C++ span::size方法代码示例

bool CommObject::SendFrame(span<const std::uint8_t> frame)
{
    if (frame.size() > CommMaxFrameSize)
    {
        LOGF(LOG_LEVEL_ERROR, "Frame payload is too long. Allowed: %d, Requested: '%d'.", CommMaxFrameSize, frame.size());
        return false;
    }

    uint8_t cmd[ComPrefferedBufferSize];
    cmd[0] = TransmitterSendFrame;
    memcpy(cmd + 1, frame.data(), frame.size());
    uint8_t remainingBufferSize;

    const bool status = (this->_low.WriteRead(CommTransmitter,           //
                             span<const uint8_t>(cmd, 1 + frame.size()), //
                             span<uint8_t>(&remainingBufferSize, 1)      //
                             ) == I2CResult::OK);
    if (!status)
    {
        LOG(LOG_LEVEL_ERROR, "[comm] Failed to send frame");
    }

    if (remainingBufferSize == 0xff)
    {
        LOG(LOG_LEVEL_ERROR, "[comm] Frame was not accepted by the transmitter.");
    }

    return status && remainingBufferSize != 0xff;
}

	void iterate_every_other_element(span<int, dynamic_range> av)
	{
		// pick every other element

		auto length = av.size() / 2;
#if _MSC_VER > 1800
		auto bounds = strided_bounds<1>({ length }, { 2 });
#else
		auto bounds = strided_bounds<1>(index<1>{ length }, index<1>{ 2 });
#endif
		strided_span<int, 1> strided(&av.data()[1], av.size() - 1, bounds);

		CHECK(strided.size() == length);
		CHECK(strided.bounds().index_bounds()[0] == length);
		for (auto i = 0; i < strided.size(); ++i)
		{
			CHECK(strided[i] == av[2 * i + 1]);
		}

		int idx = 0;
		for (auto num : strided)
		{
			CHECK(num == av[2 * idx + 1]);
			idx++;
		}
	}

	bool udp_tracker_connection::on_announce_response(span<char const> buf)
	{
		if (buf.size() < 20) return false;

		buf = buf.subspan(8);
		restart_read_timeout();

		tracker_response resp;

		resp.interval = aux::read_int32(buf);
		resp.min_interval = 60;
		resp.incomplete = aux::read_int32(buf);
		resp.complete = aux::read_int32(buf);
		int const num_peers = int(buf.size()) / 6;
		if ((buf.size() % 6) != 0)
		{
			fail(error_code(errors::invalid_tracker_response_length));
			return false;
		}

		boost::shared_ptr<request_callback> cb = requester();
#ifndef TORRENT_DISABLE_LOGGING
		if (cb)
		{
			cb->debug_log("<== UDP_TRACKER_RESPONSE [ url: %s ]", tracker_req().url.c_str());
		}
#endif

		if (!cb)
		{
			close();
			return true;
		}

		std::vector<peer_entry> peer_list;
		resp.peers4.reserve(num_peers);
		for (int i = 0; i < num_peers; ++i)
		{
			ipv4_peer_entry e;
			memcpy(&e.ip[0], buf.data(), 4);
			buf = buf.subspan(4);
			e.port = aux::read_uint16(buf);
			resp.peers4.push_back(e);
		}

		std::list<address> ip_list;
		for (std::vector<tcp::endpoint>::const_iterator i = m_endpoints.begin()
			, end(m_endpoints.end()); i != end; ++i)
		{
			ip_list.push_back(i->address());
		}

		cb->tracker_response(tracker_req(), m_target.address(), ip_list
			, resp);

		close();
		return true;
	}

	// allocate an uninitialized buffer of the specified size
	// and copy the initialization range into the start of the buffer
	buffer(std::size_t const size, span<char const> initialize)
		: buffer(size)
	{
		TORRENT_ASSERT(initialize.size() <= size);
		if (!initialize.empty())
		{
			std::memcpy(m_begin, initialize.data(), (std::min)(initialize.size(), size));
		}
	}

	bool udp_tracker_connection::on_scrape_response(span<char const> buf)
	{
		using namespace libtorrent::aux;

