114 lines
3.2 KiB
C++
114 lines
3.2 KiB
C++
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/*
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* Copyright (C) 2013-2018 Max Kellermann <max.kellermann@gmail.com>
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*
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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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*
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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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*
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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 the
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* documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* 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
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "SparseBuffer.hxx"
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SparseMap::CheckResult
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SparseMap::Check(size_type offset) const noexcept
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{
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assert(!map.empty());
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assert(offset < GetEndOffset());
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auto i = map.lower_bound(offset);
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if (i == map.end())
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/* from here up until the end of the file is
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defined */
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return {0, std::prev(i)->second - offset};
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assert(i->first >= offset);
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if (offset == i->first)
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/* at the beginning of this chunk: the whole chunk can
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be read */
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return {0, i->second - offset};
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if (i == map.begin())
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/* before the very first chunk: there's a hole, and
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after the hole, the whole chunk can be read */
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return {i->first - offset, i->second - i->first};
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auto p = std::prev(i);
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assert(p->first < offset);
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if (offset >= p->second)
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/* between two chunks */
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return {i->first - offset, i->second - i->first};
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/* inside a chunk: the rest of the chunk can be read */
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return {0, p->second - offset};
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}
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void
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SparseMap::Commit(size_type start_offset, size_type end_offset) noexcept
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{
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assert(start_offset < end_offset);
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auto e = map.emplace(start_offset, end_offset);
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if (!e.second && end_offset > e.first->second)
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e.first->second = end_offset;
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CheckCollapseNext(CheckCollapsePrevious(e.first));
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}
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inline SparseMap::Iterator
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SparseMap::CheckCollapsePrevious(Iterator i) noexcept
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{
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assert(i != map.end());
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while (i != map.begin()) {
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auto previous = std::prev(i);
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if (previous->second < i->first)
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break;
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if (i->second > previous->second)
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previous->second = i->second;
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map.erase(i);
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i = previous;
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}
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return i;
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}
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inline SparseMap::Iterator
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SparseMap::CheckCollapseNext(Iterator i) noexcept
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{
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assert(i != map.end());
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for (auto next = std::next(i);
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next != map.end() && i->second >= next->first;) {
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if (next->second > i->second)
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i->second = next->second;
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next = map.erase(next);
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}
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return i;
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}
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