| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: darray.c,v 1.1 1999/10/22 22:37:26 mdw Exp $ |
| 4 | * |
| 5 | * Dynamically growing dense arrays |
| 6 | * |
| 7 | * (c) 1999 Straylight/Edgeware |
| 8 | */ |
| 9 | |
| 10 | /*----- Licensing notice --------------------------------------------------* |
| 11 | * |
| 12 | * This file is part of the mLib utilities library. |
| 13 | * |
| 14 | * mLib is free software; you can redistribute it and/or modify |
| 15 | * it under the terms of the GNU Library General Public License as |
| 16 | * published by the Free Software Foundation; either version 2 of the |
| 17 | * License, or (at your option) any later version. |
| 18 | * |
| 19 | * mLib is distributed in the hope that it will be useful, |
| 20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 22 | * GNU Library General Public License for more details. |
| 23 | * |
| 24 | * You should have received a copy of the GNU Library General Public |
| 25 | * License along with mLib; if not, write to the Free |
| 26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
| 27 | * MA 02111-1307, USA. |
| 28 | */ |
| 29 | |
| 30 | /*----- Revision history --------------------------------------------------* |
| 31 | * |
| 32 | * $Log: darray.c,v $ |
| 33 | * Revision 1.1 1999/10/22 22:37:26 mdw |
| 34 | * New dynamic array implementation replaces `dynarray.h'. |
| 35 | * |
| 36 | */ |
| 37 | |
| 38 | /*----- Header files ------------------------------------------------------*/ |
| 39 | |
| 40 | #include <stdio.h> |
| 41 | #include <string.h> |
| 42 | #include <stdlib.h> |
| 43 | |
| 44 | #include "alloc.h" |
| 45 | #include "darray.h" |
| 46 | |
| 47 | /*----- Magic numbers -----------------------------------------------------*/ |
| 48 | |
| 49 | #define DA_INITSZ 64 /* Default size for new array */ |
| 50 | #define DA_SLOTS 8 /* Number of preshifted slots */ |
| 51 | |
| 52 | /*----- Main code ---------------------------------------------------------*/ |
| 53 | |
| 54 | /* --- @da_ensure@ --- * |
| 55 | * |
| 56 | * Arguments: @da_base *b@ = pointer to array base structure |
| 57 | * @void *v@ = pointer to array vector |
| 58 | * @size_t sz@ = size of individual array elements |
| 59 | * @size_t n@ = number of items required at the end |
| 60 | * |
| 61 | * Returns: Pointer to newly allocated or adjusted array vector. |
| 62 | * |
| 63 | * Use: Extends a dynamic array to accommodate a number of new items |
| 64 | * at its end. This function is a helper for the @DA_ENSURE@ |
| 65 | * macro, which should be used by preference. |
| 66 | */ |
| 67 | |
| 68 | void *da_ensure(da_base *b, void *v, size_t sz, size_t n) |
| 69 | { |
| 70 | size_t rq = n + b->len; |
| 71 | char *p = v, *q; |
| 72 | size_t nsz; |
| 73 | size_t slots; |
| 74 | |
| 75 | /* --- Make sure there's something which needs doing --- * |
| 76 | * |
| 77 | * If there's enough space already then return immediately. |
| 78 | */ |
| 79 | |
| 80 | if (rq < b->sz) |
| 81 | return (p); |
| 82 | |
| 83 | /* --- Compute a number of `unshift' slots --- * |
| 84 | * |
| 85 | * When returning from this function, the offset will be set to @slots@. |
| 86 | * If @unshift@ is zero, there's no point in reserving slots. Otherwise |
| 87 | * choose a power of two greater than @unshift@, with a minimum of |
| 88 | * @DA_SLOTS@. Then add the number of slots to the requirement. |
| 89 | */ |
| 90 | |
| 91 | if (!b->unshift) |
| 92 | slots = 0; |
| 93 | else { |
| 94 | slots = DA_SLOTS; |
| 95 | while (slots < b->unshift) |
| 96 | slots <<= 1; |
| 97 | } |
| 98 | rq += slots; |
| 99 | |
| 100 | /* --- Maybe just shunt data around a bit --- * |
| 101 | * |
| 102 | * If the vector is large enough, then theoretically we could cope by |
| 103 | * moving the objects about in their existing storage. |
| 104 | */ |
| 105 | |
| 106 | if (rq < b->sz + b->off) { |
| 107 | q = p - (b->off - slots) * sz; |
| 108 | memmove(q, p, b->len * sz); |
| 109 | b->sz += b->off - slots; |
| 110 | b->off = slots; |
| 111 | b->unshift = b->push = 0; |
| 112 | return (q); |
| 113 | } |
| 114 | |
| 115 | /* --- Reallocate the array --- */ |
| 116 | |
| 117 | nsz = v ? b->sz + b->off : DA_INITSZ; |
| 118 | do nsz <<= 1; while (nsz < rq); |
| 119 | q = xmalloc(nsz * sz); |
| 120 | q += slots * sz; |
| 121 | memcpy(q, p, b->len * sz); |
| 122 | if (p) |
| 123 | free(p - b->off * sz); |
| 124 | b->off = slots; |
| 125 | b->sz = nsz - slots; |
| 126 | b->unshift = b->push = 0; |
| 127 | return (q); |
| 128 | } |
| 129 | |
| 130 | /* --- @da_shunt@ --- * |
| 131 | * |
