Fix #2 Preserve unsigned 64-bit decoded values

tests/README.md

@@ -22,6 +22,7 @@ The executable returns a nonzero exit code if any case fails. Checks remain
 active in release builds and do not depend on `assert` or an external test framework.
 
 Coverage includes Motorola bit numbering within and across bytes, unaligned
-signals, signed values, scaling, 64-bit extraction, invalid lengths, insufficient
+signals, signed values, scaling, 64-bit extraction, signed/unsigned boundary values
+(including `INT64_MIN`, `INT64_MAX`, and `UINT64_MAX`), numeric output, invalid lengths, insufficient
 payloads, and Intel regression cases. Frame validity means the definition was
 found; insufficient payloads are checked through signal validity.

tests/dbc_decoder_test.cpp

@@ -2,6 +2,7 @@
 
 #include <iostream>
 #include <limits>
+#include <sstream>
 
 struct DecodeCase {
   const char *name;
@@ -83,15 +84,71 @@ int main() {
       (result.signals.size() == 1U) &&
       (result.signals[0].definition == &database.frames[0].signals[0]) &&
       (result.signals[0].valid == test.valid) &&
-      (!test.valid || ((result.signals[0].rawValue == test.rawValue) &&
+      (!test.valid || (((test.valueType == ValueType::Signed)
+        ? (std::get_if<std::int64_t> (&result.signals[0].rawValue) &&
+           std::get<std::int64_t> (result.signals[0].rawValue) == test.rawValue)
+        : (std::get_if<std::uint64_t> (&result.signals[0].rawValue) &&
+           std::get<std::uint64_t> (result.signals[0].rawValue) ==
+             static_cast<std::uint64_t> (test.rawValue))) &&
                       (result.signals[0].physicalValue == test.physicalValue)));
     if (!passed) {
       std::cerr << "FAIL: " << test.name << '\n';
       ++failures;
     }
   }
+  std::size_t boundaryCases = 0U;
+  for (ByteOrder order : {ByteOrder::Intel, ByteOrder::Motorola}) {
+    for (ValueType type : {ValueType::Unsigned, ValueType::Signed}) {
+      for (std::uint64_t bits : {std::uint64_t (0U), std::uint64_t (0x7FFFFFFFFFFFFFFFULL),
+                                std::uint64_t (0x8000000000000000ULL),
+                                std::uint64_t (0x8000000000000001ULL),
+                                std::uint64_t (0xFFFFFFFFFFFFFFFFULL)}) {
+        DecodeDatabase database;
+        DecodeFrame definition;
+        DecodeSignal signal;
+        signal.startBit = order == ByteOrder::Intel ? 0U : 7U;
+        signal.length = 64U;
+        signal.byteOrder = order;
+        signal.valueType = type;
+        signal.factor = 0.5;
+        signal.offset = 10.0;
+        definition.signals.push_back (signal);
+        database.frames.push_back (definition);
+        database.frameIndexByKey.emplace (FrameKey (0U, false), 0U);
+        RawCanFrame frame;
+        for (unsigned byte = 0U; byte < 8U; ++byte) {
+          const unsigned shift = (order == ByteOrder::Intel ? byte : 7U - byte) * 8U;
+          frame.data.push_back (static_cast<std::uint8_t> (bits >> shift));
+        }
+        const auto result = DbcDecoder().Decode (database, frame);
+        const std::int64_t signedExpected = bits <= 0x7FFFFFFFFFFFFFFFULL
+          ? static_cast<std::int64_t> (bits)
+          : std::numeric_limits<std::int64_t>::min() +
+            static_cast<std::int64_t> (bits - 0x8000000000000000ULL);
+        const auto &decoded = result.signals.at (0U);
+        const auto expected = type == ValueType::Unsigned
+          ? std::variant<std::int64_t, std::uint64_t> (bits)
+          : std::variant<std::int64_t, std::uint64_t> (signedExpected);
+        const double physical = (type == ValueType::Unsigned
+          ? static_cast<double> (bits) : static_cast<double> (signedExpected)) * 0.5 + 10.0;
+        std::ostringstream actualText;
+        std::ostringstream expectedText;
+        std::visit ([&actualText] (auto raw) { actualText << raw; }, decoded.rawValue);
+        if (type == ValueType::Unsigned)
+          expectedText << bits;
+        else
+          expectedText << signedExpected;
+        if (!decoded.valid || decoded.rawValue != expected ||
+            decoded.physicalValue != physical || actualText.str() != expectedText.str()) {
+          std::cerr << "FAIL: 64-bit boundary " << bits << '\n';
+          ++failures;
+        }
+        ++boundaryCases;
+      }
+    }
+  }
   if (failures != 0)
     return 1;
-  std::cout << "All " << sizeof (cases) / sizeof (cases[0]) << " decoder cases passed.\n";
+  std::cout << "All " << sizeof (cases) / sizeof (cases[0]) + boundaryCases << " decoder cases passed.\n";
   return 0;
 }