thread_apple.h

/**************************************************************************/
/*  thread_apple.h                                                        */
/**************************************************************************/
/*                         This file is part of:                          */
/*                             GODOT ENGINE                               */
/*                        https://godotengine.org                         */
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/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
/*                                                                        */
/* 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  */
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/* 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     */
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#pragma once

#include "core/templates/safe_refcount.h"
#include "core/typedefs.h"

#include <pthread.h>
#include <new> // For hardware interference size

class String;

class Thread {
public:
	typedef void (*Callback)(void *p_userdata);

	typedef uint64_t ID;

	enum : ID {
		UNASSIGNED_ID = 0,
		MAIN_ID = 1
	};

	enum Priority {
		PRIORITY_LOW,
		PRIORITY_NORMAL,
		PRIORITY_HIGH
	};

	struct Settings {
		Priority priority;
		/// Override the default stack size (0 means default)
		uint64_t stack_size = 0;
		Settings() { priority = PRIORITY_NORMAL; }
	};

#if defined(__cpp_lib_hardware_interference_size)
	GODOT_GCC_WARNING_PUSH_AND_IGNORE("-Winterference-size")
	static constexpr size_t CACHE_LINE_BYTES = std::hardware_destructive_interference_size;
	GODOT_GCC_WARNING_POP
#else
	// At a negligible memory cost, we use a conservatively high value.
	static constexpr size_t CACHE_LINE_BYTES = 128;
#endif

private:
	friend class Main;

	ID id = UNASSIGNED_ID;
	pthread_t pthread;

	static SafeNumeric<uint64_t> id_counter;
	static thread_local ID caller_id;

	static void *thread_callback(void *p_data);

	static void make_main_thread() { caller_id = MAIN_ID; }
	static void release_main_thread() { caller_id = id_counter.increment(); }

public:
	_FORCE_INLINE_ static void yield() { pthread_yield_np(); }

	_FORCE_INLINE_ ID get_id() const { return id; }
	// get the ID of the caller thread
	_FORCE_INLINE_ static ID get_caller_id() {
		return caller_id;
	}
	// get the ID of the main thread
	_FORCE_INLINE_ static ID get_main_id() { return MAIN_ID; }

	_FORCE_INLINE_ static bool is_main_thread() { return caller_id == MAIN_ID; }

	static Error set_name(const String &p_name);

	ID start(Thread::Callback p_callback, void *p_user, const Settings &p_settings = Settings());
	bool is_started() const { return id != UNASSIGNED_ID; }
	/// Waits until thread is finished, and deallocates it.
	void wait_to_finish();

	Thread() = default;
	~Thread();
};