| 132 | * Arguments: @da_base *b@ = pointer to array base structure |
| 133 | * @void *v@ = pointer to array vector |
| 134 | * @size_t sz@ = size of the array elements |
| 135 | * @size_t n@ = number of items required at the start |
| 136 | * |
| 137 | * Returns: Pointer to appropriately bodged vector. |
| 138 | * |
| 139 | * Use: Extends an array to accommodate items inserted at its front. |
| 140 | * This function is a helper for the @DA_SHUNT@ macro, which |
| 141 | * should be used by preference. |
| 142 | */ |
| 143 | |
| 144 | void *da_shunt(da_base *b, void *v, size_t sz, size_t n) |
| 145 | { |
| 146 | size_t rq; |
| 147 | char *p = v, *q; |
| 148 | size_t nsz; |
| 149 | size_t slots; |
| 150 | |
| 151 | /* --- Make sure there's something which needs doing --- * |
| 152 | * |
| 153 | * If there's enough space already then return immediately. |
| 154 | */ |
| 155 | |
| 156 | if (n < b->off) |
| 157 | return (p); |
| 158 | |
| 159 | /* --- Compute a number of `push' slots --- * |
| 160 | * |
| 161 | * When returning from this function, there will be @slots@ free spaces at |
| 162 | * the end of the array. If @push@ is zero, there's no point in reserving |
| 163 | * slots. Otherwise choose a power of two greater than @push@, with a |
| 164 | * minimum of @DA_SLOTS@. To simplify matters, add the number of items |
| 165 | * already in the array to @slots@, and then add the number of slots to the |
| 166 | * requirement. |
| 167 | */ |
| 168 | |
| 169 | if (!b->push) |
| 170 | slots = 0; |
| 171 | else { |
| 172 | slots = DA_SLOTS; |
| 173 | while (slots < b->push) |
| 174 | slots <<= 1; |
| 175 | } |
| 176 | slots += b->len; |
| 177 | rq = n + slots; |
| 178 | |
| 179 | /* --- Maybe just shunt data around a bit --- * |
| 180 | * |
| 181 | * If the vector is large enough, then theoretically we could cope by |
| 182 | * moving the objects about in their existing storage. |
| 183 | */ |
| 184 | |
| 185 | if (rq < b->sz + b->off) { |
| 186 | q = p + (b->sz - slots) * sz; |
| 187 | memmove(q, p, b->len * sz); |
| 188 | b->off += b->sz - slots; |
| 189 | b->sz = slots; |
| 190 | b->unshift = b->push = 0; |
| 191 | return (q); |
| 192 | } |
| 193 | |
| 194 | /* --- Reallocate the array --- */ |
| 195 | |
| 196 | nsz = v ? b->sz + b->off : DA_INITSZ; |
| 197 | do nsz <<= 1; while (nsz < rq); |
| 198 | q = xmalloc(nsz * sz); |
| 199 | q += (nsz - slots) * sz; |
| 200 | memcpy(q, p, b->len * sz); |
| 201 | if (p) |
| 202 | free(p - b->off * sz); |
| 203 | b->off = nsz - slots; |
| 204 | b->sz = slots; |
| 205 | b->unshift = b->push = 0; |
| 206 | return (q); |
| 207 | } |
| 208 | |
| 209 | /* --- @da_tidy@ --- * |
| 210 | * |
| 211 | * Arguments: @da_base *b@ = pointer to array base structure |
| 212 | * @void *v@ = pointer to vector |
| 213 | * @size_t sz@ = size of the array elements |
| 214 | * |
| 215 | * Returns: Newly allocated vector. |
| 216 | * |
| 217 | * Use: Minimizes the space occupied by an array. This function is a |
| 218 | * helper for the @DA_TIDY@ macro, which should be used by |
| 219 | * preference. |
| 220 | */ |
| 221 | |
| 222 | void *da_tidy(da_base *b, void *v, size_t sz) |
| 223 | { |
| 224 | char *p = v, *q; |
| 225 | |
| 226 | b->unshift = b->push = 0; |
| 227 | |
| 228 | if (!p) |
| 229 | return (0); |
| 230 | if (b->sz == b->len && b->off == 0) |
| 231 | return (p); |
| 232 | |
| 233 | if (!b->len) { |
| 234 | free(p - b->off * sz); |
| 235 | return (0); |
| 236 | } |
| 237 | |
| 238 | q = xmalloc(b->len * sz); |
| 239 | memcpy(q, p, b->len * sz); |
| 240 | free(p - b->off * sz); |
| 241 | b->sz = b->len; |
| 242 | b->off = 0; |
| 243 | return (q); |
| 244 | } |
| 245 | |
| 246 | /* --- Note about testing --- * |
| 247 | * |
| 248 | * The test rig for this code is split into three parts. There's `da-gtest', |
| 249 | * which is a Perl script which generates a list of commands. The `da-ref' |
| 250 | * Perl script interprets these commands as operations on a Perl array. It's |
| 251 | * relatively conservatively written and believed to be reliable. The |
| 252 | * `da-test.c' file implements a command reader for the same syntax and |
| 253 | * performs the operations on an integer darray, producing output in the same |
| 254 | * format. To test darray, generate a command script with `da-gtest', pass |
| 255 | * it through both `da-ref' and `da-test' (the result of compiling |
| 256 | * da-test.c'), and compare the results. If they're not byte-for-byte |
| 257 | * identical, there's something wrong. |
| 258 | */ |
| 259 | |
| 260 | /*----- That's all, folks -------------------------------------------------*/ |