Convert DrivenEngine rlog/wlog to use BaseWriter

luprex/ext/base-writer.hpp

@@ -31,14 +31,13 @@
 //     void write_length(size_t data)
 //     void write_string(std::string_view data)
 //
-// In order to derive from BaseWriter, you must use the CRTP pattern:
+// You should derive from BaseWriter using the CRTP pattern:
 //
 //     class DerivedWriter : public BaseWriter<DerivedWriter>
 //
-// And you must provide two methods in the derived class:
+// You must provide two methods in the derived class:
 //
 //     write_bytes(const char *n, size_t size)
-//
 //     raise_truncated()
 //
 ///////////////////////////////////////////////////////////////
@@ -111,15 +110,16 @@ public:
 //     String read_string_limit(uint64_t size);
 //     String read_string();
 //
-// In order to derive from BaseReader, you must use the CRTP pattern:
+// You should derive from BaseReader using the CRTP pattern:
 //
 //     class DerivedReader : public BaseReader<DerivedReader>
 //
 // The derived class must provide:
 //
-//     using read_string_type = std::string; // or similar
+//     using read_string_type = std::string; // or compatible
 //     void read_bytes_into(char *n, size_t size)
 //     void raise_string_too_long();
+//     bool read_beyond_eof();
 //
 ///////////////////////////////////////////////////////////////
 
@@ -129,7 +129,9 @@ protected:
     template<class T>
     T read_value_core() {
         T result;
-        static_cast<Derived*>(this)->read_bytes_into((char *)(&result), sizeof(result));
+        Derived *dthis = static_cast<Derived*>(this);
+        dthis->read_bytes_into((char *)(&result), sizeof(result));
+        if (dthis->read_beyond_eof()) result = 0;
         return result;
     }
 
@@ -159,9 +161,11 @@ public:
 
     auto read_string_limit(uint64_t limit) {
         size_t len = read_length();
-        if (len > limit) static_cast<Derived*>(this)->raise_string_too_long();
+        Derived *dthis = static_cast<Derived*>(this);
+        if (len > limit) dthis->raise_string_too_long();
         typename Derived::read_string_type result(len, ' ');
-        static_cast<Derived*>(this)->read_bytes_into(&(result[0]), len);
+        dthis->read_bytes_into(&(result[0]), len);
+        if (dthis->read_beyond_eof()) result.clear();
         return result;
     }