337 lines
8.1 KiB
C++
337 lines
8.1 KiB
C++
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/*
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Copyright (c) 2003 - 2005, Arvid Norberg, Daniel Wallin
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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 Rasterbar Software 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 LIBTORRENT_BUFFER_HPP
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#define LIBTORRENT_BUFFER_HPP
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#include <memory>
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namespace libtorrent {
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class buffer
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{
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public:
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struct interval
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{
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interval(char* begin, char* end)
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: begin(begin)
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, end(end)
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{}
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char* begin;
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char* end;
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};
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struct const_interval
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{
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const_interval(char const* begin, char const* end)
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: begin(begin)
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, end(end)
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{}
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char const* begin;
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char const* end;
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};
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typedef std::pair<const_interval, const_interval> interval_type;
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buffer(std::size_t n = 0);
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~buffer();
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interval allocate(std::size_t n);
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void insert(char const* first, char const* last);
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void erase(std::size_t n);
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std::size_t size() const;
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std::size_t capacity() const;
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void reserve(std::size_t n);
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interval_type data() const;
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bool empty() const;
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std::size_t space_left() const;
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char const* raw_data() const
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{
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return m_first;
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}
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private:
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char* m_first;
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char* m_last;
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char* m_write_cursor;
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char* m_read_cursor;
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char* m_read_end;
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bool m_empty;
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};
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inline buffer::buffer(std::size_t n)
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: m_first((char*)::operator new(n))
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, m_last(m_first + n)
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, m_write_cursor(m_first)
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, m_read_cursor(m_first)
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, m_read_end(m_last)
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, m_empty(true)
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{}
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inline buffer::~buffer()
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{
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::operator delete (m_first);
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}
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inline buffer::interval buffer::allocate(std::size_t n)
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{
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assert(m_read_cursor <= m_read_end || m_empty);
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if (m_read_cursor < m_write_cursor || m_empty)
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{
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// ..R***W..
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if (m_last - m_write_cursor >= (std::ptrdiff_t)n)
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{
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interval ret(m_write_cursor, m_write_cursor + n);
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m_write_cursor += n;
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m_read_end = m_write_cursor;
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assert(m_read_cursor <= m_read_end);
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if (n) m_empty = false;
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return ret;
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}
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if (m_read_cursor - m_first >= (std::ptrdiff_t)n)
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{
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m_read_end = m_write_cursor;
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interval ret(m_first, m_first + n);
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m_write_cursor = m_first + n;
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assert(m_read_cursor <= m_read_end);
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if (n) m_empty = false;
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return ret;
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}
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reserve(capacity() + n - (m_last - m_write_cursor));
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assert(m_last - m_write_cursor >= (std::ptrdiff_t)n);
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interval ret(m_write_cursor, m_write_cursor + n);
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m_write_cursor += n;
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m_read_end = m_write_cursor;
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if (n) m_empty = false;
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assert(m_read_cursor <= m_read_end);
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return ret;
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}
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//**W...R**
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if (m_read_cursor - m_write_cursor >= (std::ptrdiff_t)n)
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{
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interval ret(m_write_cursor, m_write_cursor + n);
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m_write_cursor += n;
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if (n) m_empty = false;
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return ret;
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}
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reserve(capacity() + n - (m_read_cursor - m_write_cursor));
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assert(m_read_cursor - m_write_cursor >= (std::ptrdiff_t)n);
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interval ret(m_write_cursor, m_write_cursor + n);
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m_write_cursor += n;
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if (n) m_empty = false;
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return ret;
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}
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inline void buffer::insert(char const* first, char const* last)
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{
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std::size_t n = last - first;
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if (space_left() < n)
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{
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reserve(capacity() + n);
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}
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m_empty = false;
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char const* end = (m_last - m_write_cursor) < (std::ptrdiff_t)n ?
