text: // Copyright (c) 2017-2021, The Khronos Group Inc.
  // Copyright (c) 2017-2019 Valve Corporation
  // Copyright (c) 2017-2019 LunarG, Inc.
  //
  // SPDX-License-Identifier: Apache-2.0 OR MIT
  //
  // Initial Author: Mark Young <marky@lunarg.com>
  //
  
  #pragma once
  
  #include "loader_platform.hpp"
  
  #include <openxr/openxr.h>
  
  #include <string>
  #include <vector>
  #include <unordered_map>
  #include <mutex>
  #include <memory>
  
  #ifdef XR_USE_PLATFORM_ANDROID
  #define XR_KHR_LOADER_INIT_SUPPORT
  #endif
  
  class RuntimeManifestFile;
  struct XrGeneratedDispatchTable;
  
  #ifdef XR_KHR_LOADER_INIT_SUPPORT
  //! Initialize loader, where required.
  XrResult InitializeLoader(const XrLoaderInitInfoBaseHeaderKHR* loaderInitInfo);
  #endif
  
  class RuntimeInterface {
     public:
      virtual ~RuntimeInterface();
  
      // Helper functions for loading and unloading the runtime (but only when necessary)
      static XrResult LoadRuntime(const std::string& openxr_command);
      static void UnloadRuntime(const std::string& openxr_command);
      static RuntimeInterface& GetRuntime() { return *(GetInstance().get()); }
      static XrResult GetInstanceProcAddr(XrInstance instance, const char* name, PFN_xrVoidFunction* function);
  
      // Get the direct dispatch table to this runtime, without API layers or loader terminators.
      static const XrGeneratedDispatchTable* GetDispatchTable(XrInstance instance);
      static const XrGeneratedDispatchTable* GetDebugUtilsMessengerDispatchTable(XrDebugUtilsMessengerEXT messenger);
  
      void GetInstanceExtensionProperties(std::vector<XrExtensionProperties>& extension_properties);
      bool SupportsExtension(const std::string& extension_name);
      XrResult CreateInstance(const XrInstanceCreateInfo* info, XrInstance* instance);
      XrResult DestroyInstance(XrInstance instance);
      bool TrackDebugMessenger(XrInstance instance, XrDebugUtilsMessengerEXT messenger);
      void ForgetDebugMessenger(XrDebugUtilsMessengerEXT messenger);
  
      // No default construction
      RuntimeInterface() = delete;
  
      // Non-copyable
      RuntimeInterface(const RuntimeInterface&) = delete;
      RuntimeInterface& operator=(const RuntimeInterface&) = delete;
  
     private:
      RuntimeInterface(LoaderPlatformLibraryHandle runtime_library, PFN_xrGetInstanceProcAddr get_instance_proc_addr);
      void SetSupportedExtensions(std::vector<std::string>& supported_extensions);
      static XrResult TryLoadingSingleRuntime(const std::string& openxr_command, std::unique_ptr<RuntimeManifestFile>& manifest_file);
  
      static std::unique_ptr<RuntimeInterface>& GetInstance() {
          static std::unique_ptr<RuntimeInterface> instance;
          return instance;
      }
  
      LoaderPlatformLibraryHandle _runtime_library;
      PFN_xrGetInstanceProcAddr _get_instance_proc_addr;
      std::unordered_map<XrInstance, std::unique_ptr<XrGeneratedDispatchTable>> _dispatch_table_map;
      std::mutex _dispatch_table_mutex;
      std::unordered_map<XrDebugUtilsMessengerEXT, XrInstance> _messenger_to_instance_map;
      std::mutex _messenger_to_instance_mutex;
      std::vector<std::string> _supported_extensions;
  };
  