1/* -*- mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- */
2// vim: ft=cpp:expandtab:ts=8:sw=4:softtabstop=4:
3#ident "$Id$"
4/*======
5This file is part of PerconaFT.
6
7
8Copyright (c) 2006, 2015, Percona and/or its affiliates. All rights reserved.
9
10 PerconaFT is free software: you can redistribute it and/or modify
11 it under the terms of the GNU General Public License, version 2,
12 as published by the Free Software Foundation.
13
14 PerconaFT is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License for more details.
18
19 You should have received a copy of the GNU General Public License
20 along with PerconaFT. If not, see <http://www.gnu.org/licenses/>.
21
22----------------------------------------
23
24 PerconaFT is free software: you can redistribute it and/or modify
25 it under the terms of the GNU Affero General Public License, version 3,
26 as published by the Free Software Foundation.
27
28 PerconaFT is distributed in the hope that it will be useful,
29 but WITHOUT ANY WARRANTY; without even the implied warranty of
30 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
31 GNU Affero General Public License for more details.
32
33 You should have received a copy of the GNU Affero General Public License
34 along with PerconaFT. If not, see <http://www.gnu.org/licenses/>.
35======= */
36
37#ident "Copyright (c) 2006, 2015, Percona and/or its affiliates. All rights reserved."
38
39#pragma once
40
41/*
42 * A memarena is used to efficiently store a collection of objects that never move
43 * The pattern is allocate more and more stuff and free all of the items at once.
44 * The underlying memory will store 1 or more objects per chunk. Each chunk is
45 * contiguously laid out in memory but chunks are not necessarily contiguous with
46 * each other.
47 */
48class memarena {
49public:
50 memarena() :
51 _current_chunk(arena_chunk()),
52 _other_chunks(nullptr),
53 _n_other_chunks(0),
54 _size_of_other_chunks(0),
55 _footprint_of_other_chunks(0) {
56 }
57
58 // Effect: Create a memarena with the specified initial size
59 void create(size_t initial_size);
60
61 void destroy(void);
62
63 // Effect: Allocate some memory. The returned value remains valid until the memarena is cleared or closed.
64 // In case of ENOMEM, aborts.
65 void *malloc_from_arena(size_t size);
66
67 // Effect: Move all the memory from this memarena into DEST.
68 // When SOURCE is closed the memory won't be freed.
69 // When DEST is closed, the memory will be freed, unless DEST moves its memory to another memarena...
70 void move_memory(memarena *dest);
71
72 // Effect: Calculate the amount of memory used by a memory arena.
73 size_t total_memory_size(void) const;
74
75 // Effect: Calculate the used space of the memory arena (ie: excludes unused space)
76 size_t total_size_in_use(void) const;
77
78 // Effect: Calculate the amount of memory used, according to toku_memory_footprint(),
79 // which is a more expensive but more accurate count of memory used.
80 size_t total_footprint(void) const;
81
82 // iterator over the underlying chunks that store objects in the memarena.
83 // a chunk is represented by a pointer to const memory and a usable byte count.
84 class chunk_iterator {
85 public:
86 chunk_iterator(const memarena *ma) :
87 _ma(ma), _chunk_idx(-1) {
88 }
89
90 // returns: base pointer to the current chunk
91 // *used set to the number of usable bytes
92 // if more() is false, returns nullptr and *used = 0
93 const void *current(size_t *used) const;
94
95 // requires: more() is true
96 void next();
97
98 bool more() const;
99
100 private:
101 // -1 represents the 'initial' chunk in a memarena, ie: ma->_current_chunk
102 // >= 0 represents the i'th chunk in the ma->_other_chunks array
103 const memarena *_ma;
104 int _chunk_idx;
105 };
106
107private:
108 struct arena_chunk {
109 arena_chunk() : buf(nullptr), used(0), size(0) { }
110 char *buf;
111 size_t used;
112 size_t size;
113 };
114
115 struct arena_chunk _current_chunk;
116 struct arena_chunk *_other_chunks;
117 int _n_other_chunks;
118 size_t _size_of_other_chunks; // the buf_size of all the other chunks.
119 size_t _footprint_of_other_chunks; // the footprint of all the other chunks.
120
121 friend class memarena_unit_test;
122};
123