122 lines
3.4 KiB
C++
122 lines
3.4 KiB
C++
/*
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* Copyright (c) 2018, 2022, Oracle and/or its affiliates.
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*
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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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*
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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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*
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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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*
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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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*/
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#pragma once
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#include <cassert>
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#include <cstdint>
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#include <vector>
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namespace protocol {
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class Page {
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public:
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Page(const uint32_t size, char *data_ptr)
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: m_begin_data(reinterpret_cast<uint8_t *>(data_ptr)),
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m_end_data(m_begin_data + size),
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m_current_data(reinterpret_cast<uint8_t *>(data_ptr)) {}
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~Page() {
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m_current_data = nullptr;
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m_next_page = nullptr;
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}
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void reset() {
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m_current_data = m_begin_data;
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m_next_page = nullptr;
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}
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bool is_at_least(const uint32_t needed_size) const {
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return m_end_data > m_current_data + needed_size;
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}
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bool is_full() const { return m_end_data <= m_current_data; }
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bool is_empty() const { return m_begin_data == m_current_data; }
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uint32_t get_used_bytes() const { return m_current_data - m_begin_data; }
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uint32_t get_free_bytes() const { return m_end_data - m_current_data; }
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uint8_t *const m_begin_data;
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uint8_t *const m_end_data;
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uint8_t *m_current_data;
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Page *m_next_page = nullptr;
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};
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class Encoding_pool {
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public:
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explicit Encoding_pool(const uint32_t local_cache, const uint32_t page_size)
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: m_local_cache(local_cache), m_page_size(page_size) {}
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~Encoding_pool() {
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while (m_empty_pages) {
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auto page = m_empty_pages;
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m_empty_pages = m_empty_pages->m_next_page;
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--m_pages;
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/// destruct and free
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page->~Page();
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delete[] reinterpret_cast<char *>(page);
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}
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assert(0 == m_pages);
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m_empty_pages = nullptr;
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}
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Page *alloc_page() {
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if (m_empty_pages) {
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auto result = m_empty_pages;
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m_empty_pages = m_empty_pages->m_next_page;
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result->reset();
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return result;
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}
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++m_pages;
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auto page = new char[m_page_size];
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return new (page) Page(m_page_size - sizeof(Page), page + sizeof(Page));
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}
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void release_page(Page *page) {
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if (m_pages < m_local_cache) {
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page->m_next_page = m_empty_pages;
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m_empty_pages = page;
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return;
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}
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--m_pages;
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/// destruct and free
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page->~Page();
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delete[] reinterpret_cast<char *>(page);
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}
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uint32_t get_page_size() const { return m_page_size; }
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private:
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const uint32_t m_local_cache = 0;
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const uint32_t m_page_size = 0;
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Page *m_empty_pages = nullptr;
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uint32_t m_pages = 0;
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};
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} // namespace protocol
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