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1 | /* -*-c-*- |
2 | * |
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3 | * Dynamically growing dense arrays |
4 | * |
5 | * (c) 1999 Straylight/Edgeware |
6 | */ |
7 | |
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8 | /*----- Licensing notice --------------------------------------------------* |
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9 | * |
10 | * This file is part of the mLib utilities library. |
11 | * |
12 | * mLib is free software; you can redistribute it and/or modify |
13 | * it under the terms of the GNU Library General Public License as |
14 | * published by the Free Software Foundation; either version 2 of the |
15 | * License, or (at your option) any later version. |
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16 | * |
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17 | * mLib is distributed in the hope that it will be useful, |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
20 | * GNU Library General Public License for more details. |
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21 | * |
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22 | * You should have received a copy of the GNU Library General Public |
23 | * License along with mLib; if not, write to the Free |
24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
25 | * MA 02111-1307, USA. |
26 | */ |
27 | |
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28 | /*----- Header files ------------------------------------------------------*/ |
29 | |
30 | #include <stdio.h> |
31 | #include <string.h> |
32 | #include <stdlib.h> |
33 | |
34 | #include "alloc.h" |
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35 | #include "arena.h" |
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36 | #include "darray.h" |
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37 | #include "growbuf.h" |
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38 | |
39 | /*----- Magic numbers -----------------------------------------------------*/ |
40 | |
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41 | #define DA_INITSZ 16 /* Default size for new array */ |
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42 | #define DA_SLOTS 8 /* Number of preshifted slots */ |
43 | |
44 | /*----- Main code ---------------------------------------------------------*/ |
45 | |
46 | /* --- @da_ensure@ --- * |
47 | * |
48 | * Arguments: @da_base *b@ = pointer to array base structure |
49 | * @void *v@ = pointer to array vector |
50 | * @size_t sz@ = size of individual array elements |
51 | * @size_t n@ = number of items required at the end |
52 | * |
53 | * Returns: Pointer to newly allocated or adjusted array vector. |
54 | * |
55 | * Use: Extends a dynamic array to accommodate a number of new items |
56 | * at its end. This function is a helper for the @DA_ENSURE@ |
57 | * macro, which should be used by preference. |
58 | */ |
59 | |
60 | void *da_ensure(da_base *b, void *v, size_t sz, size_t n) |
61 | { |
62 | size_t rq = n + b->len; |
63 | char *p = v, *q; |
64 | size_t nsz; |
65 | size_t slots; |
66 | |
67 | /* --- Make sure there's something which needs doing --- * |
68 | * |
69 | * If there's enough space already then return immediately. |
70 | */ |
71 | |
72 | if (rq < b->sz) |
73 | return (p); |
74 | |
75 | /* --- Compute a number of `unshift' slots --- * |
76 | * |
77 | * When returning from this function, the offset will be set to @slots@. |
78 | * If @unshift@ is zero, there's no point in reserving slots. Otherwise |
79 | * choose a power of two greater than @unshift@, with a minimum of |
80 | * @DA_SLOTS@. Then add the number of slots to the requirement. |
81 | */ |
82 | |
83 | if (!b->unshift) |
84 | slots = 0; |
85 | else { |
86 | slots = DA_SLOTS; |
87 | while (slots < b->unshift) |
88 | slots <<= 1; |
89 | } |
90 | rq += slots; |
91 | |
92 | /* --- Maybe just shunt data around a bit --- * |
93 | * |
94 | * If the vector is large enough, then theoretically we could cope by |
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95 | * moving the objects about in their existing storage. It's not worth |
96 | * bothering if there's not actually double the amount of space I need. |
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97 | */ |
98 | |
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99 | if (rq * 2 < b->sz + b->off) { |
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100 | q = p - (b->off - slots) * sz; |
101 | memmove(q, p, b->len * sz); |
102 | b->sz += b->off - slots; |
103 | b->off = slots; |
104 | b->unshift = b->push = 0; |
105 | return (q); |
106 | } |
107 | |
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108 | /* --- Decide on a new size --- * |
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109 | * |
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110 | * There's a minimum possible size for the array which is used if it's |
111 | * currently completely empty. Otherwise I choose the smallest power of |
112 | * two which is big enough, starting at double the current size. |
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113 | */ |
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114 | |
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115 | nsz = b->sz + b->off; |
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116 | GROWBUF_SIZE(size_t, nsz, rq, DA_INITSZ, sz); |
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117 | |
118 | /* --- Reallocate the block --- * |
119 | * |
120 | * If I'm not changing the base offset then it's worth using @realloc@; |
121 | * otherwise there'll probably be two calls to @memcpy@ to shunt the data |
122 | * around so it's not worth bothering. |
123 | */ |
124 | |
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125 | if (p && slots == b->off) { |
