/*

Copyright (c) 2011, 2013-2021, Arvid Norberg
Copyright (c) 2016, 2018, 2020, Alden Torres
Copyright (c) 2016, Steven Siloti
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in
      the documentation and/or other materials provided with the distribution.
    * Neither the name of the author nor the names of its
      contributors may be used to endorse or promote products derived
      from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.

*/

#include "libtorrent/config.hpp"
#include "libtorrent/aux_/disk_buffer_pool.hpp"
#include "libtorrent/assert.hpp"
#include "libtorrent/settings_pack.hpp" // for settings_interface
#include "libtorrent/io_context.hpp"
#include "libtorrent/disk_observer.hpp"
#include "libtorrent/disk_interface.hpp" // for default_block_size

#include "libtorrent/aux_/disable_warnings_push.hpp"

#ifdef TORRENT_BSD
#include <sys/sysctl.h>
#endif

#ifdef TORRENT_LINUX
#include <linux/unistd.h>
#endif

#include "libtorrent/aux_/disable_warnings_pop.hpp"

namespace libtorrent {
namespace aux {

namespace {

	// this is posted to the network thread
	void watermark_callback(std::vector<std::weak_ptr<disk_observer>> const& cbs)
	{
		for (auto const& i : cbs)
		{
			std::shared_ptr<disk_observer> o = i.lock();
			if (o) o->on_disk();
		}
	}

} // anonymous namespace

	disk_buffer_pool::disk_buffer_pool(io_context& ios)
		: m_in_use(0)
		, m_max_use(64)
		, m_low_watermark(std::max(m_max_use - 32, 0))
		, m_exceeded_max_size(false)
		, m_ios(ios)
	{}

	disk_buffer_pool::~disk_buffer_pool()
	{
		TORRENT_ASSERT(m_magic == 0x1337);
#if TORRENT_USE_ASSERTS
		m_magic = 0;
#endif
	}

	// checks to see if we're no longer exceeding the high watermark,
	// and if we're in fact below the low watermark. If so, we need to
	// post the notification messages to the peers that are waiting for
	// more buffers to received data into
	void disk_buffer_pool::check_buffer_level(std::unique_lock<std::mutex>& l)
	{
		TORRENT_ASSERT(l.owns_lock());
		if (!m_exceeded_max_size || m_in_use > m_low_watermark) return;

		m_exceeded_max_size = false;

		std::vector<std::weak_ptr<disk_observer>> cbs;
		m_observers.swap(cbs);
		l.unlock();
		post(m_ios, std::bind(&watermark_callback, std::move(cbs)));
	}

	char* disk_buffer_pool::allocate_buffer(char const* category)
	{
		std::unique_lock<std::mutex> l(m_pool_mutex);
		return allocate_buffer_impl(l, category);
	}

	// we allow allocating more blocks even after we exceed the max size,
	// but communicate back to the allocator (typically the peer_connection)
	// that we have exceeded the limit via the out-parameter "exceeded". The
	// caller is expected to honor this by not allocating any more buffers
	// until the disk_observer object (passed in as "o") is invoked, indicating
	// that there's more room in the pool now. This caps the amount of over-
	// allocation to one block per peer connection.
	char* disk_buffer_pool::allocate_buffer(bool& exceeded
		, std::shared_ptr<disk_observer> o, char const* category)
	{
		std::unique_lock<std::mutex> l(m_pool_mutex);
		char* ret = allocate_buffer_impl(l, category);
		if (m_exceeded_max_size)
		{
			exceeded = true;
			if (o) m_observers.push_back(o);
		}
		return ret;
	}

	char* disk_buffer_pool::allocate_buffer_impl(std::unique_lock<std::mutex>& l
		, char const*)
	{
		TORRENT_ASSERT(m_settings_set);
		TORRENT_ASSERT(m_magic == 0x1337);
		TORRENT_ASSERT(l.owns_lock());
		TORRENT_UNUSED(l);

		char* ret = static_cast<char*>(std::malloc(default_block_size));

		if (ret == nullptr)
		{
			m_exceeded_max_size = true;
			return nullptr;
		}

		++m_in_use;

#if TORRENT_USE_INVARIANT_CHECKS
		try
		{
			TORRENT_ASSERT(m_buffers_in_use.count(ret) == 0);
			m_buffers_in_use.insert(ret);
		}
		catch (...)
		{
			free_buffer_impl(ret, l);
			return nullptr;
		}
#endif

		if (m_in_use >= m_low_watermark + (m_max_use - m_low_watermark)
			/ 2 && !m_exceeded_max_size)
		{
			m_exceeded_max_size = true;
		}

		return ret;
	}

	void disk_buffer_pool::free_multiple_buffers(span<char*> bufvec)
	{
		// sort the pointers in order to maximize cache hits
		std::sort(bufvec.begin(), bufvec.end());

		std::unique_lock<std::mutex> l(m_pool_mutex);
		for (char* buf : bufvec)
		{
			remove_buffer_in_use(buf);
			free_buffer_impl(buf, l);
		}

		check_buffer_level(l);
	}

	void disk_buffer_pool::free_buffer(char* buf)
	{
		std::unique_lock<std::mutex> l(m_pool_mutex);
		remove_buffer_in_use(buf);
		free_buffer_impl(buf, l);
		check_buffer_level(l);
	}

	void disk_buffer_pool::set_settings(settings_interface const& sett)
	{
		std::unique_lock<std::mutex> l(m_pool_mutex);

		int const pool_size = std::max(1, sett.get_int(settings_pack::max_queued_disk_bytes) / default_block_size);
		m_max_use = pool_size;
		m_low_watermark = m_max_use / 2;
		if (m_in_use >= m_max_use && !m_exceeded_max_size)
		{
			m_exceeded_max_size = true;
		}

#if TORRENT_USE_ASSERTS
		m_settings_set = true;
#endif
	}

	void disk_buffer_pool::remove_buffer_in_use(char* buf)
	{
		TORRENT_UNUSED(buf);
#if TORRENT_USE_INVARIANT_CHECKS
		std::set<char*>::iterator i = m_buffers_in_use.find(buf);
		TORRENT_ASSERT(i != m_buffers_in_use.end());
		m_buffers_in_use.erase(i);
#endif
	}

	void disk_buffer_pool::free_buffer_impl(char* buf, std::unique_lock<std::mutex>& l)
	{
		TORRENT_ASSERT(buf);
		TORRENT_ASSERT(m_magic == 0x1337);
		TORRENT_ASSERT(m_settings_set);
		TORRENT_ASSERT(l.owns_lock());
		TORRENT_UNUSED(l);

		std::free(buf);

		--m_in_use;
	}

}
}
