[Unwrap] Migrate dcsctp sequence numbers to SeqNumUnwrapper

Bug: webrtc:13982
Change-Id: Ic900a967d1b8e96a2b1ec99424674ccb33eb7165
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/288940
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Victor Boivie <boivie@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Auto-Submit: Evan Shrubsole <eshr@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#39084}

net/dcsctp/common/BUILD.gn

@@ -22,7 +22,10 @@ rtc_source_set("math") {
 }
 
 rtc_source_set("sequence_numbers") {
-  deps = [ ":internal_types" ]
+  deps = [
+    ":internal_types",
+    "../../../rtc_base:rtc_numerics",
+  ]
   sources = [ "sequence_numbers.h" ]
 }
 

net/dcsctp/common/sequence_numbers.h

@@ -15,6 +15,7 @@
 #include <utility>
 
 #include "net/dcsctp/common/internal_types.h"
+#include "rtc_base/numerics/sequence_number_unwrapper.h"
 
 namespace dcsctp {
 
@@ -42,7 +43,7 @@ class UnwrappedSequenceNumber {
   // unwrapped ones.
   class Unwrapper {
    public:
-    Unwrapper() : largest_(kValueLimit) {}
+    Unwrapper() = default;
     Unwrapper(const Unwrapper&) = default;
     Unwrapper& operator=(const Unwrapper&) = default;
 
@@ -53,40 +54,21 @@ class UnwrappedSequenceNumber {
     // This will also update the Unwrapper's state, to track the last seen
     // largest value.
     UnwrappedSequenceNumber<WrappedType> Unwrap(WrappedType value) {
-      WrappedType wrapped_largest =
-          static_cast<WrappedType>(largest_ % kValueLimit);
-      int64_t result = largest_ + Delta(value, wrapped_largest);
-      if (largest_ < result) {
-        largest_ = result;
-      }
-      return UnwrappedSequenceNumber<WrappedType>(result);
+      return UnwrappedSequenceNumber<WrappedType>(unwrapper_.Unwrap(*value));
     }
 
     // Similar to `Unwrap`, but will not update the Unwrappers's internal state.
     UnwrappedSequenceNumber<WrappedType> PeekUnwrap(WrappedType value) const {
-      WrappedType uint32_largest =
-          static_cast<WrappedType>(largest_ % kValueLimit);
-      int64_t result = largest_ + Delta(value, uint32_largest);
-      return UnwrappedSequenceNumber<WrappedType>(result);
+      return UnwrappedSequenceNumber<WrappedType>(
+          unwrapper_.PeekUnwrap(*value));
     }
 
     // Resets the Unwrapper to its pristine state. Used when a sequence number
     // is to be reset to zero.
-    void Reset() { largest_ = kValueLimit; }
+    void Reset() { unwrapper_.Reset(); }
 
    private:
-    static int64_t Delta(WrappedType value, WrappedType 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);
-      }
-      return static_cast<int64_t>(diff) - kValueLimit;
-    }
-
-    int64_t largest_;
+    webrtc::SeqNumUnwrapper<typename WrappedType::UnderlyingType> unwrapper_;
   };
 
   // Returns the wrapped value this type represents.

rtc_base/BUILD.gn

@@ -2140,7 +2140,6 @@ if (rtc_include_tests) {
         ":strong_alias",
         ":timeutils",
         "../modules:module_api_public",
-        "../net/dcsctp/common:sequence_numbers",
         "../test:test_main",
         "../test:test_support",
       ]

rtc_base/DEPS

@@ -12,7 +12,4 @@ specific_include_rules = {
   "gunit\.h": [
     "+testing/base/public/gunit.h"
   ],
-  "sequence_numbers_conformance_test\.cc": [
-    "+net/dcsctp/common/sequence_numbers.h",
-  ],
 }

rtc_base/numerics/sequence_numbers_conformance_test.cc

@@ -13,9 +13,7 @@
 #include <type_traits>
 
 #include "modules/include/module_common_types_public.h"
-#include "net/dcsctp/common/sequence_numbers.h"
 #include "rtc_base/numerics/sequence_number_unwrapper.h"
-#include "rtc_base/strong_alias.h"
 #include "rtc_base/time_utils.h"
 #include "test/gmock.h"
 #include "test/gtest.h"
@@ -25,27 +23,6 @@ namespace {
 
 using ::testing::Test;
 
-using dcsctp::UnwrappedSequenceNumber;
-using Wrapped = StrongAlias<class WrappedTag, uint32_t>;
-using TestSequence = UnwrappedSequenceNumber<Wrapped>;
-
-template <typename T>
-class UnwrapperHelper;
-
-template <>
-class UnwrapperHelper<TestSequence::Unwrapper> {
- public:
-  int64_t Unwrap(uint32_t val) {
-    TestSequence s = unwrapper_.Unwrap(Wrapped(val));
-    // UnwrappedSequenceNumber starts counting at 2^32.
-    constexpr int64_t kDcsctpUnwrapStart = int64_t{1} << 32;
-    return s.value() - kDcsctpUnwrapStart;
-  }
-
- private:
-  TestSequence::Unwrapper unwrapper_;
-};
-
 // MaxVal is the max of the wrapped space, ie MaxVal + 1 = 0 when wrapped.
 template <typename U, int64_t MaxVal = std::numeric_limits<uint32_t>::max()>
 struct FixtureParams {
@@ -138,8 +115,6 @@ TYPED_TEST_P(UnwrapperConformanceFixture, MultipleNegativeWrapArounds) {
   // SequenceNumberUnwrapper can only wrap negative once.
   // rtc::TimestampWrapAroundHandler does not wrap around correctly.
   if constexpr (std::is_same<UnwrapperT, TimestampUnwrapper>() ||
-                std::is_same<UnwrapperT,
-                             UnwrapperHelper<TestSequence::Unwrapper>>() ||
                 std::is_same<UnwrapperT, rtc::TimestampWrapAroundHandler>()) {
     return;
   }
@@ -166,7 +141,6 @@ using UnwrapperTypes = ::testing::Types<
     FixtureParams<rtc::TimestampWrapAroundHandler>,
     FixtureParams<TimestampUnwrapper>,
     FixtureParams<RtpTimestampUnwrapper>,
-    FixtureParams<UnwrapperHelper<TestSequence::Unwrapper>>,
     // SeqNumUnwrapper supports arbitrary limits.
     FixtureParams<SeqNumUnwrapper<uint32_t, k15BitMax + 1>, k15BitMax>>;
 
@@ -185,9 +159,6 @@ class TestNames {
     if constexpr (std::is_same<typename T::Unwrapper,
                                SeqNumUnwrapper<uint32_t, k15BitMax + 1>>())
       return "SeqNumUnwrapper15bit";
-    if constexpr (std::is_same<typename T::Unwrapper,
-                               UnwrapperHelper<TestSequence::Unwrapper>>())
-      return "UnwrappedSequenceNumber";
   }
 };