[Net] Modularize multiplayer, expose MultiplayerAPI to extensions.

- RPC configurations are now dictionaries.
- Script.get_rpc_methods renamed to Script.get_rpc_config.
- Node.rpc[_id] and Callable.rpc now return an Error.
- Refactor MultiplayerAPI to allow extension.
- New MultiplayerAPI.rpc method with Array argument (for scripts).
- Move the default MultiplayerAPI implementation to a module.

1 files changed, 416 insertions, 0 deletions

diff --git a/scene/main/multiplayer_api.cpp b/scene/main/multiplayer_api.cpp
new file mode 100644
index 0000000000..95574042a8
--- /dev/null
+++ b/scene/main/multiplayer_api.cpp
@@ -0,0 +1,416 @@
+/*************************************************************************/
+/*  multiplayer_api.cpp                                                  */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2022 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+#include "multiplayer_api.h"
+
+#include "core/debugger/engine_debugger.h"
+#include "core/io/marshalls.h"
+
+#include <stdint.h>
+
+#ifdef DEBUG_ENABLED
+#include "core/os/os.h"
+#endif
+
+StringName MultiplayerAPI::default_interface = StringName();
+
+void MultiplayerAPI::set_default_interface(const StringName &p_interface) {
+	ERR_FAIL_COND_MSG(!ClassDB::is_parent_class(p_interface, MultiplayerAPI::get_class_static()), vformat("Can't make %s the default multiplayer interface since it does not extend MultiplayerAPI.", p_interface));
+	default_interface = p_interface;
+}
+
+StringName MultiplayerAPI::get_default_interface() {
+	return default_interface;
+}
+
+Ref<MultiplayerAPI> MultiplayerAPI::create_default_interface() {
+	if (default_interface != StringName()) {
+		return Ref<MultiplayerAPI>(Object::cast_to<MultiplayerAPI>(ClassDB::instantiate(default_interface)));
+	}
+	return Ref<MultiplayerAPI>(memnew(MultiplayerAPIExtension));
+}
+
+// The variant is compressed and encoded; The first byte contains all the meta
+// information and the format is:
+// - The first LSB 5 bits are used for the variant type.
+// - The next two bits are used to store the encoding mode.
+// - The most significant is used to store the boolean value.
+#define VARIANT_META_TYPE_MASK 0x1F
+#define VARIANT_META_EMODE_MASK 0x60
+#define VARIANT_META_BOOL_MASK 0x80
+#define ENCODE_8 0 << 5
+#define ENCODE_16 1 << 5
+#define ENCODE_32 2 << 5
+#define ENCODE_64 3 << 5
+Error MultiplayerAPI::encode_and_compress_variant(const Variant &p_variant, uint8_t *r_buffer, int &r_len, bool p_allow_object_decoding) {
+	// Unreachable because `VARIANT_MAX` == 27 and `ENCODE_VARIANT_MASK` == 31
+	CRASH_COND(p_variant.get_type() > VARIANT_META_TYPE_MASK);
+
+	uint8_t *buf = r_buffer;
+	r_len = 0;
+	uint8_t encode_mode = 0;
+
+	switch (p_variant.get_type()) {
+		case Variant::BOOL: {
+			if (buf) {
+				// We still have 1 free bit in the meta, so let's use it.
+				buf[0] = (p_variant.operator bool()) ? (1 << 7) : 0;
+				buf[0] |= encode_mode | p_variant.get_type();
+			}
+			r_len += 1;
+		} break;
+		case Variant::INT: {
+			if (buf) {
+				// Reserve the first byte for the meta.
+				buf += 1;
+			}
+			r_len += 1;
+			int64_t val = p_variant;
+			if (val <= (int64_t)INT8_MAX && val >= (int64_t)INT8_MIN) {
+				// Use 8 bit
+				encode_mode = ENCODE_8;
+				if (buf) {
+					buf[0] = val;
+				}
+				r_len += 1;
+			} else if (val <= (int64_t)INT16_MAX && val >= (int64_t)INT16_MIN) {
+				// Use 16 bit
+				encode_mode = ENCODE_16;
+				if (buf) {
+					encode_uint16(val, buf);
+				}
+				r_len += 2;
+			} else if (val <= (int64_t)INT32_MAX && val >= (int64_t)INT32_MIN) {
+				// Use 32 bit
+				encode_mode = ENCODE_32;
+				if (buf) {
+					encode_uint32(val, buf);
+				}
+				r_len += 4;
+			} else {
+				// Use 64 bit
+				encode_mode = ENCODE_64;
+				if (buf) {
+					encode_uint64(val, buf);
+				}
+				r_len += 8;
+			}
+			// Store the meta
+			if (buf) {
+				buf -= 1;
+				buf[0] = encode_mode | p_variant.get_type();
+			}
+		} break;
+		default:
+			// Any other case is not yet compressed.
