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util/SortList: library which sorts linked lists

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This commit is contained in:
Max Kellermann 2022-11-10 11:31:19 +01:00
parent 60e640af5a
commit a448d04d46
2 changed files with 191 additions and 3 deletions
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121
src/util/SortList.hxx Normal file
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@ -0,0 +1,121 @@
/*
* Copyright 2022 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.
*/
#pragma once
#include "StaticVector.hxx"
#include <algorithm> // for std::find_if()
#include <concepts> // for std::predicate
/**
* Move all items from #src to #dest, keeping both sorted.
*
* @param p the predicate by which both lists are already
* sorted
*/
template<typename List>
constexpr void
MergeList(List &dest, List &src,
std::predicate<typename List::const_reference, typename List::const_reference> auto p) noexcept
{
const auto dest_end = dest.end(), src_end = src.end();
auto dest_at = dest.begin();
while (!src.empty()) {
const auto src_begin = src.begin();
/* find the first item of "dest" that is larger than
the front of "src"; this is the next insertion
position */
dest_at = std::find_if(dest_at, dest_end, [&p, &src_front = *src_begin](const auto &i){
return p(src_front, i);
});
if (dest_at == dest_end) {
/* all items in "src" are larger than
"this": splice the whole list at
the end of "this" */
dest.splice(dest_end, src);
break;
}
/* find the first item of "src" that is not smaller
than the "dest" insertion anchor; this is the end
of the range of items to be spliced */
const auto &dest_anchor = *dest_at;
typename List::size_type n = 1;
auto src_until = std::next(src_begin);
while (src_until != src_end && p(*src_until, dest_anchor)) {
++src_until;
++n;
}
dest.splice(dest_at, src, src_begin, src_until, n);
}
}
template<typename List>
constexpr void
SortList(List &list,
std::predicate<typename List::const_reference, typename List::const_reference> auto p) noexcept
{
using std::swap;
if (list.empty())
return;
/* bottom-up merge sort */
List carry;
StaticVector<List, 64> array;
while (!list.empty()) {
carry.splice(carry.begin(), list, list.begin());
std::size_t i = 0;
while (i < array.size() && !array[i].empty()) {
auto &c = array[i++];
MergeList(c, carry, p);
swap(carry, c);
}
if (i == array.size())
array.emplace_back();
swap(carry, array[i]);
}
assert(!array.empty());
for (std::size_t i = 1; i < array.size(); ++i)
MergeList(array[i], array[i - 1], p);
swap(list, array.back());
}

73
test/util/TestIntrusiveList.cxx
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@ -1,8 +1,5 @@
/*
* Copyright 2020-2022 Max Kellermann <max.kellermann@gmail.com>
* All rights reserved.
*
* author: Max Kellermann <mk@cm4all.com>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
@ -31,6 +28,7 @@
*/
#include "util/IntrusiveList.hxx"
#include "util/SortList.hxx"
#include <gtest/gtest.h>
@ -201,3 +199,72 @@ TEST(IntrusiveList, AutoUnlink)
ASSERT_TRUE(a.is_linked());
ASSERT_TRUE(b.is_linked());
}
TEST(IntrusiveList, Merge)
{
using Item = CharItem<IntrusiveListHook>;
const auto predicate = [](const Item &a, const Item &b){
return a.ch < b.ch;
};
Item items[]{'c', 'k', 'u'};
IntrusiveList<Item> list;
for (auto &i : items)
list.push_back(i);
IntrusiveList<Item> other_list;
Item other_items[]{'a', 'b', 'g', 'm', 'n', 'x', 'y', 'z'};
for (auto &i : other_items)
other_list.push_back(i);
MergeList(list, other_list, predicate);
ASSERT_EQ(ToString(list, list.begin(), 13), "abcgkmnuxyz_a");
ASSERT_TRUE(other_list.empty());
Item more_items[]{'a', 'o', 'p', 'q'};
for (auto &i : more_items)
other_list.push_back(i);
MergeList(list, other_list, predicate);
ASSERT_EQ(ToString(list, list.begin(), 17), "aabcgkmnopquxyz_a");
ASSERT_EQ(&*list.begin(), &other_items[0]);
ASSERT_EQ(&*std::next(list.begin()), &more_items[0]);
}
TEST(IntrusiveList, Sort)
{
using Item = CharItem<IntrusiveListHook>;
const auto predicate = [](const Item &a, const Item &b){
return a.ch < b.ch;
};
Item items[]{'z', 'a', 'b', 'q', 'b', 'c', 't', 'm', 'y'};
IntrusiveList<Item> list;
SortList(list, predicate);
ASSERT_EQ(ToString(list, list.begin(), 2), "__");
list.push_back(items[0]);
SortList(list, predicate);
ASSERT_EQ(ToString(list, list.begin(), 3), "z_z");
list.push_back(items[1]);
SortList(list, predicate);
ASSERT_EQ(ToString(list, list.begin(), 4), "az_a");
SortList(list, predicate);
ASSERT_EQ(ToString(list, list.begin(), 4), "az_a");
list.clear();
for (auto &i : items)
list.push_back(i);
SortList(list, predicate);
ASSERT_EQ(ToString(list, list.begin(), 11), "abbcmqtyz_a");
ASSERT_EQ(&*std::next(list.begin(), 1), &items[2]);
ASSERT_EQ(&*std::next(list.begin(), 2), &items[4]);
}