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m_last : m_write_cursor + n;
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std::size_t copied = end - m_write_cursor;
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std::memcpy(m_write_cursor, first, copied);
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m_write_cursor += copied;
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if (m_write_cursor > m_read_end) m_read_end = m_write_cursor;
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first += copied;
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n -= copied;
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if (n == 0) return;
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if (m_write_cursor == m_last) m_write_cursor = m_first;
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memcpy(m_write_cursor, first, n);
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m_write_cursor += n;
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}
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inline void buffer::erase(std::size_t n)
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{
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assert(!m_empty);
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#ifndef NDEBUG
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int prev_size = size();
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#endif
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assert(m_read_cursor <= m_read_end);
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m_read_cursor += n;
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if (m_read_cursor > m_read_end)
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{
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m_read_cursor = m_first + (m_read_cursor - m_read_end);
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assert(m_read_cursor <= m_write_cursor);
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}
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m_empty = m_read_cursor == m_write_cursor;
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assert(prev_size - n == size());
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}
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inline std::size_t buffer::size() const
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{
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// ...R***W.
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if (m_read_cursor < m_write_cursor)
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{
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return m_write_cursor - m_read_cursor;
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}
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// ***W..R*
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else
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{
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if (m_empty) return 0;
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return (m_write_cursor - m_first) + (m_read_end - m_read_cursor);
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}
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}
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inline std::size_t buffer::capacity() const
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{
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return m_last - m_first;
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}
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inline void buffer::reserve(std::size_t size)
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{
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std::size_t n = (std::size_t)(capacity() * 1.f);
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if (n < size) n = size;
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char* buf = (char*)::operator new(n);
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char* old = m_first;
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if (m_read_cursor < m_write_cursor)
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{
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// ...R***W.<>.
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std::memcpy(
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buf + (m_read_cursor - m_first)
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, m_read_cursor
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, m_write_cursor - m_read_cursor
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);
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m_write_cursor = buf + (m_write_cursor - m_first);
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m_read_cursor = buf + (m_read_cursor - m_first);
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m_read_end = 0;
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m_first = buf;
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m_last = buf + n;
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}
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else
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{
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// **W..<>.R**
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std::size_t skip = n - (m_last - m_first);
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std::memcpy(buf, m_first, m_write_cursor - m_first);
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std::memcpy(
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buf + (m_read_cursor - m_first) + skip
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, m_read_cursor
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, m_last - m_read_cursor
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);
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m_write_cursor = buf + (m_write_cursor - m_first);
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if (!m_empty)
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{
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m_read_cursor = buf + (m_read_cursor - m_first) + skip;
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m_read_end = buf + (m_read_end - m_first) + skip;
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}
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else
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{
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m_read_cursor = m_write_cursor;
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m_read_end = m_write_cursor;
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}
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m_first = buf;
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m_last = buf + n;
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}
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::operator delete (old);
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}
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inline buffer::interval_type buffer::data() const
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{
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// ...R***W.
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if (m_read_cursor < m_write_cursor)
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{
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return interval_type(
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const_interval(m_read_cursor, m_write_cursor)
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, const_interval(m_last, m_last)
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);
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}
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// **W...R**
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else
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{
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if (m_read_cursor == m_read_end)
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{
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return interval_type(
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const_interval(m_first, m_write_cursor)
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, const_interval(m_last, m_last));
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}
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assert(m_read_cursor <= m_read_end || m_empty);
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return interval_type(
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const_interval(m_read_cursor, m_read_end)
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, const_interval(m_first, m_write_cursor)
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);
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}
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}
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inline bool buffer::empty() const
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{
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return m_empty;
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}
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inline std::size_t buffer::space_left() const
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{
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if (m_empty) return m_last - m_first;
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// ...R***W.
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if (m_read_cursor < m_write_cursor)
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{
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return (m_last - m_write_cursor) + (m_read_cursor - m_first);
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}
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// ***W..R*
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else
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{
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return m_read_cursor - m_write_cursor;
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}
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}
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}
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#endif // LIBTORRENT_BUFFER_HPP
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