+			Error err = encode_variant(p_variant, r_buffer, r_len, p_allow_object_decoding);
+			if (err != OK) {
+				return err;
+			}
+			if (r_buffer) {
+				// The first byte is not used by the marshalling, so store the type
+				// so we know how to decompress and decode this variant.
+				r_buffer[0] = p_variant.get_type();
+			}
+	}
+
+	return OK;
+}
+
+Error MultiplayerAPI::decode_and_decompress_variant(Variant &r_variant, const uint8_t *p_buffer, int p_len, int *r_len, bool p_allow_object_decoding) {
+	const uint8_t *buf = p_buffer;
+	int len = p_len;
+
+	ERR_FAIL_COND_V(len < 1, ERR_INVALID_DATA);
+	uint8_t type = buf[0] & VARIANT_META_TYPE_MASK;
+	uint8_t encode_mode = buf[0] & VARIANT_META_EMODE_MASK;
+
+	ERR_FAIL_COND_V(type >= Variant::VARIANT_MAX, ERR_INVALID_DATA);
+
+	switch (type) {
+		case Variant::BOOL: {
+			bool val = (buf[0] & VARIANT_META_BOOL_MASK) > 0;
+			r_variant = val;
+			if (r_len) {
+				*r_len = 1;
+			}
+		} break;
+		case Variant::INT: {
+			buf += 1;
+			len -= 1;
+			if (r_len) {
+				*r_len = 1;
+			}
+			if (encode_mode == ENCODE_8) {
+				// 8 bits.
+				ERR_FAIL_COND_V(len < 1, ERR_INVALID_DATA);
+				int8_t val = buf[0];
+				r_variant = val;
+				if (r_len) {
+					(*r_len) += 1;
+				}
+			} else if (encode_mode == ENCODE_16) {
+				// 16 bits.
+				ERR_FAIL_COND_V(len < 2, ERR_INVALID_DATA);
+				int16_t val = decode_uint16(buf);
+				r_variant = val;
+				if (r_len) {
+					(*r_len) += 2;
+				}
+			} else if (encode_mode == ENCODE_32) {
+				// 32 bits.
+				ERR_FAIL_COND_V(len < 4, ERR_INVALID_DATA);
+				int32_t val = decode_uint32(buf);
+				r_variant = val;
+				if (r_len) {
+					(*r_len) += 4;
+				}
+			} else {
+				// 64 bits.
+				ERR_FAIL_COND_V(len < 8, ERR_INVALID_DATA);
+				int64_t val = decode_uint64(buf);
+				r_variant = val;
+				if (r_len) {
+					(*r_len) += 8;
+				}
+			}
+		} break;
+		default:
+			Error err = decode_variant(r_variant, p_buffer, p_len, r_len, p_allow_object_decoding);
+			if (err != OK) {
+				return err;
+			}
+	}
+
+	return OK;
+}
+
+Error MultiplayerAPI::encode_and_compress_variants(const Variant **p_variants, int p_count, uint8_t *p_buffer, int &r_len, bool *r_raw, bool p_allow_object_decoding) {
+	r_len = 0;
+	int size = 0;
+
+	if (p_count == 0) {
+		if (r_raw) {
+			*r_raw = true;
+		}
+		return OK;
+	}
+
+	// Try raw encoding optimization.
+	if (r_raw && p_count == 1) {
+		*r_raw = false;
+		const Variant &v = *(p_variants[0]);
+		if (v.get_type() == Variant::PACKED_BYTE_ARRAY) {
+			*r_raw = true;
+			const PackedByteArray pba = v;
+			if (p_buffer) {
+				memcpy(p_buffer, pba.ptr(), pba.size());
+			}
+			r_len += pba.size();
+		} else {
+			encode_and_compress_variant(v, p_buffer, size, p_allow_object_decoding);
+			r_len += size;
+		}
+		return OK;
+	}
+
+	// Regular encoding.
