Some changes to the design of base-writer.hpp

luprex/cpp/core/drivenengine.cpp

@@ -235,8 +235,12 @@ class ReplayLogfile : public BaseReader<ReplayLogfile>, public std::ifstream {
     using std::ifstream::ifstream;
 public:
     using read_string_type = std::string;
-    void read_bytes_into(char *n, size_t size) { read(n, size); }
-    bool read_beyond_eof() { return !good(); }
+    void read_bytes_into(char *n, size_t size) {
+        read(n, size);
+        if (!good()) {
+            memset(n, 0, size);
+        }
+    }
     void raise_string_too_long() {
         fprintf(stderr, "string in logfile is too long");
         std::abort();

luprex/cpp/core/streambuffer.hpp

@@ -302,6 +302,8 @@ public:
 
     // Copy bytes from the StreamBuffer into an external buffer.
     //
+    // Returns true if the bytes were successfully read.
+    //
     void read_bytes_into(char *target, int64_t len);
     
     // Read a string as a string_view.
@@ -387,10 +389,6 @@ public:
     void raise_truncated() { throw StreamCorruption(); }
     void raise_string_too_long() { throw StreamCorruption(); }
     
-    // This is always false, because this module throws exceptions
-    // when reading beyond EOF.
-    bool read_beyond_eof() { return false; }
-
 private:
     // Start and end of the allocated block.
     char *buf_lo_;

luprex/ext/base-writer.hpp

@@ -118,8 +118,21 @@ public:
 //
 //     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();
+//     void handle_string_too_long();
+//
+// Error Handling:
+//
+//     It is up to the derived class whether it wants
+//     to report errors using exceptions or flags.
+//
+//     If read_bytes_into discovers there's not enough bytes,
+//     there are two valid options: throw an exception, OR,
+//     set an error flag and fill the buffer with zeros.
+//
+//     If read_string discovers that the string is longer than
+//     the allowed limit, it will call handle_string_too_long.
+//     This function may either throw an exception, or set an
+//     error flag.
 //
 ///////////////////////////////////////////////////////////////
 
@@ -131,7 +144,6 @@ protected:
         T result;
         Derived *dthis = static_cast<Derived*>(this);
         dthis->read_bytes_into((char *)(&result), sizeof(result));
-        if (dthis->read_beyond_eof()) result = 0;
         return result;
     }
 
@@ -146,7 +158,7 @@ public:
     int32_t read_int32() { return read_value_core<int32_t>(); }
     int64_t read_int64() { return read_value_core<int64_t>(); }
     
-    bool read_bool() { return read_uint8(); }
+    bool read_bool() { return (bool)read_uint8(); }
     char read_char() { return read_value_core<char>(); }
     float read_float() { return read_value_core<float>(); }
     double read_double() { return read_value_core<double>(); }
@@ -162,10 +174,12 @@ public:
     auto read_string_limit(uint64_t limit) {
         size_t len = read_length();
         Derived *dthis = static_cast<Derived*>(this);
-        if (len > limit) dthis->raise_string_too_long();
+        if (len > limit) {
+            dthis->raise_string_too_long();
+            len = 0;
+        }
         typename Derived::read_string_type result(len, ' ');
         dthis->read_bytes_into(&(result[0]), len);
-        if (dthis->read_beyond_eof()) result.clear();
         return result;
     }