Saveload: Change SlLoadFromBuffer to take a template functor

src/saveload/company_sl.cpp

@@ -591,7 +591,7 @@ static void Load_PLYP()
 	ReadBuffer::GetCurrent()->CopyBytes(buffer.data(), buffer.size());
 
 	if (crypto_unlock(buffer.data(), _network_company_password_storage_key, nonce, mac, buffer.data(), buffer.size()) == 0) {
-		SlLoadFromBuffer(buffer.data(), buffer.size(), [](void *) {
+		SlLoadFromBuffer(buffer.data(), buffer.size(), []() {
 			_network_company_server_id.resize(SlReadUint32());
 			ReadBuffer::GetCurrent()->CopyBytes((uint8 *)_network_company_server_id.data(), _network_company_server_id.size());
 
@@ -605,7 +605,7 @@ static void Load_PLYP()
 			}
 
 			ReadBuffer::GetCurrent()->SkipBytes(SlReadByte()); // Skip padding
-		}, nullptr);
+		});
 		DEBUG(sl, 2, "Decrypted company passwords");
 	} else {
 		DEBUG(sl, 2, "Failed to decrypt company passwords");

src/saveload/saveload.cpp

@@ -2071,33 +2071,34 @@ std::vector<byte> SlSaveToVector(AutolengthProc *proc, void *arg)
 	return std::vector<uint8>(result.first, result.first + result.second);
 }
 
-/**
- * Run proc, loading exactly length bytes from the contents of buffer
- * @param proc The callback procedure that is called
- * @param arg The variable that will be used for the callback procedure
- */
-void SlLoadFromBuffer(const byte *buffer, size_t length, AutolengthProc *proc, void *arg)
+SlLoadFromBufferState SlLoadFromBufferSetup(const byte *buffer, size_t length)
 {
 	assert(_sl.action == SLA_LOAD || _sl.action == SLA_LOAD_CHECK);
 
-	size_t old_obj_len = _sl.obj_len;
+	SlLoadFromBufferState state;
+
+	state.old_obj_len = _sl.obj_len;
 	_sl.obj_len = length;
 
 	ReadBuffer *reader = ReadBuffer::GetCurrent();
-	byte *old_bufp = reader->bufp;
-	byte *old_bufe = reader->bufe;
+	state.old_bufp = reader->bufp;
+	state.old_bufe = reader->bufe;
 	reader->bufp = const_cast<byte *>(buffer);
 	reader->bufe = const_cast<byte *>(buffer) + length;
 
-	proc(arg);
+	return state;
+}
 
+void SlLoadFromBufferRestore(const SlLoadFromBufferState &state, const byte *buffer, size_t length)
+{
+	ReadBuffer *reader = ReadBuffer::GetCurrent();
 	if (reader->bufp != reader->bufe || reader->bufe != buffer + length) {
 		SlErrorCorrupt("SlLoadFromBuffer: Wrong number of bytes read");
 	}
 
-	_sl.obj_len = old_obj_len;
-	reader->bufp = old_bufp;
-	reader->bufe = old_bufe;
+	_sl.obj_len = state.old_obj_len;
+	reader->bufp = state.old_bufp;
+	reader->bufe = state.old_bufe;
 }
 
 /*

src/saveload/saveload.h

@@ -629,12 +629,32 @@ int SlIterateArray();
 
 void SlAutolength(AutolengthProc *proc, void *arg);
 std::vector<uint8> SlSaveToVector(AutolengthProc *proc, void *arg);
-void SlLoadFromBuffer(const byte *buffer, size_t length, AutolengthProc *proc, void *arg);
 size_t SlGetFieldLength();
 void SlSetLength(size_t length);
 size_t SlCalcObjMemberLength(const void *object, const SaveLoad &sld);
 size_t SlCalcObjLength(const void *object, const SaveLoadTable &slt);
 
+struct SlLoadFromBufferState {
+	size_t old_obj_len;
+	byte *old_bufp;
+	byte *old_bufe;
+};
+
+/**
+ * Run proc, loading exactly length bytes from the contents of buffer
+ * @param proc The callback procedure that is called
+ */
+template <typename F>
+void SlLoadFromBuffer(const byte *buffer, size_t length, F proc)
+{
+	extern SlLoadFromBufferState SlLoadFromBufferSetup(const byte *buffer, size_t length);
+	extern void SlLoadFromBufferRestore(const SlLoadFromBufferState &state, const byte *buffer, size_t length);
+
+	SlLoadFromBufferState state = SlLoadFromBufferSetup(buffer, length);
+	proc();
+	SlLoadFromBufferRestore(state, buffer, length);
+}
+
 void SlGlobList(const SaveLoadTable &slt);
 void SlArray(void *array, size_t length, VarType conv);
 void SlObject(void *object, const SaveLoadTable &slt);