docs/object-serialization/cpp/configuration.md - fory - Git at Google

 ---
 title: Configuration
 sidebar_position: 4
 id: configuration
 license: |
   Licensed to the Apache Software Foundation (ASF) under one or more
   contributor license agreements.  See the NOTICE file distributed with
   this work for additional information regarding copyright ownership.
   The ASF licenses this file to You under the Apache License, Version 2.0
   (the "License"); you may not use this file except in compliance with
   the License.  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
 ---

 This page covers C++ Fory instance configuration. `Fory::builder()` creates xlang
 payloads by default. Compatible mode is also enabled by default. Select native
 mode only when the payload stays in C++.

 ## Builder Pattern

 Use `Fory::builder()` to construct Fory instances with custom configuration:

 ```cpp
 #include "fory/serialization/fory.h"

 using namespace fory::serialization;

 // Default xlang mode.
 auto fory = Fory::builder().build();

 // Native mode for C++-only payloads.
 auto fory = Fory::builder()
     .xlang(false)
     .build();

 // Same-schema optimization. Use only when every reader and writer
 // always uses the same schema.
 auto fory = Fory::builder()
     .compatible(false)
     .build();
 ```

 ## Configuration

 ### xlang(bool)

 Select the wire mode.

 ```cpp
 auto fory = Fory::builder()
     .xlang(false)
     .build();
 ```

 When `true`, C++ writes the xlang wire format used by Java, Python, Go, Rust,
 JavaScript/TypeScript, C#, Swift, Dart, Scala, and Kotlin. When `false`, C++
 writes native-mode payloads for C++-only traffic.

 **Default:** `true`

 ### compatible(bool)

 Compatible mode is enabled by default. No builder call is required for the
 default compatible mode. Set `.compatible(false)` only when every reader and
 writer always uses the same schema and you want faster serialization and smaller
 size.

 ```cpp
 auto fory = Fory::builder()
     .compatible(false)
     .build();
 ```

 For xlang payloads, use `.compatible(false)` only after verifying that every language uses the same schema, or when native types are generated from Fory schema IDL.

 **Default:** `true`

 ### track_ref(bool)

 Enable/disable reference tracking for shared and circular references.

 ```cpp
 auto fory = Fory::builder()
     .track_ref(true)  // Enable reference tracking
     .build();
 ```

 When enabled, avoids duplicating shared objects and handles cycles.

 **Default:** `true`

 ### max_graph_memory_bytes(int64_t)

 Set an approximate graph-memory gate for one root deserialization.

 ```cpp
 auto fory = Fory::builder()
     .max_graph_memory_bytes(64 * 1024 * 1024)
     .build();
 ```

 The default limit is a fixed `128 MiB` for byte-array, `Buffer`, and stream
 roots. Positive values override the default. Explicit non-positive values are
 rejected when the Fory instance is created.

 This budget is an approximate lower-bound estimate for materialized graph
 owners, mainly collections, maps, arrays, structs, and objects. It is not an
 exact process heap limit; actual process memory can be higher. Dedicated
 string, binary, primitive scalar, and primitive dense-array leaf values are
 skipped by this budget and continue to rely on byte-availability checks: if the
 unread input does not contain enough bytes, Fory will not read or create that
 leaf value.

 **Default:** `128 MiB`

 ### max_unbacked_container_items(int64_t)

 Limit collection elements and map entries whose repeated read bodies do not
 consume proportional input during one root deserialization. The default is
 `8192`; zero is a strict limit.

 ```cpp
 auto fory = Fory::builder()
     .max_unbacked_container_items(8192)
     .build();
 ```

 ### max_dyn_depth(uint32_t)

 Set maximum allowed nesting depth for dynamically-typed objects.

 ```cpp
 auto fory = Fory::builder()
     .max_dyn_depth(10)  // Allow up to 10 levels
     .build();
 ```

 This limits the maximum depth for nested polymorphic object serialization (e.g., `shared_ptr<Base>`, `unique_ptr<Base>`). This prevents stack overflow from deeply nested structures in dynamic serialization scenarios.

