Add an empty friend service implementation

This is used to access a users friends. It is used by Super Mario
Odyssey.

app/CMakeLists.txt

@@ -115,6 +115,8 @@ add_library(skyline SHARED
         ${source_DIR}/skyline/services/lm/ILogger.cpp
         ${source_DIR}/skyline/services/account/IAccountServiceForApplication.cpp
         ${source_DIR}/skyline/services/account/IManagerForApplication.cpp
+        ${source_DIR}/skyline/services/friends/IServiceCreator.cpp
+        ${source_DIR}/skyline/services/friends/IFriendService.cpp
         ${source_DIR}/skyline/vfs/partition_filesystem.cpp
         ${source_DIR}/skyline/vfs/rom_filesystem.cpp
         ${source_DIR}/skyline/vfs/os_backing.cpp

app/src/main/cpp/skyline/services/base_service.h

@@ -71,6 +71,8 @@ namespace skyline::service {
         lm_ILogger,
         account_IAccountServiceForApplication,
         account_IManagerForApplication,
+        friends_IServiceCreator,
+        friends_IFriendService,
     };
 
     /**
@@ -105,6 +107,7 @@ namespace skyline::service {
         {"pctl:r", Service::pctl_IParentalControlServiceFactory},
         {"lm", Service::lm_ILogService},
         {"acc:u0", Service::account_IAccountServiceForApplication},
+        {"friend:u", Service::friends_IServiceCreator},
     };
 
     class ServiceManager;

app/src/main/cpp/skyline/services/friends/IFriendService.cpp

@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: MPL-2.0
+// Copyright © 2020 Skyline Team and Contributors (https://github.com/skyline-emu/)
+
+#include "IFriendService.h"
+
+namespace skyline::service::friends {
+    IFriendService::IFriendService(const DeviceState &state, ServiceManager &manager) : BaseService(state, manager, Service::friends_IFriendService, "friends:IFriendService", {
+    }) {}
+}

app/src/main/cpp/skyline/services/friends/IFriendService.h

@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: MPL-2.0
+// Copyright © 2020 Skyline Team and Contributors (https://github.com/skyline-emu/)
+
+#pragma once
+
+#include <services/base_service.h>
+#include <services/serviceman.h>
+
+namespace skyline::service::friends {
+    /**
+     * @brief IFriendService is used by applications to access information about a user's friends (https://switchbrew.org/wiki/Friend_services#IFriendService)
+     */
+    class IFriendService : public BaseService {
+      public:
+        IFriendService(const DeviceState &state, ServiceManager &manager);
+    };
+}

app/src/main/cpp/skyline/services/friends/IServiceCreator.cpp

@@ -0,0 +1,15 @@
+// SPDX-License-Identifier: MPL-2.0
+// Copyright © 2020 Skyline Team and Contributors (https://github.com/skyline-emu/)
+
+#include "IFriendService.h"
+#include "IServiceCreator.h"
+
+namespace skyline::service::friends {
+    IServiceCreator::IServiceCreator(const DeviceState &state, ServiceManager &manager) : BaseService(state, manager, Service::friends_IServiceCreator, "friends:IServiceCreator", {
+        {0x0, SFUNC(IServiceCreator::CreateFriendService)}
+    }) {}
+
+    void IServiceCreator::CreateFriendService(type::KSession &session, ipc::IpcRequest &request, ipc::IpcResponse &response) {
+        manager.RegisterService(SRVREG(IFriendService), session, response);
+    }
+}

app/src/main/cpp/skyline/services/friends/IServiceCreator.h

@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: MPL-2.0
+// Copyright © 2020 Skyline Team and Contributors (https://github.com/skyline-emu/)
+
+#pragma once
+
+#include <services/base_service.h>
+#include <services/serviceman.h>
+
+namespace skyline::service::friends {
+    /**
+     * @brief IServiceCreator or friend:u is used by applications to open an IFriendService instance for accessing user friend info (https://switchbrew.org/wiki/Friend_services#friend:u.2C_friend:v.2C_friend:m.2C_friend:s.2C_friend:a)
+     */
+    class IServiceCreator : public BaseService {
+      public:
+        IServiceCreator(const DeviceState &state, ServiceManager &manager);
+
+        /**
+         * @brief This opens an IFriendService that can be used by applications to access user friend info
+         */
+        void CreateFriendService(type::KSession &session, ipc::IpcRequest &request, ipc::IpcResponse &response);
+    };
+}

app/src/main/cpp/skyline/services/serviceman.cpp

@@ -21,6 +21,7 @@
 #include "pctl/IParentalControlServiceFactory.h"
 #include "lm/ILogService.h"
 #include "account/IAccountServiceForApplication.h"
+#include "friends/IServiceCreator.h"
 #include "serviceman.h"
 
 namespace skyline::service {
@@ -90,6 +91,9 @@ namespace skyline::service {
             case Service::account_IAccountServiceForApplication:
                 serviceObj = std::make_shared<account::IAccountServiceForApplication>(state, *this);
                 break;
+            case Service::friends_IServiceCreator:
+                serviceObj = std::make_shared<friends::IServiceCreator>(state, *this);
+                break;
             default:
                 throw exception("CreateService called on missing object, type: {}", serviceType);
         }