From 44c6b8c6091a32c2f356e7dbfb290cad03d9e189 Mon Sep 17 00:00:00 2001
From: Martchus <martchus@gmx.net>
Date: Sun, 25 Jul 2021 19:19:02 +0200
Subject: [PATCH] Throw exception during binary deserialization when version is
 not supported

---
 README.md                                      | 11 +++++++----
 generator/binaryserializationcodegenerator.cpp |  9 ++++++---
 lib/binary/serializable.h                      |  3 +++
 lib/versioning.h                               | 16 ++++++++++++++++
 4 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/README.md b/README.md
index 6dc71e2..8b9d394 100644
--- a/README.md
+++ b/README.md
@@ -364,7 +364,7 @@ The binary (de)serializer supports *very* experimental versioning. Otherwise add
 members is a breaking change. The versioning looks like this:
 
 <pre>
-// enable definition of the macros shown below (otherwise use long macros defined  in
+// enable definition of the macros shown below (otherwise use long macros defined in
 // `lib/versioning.h`)
 #define REFLECTIVE_RAPIDJSON_SHORT_MACROS
 
@@ -379,7 +379,7 @@ as_of_version(3):
     std::uint32_t bar; // will be read/written if outer scope version is &gt;= 3
 };
 
-// example struct where version is serialized/deserialized; defaults to version when writing
+// example struct where version is serialized/deserialized; defaults to version 3 when writing
 struct Example : public BinarySerializable&lt;Example, 3&gt; {
     Nested nested;      // will be read/written in any case, version is "propagated down"
     std::uint32_t a, b; // will be read/written in any case
@@ -395,8 +395,11 @@ as_of_version(4):
 };
 </pre>
 
-A mechanism to catch unsupported versions during deserialization is yet to be implemented.
-Additionally, the versioning is completely untested at this point.
+The version specified as template argument is also assumed to be the highest supported version.
+If a higher version is encountered during deserialization, `BinaryVersionNotSupported` is thrown
+and the deserialization aborted.
+
+Note that the versioning is mostly untested at this point.
 
 ### Remarks
 * Static member variables and member functions are currently ignored by the generator.
diff --git a/generator/binaryserializationcodegenerator.cpp b/generator/binaryserializationcodegenerator.cpp
index b8b9b9b..83bce11 100644
--- a/generator/binaryserializationcodegenerator.cpp
+++ b/generator/binaryserializationcodegenerator.cpp
@@ -308,10 +308,13 @@ void BinarySerializationCodeGenerator::generate(std::ostream &os) const
            << ">(BinaryDeserializer &deserializer, ::" << relevantClass.qualifiedName << " &customObject, BinaryVersion version)\n{\n";
         if (!relevantClass.relevantBase.empty()) {
             os << "    // read version\n"
-                  "    if constexpr (Versioning<"
+                  "    using V = Versioning<"
                << relevantClass.relevantBase
-               << ">::enabled) {\n"
-                  "        version = deserializer.readVariableLengthUIntBE();\n"
+               << ">;\n"
+                  "    if constexpr (V::enabled) {\n"
+                  "        V::assertVersion(version = deserializer.readVariableLengthUIntBE(), \""
+               << relevantClass.qualifiedName
+               << "\");\n"
                   "    }\n";
         }
         os << "    // read base classes\n";
diff --git a/lib/binary/serializable.h b/lib/binary/serializable.h
index ff0cd26..e5f564d 100644
--- a/lib/binary/serializable.h
+++ b/lib/binary/serializable.h
@@ -14,10 +14,13 @@
 
 namespace ReflectiveRapidJSON {
 
+using BinaryVersionNotSupported = VersionNotSupported<BinaryVersion>;
+
 /*!
  * \brief The BinarySerializable class provides the CRTP-base for (de)serializable objects.
  */
 template <typename Type, BinaryVersion v> struct BinarySerializable {
+    using VersionNotSupported = BinaryVersionNotSupported;
     void toBinary(std::ostream &outputStream, BinaryVersion version = 0) const;
     BinaryVersion restoreFromBinary(std::istream &inputStream);
     static Type fromBinary(std::istream &inputStream);
diff --git a/lib/versioning.h b/lib/versioning.h
index ec7fa39..bd05de7 100644
--- a/lib/versioning.h
+++ b/lib/versioning.h
@@ -26,6 +26,11 @@ public
 
 CPP_UTILITIES_TRAITS_DEFINE_TYPE_CHECK(IsVersioned, T::version);
 
+template <typename VersionType> struct VersionNotSupported {
+    VersionType presentVersion = 0, maxVersion = 0;
+    const char *record = nullptr;
+};
+
 template <typename Type, bool Condition = IsVersioned<Type>::value> struct Versioning {
     static constexpr auto enabled = false;
 };
@@ -33,10 +38,21 @@ template <typename Type, bool Condition = IsVersioned<Type>::value> struct Versi
 template <typename Type> struct Versioning<Type, true> {
     static constexpr auto enabled = Type::version != 0;
     static constexpr auto serializationDefault = Type::version;
+    static constexpr auto maxSupported = Type::version;
     static constexpr auto applyDefault(decltype(serializationDefault) version)
     {
         return version ? version : serializationDefault;
     }
+    static constexpr auto isSupported(decltype(maxSupported) version)
+    {
+        return version <= maxSupported;
+    }
+    static constexpr auto assertVersion(decltype(maxSupported) version, const char *record = nullptr)
+    {
+        if (!isSupported(version)) {
+            throw typename Type::VersionNotSupported({ .presentVersion = version, .maxVersion = maxSupported, .record = record });
+        }
+    }
 };
 
 } // namespace ReflectiveRapidJSON