1/* -*- mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- */
2#ident "$Id$"
3/*======
4This file is part of PerconaFT.
5
6
7Copyright (c) 2006, 2015, Percona and/or its affiliates. All rights reserved.
8
9 PerconaFT is free software: you can redistribute it and/or modify
10 it under the terms of the GNU General Public License, version 2,
11 as published by the Free Software Foundation.
12
13 PerconaFT is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
17
18 You should have received a copy of the GNU General Public License
19 along with PerconaFT. If not, see <http://www.gnu.org/licenses/>.
20
21----------------------------------------
22
23 PerconaFT is free software: you can redistribute it and/or modify
24 it under the terms of the GNU Affero General Public License, version 3,
25 as published by the Free Software Foundation.
26
27 PerconaFT is distributed in the hope that it will be useful,
28 but WITHOUT ANY WARRANTY; without even the implied warranty of
29 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
30 GNU Affero General Public License for more details.
31
32 You should have received a copy of the GNU Affero General Public License
33 along with PerconaFT. If not, see <http://www.gnu.org/licenses/>.
34======= */
35
36#ident "Copyright (c) 2006, 2015, Percona and/or its affiliates. All rights reserved."
37
38#include <algorithm>
39#include <cassert>
40#include <cstdlib>
41#include <memory>
42
43#include "buffer.hpp"
44#include "malloc_utils.hpp"
45
46namespace mu = malloc_utils;
47
48namespace ftcxx {
49
50 const size_t Buffer::INITIAL_CAPACITY = 1<<10;
51 const size_t Buffer::MAXIMUM_CAPACITY = 1<<18;
52 const double Buffer::FULLNESS_RATIO = 0.9;
53
54 Buffer::Buffer()
55 : _cur(0),
56 _end(0),
57 _capacity(INITIAL_CAPACITY),
58 _buf(nullptr, &std::free)
59 {
60 init();
61 }
62
63 Buffer::Buffer(size_t capacity)
64 : _end(0),
65 _capacity(capacity),
66 _buf(nullptr, &std::free)
67 {
68 init();
69 }
70
71 char *Buffer::alloc(size_t sz) {
72 grow(sz);
73 char *p = raw(_end);
74 _end += sz;
75 return p;
76 }
77
78 bool Buffer::full() const {
79 return _end > MAXIMUM_CAPACITY * FULLNESS_RATIO;
80 }
81
82 bool Buffer::more() const {
83 return _cur < _end;
84 }
85
86 char *Buffer::current() const {
87 return raw(_cur);
88 }
89
90 void Buffer::advance(size_t sz) {
91 _cur += sz;
92 }
93
94 void Buffer::clear() {
95 _cur = 0;
96 _end = 0;
97 }
98
99 void Buffer::init() {
100 _buf.reset(static_cast<char *>(mu::checkedMalloc(_capacity)));
101 }
102
103 /**
104 * Implements our growth strategy. Currently we double until we get
105 * up to 4kB so that we can quickly reach the point where jemalloc can
106 * help us resize in-place, but after that point we grow by a factor
107 * of 1.5x.
108 *
109 * FBVector doubles once it is bigger than 128kB, but I don't think we
110 * actually want to because that's about when we want to stop growing.
111 */
112 size_t Buffer::next_alloc_size(size_t sz) {
113 if (sz < mu::jemallocMinInPlaceExpandable) {
114 return sz * 2;
115 }
116#if 0
117 else if (sz > (128<<10)) {
118 return sz * 2;
119 }
120#endif
121 else {
122 return (sz * 3 + 1) / 2;
123 }
124 }
125
126 void Buffer::grow(size_t sz) {
127 size_t new_capacity = _capacity;
128 while (new_capacity < _end + sz) {
129 new_capacity = next_alloc_size(new_capacity);
130 }
131 assert(new_capacity >= _capacity); // overflow?
132 if (new_capacity > _capacity) {
133 // This section isn't exception-safe, but smartRealloc already
134 // isn't. The only thing we can throw in here is
135 // std::bad_alloc, in which case we're kind of screwed anyway.
136 new_capacity = mu::goodMallocSize(new_capacity);
137 _buf.reset(static_cast<char *>(mu::smartRealloc(_buf.release(), _end, _capacity, new_capacity, _capacity)));
138 }
139 }
140
141} // namespace ftcxx
142