 **Default:** `5`

 **When to adjust:**

 - **Increase**: For legitimate deeply nested data structures
 - **Decrease**: For stricter security requirements or shallow data structures

 ### max_schema_versions_per_type(uint32_t)

 Set the maximum accepted remote metadata versions for one logical type.

 ```cpp
 auto fory = Fory::builder()
     .max_schema_versions_per_type(10)
     .build();
 ```

 **Default:** `10`

 ### max_type_fields(uint32_t)

 Set the maximum fields accepted in one received remote struct metadata body.

 ```cpp
 auto fory = Fory::builder()
     .max_type_fields(512)
     .build();
 ```

 **Default:** `512`

 ### max_type_meta_bytes(uint32_t)

 Set the maximum encoded body bytes accepted for one received TypeDef body,
 excluding the 8-byte header and any extended-size varint.

 ```cpp
 auto fory = Fory::builder()
     .max_type_meta_bytes(4096)
     .build();
 ```

 **Default:** `4096`

 ### max_average_schema_versions_per_type(uint32_t)

 Set the average accepted remote metadata versions across accepted remote types.
 The effective global floor is `8192` schemas.

 ```cpp
 auto fory = Fory::builder()
     .max_average_schema_versions_per_type(3)
     .build();
 ```

 **Default:** `3`

 ### check_struct_version(bool)

 Enable/disable struct version checking.

 ```cpp
 auto fory = Fory::builder()
     .compatible(false)
     .check_struct_version(true)  // Enable version checking
     .build();
 ```

 When enabled, validates type hashes to detect schema mismatches.

 **Default:** `false`

 ## Thread-Safe vs Single-Threaded

 ### Single-Threaded (Fastest)

 ```cpp
 auto fory = Fory::builder().build();  // Returns Fory
 ```

 Single-threaded `Fory` is the fastest option, but NOT thread-safe. Use one instance per thread.

 ### Thread-Safe

 ```cpp
 auto fory = Fory::builder().build_thread_safe();  // Returns ThreadSafeFory
 ```

 `ThreadSafeFory` uses a pool of Fory instances to provide thread-safe serialization. Slightly slower due to pool overhead, but safe to use from multiple threads concurrently.

 ## Configuration Summary

 | Option                                           | Description                                       | Default   |
 | ------------------------------------------------ | ------------------------------------------------- | --------- |
 | `xlang(bool)`                                    | Use xlang mode                                    | `true`    |
 | `compatible(bool)`                               | Enable schema evolution                           | `true`    |
 | `track_ref(bool)`                                | Enable reference tracking                         | `true`    |
 | `max_graph_memory_bytes(int64_t)`                | Approximate graph-memory gate per root read       | `128 MiB` |
 | `max_unbacked_container_items(int64_t)`          | Unbacked collection/map work per root read        | `8192`    |
 | `max_dyn_depth(uint32_t)`                        | Maximum nesting depth for dynamic types           | `5`       |
 | `max_type_fields(uint32_t)`                      | Max fields in one received struct metadata body   | `512`     |
 | `max_type_meta_bytes(uint32_t)`                  | Max encoded bytes in one received metadata body   | `4096`    |
 | `max_schema_versions_per_type(uint32_t)`         | Max remote metadata versions for one logical type | `10`      |
 | `max_average_schema_versions_per_type(uint32_t)` | Average remote metadata versions across types     | `3`       |
 | `check_struct_version(bool)`                     | Enable struct version checking                    | `false`   |

 ## Security

 See [C++ Security](security.md) for trust boundaries, safe reader configuration, and verification.