+	for (int i = 0; i < p_count; i++) {
+		const Variant &v = *(p_variants[i]);
+		encode_and_compress_variant(v, p_buffer ? p_buffer + r_len : nullptr, size, p_allow_object_decoding);
+		r_len += size;
+	}
+	return OK;
+}
+
+Error MultiplayerAPI::decode_and_decompress_variants(Vector<Variant> &r_variants, const uint8_t *p_buffer, int p_len, int &r_len, bool p_raw, bool p_allow_object_decoding) {
+	r_len = 0;
+	int argc = r_variants.size();
+	if (argc == 0 && p_raw) {
+		return OK;
+	}
+	ERR_FAIL_COND_V(p_raw && argc != 1, ERR_INVALID_DATA);
+	if (p_raw) {
+		r_len = p_len;
+		PackedByteArray pba;
+		pba.resize(p_len);
+		memcpy(pba.ptrw(), p_buffer, p_len);
+		r_variants.write[0] = pba;
+		return OK;
+	}
+
+	Vector<Variant> args;
+	Vector<const Variant *> argp;
+	args.resize(argc);
+
+	for (int i = 0; i < argc; i++) {
+		ERR_FAIL_COND_V_MSG(r_len >= p_len, ERR_INVALID_DATA, "Invalid packet received. Size too small.");
+
+		int vlen;
+		Error err = MultiplayerAPI::decode_and_decompress_variant(r_variants.write[i], &p_buffer[r_len], p_len - r_len, &vlen, p_allow_object_decoding);
+		ERR_FAIL_COND_V_MSG(err != OK, err, "Invalid packet received. Unable to decode state variable.");
+		r_len += vlen;
+	}
+	return OK;
+}
+
+Error MultiplayerAPI::_rpc_bind(int p_peer, Object *p_object, const StringName &p_method, Array p_args) {
+	Vector<Variant> args;
+	Vector<const Variant *> argsp;
+	args.resize(p_args.size());
+	argsp.resize(p_args.size());
+	Variant *ptr = args.ptrw();
+	const Variant **pptr = argsp.ptrw();
+	for (int i = 0; i < p_args.size(); i++) {
+		ptr[i] = p_args[i];
+		pptr[i] = &ptr[i];
+	}
+	return rpcp(p_object, p_peer, p_method, argsp.size() ? argsp.ptrw() : nullptr, argsp.size());
+}
+
+void MultiplayerAPI::_bind_methods() {
+	ClassDB::bind_method(D_METHOD("has_multiplayer_peer"), &MultiplayerAPI::has_multiplayer_peer);
+	ClassDB::bind_method(D_METHOD("get_multiplayer_peer"), &MultiplayerAPI::get_multiplayer_peer);
+	ClassDB::bind_method(D_METHOD("set_multiplayer_peer", "peer"), &MultiplayerAPI::set_multiplayer_peer);
+	ClassDB::bind_method(D_METHOD("get_unique_id"), &MultiplayerAPI::get_unique_id);
+	ClassDB::bind_method(D_METHOD("is_server"), &MultiplayerAPI::is_server);
+	ClassDB::bind_method(D_METHOD("get_remote_sender_id"), &MultiplayerAPI::get_remote_sender_id);
+	ClassDB::bind_method(D_METHOD("poll"), &MultiplayerAPI::poll);
+	ClassDB::bind_method(D_METHOD("rpc", "peer", "object", "method", "arguments"), &MultiplayerAPI::_rpc_bind, DEFVAL(Array()));
+	ClassDB::bind_method(D_METHOD("object_configuration_add", "object", "configuration"), &MultiplayerAPI::object_configuration_add);
+	ClassDB::bind_method(D_METHOD("object_configuration_remove", "object", "configuration"), &MultiplayerAPI::object_configuration_remove);
+
+	ClassDB::bind_method(D_METHOD("get_peers"), &MultiplayerAPI::get_peer_ids);
+
+	ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "multiplayer_peer", PROPERTY_HINT_RESOURCE_TYPE, "MultiplayerPeer", PROPERTY_USAGE_NONE), "set_multiplayer_peer", "get_multiplayer_peer");
+
