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1 | /* -*-c-*- |
2 | * | |
3 | * Grow a buffer if it's too small | |
4 | * | |
5 | * (c) 2024 Straylight/Edgeware | |
6 | */ | |
7 | ||
8 | /*----- Licensing notice --------------------------------------------------* | |
9 | * | |
10 | * This file is part of the mLib utilities library. | |
11 | * | |
12 | * mLib is free software: you can redistribute it and/or modify it under | |
13 | * the terms of the GNU Library General Public License as published by | |
14 | * the Free Software Foundation; either version 2 of the License, or (at | |
15 | * your option) any later version. | |
16 | * | |
17 | * mLib is distributed in the hope that it will be useful, but WITHOUT | |
18 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
19 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public | |
20 | * License for more details. | |
21 | * | |
22 | * You should have received a copy of the GNU Library General Public | |
23 | * License along with mLib. If not, write to the Free Software | |
24 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, | |
25 | * USA. | |
26 | */ | |
27 | ||
28 | #ifndef MLIB_GROWBUF_H | |
29 | #define MLIB_GROWBUF_H | |
30 | ||
31 | #ifdef __cplusplus | |
32 | extern "C" { | |
33 | #endif | |
34 | ||
35 | /*----- Header files ------------------------------------------------------*/ | |
36 | ||
37 | #include <assert.h> | |
38 | #include <stddef.h> | |
39 | ||
40 | #ifndef MLIB_ALLOC_H | |
41 | # include "alloc.h" | |
42 | #endif | |
43 | ||
44 | /*----- Macros provided ---------------------------------------------------*/ | |
45 | ||
46 | /* --- @GROWBUF_LIMIT@ --- * | |
47 | * | |
48 | * Arguments: @size_t granule@ = allocation granule | |
49 | * | |
50 | * Returns: The largest number %$n$% such that the total size of %$n$% | |
51 | * objects, each of size @granule@, can be represented in a | |
52 | * @size_t@. | |
53 | */ | |
54 | ||
55 | #define GROWBUF_LIMIT(granule) (~(size_t)0/(granule)) | |
56 | ||
57 | /* --- @GROWBUF_SIZE@ --- * | |
58 | * | |
59 | * Arguments: @size_t sz@ = the current size (updated) | |
60 | * @size_t want@ = the desired minimum size | |
61 | * @size_t init@ = a suitable initial size | |
62 | * @size_t granule@ = the allocation granule size | |
63 | * | |
64 | * Returns: --- | |
65 | * | |
66 | * Use: On entry, @sz@ should be the current capacity of some buffer, | |
67 | * in terms of objects of size @granule@, and @want@ a needed | |
68 | * capacity, in the same terms, with @want > sz@; @init@ should | |
69 | * be some suitable positive initial size, in case the current | |
70 | * size is zero. The macro updates @sz@ to be some suitable new | |
71 | * positive size at least as large as @want@. | |
72 | */ | |
73 | ||
74 | #define GROWBUF_SIZE(sz, want, init, granule) do { \ | |
75 | size_t _sz_ = (sz), _want_ = (want); \ | |
76 | \ | |
77 | assert(_want_ < GROWBUF_LIMIT(granule)/2); \ | |
78 | if (!_sz_) _sz_ = (init); \ | |
79 | while (_sz_ < _want_) _sz_ *= 2; \ | |
80 | (sz) = _sz_; \ | |
81 | } while (0) | |
82 | ||
83 | /* --- @GROWBUF_EXTEND@, @GROWBUF_REPLACE@ --- * | |
84 | * | |
85 | * Arguments: @arena *a@ = pointer to an arena | |
86 | * @type *buf@ = pointer to some buffer, possibly null (updated) | |
87 | * @size_t sz@ = current buffer size (updated) | |
88 | * @size_t want@ = desired minimum size | |
89 | * @size_t init@ = a suitable initial size | |
90 | * @size_t granule@ = the allocation granule size | |
91 | * | |
92 | * Returns: --- | |
93 | * | |
94 | * Use: On entry, @buf@ should be a pointer to a buffer, allocated | |
95 | * from the arena @a@, with space for @sz@ objects of size | |
96 | * @granule@; @buf@ may be null if @sz@ is zero. On exit, @buf@ | |
97 | * and @sz@ will be updated to refer to a possibly different | |
98 | * buffer, with space for at least @want@ objects (but certainly | |
99 | * not smaller than before). | |
100 | * | |
101 | * @GROWBUF_EXTEND@ preserves the contents of the buffer; | |
102 | * @GROWBUF_REPLACE@ discards the existing contents. | |
103 | */ | |
104 | ||
105 | #define GROWBUF_EXTEND(a, buf, sz, want, init, granule) do { \ | |
106 | size_t _sz0 = (sz), _sz = _sz0, _want = (want), _gr = (granule); \ | |
107 | void *_p = (buf); \ | |
108 | arena *_a = (a); \ | |
109 | \ | |
110 | if (_sz < _want) { \ | |
111 | GROWBUF_SIZE(_sz, _want, init, _gr); \ | |
112 | if (!_p) _p = x_alloc(_a, _sz*_gr); \ | |
113 | else _p = x_realloc(_a, _p, _sz*_gr, _sz0*_gr); \ | |
114 | (buf) = _p; (sz) = _sz; \ | |
115 | } \ | |
116 | } while (0) | |
117 | ||
118 | #define GROWBUF_REPLACE(a, buf, sz, want, init, granule) do { \ | |
119 | size_t _sz0 = (sz), _sz = _sz0, _want = (want), _gr = (granule); \ | |
120 | void *_p = (buf); \ | |
121 | arena *_a = (a); \ | |
122 | \ | |
123 | if (_sz < _want) { \ | |
124 | GROWBUF_SIZE(_sz, want, init, _gr); \ | |
125 | if (_p) x_free(_a, _p); \ | |
126 | _p = x_alloc(_a, _sz*_gr); \ | |
127 | (buf) = _p; (sz) = _sz; \ | |
128 | } \ | |
129 | } while (0) | |
130 | ||
131 | /*----- That's all, folks -------------------------------------------------*/ | |
132 | ||
133 | #ifdef __cplusplus | |
134 | } | |
135 | #endif | |
136 | ||
137 | #endif |