 ## Related Topics

 - [Basic Serialization](basic-serialization.md) - Using configured Fory
 - [Cross-Language Interoperability](basic-serialization.md#cross-language-interoperability) - xlang mode details
 - [Type Registration](type-registration.md) - Registering types
	---
	title: Configuration
	sidebar_position: 4
	id: configuration
	license: \|
	Licensed to the Apache Software Foundation (ASF) under one or more
	contributor license agreements. See the NOTICE file distributed with
	this work for additional information regarding copyright ownership.
	The ASF licenses this file to You under the Apache License, Version 2.0
	(the "License"); you may not use this file except in compliance with
	the License. You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
	---

	This page covers C++ Fory instance configuration. `Fory::builder()` creates xlang
	payloads by default. Compatible mode is also enabled by default. Select native
	mode only when the payload stays in C++.

	## Builder Pattern

	Use `Fory::builder()` to construct Fory instances with custom configuration:

	```cpp
	#include "fory/serialization/fory.h"

	using namespace fory::serialization;

	// Default xlang mode.
	auto fory = Fory::builder().build();

	// Native mode for C++-only payloads.
	auto fory = Fory::builder()
	.xlang(false)
	.build();

	// Same-schema optimization. Use only when every reader and writer
	// always uses the same schema.
	auto fory = Fory::builder()
	.compatible(false)
	.build();
	```

	## Configuration

	### xlang(bool)

	Select the wire mode.

	```cpp
	auto fory = Fory::builder()
	.xlang(false)
	.build();
	```

	When `true`, C++ writes the xlang wire format used by Java, Python, Go, Rust,
	JavaScript/TypeScript, C#, Swift, Dart, Scala, and Kotlin. When `false`, C++
	writes native-mode payloads for C++-only traffic.

	Default: `true`

	### compatible(bool)

	Compatible mode is enabled by default. No builder call is required for the
	default compatible mode. Set `.compatible(false)` only when every reader and
	writer always uses the same schema and you want faster serialization and smaller
	size.

	```cpp
	auto fory = Fory::builder()
	.compatible(false)
	.build();
	```

	For xlang payloads, use `.compatible(false)` only after verifying that every language uses the same schema, or when native types are generated from Fory schema IDL.

	Default: `true`

	### track_ref(bool)

	Enable/disable reference tracking for shared and circular references.

	```cpp
	auto fory = Fory::builder()
	.track_ref(true) // Enable reference tracking
	.build();
	```

	When enabled, avoids duplicating shared objects and handles cycles.

	Default: `true`

	### max_graph_memory_bytes(int64_t)

	Set an approximate graph-memory gate for one root deserialization.

	```cpp
	auto fory = Fory::builder()
	.max_graph_memory_bytes(64 * 1024 * 1024)
	.build();
	```

	The default limit is a fixed `128 MiB` for byte-array, `Buffer`, and stream
	roots. Positive values override the default. Explicit non-positive values are
	rejected when the Fory instance is created.

	This budget is an approximate lower-bound estimate for materialized graph
	owners, mainly collections, maps, arrays, structs, and objects. It is not an
	exact process heap limit; actual process memory can be higher. Dedicated
	string, binary, primitive scalar, and primitive dense-array leaf values are
	skipped by this budget and continue to rely on byte-availability checks: if the
	unread input does not contain enough bytes, Fory will not read or create that
	leaf value.

	Default: `128 MiB`

	### max_unbacked_container_items(int64_t)

	Limit collection elements and map entries whose repeated read bodies do not
	consume proportional input during one root deserialization. The default is
	`8192`; zero is a strict limit.

	```cpp
	auto fory = Fory::builder()
	.max_unbacked_container_items(8192)
	.build();
	```

	### max_dyn_depth(uint32_t)

	Set maximum allowed nesting depth for dynamically-typed objects.

	```cpp
	auto fory = Fory::builder()
	.max_dyn_depth(10) // Allow up to 10 levels
	.build();
	```

	This limits the maximum depth for nested polymorphic object serialization (e.g., `shared_ptr<Base>`, `unique_ptr<Base>`). This prevents stack overflow from deeply nested structures in dynamic serialization scenarios.

