73 lines
2.1 KiB
C++
73 lines
2.1 KiB
C++
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/*
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Copyright (c) 2006, 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 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_RANDOM_SAMPLE_HPP
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#define TORRENT_RANDOM_SAMPLE_HPP
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#include <iterator>
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#include <cstdlib>
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namespace libtorrent
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{
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template<class InIter, class OutIter, class Distance>
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inline void random_sample_n(InIter start, InIter end
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, OutIter out, Distance n)
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{
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Distance t = 0;
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Distance m = 0;
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Distance N = std::distance(start, end);
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assert(N >= n);
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while (m < n)
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{
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if ((rand() / (RAND_MAX + 1.f)) * (N - t) >= n - m)
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{
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++start;
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++t;
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}
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else
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{
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*out = *start;
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++out;
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++start;
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++t;
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++m;
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}
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}
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}
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}
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#endif
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