		restart_read_timeout();
		int const action = aux::read_int32(buf);
		std::uint32_t const transaction = read_uint32(buf);

		if (transaction != m_transaction_id)
		{
			fail(error_code(errors::invalid_tracker_transaction_id));
			return false;
		}

		if (action == action_error)
		{
			fail(error_code(errors::tracker_failure), -1
				, std::string(buf.data(), buf.size()).c_str());
			return true;
		}

		if (action != action_scrape)
		{
			fail(error_code(errors::invalid_tracker_action));
			return true;
		}

		if (buf.size() < 12)
		{
			fail(error_code(errors::invalid_tracker_response_length));
			return true;
		}

		int const complete = aux::read_int32(buf);
		int const downloaded = aux::read_int32(buf);
		int const incomplete = aux::read_int32(buf);

		boost::shared_ptr<request_callback> cb = requester();
		if (!cb)
		{
			close();
			return true;
		}

		cb->tracker_scrape_response(tracker_req()
			, complete, incomplete, downloaded, -1);

		close();
		return true;
	}

		void random_bytes(span<char> buffer)
		{
#if TORRENT_USE_CRYPTOAPI
			HCRYPTPROV prov;

			if (!CryptAcquireContext(&prov, NULL, NULL
				, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT))
			{
#ifndef BOOST_NO_EXCEPTIONS
				throw system_error(error_code(GetLastError(), system_category()));
#else
				std::terminate();
#endif
			}

			if (!CryptGenRandom(prov, int(buffer.size())
				, reinterpret_cast<BYTE*>(buffer.data())))
			{
				CryptReleaseContext(prov, 0);
#ifndef BOOST_NO_EXCEPTIONS
				throw system_error(error_code(GetLastError(), system_category()));
#else
				std::terminate();
#endif
			}

			CryptReleaseContext(prov, 0);
#elif defined TORRENT_USE_LIBCRYPTO
#ifdef TORRENT_MACOS_DEPRECATED_LIBCRYPTO
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
#endif
			int r = RAND_bytes(reinterpret_cast<unsigned char*>(buffer.data())
				, int(buffer.size()));
			if (r != 1)
			{
#ifndef BOOST_NO_EXCEPTIONS
				throw system_error(error_code(int(::ERR_get_error()), system_category()));
#else
				std::terminate();
#endif
			}
#ifdef TORRENT_MACOS_DEPRECATED_LIBCRYPTO
#pragma clang diagnostic pop
#endif
#else
			for (auto& b : buffer) b = char(random(0xff));
#endif
		}

	int count_trailing_ones_hw(span<std::uint32_t const> buf)
	{
		auto const num = int(buf.size());
		std::uint32_t const* ptr = buf.data();

		TORRENT_ASSERT(num >= 0);
		TORRENT_ASSERT(ptr != nullptr);

		for (int i = num - 1; i >= 0; i--)
		{
			if (ptr[i] == 0xffffffff) continue;

#if TORRENT_HAS_BUILTIN_CTZ
			std::uint32_t const v = ~aux::network_to_host(ptr[i]);
			return (num - i - 1) * 32 + __builtin_ctz(v);
#elif defined _MSC_VER
			std::uint32_t const v = ~aux::network_to_host(ptr[i]);
			DWORD pos;
			_BitScanForward(&pos, v);
			return (num - i - 1) * 32 + pos;
#else
			TORRENT_ASSERT_FAIL();
			return -1;
#endif
		}

		return num * 32;
	}

	bool tracker_manager::incoming_packet(char const* hostname
		, span<char const> const buf)
	{
		TORRENT_ASSERT(is_single_thread());
		// ignore packets smaller than 8 bytes
		if (buf.size() < 16) return false;

		// the first word is the action, if it's not [0, 3]
		// it's not a valid udp tracker response
		span<const char> ptr = buf;
		std::uint32_t const action = aux::read_uint32(ptr);
		if (action > 3) return false;

		std::uint32_t const transaction = aux::read_uint32(ptr);
		auto const i = m_udp_conns.find(transaction);

		if (i == m_udp_conns.end())
		{
#ifndef TORRENT_DISABLE_LOGGING
			// now, this may not have been meant to be a tracker response,
			// but chances are pretty good, so it's probably worth logging
			m_ses.session_log("incoming UDP tracker packet from %s has invalid "
				"transaction ID (%x)", hostname, int(transaction));
#endif
			return false;
		}

		std::shared_ptr<udp_tracker_connection> const p = i->second;
		// on_receive() may remove the tracker connection from the list
		return p->on_receive_hostname(hostname, buf);
	}