	Default: `5`

	When to adjust:

	- Increase: For legitimate deeply nested data structures
	- Decrease: For stricter security requirements or shallow data structures

	### max_schema_versions_per_type(uint32_t)

	Set the maximum accepted remote metadata versions for one logical type.

	```cpp
	auto fory = Fory::builder()
	.max_schema_versions_per_type(10)
	.build();
	```

	Default: `10`

	### max_type_fields(uint32_t)

	Set the maximum fields accepted in one received remote struct metadata body.

	```cpp
	auto fory = Fory::builder()
	.max_type_fields(512)
	.build();
	```

	Default: `512`

	### max_type_meta_bytes(uint32_t)

	Set the maximum encoded body bytes accepted for one received TypeDef body,
	excluding the 8-byte header and any extended-size varint.

	```cpp
	auto fory = Fory::builder()
	.max_type_meta_bytes(4096)
	.build();
	```

	Default: `4096`

	### max_average_schema_versions_per_type(uint32_t)

	Set the average accepted remote metadata versions across accepted remote types.
	The effective global floor is `8192` schemas.

	```cpp
	auto fory = Fory::builder()
	.max_average_schema_versions_per_type(3)
	.build();
	```

	Default: `3`

	### check_struct_version(bool)

	Enable/disable struct version checking.

	```cpp
	auto fory = Fory::builder()
	.compatible(false)
	.check_struct_version(true) // Enable version checking
	.build();
	```

	When enabled, validates type hashes to detect schema mismatches.

	Default: `false`

	## Thread-Safe vs Single-Threaded

	### Single-Threaded (Fastest)

	```cpp
	auto fory = Fory::builder().build(); // Returns Fory
	```

	Single-threaded `Fory` is the fastest option, but NOT thread-safe. Use one instance per thread.

	### Thread-Safe

	```cpp
	auto fory = Fory::builder().build_thread_safe(); // Returns ThreadSafeFory
	```

	`ThreadSafeFory` uses a pool of Fory instances to provide thread-safe serialization. Slightly slower due to pool overhead, but safe to use from multiple threads concurrently.

	## Configuration Summary

	\| Option \| Description \| Default \|
	\| ------------------------------------------------ \| ------------------------------------------------- \| --------- \|
	\| `xlang(bool)` \| Use xlang mode \| `true` \|
	\| `compatible(bool)` \| Enable schema evolution \| `true` \|
	\| `track_ref(bool)` \| Enable reference tracking \| `true` \|
	\| `max_graph_memory_bytes(int64_t)` \| Approximate graph-memory gate per root read \| `128 MiB` \|
	\| `max_unbacked_container_items(int64_t)` \| Unbacked collection/map work per root read \| `8192` \|
	\| `max_dyn_depth(uint32_t)` \| Maximum nesting depth for dynamic types \| `5` \|
	\| `max_type_fields(uint32_t)` \| Max fields in one received struct metadata body \| `512` \|
	\| `max_type_meta_bytes(uint32_t)` \| Max encoded bytes in one received metadata body \| `4096` \|
	\| `max_schema_versions_per_type(uint32_t)` \| Max remote metadata versions for one logical type \| `10` \|
	\| `max_average_schema_versions_per_type(uint32_t)` \| Average remote metadata versions across types \| `3` \|
	\| `check_struct_version(bool)` \| Enable struct version checking \| `false` \|

	## Security

	See [C++ Security](security.md) for trust boundaries, safe reader configuration, and verification.

	## Related Topics

	- [Basic Serialization](basic-serialization.md) - Using configured Fory
	- [Cross-Language Interoperability](basic-serialization.md#cross-language-interoperability) - xlang mode details
	- [Type Registration](type-registration.md) - Registering types