text: /*
  
  Copyright (c) 2008-2018, Arvid Norberg
  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/bitfield.hpp"
  #include "libtorrent/aux_/numeric_cast.hpp"
  #include "libtorrent/aux_/cpuid.hpp"
  
  #ifdef _MSC_VER
  #include <intrin.h>
  #endif
  
  namespace libtorrent {
  
  	bool bitfield::all_set() const noexcept
  	{
  		if(size() == 0) return false;
  
  		int const words = size() / 32;
  		for (int i = 1; i < words + 1; ++i)
  		{
  			if (m_buf[i] != 0xffffffff) return false;
  		}
  		int const rest = size() & 31;
  		if (rest > 0)
  		{
  			std::uint32_t const mask = aux::host_to_network(0xffffffff << (32 - rest));
  			if ((m_buf[words + 1] & mask) != mask) return false;
  		}
  		return true;
  	}
  
  	int bitfield::count() const noexcept
  	{
  		int ret = 0;
  		int const words = num_words();
  #if TORRENT_HAS_SSE
  		if (aux::mmx_support)
  		{
  			for (int i = 1; i < words + 1; ++i)
  			{
  #ifdef __GNUC__
  				std::uint32_t cnt = 0;
  				__asm__("popcnt %1, %0"
  					: "=r"(cnt)
  					: "r"(m_buf[i]));
  				ret += cnt;
  #else
  				ret += _mm_popcnt_u32(m_buf[i]);
  #endif
  			}
  
  			TORRENT_ASSERT(ret <= size());
  			TORRENT_ASSERT(ret >= 0);
  			return ret;
  		}
  #endif // TORRENT_HAS_SSE
  
  #if TORRENT_HAS_ARM_NEON && defined __arm__
  		if (aux::arm_neon_support)
  		{
  			for (int i = 1; i < words + 1; ++i)
  			{
  				std::uint32_t cnt;
  				__asm__(
  					"vld1.u32 d0[0], [%1] \n"
  					"vcnt.u8 d0, d0 \n"
  					"vpaddl.u8 d0, d0 \n"
  					"vpaddl.u16 d0, d0 \n"
  					"vst1.u32 d0[0], [%0]"
  					:: "r"(&cnt), "r"(&m_buf[i])
  					: "d0", "memory");
  				ret += cnt;
  			}
  
  			TORRENT_ASSERT(ret <= size());
  			TORRENT_ASSERT(ret >= 0);
  			return ret;
  		}
  #endif // TORRENT_HAS_ARM_NEON
  
  		for (int i = 1; i < words + 1; ++i)
  		{
  			std::uint32_t const v = m_buf[i];
  			// from:
  			// http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
  			static const int S[] = {1, 2, 4, 8, 16}; // Magic Binary Numbers
  			static const std::uint32_t B[] = {0x55555555, 0x33333333, 0x0F0F0F0F, 0x00FF00FF, 0x0000FFFF};
  
  			std::uint32_t c = v - ((v >> 1) & B[0]);
  			c = ((c >> S[1]) & B[1]) + (c & B[1]);
  			c = ((c >> S[2]) + c) & B[2];
  			c = ((c >> S[3]) + c) & B[3];
  			c = ((c >> S[4]) + c) & B[4];
  			ret += c;
  			TORRENT_ASSERT(ret <= size());
  		}
  
  		TORRENT_ASSERT(ret <= size());
  		TORRENT_ASSERT(ret >= 0);
  		return ret;
  	}
  
  	void bitfield::resize(int const bits, bool const val)
  	{
  		if (bits == size()) return;
  
  		int const s = size();
  		int const b = size() & 31;
  		resize(bits);
  		if (s >= size()) return;
  		int const old_size_words = (s + 31) / 32;
  		int const new_size_words = num_words();
  		if (val)
  		{
  			if (old_size_words && b) buf()[old_size_words - 1] |= aux::host_to_network(0xffffffff >> b);
  			if (old_size_words < new_size_words)
  				std::memset(buf() + old_size_words, 0xff
  					, std::size_t((new_size_words - old_size_words) * 4));
  			clear_trailing_bits();
  		}
  		else
  		{
  			if (old_size_words < new_size_words)
  				std::memset(buf() + old_size_words, 0x00
  					, std::size_t((new_size_words - old_size_words) * 4));
  		}
  		TORRENT_ASSERT(size() == bits);
  	}
  
  	void bitfield::resize(int const bits)
  	{
  		if (bits == size()) return;
  
  		TORRENT_ASSERT(bits >= 0);
  		if (bits == 0)
  		{
  			m_buf.reset();
  			return;
  		}
  		int const new_size_words = (bits + 31) / 32;
  		int const cur_size_words = num_words();
  		if (cur_size_words != new_size_words)
  		{
  			aux::unique_ptr<std::uint32_t[]> b(new std::uint32_t[std::size_t(new_size_words + 1)]);
  #ifdef BOOST_NO_EXCEPTIONS
  			if (b == nullptr) std::terminate();
  #endif
  			b[0] = aux::numeric_cast<std::uint32_t>(bits);
  			if (m_buf) std::memcpy(&b[1], buf()
  				, aux::numeric_cast<std::size_t>(std::min(new_size_words, cur_size_words) * 4));
  			if (new_size_words > cur_size_words)
  			{
  				std::memset(&b[1 + cur_size_words], 0
  					, aux::numeric_cast<std::size_t>((new_size_words - cur_size_words) * 4));
  			}
  			m_buf = std::move(b);
  		}
  		else
  		{
  			m_buf[0] = aux::numeric_cast<std::uint32_t>(bits);
  		}
  
  		clear_trailing_bits();
  		TORRENT_ASSERT(size() == bits);
  	}
  
  	int bitfield::find_first_set() const noexcept
  	{
  		int const num = num_words();
  		if (num == 0) return -1;
  		int const count = aux::count_leading_zeros({&m_buf[1], num});
  		return count != num * 32 ? count : -1;
  	}
  
  	int bitfield::find_last_clear() const noexcept
  	{
  		int const num = num_words();
  		if (num == 0) return - 1;
  		int const size = this->size();
  		std::uint32_t const mask = 0xffffffff << (32 - (size & 31));
  		std::uint32_t const last = m_buf[num] ^ aux::host_to_network(mask);
  		int const ext = aux::count_trailing_ones(~last) - (31 - (size % 32));
  		return last != 0
  			? (num - 1) * 32 + ext
  			: size - (aux::count_trailing_ones({&m_buf[1], num - 1}) + ext);
  	}
  
  	static_assert(std::is_nothrow_move_constructible<bitfield>::value
  		, "should be nothrow move constructible");
  	static_assert(std::is_nothrow_move_assignable<bitfield>::value
  		, "should be nothrow move assignable");
  	static_assert(std::is_nothrow_default_constructible<bitfield>::value
  		, "should be nothrow default constructible");
  
  	static_assert(std::is_nothrow_move_constructible<typed_bitfield<int>>::value
  		, "should be nothrow move constructible");
  	static_assert(std::is_nothrow_move_assignable<typed_bitfield<int>>::value
  		, "should be nothrow move assignable");
  	static_assert(std::is_nothrow_default_constructible<typed_bitfield<int>>::value
  		, "should be nothrow default constructible");
  }
  