294 lines
7.6 KiB
C++
294 lines
7.6 KiB
C++
/*
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Copyright (c) 2008-2012, 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 <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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namespace libtorrent
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{
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struct TORRENT_EXPORT bitfield
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{
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bitfield(): m_bytes(0), m_size(0), m_own(false) {}
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bitfield(int bits): m_bytes(0), m_size(0), m_own(false)
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{ resize(bits); }
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bitfield(int bits, bool val): m_bytes(0), m_size(0), m_own(false)
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{ resize(bits, val); }
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bitfield(char const* b, int bits): m_bytes(0), m_size(0), m_own(false)
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{ assign(b, bits); }
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bitfield(bitfield const& rhs): m_bytes(0), m_size(0), m_own(false)
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{ assign(rhs.bytes(), rhs.size()); }
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void borrow_bytes(char* b, int bits)
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{
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dealloc();
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m_bytes = (unsigned char*)b;
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m_size = bits;
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m_own = false;
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}
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~bitfield() { dealloc(); }
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void assign(char const* b, int bits)
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{ resize(bits); std::memcpy(m_bytes, b, (bits + 7) / 8); clear_trailing_bits(); }
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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 < m_size);
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return (m_bytes[index / 8] & (0x80 >> (index & 7))) != 0;
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}
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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 < m_size);
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m_bytes[index / 8] &= ~(0x80 >> (index & 7));
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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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{
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const int num_words = m_size / 32;
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const int num_bytes = m_size / 8;
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boost::uint32_t* bits = (boost::uint32_t*)m_bytes;
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for (int i = 0; i < num_words; ++i)
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{
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if (bits[i] != 0xffffffff) return false;
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}
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for (int i = num_words * 4; i < num_bytes; ++i)
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{
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if (m_bytes[i] != 0xff) return false;
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}
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int rest = m_size - num_bytes * 8;
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boost::uint8_t mask = 0xff << (8-rest);
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if (rest > 0 && (m_bytes[num_bytes] & mask) != mask)
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return false;
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return true;
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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 < m_size);
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m_bytes[index / 8] |= (0x80 >> (index & 7));
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}
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std::size_t size() const { return m_size; }
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bool empty() const { return m_size == 0; }
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char const* bytes() const { return (char*)m_bytes; }
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bitfield& operator=(bitfield const& rhs)
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{
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assign(rhs.bytes(), rhs.size());
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return *this;
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}
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int count() const
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{
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// 0000, 0001, 0010, 0011, 0100, 0101, 0110, 0111,
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// 1000, 1001, 1010, 1011, 1100, 1101, 1110, 1111
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const static char num_bits[] =
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{
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0, 1, 1, 2, 1, 2, 2, 3,
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1, 2, 2, 3, 2, 3, 3, 4
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};
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int ret = 0;
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const int num_bytes = m_size / 8;
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for (int i = 0; i < num_bytes; ++i)
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{
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ret += num_bits[m_bytes[i] & 0xf] + num_bits[m_bytes[i] >> 4];
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}
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int rest = m_size - num_bytes * 8;
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for (int i = 0; i < rest; ++i)
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{
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ret += (m_bytes[num_bytes] >> (7-i)) & 1;
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}
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TORRENT_ASSERT(ret <= m_size);
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TORRENT_ASSERT(ret >= 0);
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return ret;
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}
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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 (*byte & 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(): byte(0), bit(0x80) {}
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bool operator==(const_iterator const& rhs) const
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{ return byte == rhs.byte && bit == rhs.bit; }
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bool operator!=(const_iterator const& rhs) const
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{ return byte != rhs.byte || bit != rhs.bit; }
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private:
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void inc()
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{
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TORRENT_ASSERT(byte);
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if (bit == 0x01)
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{
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bit = 0x80;
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++byte;
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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(byte);
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if (bit == 0x80)
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{
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bit = 0x01;
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--byte;
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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(unsigned char const* ptr, int offset)
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: byte(ptr), bit(0x80 >> offset) {}
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unsigned char const* byte;
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int bit;
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};
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const_iterator begin() const { return const_iterator(m_bytes, 0); }
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const_iterator end() const { return const_iterator(m_bytes + m_size / 8, m_size & 7); }
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void resize(int bits, bool val)
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{
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int s = m_size;
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int b = m_size & 7;
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resize(bits);
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if (s >= m_size) return;
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int old_size_bytes = (s + 7) / 8;
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int new_size_bytes = (m_size + 7) / 8;
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if (val)
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{
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if (old_size_bytes && b) m_bytes[old_size_bytes - 1] |= (0xff >> b);
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if (old_size_bytes < new_size_bytes)
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std::memset(m_bytes + old_size_bytes, 0xff, new_size_bytes - old_size_bytes);
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clear_trailing_bits();
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}
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else
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{
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if (old_size_bytes < new_size_bytes)
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std::memset(m_bytes + old_size_bytes, 0x00, new_size_bytes - old_size_bytes);
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}
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}
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void set_all()
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{
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std::memset(m_bytes, 0xff, (m_size + 7) / 8);
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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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std::memset(m_bytes, 0x00, (m_size + 7) / 8);
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}
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void resize(int bits)
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{
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TORRENT_ASSERT(bits >= 0);
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const int b = (bits + 7) / 8;
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if (m_bytes)
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{
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if (m_own)
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{
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m_bytes = (unsigned char*)std::realloc(m_bytes, b);
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m_own = true;
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}
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else if (bits > m_size)
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{
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unsigned char* tmp = (unsigned char*)std::malloc(b);
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std::memcpy(tmp, m_bytes, (std::min)(int(m_size + 7)/ 8, b));
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m_bytes = tmp;
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m_own = true;
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}
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}
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else if (bits > 0)
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{
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m_bytes = (unsigned char*)std::malloc(b);
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m_own = true;
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}
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m_size = bits;
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clear_trailing_bits();
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}
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void free() { dealloc(); m_size = 0; }
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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 (m_size & 7) m_bytes[(m_size + 7) / 8 - 1] &= 0xff << (8 - (m_size & 7));
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}
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void dealloc() { if (m_own) std::free(m_bytes); m_bytes = 0; }
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unsigned char* m_bytes;
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int m_size:31; // in bits
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bool m_own:1;
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};
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}
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#endif // TORRENT_BITFIELD_HPP_INCLUDED
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