+	ClassDB::bind_static_method("MultiplayerAPI", D_METHOD("set_default_interface", "interface_name"), &MultiplayerAPI::set_default_interface);
+	ClassDB::bind_static_method("MultiplayerAPI", D_METHOD("get_default_interface"), &MultiplayerAPI::get_default_interface);
+	ClassDB::bind_static_method("MultiplayerAPI", D_METHOD("create_default_interface"), &MultiplayerAPI::create_default_interface);
+
+	ADD_SIGNAL(MethodInfo("peer_connected", PropertyInfo(Variant::INT, "id")));
+	ADD_SIGNAL(MethodInfo("peer_disconnected", PropertyInfo(Variant::INT, "id")));
+	ADD_SIGNAL(MethodInfo("connected_to_server"));
+	ADD_SIGNAL(MethodInfo("connection_failed"));
+	ADD_SIGNAL(MethodInfo("server_disconnected"));
+
+	BIND_ENUM_CONSTANT(RPC_MODE_DISABLED);
+	BIND_ENUM_CONSTANT(RPC_MODE_ANY_PEER);
+	BIND_ENUM_CONSTANT(RPC_MODE_AUTHORITY);
+}
+
+/// MultiplayerAPIExtension
+
+Error MultiplayerAPIExtension::poll() {
+	int err;
+	if (GDVIRTUAL_CALL(_poll, err)) {
+		return (Error)err;
+	}
+	return OK;
+}
+
+void MultiplayerAPIExtension::set_multiplayer_peer(const Ref<MultiplayerPeer> &p_peer) {
+	GDVIRTUAL_CALL(_set_multiplayer_peer, p_peer);
+}
+
+Ref<MultiplayerPeer> MultiplayerAPIExtension::get_multiplayer_peer() {
+	Ref<MultiplayerPeer> peer;
+	if (GDVIRTUAL_CALL(_get_multiplayer_peer, peer)) {
+		return peer;
+	}
+	return nullptr;
+}
+
+int MultiplayerAPIExtension::get_unique_id() {
+	int id;
+	if (GDVIRTUAL_CALL(_get_unique_id, id)) {
+		return id;
+	}
+	return 1;
+}
+
+Vector<int> MultiplayerAPIExtension::get_peer_ids() {
+	Vector<int> ids;
+	if (GDVIRTUAL_CALL(_get_peer_ids, ids)) {
+		return ids;
+	}
+	return Vector<int>();
+}
+
+Error MultiplayerAPIExtension::rpcp(Object *p_obj, int p_peer_id, const StringName &p_method, const Variant **p_arg, int p_argcount) {
+	if (!GDVIRTUAL_IS_OVERRIDDEN(_rpc)) {
+		return ERR_UNAVAILABLE;
+	}
+	Array args;
+	for (int i = 0; i < p_argcount; i++) {
+		args.push_back(*p_arg[i]);
+	}
+	int ret;
+	if (GDVIRTUAL_CALL(_rpc, p_peer_id, p_obj, p_method, args, ret)) {
+		return (Error)ret;
+	}
+	return FAILED;
+}
+
+int MultiplayerAPIExtension::get_remote_sender_id() {
+	int id;
+	if (GDVIRTUAL_CALL(_get_remote_sender_id, id)) {
+		return id;
+	}
+	return 0;
+}
+
+Error MultiplayerAPIExtension::object_configuration_add(Object *p_object, Variant p_config) {
+	int err;
+	if (GDVIRTUAL_CALL(_object_configuration_add, p_object, p_config, err)) {
+		return (Error)err;
+	}
+	return ERR_UNAVAILABLE;
+}
+
+Error MultiplayerAPIExtension::object_configuration_remove(Object *p_object, Variant p_config) {
+	int err;
+	if (GDVIRTUAL_CALL(_object_configuration_remove, p_object, p_config, err)) {
+		return (Error)err;
+	}
+	return ERR_UNAVAILABLE;
+}
+
+void MultiplayerAPIExtension::_bind_methods() {
+	GDVIRTUAL_BIND(_poll);
+	GDVIRTUAL_BIND(_set_multiplayer_peer, "multiplayer_peer");
+	GDVIRTUAL_BIND(_get_multiplayer_peer);
+	GDVIRTUAL_BIND(_get_unique_id);
+	GDVIRTUAL_BIND(_get_peer_ids);
+	GDVIRTUAL_BIND(_rpc, "peer", "object", "method", "args");
+	GDVIRTUAL_BIND(_get_remote_sender_id);
+	GDVIRTUAL_BIND(_object_configuration_add, "object", "configuration");
+	GDVIRTUAL_BIND(_object_configuration_remove, "object", "configuration");
+}