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/*
* Copyright (C) 2013-2018 Max Kellermann <max.kellermann@gmail.com>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "SparseBuffer.hxx"
SparseMap::CheckResult
SparseMap::Check(size_type offset) const noexcept
{
assert(!map.empty());
assert(offset < GetEndOffset());
auto i = map.lower_bound(offset);
if (i == map.end())
/* from here up until the end of the file is
defined */
return {0, std::prev(i)->second - offset};
assert(i->first >= offset);
if (offset == i->first)
/* at the beginning of this chunk: the whole chunk can
be read */
return {0, i->second - offset};
if (i == map.begin())
/* before the very first chunk: there's a hole, and
after the hole, the whole chunk can be read */
return {i->first - offset, i->second - i->first};
auto p = std::prev(i);
assert(p->first < offset);
if (offset >= p->second)
/* between two chunks */
return {i->first - offset, i->second - i->first};
/* inside a chunk: the rest of the chunk can be read */
return {0, p->second - offset};
}
void
SparseMap::Commit(size_type start_offset, size_type end_offset) noexcept
{
assert(start_offset < end_offset);
auto e = map.emplace(start_offset, end_offset);
if (!e.second && end_offset > e.first->second)
e.first->second = end_offset;
CheckCollapseNext(CheckCollapsePrevious(e.first));
}
inline SparseMap::Iterator
SparseMap::CheckCollapsePrevious(Iterator i) noexcept
{
assert(i != map.end());
while (i != map.begin()) {
auto previous = std::prev(i);
if (previous->second < i->first)
break;
if (i->second > previous->second)
previous->second = i->second;
map.erase(i);
i = previous;
}
return i;
}
inline SparseMap::Iterator
SparseMap::CheckCollapseNext(Iterator i) noexcept
{
assert(i != map.end());
for (auto next = std::next(i);
next != map.end() && i->second >= next->first;) {
if (next->second > i->second)
i->second = next->second;
next = map.erase(next);
}
return i;
}
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