godot/core/os/threaded_array_processor.h

/*************************************************************************/
/*  threaded_array_processor.h                                           */
/*************************************************************************/
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#ifndef THREADED_ARRAY_PROCESSOR_H
#define THREADED_ARRAY_PROCESSOR_H

#include "core/os/mutex.h"
#include "core/os/os.h"
#include "core/os/thread.h"
#include "core/os/thread_safe.h"
#include "core/safe_refcount.h"

template <class C, class U>
struct ThreadArrayProcessData {
	uint32_t elements;
	SafeNumeric<uint32_t> index;
	C *instance;
	U userdata;
	void (C::*method)(uint32_t, U);

	void process(uint32_t p_index) {
		(instance->*method)(p_index, userdata);
	}
};

#ifndef NO_THREADS

template <class T>
void process_array_thread(void *ud) {
	T &data = *(T *)ud;
	while (true) {
		uint32_t index = data.index.increment();
		if (index >= data.elements) {
			break;
		}
		data.process(index);
	}
}

// p_num_threads is the number of logical CPU cores to use (0 = use all logical CPU cores available).
// Negative values subtract from the total number of logical CPU cores available.
template <class C, class M, class U>
void thread_process_array(uint32_t p_elements, C *p_instance, M p_method, U p_userdata, int p_num_threads = 0) {
	ThreadArrayProcessData<C, U> data;
	data.method = p_method;
	data.instance = p_instance;
	data.userdata = p_userdata;
	data.index.set(0);
	data.elements = p_elements;
	data.process(0); //process first, let threads increment for next

	int thread_count;
	if (p_num_threads <= 0) {
		thread_count = MAX(1, OS::get_singleton()->get_processor_count() + p_num_threads);
	} else {
		thread_count = p_num_threads;
	}

	Thread *threads = memnew_arr(Thread, thread_count);

	for (int i = 0; i < thread_count; i++) {
		threads[i].start(process_array_thread<ThreadArrayProcessData<C, U>>, &data);
	}

	for (int i = 0; i < thread_count; i++) {
		threads[i].wait_to_finish();
	}
	memdelete_arr(threads);
}

#else

// p_num_threads is intentionally unused when threads are disabled.
template <class C, class M, class U>
void thread_process_array(uint32_t p_elements, C *p_instance, M p_method, U p_userdata, int p_num_threads = 0) {
	ThreadArrayProcessData<C, U> data;
	data.method = p_method;
	data.instance = p_instance;
	data.userdata = p_userdata;
	data.index.set(0);
	data.elements = p_elements;
	for (uint32_t i = 0; i < p_elements; i++) {
		data.process(i);
	}
}

#endif

#endif // THREADED_ARRAY_PROCESSOR_H