unwrapper.Unwrap(0);
TestSequence s0 = unwrapper.Unwrap(Wrapped(0));
for (uint32_t i = 1; i < 65536 * 2; i++) {
uint16_t wrapped = static_cast<uint16_t>(i);
TestSequence si = unwrapper.Unwrap(wrapped);
TestSequence si = unwrapper.Unwrap(Wrapped(wrapped));
s0.Increment();
EXPECT_EQ(s0, si);
@ -159,12 +160,12 @@ TEST(SequenceNumbersTest, UnwrappingLargerNumberIsAlwaysLarger) {
for (uint32_t i = 1; i < 65536 * 2; i++) {
uint16_t wrapped = static_cast<uint16_t>(i);
TestSequence si = unwrapper.Unwrap(wrapped);
TestSequence si = unwrapper.Unwrap(Wrapped(wrapped));
EXPECT_GT(unwrapper.Unwrap(wrapped + 1), si);
EXPECT_GT(unwrapper.Unwrap(wrapped + 5), si);
EXPECT_GT(unwrapper.Unwrap(wrapped + 10), si);
EXPECT_GT(unwrapper.Unwrap(wrapped + 100), si);
EXPECT_GT(unwrapper.Unwrap(Wrapped(wrapped + 1)), si);
EXPECT_GT(unwrapper.Unwrap(Wrapped(wrapped + 5)), si);
EXPECT_GT(unwrapper.Unwrap(Wrapped(wrapped + 10)), si);
EXPECT_GT(unwrapper.Unwrap(Wrapped(wrapped + 100)), si);
}
}
@ -173,12 +174,12 @@ TEST(SequenceNumbersTest, UnwrappingSmallerNumberIsAlwaysSmaller) {
for (uint32_t i = 1; i < 65536 * 2; i++) {
uint16_t wrapped = static_cast<uint16_t>(i);
TestSequence si = unwrapper.Unwrap(wrapped);
TestSequence si = unwrapper.Unwrap(Wrapped(wrapped));
EXPECT_LT(unwrapper.Unwrap(wrapped - 1), si);
EXPECT_LT(unwrapper.Unwrap(wrapped - 5), si);
EXPECT_LT(unwrapper.Unwrap(wrapped - 10), si);
EXPECT_LT(unwrapper.Unwrap(wrapped - 100), si);
EXPECT_LT(unwrapper.Unwrap(Wrapped(wrapped - 1)), si);
EXPECT_LT(unwrapper.Unwrap(Wrapped(wrapped - 5)), si);
EXPECT_LT(unwrapper.Unwrap(Wrapped(wrapped - 10)), si);
EXPECT_LT(unwrapper.Unwrap(Wrapped(wrapped - 100)), si);
}
}

5
net/dcsctp/public/strong_alias.h
View File

@ -20,11 +20,12 @@ namespace dcsctp {
// https://source.chromium.org/chromium/chromium/src/+/master:base/types/strong_alias.h
// as the API (and internals) are using type-safe integral identifiers, but this
// library can't depend on that file. The ostream operator has been removed
// per WebRTC library conventions.
// per WebRTC library conventions, and the underlying type is exposed.
template <typename TagType, typename UnderlyingType>
template <typename TagType, typename TheUnderlyingType>
class StrongAlias {
public:
using UnderlyingType = TheUnderlyingType;
constexpr StrongAlias() = default;
constexpr explicit StrongAlias(const UnderlyingType& v) : value_(v) {}
constexpr explicit StrongAlias(UnderlyingType&& v) noexcept