| 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 |