129 lines
3.8 KiB
C++
129 lines
3.8 KiB
C++
/* Copyright (c) 2015, 2017, Oracle and/or its affiliates. All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License, version 2.0,
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as published by the Free Software Foundation.
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This program is also distributed with certain software (including
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but not limited to OpenSSL) that is licensed under separate terms,
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as designated in a particular file or component or in included license
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documentation. The authors of MySQL hereby grant you an additional
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permission to link the program and your derivative works with the
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separately licensed software that they have included with MySQL.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License, version 2.0, for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
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#ifndef DD_CACHE__FREE_LIST_INCLUDED
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#define DD_CACHE__FREE_LIST_INCLUDED
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#include <vector> // vector
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#include "my_dbug.h"
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#include "sql/malloc_allocator.h" // Malloc_allocator.
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namespace dd {
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namespace cache {
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/**
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Template for management of a free list based on a std::vector.
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The free list template defines functions mostly wrapping the std::vector
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functions, but additionally doing some asserts to ensure correct usage.
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The first element in the free list is the least recently used element.
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When a new element becomes unused, it is added to the end of the free list.
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An element may also be removed from within the middle of the free list
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when the element is being acquired. This use case means iterating through
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the vector to find the correct element.
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@tparam E Element type (a Cache_element wrapping some dictionary
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object type).
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*/
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template <typename E>
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class Free_list {
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private:
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typedef std::vector<E *, Malloc_allocator<E *>> List_type;
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List_type m_list; // The actual list.
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public:
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Free_list() : m_list(Malloc_allocator<E *>(PSI_INSTRUMENT_ME)) {}
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// Return the actual free list length.
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size_t length() const { return m_list.size(); }
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/**
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Add an element to the end of the free list.
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@param element Element to add to the end of the list.
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*/
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void add_last(E *element) {
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DBUG_ASSERT(element != NULL && element->usage() == 0);
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m_list.push_back(element);
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}
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/**
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Remove an element from the free list.
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@param element Element to be removed from the list.
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*/
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void remove(E *element) {
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DBUG_ASSERT(element != NULL && element->usage() == 0);
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DBUG_ASSERT(!m_list.empty());
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for (typename List_type::iterator it = m_list.begin(); it != m_list.end();
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++it)
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if (*it == element) {
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m_list.erase(it);
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return;
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}
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DBUG_ASSERT(false); /* purecov: deadcode */
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}
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/**
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Get the least recently used element in the list, i.e., the first element.
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@return The least recently used element in the list.
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*/
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E *get_lru() const {
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DBUG_ASSERT(!m_list.empty());
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if (!m_list.empty()) return m_list.front();
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return NULL;
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}
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/**
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Debug dump of the free list to stderr.
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*/
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/* purecov: begin inspected */
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void dump() const {
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#ifndef DBUG_OFF
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if (m_list.empty()) {
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fprintf(stderr, " lru-> NULL\n");
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return;
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}
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fprintf(stderr, " lru-> ");
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for (typename List_type::const_iterator it = m_list.begin();
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it != m_list.end(); ++it)
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fprintf(stderr, "%llu ", (*it)->object()->id());
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fprintf(stderr, "\n");
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#endif
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}
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/* purecov: end */
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};
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} // namespace cache
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} // namespace dd
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#endif // DD_CACHE__FREE_LIST_INCLUDED
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