ZeroTierOne/node/Buf.cpp

/*
 * Copyright (c)2013-2020 ZeroTier, Inc.
 *
 * Use of this software is governed by the Business Source License included
 * in the LICENSE.TXT file in the project's root directory.
 *
 * Change Date: 2024-01-01
 *
 * On the date above, in accordance with the Business Source License, use
 * of this software will be governed by version 2.0 of the Apache License.
 */
/****/

#include "Buf.hpp"

#ifndef __GNUC__
#include <atomic>
#endif

namespace ZeroTier {

#ifdef __GNUC__
static uintptr_t s_pool = 0;
#else
static std::atomic<uintptr_t> s_pool(0);
#endif

void Buf::operator delete(void *ptr,std::size_t sz)
{
	if (ptr) {
		uintptr_t bb;
		const uintptr_t locked = ~((uintptr_t)0);
		for (;;) {
#ifdef __GNUC__
			bb = __sync_fetch_and_or(&s_pool,locked); // get value of s_pool and "lock" by filling with all 1's
#else
			bb = s_pool.fetch_or(locked);
#endif
			if (bb != locked)
				break;
		}

		((Buf *)ptr)->__nextInPool = bb;
#ifdef __GNUC__
		__sync_fetch_and_and(&s_pool,(uintptr_t)ptr);
#else
		s_pool.store((uintptr_t)ptr);
#endif
	}
}

SharedPtr<Buf> Buf::get()
{
	uintptr_t bb;
	const uintptr_t locked = ~((uintptr_t)0);
	for (;;) {
#ifdef __GNUC__
		bb = __sync_fetch_and_or(&s_pool,locked); // get value of s_pool and "lock" by filling with all 1's
#else
		bb = s_pool.fetch_or(locked);
#endif
		if (bb != locked)
			break;
	}

	Buf *b;
	if (bb == 0) {
#ifdef __GNUC__
		__sync_fetch_and_and(&s_pool,bb);
#else
		s_pool.store(bb);
#endif
		b = (Buf *)malloc(sizeof(Buf));
		if (!b)
			return SharedPtr<Buf>();
	} else {
		b = (Buf *)bb;
#ifdef __GNUC__
		__sync_fetch_and_and(&s_pool,b->__nextInPool);
#else
		s_pool.store(b->__nextInPool);
#endif
	}

	b->__refCount.zero();
	return SharedPtr<Buf>(b);
}

void Buf::freePool()
{
	uintptr_t bb;
	const uintptr_t locked = ~((uintptr_t)0);
	for (;;) {
#ifdef __GNUC__
		bb = __sync_fetch_and_or(&s_pool,locked); // get value of s_pool and "lock" by filling with all 1's
#else
		bb = s_pool.fetch_or(locked);
#endif
		if (bb != locked)
			break;
	}

#ifdef __GNUC__
	__sync_fetch_and_and(&s_pool,(uintptr_t)0);
#else
	s_pool.store((uintptr_t)0);
#endif

	while (bb != 0) {
		uintptr_t next = ((Buf *)bb)->__nextInPool;
		free((void *)bb);
		bb = next;
	}
}

} // namespace ZeroTier