Fix issue with Timestamp overflow

Fix #140

Author: h4tr3d

src/timestamp.cpp

@@ -89,14 +89,12 @@ Timestamp::operator bool() const noexcept
 
 Timestamp operator+(const Timestamp &left, const Timestamp &right) noexcept
 {
-    // Use more good precision
-    if (left.timebase() < right.timebase()) {
-        auto ts = av_add_stable(left.timebase(), left.timestamp(),
-                                right.timebase(), right.timestamp());
+    // av_add_stable() required that rhs value less than lhs
+    if (left >= right) {
+        auto const ts = av_add_stable(left.timebase(), left.timestamp(), right.timebase(), right.timestamp());
         return {ts, left.timebase()};
     } else {
-        auto ts = av_add_stable(right.timebase(), right.timestamp(),
-                                left.timebase(), left.timestamp());
+        auto ts = av_add_stable(right.timebase(), right.timestamp(), left.timebase(), left.timestamp());
         return {ts, right.timebase()};
     }
 }

tests/CMakeLists.txt

@@ -14,7 +14,8 @@ add_executable(test_executor
     AvDeleter.cpp
     Packet.cpp
     Format.cpp
-    Rational.cpp)
+    Rational.cpp
+    Timestamp.cpp)
 target_link_libraries(test_executor PUBLIC Catch2::Catch2 test_main avcpp::avcpp)
 
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/../catch2/contrib")

tests/Timestamp.cpp

@@ -0,0 +1,57 @@
+#include <catch2/catch.hpp>
+
+#include <vector>
+
+#include "rational.h"
+#include "timestamp.h"
+
+#ifdef _MSC_VER
+#    pragma warning(disable : 4702) // Disable warning: unreachable code
+#endif
+
+
+using namespace std;
+
+TEST_CASE("Core", "[Overflow]")
+{
+    SECTION("Overflow operator+(a,b)")
+    {
+        {
+            auto const tsLimit = std::numeric_limits<int64_t>::max() / 48000;
+
+            av::Timestamp t {
+                tsLimit, av::Rational {1, 48000}
+            };
+            av::Timestamp inc {48000, t.timebase()}; // 1s
+
+            auto v1 = t;
+            v1 += inc;
+
+            auto v2 = t + inc;
+            auto v3 = inc + t;
+
+            CHECK(v1 == v2);
+            CHECK(v1 == v3);
+        }
+
+#if 0
+        av::Timestamp t1(48000, av::Rational {1, 48000}); // 1s
+        av::Timestamp t2 = t1;
+        av::Timestamp t3 = t1;
+        for (int64_t i = 0; i < 4194258; ++i) {
+            t1 = t1 + av::Timestamp {1024, t1.timebase()}; // fail case
+            t2 += av::Timestamp {1024, t2.timebase()}; // good
+            t3 = av::Timestamp {1024, t1.timebase()} + t3;
+
+            CHECK(t3 == t2);
+            CHECK(t1 == t2);
+            CHECK(t1.seconds() >= 1.0);
+
+            if (t1 != t2 || t2 != t3 || t1.seconds() < 1.0) {
+                CHECK(i < 0); // always fail, just for report
+                break;
+            }
+        }
+#endif
+    }
+}