267 lines
7.4 KiB
C++
267 lines
7.4 KiB
C++
/*
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Copyright (c) 2008-2018, Arvid Norberg
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the distribution.
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* Neither the name of the author nor the names of its
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contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef TORRENT_BITFIELD_HPP_INCLUDED
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#define TORRENT_BITFIELD_HPP_INCLUDED
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#include "libtorrent/assert.hpp"
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#include "libtorrent/config.hpp"
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#include "libtorrent/aux_/byteswap.hpp"
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#include <cstring> // for memset and memcpy
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#include <cstdlib> // for malloc, free and realloc
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#include <boost/cstdint.hpp> // uint32_t
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#include <algorithm> // for min()
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namespace libtorrent
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{
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// The bitfield type stores any number of bits as a bitfield
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// in a heap allocated array.
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struct TORRENT_EXPORT bitfield
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{
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// constructs a new bitfield. The default constructor creates an empty
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// bitfield. ``bits`` is the size of the bitfield (specified in bits).
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// ``val`` is the value to initialize the bits to. If not specified
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// all bits are initialized to 0.
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//
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// The constructor taking a pointer ``b`` and ``bits`` copies a bitfield
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// from the specified buffer, and ``bits`` number of bits (rounded up to
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// the nearest byte boundary).
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bitfield(): m_buf(NULL) {}
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bitfield(int bits): m_buf(NULL)
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{ resize(bits); }
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bitfield(int bits, bool val): m_buf(NULL)
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{ resize(bits, val); }
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bitfield(char const* b, int bits): m_buf(NULL)
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{ assign(b, bits); }
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bitfield(bitfield const& rhs): m_buf(NULL)
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{ assign(rhs.data(), rhs.size()); }
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#if __cplusplus > 199711L
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bitfield(bitfield&& rhs): m_buf(rhs.m_buf)
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{ rhs.m_buf = NULL; }
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#endif
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// hidden
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~bitfield() { dealloc(); }
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// copy bitfield from buffer ``b`` of ``bits`` number of bits, rounded up to
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// the nearest byte boundary.
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void assign(char const* b, int bits)
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{
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resize(bits);
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if (bits > 0)
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{
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std::memcpy(m_buf, b, size_t((bits + 7) / 8));
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clear_trailing_bits();
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}
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}
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// query bit at ``index``. Returns true if bit is 1, otherwise false.
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bool operator[](int index) const
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{ return get_bit(index); }
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bool get_bit(int index) const
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{
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TORRENT_ASSERT(index >= 0);
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TORRENT_ASSERT(index < size());
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return (m_buf[index / 32] & aux::host_to_network((0x80000000 >> (index & 31)))) != 0;
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}
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// set bit at ``index`` to 0 (clear_bit) or 1 (set_bit).
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void clear_bit(int index)
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{
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TORRENT_ASSERT(index >= 0);
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TORRENT_ASSERT(index < size());
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m_buf[index / 32] &= aux::host_to_network(~(0x80000000 >> (index & 31)));
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}
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void set_bit(int index)
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{
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TORRENT_ASSERT(index >= 0);
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TORRENT_ASSERT(index < size());
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m_buf[index / 32] |= aux::host_to_network((0x80000000 >> (index & 31)));
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}
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// returns true if all bits in the bitfield are set
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bool all_set() const;
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bool none_set() const
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{
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const int words = num_words();
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for (int i = 0; i < words; ++i)
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{
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if (m_buf[i] != 0) return false;
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}
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return true;
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}
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// returns the size of the bitfield in bits.
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int size() const
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{
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return m_buf == NULL ? 0 : int(m_buf[-1]);
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}
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int num_words() const
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{
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return (size() + 31) / 32;
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}
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// returns true if the bitfield has zero size.
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bool empty() const { return m_buf == NULL ? true : m_buf[-1] == 0; }
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// returns a pointer to the internal buffer of the bitfield.
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char const* data() const { return reinterpret_cast<char const*>(m_buf); }
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#ifndef TORRENT_NO_DEPRECATE
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TORRENT_DEPRECATED
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char const* bytes() const { return data(); }
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#endif
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// copy operator
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bitfield& operator=(bitfield const& rhs)
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{
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assign(rhs.data(), rhs.size());
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return *this;
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}
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// count the number of bits in the bitfield that are set to 1.
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int count() const;
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struct const_iterator
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{
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friend struct bitfield;
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typedef bool value_type;
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typedef ptrdiff_t difference_type;
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typedef bool const* pointer;
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typedef bool& reference;
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typedef std::forward_iterator_tag iterator_category;
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bool operator*() { return (*buf & aux::host_to_network(bit)) != 0; }
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const_iterator& operator++() { inc(); return *this; }
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const_iterator operator++(int)
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{ const_iterator ret(*this); inc(); return ret; }
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const_iterator& operator--() { dec(); return *this; }
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const_iterator operator--(int)
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{ const_iterator ret(*this); dec(); return ret; }
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const_iterator(): buf(0), bit(0x80000000) {}
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bool operator==(const_iterator const& rhs) const
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{ return buf == rhs.buf && bit == rhs.bit; }
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bool operator!=(const_iterator const& rhs) const
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{ return buf != rhs.buf || bit != rhs.bit; }
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private:
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void inc()
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{
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TORRENT_ASSERT(buf);
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if (bit == 0x01)
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{
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bit = 0x80000000;
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++buf;
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}
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else
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{
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bit >>= 1;
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}
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}
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void dec()
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{
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TORRENT_ASSERT(buf);
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if (bit == 0x80000000)
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{
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bit = 0x01;
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--buf;
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}
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else
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{
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bit <<= 1;
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}
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}
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const_iterator(boost::uint32_t const* ptr, int offset)
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: buf(ptr), bit(0x80000000 >> offset) {}
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boost::uint32_t const* buf;
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boost::uint32_t bit;
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};
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const_iterator begin() const { return const_iterator(m_buf, 0); }
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const_iterator end() const { return const_iterator(
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m_buf + num_words() - (((size() & 31) == 0) ? 0 : 1), size() & 31); }
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// set the size of the bitfield to ``bits`` length. If the bitfield is extended,
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// the new bits are initialized to ``val``.
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void resize(int bits, bool val);
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void resize(int bits);
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// set all bits in the bitfield to 1 (set_all) or 0 (clear_all).
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void set_all()
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{
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if (m_buf == NULL) return;
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std::memset(m_buf, 0xff, size_t(num_words() * 4));
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clear_trailing_bits();
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}
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void clear_all()
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{
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if (m_buf == NULL) return;
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std::memset(m_buf, 0x00, size_t(num_words() * 4));
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}
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// make the bitfield empty, of zero size.
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void clear() { dealloc(); }
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private:
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void clear_trailing_bits()
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{
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// clear the tail bits in the last byte
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if (size() & 31) m_buf[num_words() - 1] &= aux::host_to_network(0xffffffff << (32 - (size() & 31)));
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}
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void dealloc()
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{
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if (m_buf) std::free(m_buf-1);
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m_buf = NULL;
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}
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// the first element is not part of the bitfield, it's the
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// number of bits. For this purpose, the m_buf actually points
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// the element 1, not 0. To access the size (in bits), access
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// m_buf[-1]
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boost::uint32_t* m_buf;
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};
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}
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#endif // TORRENT_BITFIELD_HPP_INCLUDED
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