Harmonize check on class name length

CHANGELOG.md

@@ -7,6 +7,7 @@
 ### Fixed
 * <How do the end-user experience this issue? what was the impact?> ([#????](https://github.com/realm/realm-core/issues/????), since v?.?.?)
 * Update existing std exceptions thrown by the Sync Client to use Realm exceptions. ([#6255](https://github.com/realm/realm-core/issues/6255), since v10.2.0)
+* Having a class name of length 57 would make client reset crash ([#????](https://github.com/realm/realm-core/issues/????), since v10.0.0)
 
 ### Breaking changes
 * Update existing std exceptions thrown by the Sync Client to use Realm exceptions. ([PR #7141](https://github.com/realm/realm-core/pull/7141/files))

src/realm/group.cpp

@@ -728,7 +728,6 @@ Table* Group::do_add_table(StringData name, Table::Type table_type, bool do_repl
     return table;
 }
 
-
 Table* Group::create_table_accessor(size_t table_ndx)
 {
     REALM_ASSERT(m_tables.size() == m_table_accessors.size());

src/realm/group.hpp

@@ -47,6 +47,8 @@ class GroupFriend;
 /// A group is a collection of named tables.
 ///
 class Group : public ArrayParent {
+    static constexpr StringData g_class_name_prefix = "class_";
+
 public:
     /// Construct a free-standing group. This group instance will be
     /// in the attached state, but neither associated with a file, nor
@@ -272,7 +274,8 @@ class Group : public ArrayParent {
     ///
     //@{
 
-    static const size_t max_table_name_length = 63;
+    static constexpr size_t max_table_name_length = 63;
+    static constexpr size_t max_class_name_length = max_table_name_length - g_class_name_prefix.size();
 
     bool has_table(StringData name) const noexcept;
     TableKey find_table(StringData name) const noexcept;
@@ -293,6 +296,7 @@ class Group : public ArrayParent {
     using TableNameBuffer = std::array<char, max_table_name_length>;
     static StringData class_name_to_table_name(StringData class_name, TableNameBuffer& buffer)
     {
+        REALM_ASSERT(class_name.size() <= max_class_name_length);
         char* p = std::copy_n(g_class_name_prefix.data(), g_class_name_prefix.size(), buffer.data());
         size_t len = std::min(class_name.size(), buffer.size() - g_class_name_prefix.size());
         std::copy_n(class_name.data(), len, p);
@@ -535,8 +539,6 @@ class Group : public ArrayParent {
     }
 
 private:
-    static constexpr StringData g_class_name_prefix = "class_";
-
     // nullptr, if we're sharing an allocator provided during initialization
     std::unique_ptr<SlabAlloc> m_local_alloc;
     // in-use allocator. If local, then equal to m_local_alloc.

src/realm/sync/instruction_applier.cpp

@@ -87,7 +87,7 @@ BinaryData InstructionApplier::get_binary(StringBufferRange range) const
 
 TableRef InstructionApplier::table_for_class_name(StringData class_name) const
 {
-    if (class_name.size() >= Group::max_table_name_length - 6)
+    if (class_name.size() > Group::max_class_name_length)
         bad_transaction_log("class name too long");
     Group::TableNameBuffer buffer;
     return m_transaction.get_table(Group::class_name_to_table_name(class_name, buffer));

src/realm/sync/noinst/client_history_impl.cpp

@@ -1048,7 +1048,6 @@ void ClientHistory::fix_up_client_file_ident_in_stored_changesets(Transaction& g
 
     Group::TableNameBuffer buffer;
     auto get_table_for_class = [&](StringData class_name) -> ConstTableRef {
-        REALM_ASSERT(class_name.size() < Group::max_table_name_length - 6);
         return group.get_table(Group::class_name_to_table_name(class_name, buffer));
     };
 

src/realm/sync/noinst/server/server_history.cpp

@@ -2132,7 +2132,6 @@ void ServerHistory::fixup_state_and_changesets_for_assigned_file_ident(Transacti
     };
 
     auto get_table_for_class = [&](StringData class_name) -> ConstTableRef {
-        REALM_ASSERT(class_name.size() < Group::max_table_name_length - 6);
         Group::TableNameBuffer buffer;
         return group.get_table(Group::class_name_to_table_name(class_name, buffer));
     };