fork of https://github.com/oxigraph/rocksdb and https://github.com/facebook/rocksdb for nextgraph and oxigraph
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127 lines
4.3 KiB
127 lines
4.3 KiB
/* -*- mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- */
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// vim: ft=cpp:expandtab:ts=8:sw=4:softtabstop=4:
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#ident "$Id$"
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/*======
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This file is part of PerconaFT.
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Copyright (c) 2006, 2015, Percona and/or its affiliates. All rights reserved.
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PerconaFT 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,
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as published by the Free Software Foundation.
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PerconaFT 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 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 PerconaFT. If not, see <http://www.gnu.org/licenses/>.
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----------------------------------------
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PerconaFT is free software: you can redistribute it and/or modify
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it under the terms of the GNU Affero General Public License, version 3,
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as published by the Free Software Foundation.
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PerconaFT 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 Affero General Public License for more details.
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You should have received a copy of the GNU Affero General Public License
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along with PerconaFT. If not, see <http://www.gnu.org/licenses/>.
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======= */
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#ident \
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"Copyright (c) 2006, 2015, Percona and/or its affiliates. All rights reserved."
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#pragma once
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#include <stdlib.h>
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/*
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* A memarena is used to efficiently store a collection of objects that never
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* move The pattern is allocate more and more stuff and free all of the items at
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* once. The underlying memory will store 1 or more objects per chunk. Each
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* chunk is contiguously laid out in memory but chunks are not necessarily
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* contiguous with each other.
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*/
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class memarena {
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public:
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memarena()
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: _current_chunk(arena_chunk()),
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_other_chunks(nullptr),
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_n_other_chunks(0),
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_size_of_other_chunks(0),
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_footprint_of_other_chunks(0) {}
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// Effect: Create a memarena with the specified initial size
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void create(size_t initial_size);
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void destroy(void);
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// Effect: Allocate some memory. The returned value remains valid until the
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// memarena is cleared or closed.
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// In case of ENOMEM, aborts.
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void *malloc_from_arena(size_t size);
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// Effect: Move all the memory from this memarena into DEST.
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// When SOURCE is closed the memory won't be freed.
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// When DEST is closed, the memory will be freed, unless DEST moves
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// its memory to another memarena...
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void move_memory(memarena *dest);
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// Effect: Calculate the amount of memory used by a memory arena.
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size_t total_memory_size(void) const;
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// Effect: Calculate the used space of the memory arena (ie: excludes unused
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// space)
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size_t total_size_in_use(void) const;
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// Effect: Calculate the amount of memory used, according to
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// toku_memory_footprint(),
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// which is a more expensive but more accurate count of memory used.
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size_t total_footprint(void) const;
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// iterator over the underlying chunks that store objects in the memarena.
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// a chunk is represented by a pointer to const memory and a usable byte
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// count.
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class chunk_iterator {
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public:
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chunk_iterator(const memarena *ma) : _ma(ma), _chunk_idx(-1) {}
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// returns: base pointer to the current chunk
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// *used set to the number of usable bytes
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// if more() is false, returns nullptr and *used = 0
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const void *current(size_t *used) const;
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// requires: more() is true
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void next();
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bool more() const;
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private:
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// -1 represents the 'initial' chunk in a memarena, ie: ma->_current_chunk
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// >= 0 represents the i'th chunk in the ma->_other_chunks array
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const memarena *_ma;
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int _chunk_idx;
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};
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private:
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struct arena_chunk {
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arena_chunk() : buf(nullptr), used(0), size(0) {}
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char *buf;
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size_t used;
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size_t size;
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};
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struct arena_chunk _current_chunk;
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struct arena_chunk *_other_chunks;
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int _n_other_chunks;
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size_t _size_of_other_chunks; // the buf_size of all the other chunks.
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size_t _footprint_of_other_chunks; // the footprint of all the other chunks.
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friend class memarena_unit_test;
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};
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