	ImageFileInfo DetectImageFormat(span<uint8_t> data) {
		ImageFileInfo info;

		stbi__context ctx;
		stbi__start_mem(&ctx, &data[0], data.size_bytes());

		int comp;
		if (stbi__bmp_info(&ctx, &info.width, &info.height, &comp)) {
			info.hasAlpha = (comp == 4);
			info.format = ImageFileFormat::BMP;
			return info;
		}

		TjDecompressHandle handle;
		if (tjDecompressHeader(handle, &data[0], data.size_bytes(), &info.width, &info.height) == 0) {
			info.hasAlpha = false;
			info.format = ImageFileFormat::JPEG;
			return info;
		}

		if (DetectTga(data, info)) {
			return info;
		}

		// Not a very good heuristic
		if (data.size() == 256 * 256) {
			info.width = 256;
			info.height = 256;
			info.hasAlpha = true;
			info.format = ImageFileFormat::FNTART;
			return info;
		}

		return info;
	}

	bool udp_tracker_connection::on_connect_response(span<char const> buf)
	{
		// ignore packets smaller than 16 bytes
		if (buf.size() < 16) return false;

		restart_read_timeout();

		// skip header
		buf = buf.subspan(8);

		// reset transaction
		update_transaction_id();
		std::uint64_t const connection_id = aux::read_int64(buf);

		std::lock_guard<std::mutex> l(m_cache_mutex);
		connection_cache_entry& cce = m_connection_cache[m_target.address()];
		cce.connection_id = connection_id;
		cce.expires = aux::time_now() + seconds(m_man.settings().get_int(settings_pack::udp_tracker_token_expiry));

		if (0 == (tracker_req().kind & tracker_request::scrape_request))
			send_udp_announce();
		else if (0 != (tracker_req().kind & tracker_request::scrape_request))
			send_udp_scrape();
		return true;
	}

		void update(span<char const> data)
		{
			if (CryptHashData(m_hash, reinterpret_cast<BYTE const*>(data.data()), int(data.size()), 0) == false)
			{
				throw_ex<system_error>(error_code(GetLastError(), system_category()));
			}
		}

		void random_bytes(span<char> buffer)
		{
#ifdef TORRENT_BUILD_SIMULATOR
			// simulator

			for (auto& b : buffer) b = char(random(0xff));

#elif TORRENT_USE_CRYPTOAPI
			// windows

			aux::crypt_gen_random(buffer);

#elif TORRENT_USE_DEV_RANDOM
			// /dev/random

			static dev_random dev;
			dev.read(buffer);

#elif defined TORRENT_USE_LIBCRYPTO
			// openssl

			int r = RAND_bytes(reinterpret_cast<unsigned char*>(buffer.data())
				, int(buffer.size()));
			if (r != 1) aux::throw_ex<system_error>(errors::no_entropy);
#else
			// fallback

			for (auto& b : buffer) b = char(random(0xff));
#endif
		}

 explicit
 enumerated_value_range(span<const T> v)
 noexcept
     : _begin(v.data())
     , _end(v.data()+v.size())
 {
     assert(_begin <= _end);
 }

	entry::entry(span<char const> v)
		: m_type(undefined_t)
	{
#if TORRENT_USE_ASSERTS
		m_type_queried = true;
#endif
		new(&data) string_type(v.data(), v.size());
		m_type = string_t;
	}

	inline void crypt_gen_random(span<char> buffer)
	{
		static HCRYPTPROV provider = crypt_acquire_provider(PROV_RSA_FULL);
		if (!CryptGenRandom(provider, int(buffer.size())
			, reinterpret_cast<BYTE*>(buffer.data())))
		{
			throw_ex<system_error>(error_code(GetLastError(), system_category()));
		}
	}