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126 | q = x_realloc(b->a, p - b->off * sz, nsz * sz, b->sz + b->off); |
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127 | q += slots * sz; |
128 | } else { |
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129 | q = x_alloc(b->a, nsz * sz); |
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130 | q += slots * sz; |
131 | if (p) { |
132 | memcpy(q, p, b->len * sz); |
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133 | x_free(b->a, p - b->off * sz); |
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134 | } |
135 | } |
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136 | |
137 | /* --- Fill in the other parts of the base structure --- */ |
138 | |
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139 | b->off = slots; |
140 | b->sz = nsz - slots; |
141 | b->unshift = b->push = 0; |
142 | return (q); |
143 | } |
144 | |
145 | /* --- @da_shunt@ --- * |
146 | * |
147 | * Arguments: @da_base *b@ = pointer to array base structure |
148 | * @void *v@ = pointer to array vector |
149 | * @size_t sz@ = size of the array elements |
150 | * @size_t n@ = number of items required at the start |
151 | * |
152 | * Returns: Pointer to appropriately bodged vector. |
153 | * |
154 | * Use: Extends an array to accommodate items inserted at its front. |
155 | * This function is a helper for the @DA_SHUNT@ macro, which |
156 | * should be used by preference. |
157 | */ |
158 | |
159 | void *da_shunt(da_base *b, void *v, size_t sz, size_t n) |
160 | { |
161 | size_t rq; |
162 | char *p = v, *q; |
163 | size_t nsz; |
164 | size_t slots; |
165 | |
166 | /* --- Make sure there's something which needs doing --- * |
167 | * |
168 | * If there's enough space already then return immediately. |
169 | */ |
170 | |
171 | if (n < b->off) |
172 | return (p); |
173 | |
174 | /* --- Compute a number of `push' slots --- * |
175 | * |
176 | * When returning from this function, there will be @slots@ free spaces at |
177 | * the end of the array. If @push@ is zero, there's no point in reserving |
178 | * slots. Otherwise choose a power of two greater than @push@, with a |
179 | * minimum of @DA_SLOTS@. To simplify matters, add the number of items |
180 | * already in the array to @slots@, and then add the number of slots to the |
181 | * requirement. |
182 | */ |
183 | |
184 | if (!b->push) |
185 | slots = 0; |
186 | else { |
187 | slots = DA_SLOTS; |
188 | while (slots < b->push) |
189 | slots <<= 1; |
190 | } |
191 | slots += b->len; |
192 | rq = n + slots; |
193 | |
194 | /* --- Maybe just shunt data around a bit --- * |
195 | * |
196 | * If the vector is large enough, then theoretically we could cope by |
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197 | * moving the objects about in their existing storage. Again, if there's |
198 | * not actually twice the space needed, reallocate the array. |
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199 | */ |
200 | |
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201 | if (rq * 2 < b->sz + b->off) { |
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202 | q = p + (b->sz - slots) * sz; |
203 | memmove(q, p, b->len * sz); |
204 | b->off += b->sz - slots; |
205 | b->sz = slots; |
206 | b->unshift = b->push = 0; |
207 | return (q); |
208 | } |
209 | |
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210 | /* --- Reallocate the array --- * |
211 | * |
212 | * The neat @realloc@ code doesn't need to be here: the offset changes |
213 | * almost all the time -- that's the whole point of this routine! |
214 | */ |
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215 | |
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216 | /* --- Decide on a new size --- * |
217 | * |
218 | * There's a minimum possible size for the array which is used if it's |
219 | * currently completely empty. Otherwise I choose the smallest power of |
220 | * two which is big enough, starting at double the current size. |
221 | */ |
222 | |
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223 | nsz = b->sz + b->off; |
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224 | GROWBUF_SIZE(size_t, nsz, rq, DA_INITSZ, sz); |
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225 | |
226 | /* --- Reallocate the block --- * |
227 | * |
228 | * The neat @realloc@ code doesn't need to be here: the offset changes |
229 | * almost all the time -- that's the whole point of this routine! |
230 | */ |
231 | |
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232 | q = x_alloc(b->a, nsz * sz); |
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233 | q += (nsz - slots) * sz; |
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234 | if (p) { |
235 | memcpy(q, p, b->len * sz); |
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236 | x_free(b->a, p - b->off * sz); |
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237 | } |
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238 | |
239 | /* --- Fill in the other parts of the base structure --- */ |
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240 | |
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241 | b->off = nsz - slots; |
242 | b->sz = slots; |
243 | b->unshift = b->push = 0; |
244 | return (q); |
245 | } |
246 | |
247 | /* --- @da_tidy@ --- * |
248 | * |
249 | * Arguments: @da_base *b@ = pointer to array base structure |
250 | * @void *v@ = pointer to vector |
251 | * @size_t sz@ = size of the array elements |
252 | * |
253 | * Returns: Newly allocated vector. |
254 | * |
255 | * Use: Minimizes the space occupied by an array. This function is a |
256 | * helper for the @DA_TIDY@ macro, which should be used by |
257 | * preference. |
258 | */ |
259 | |
260 | void *da_tidy(da_base *b, void *v, size_t sz) |
261 | { |
262 | char *p = v, *q; |
263 | |
264 | b->unshift = b->push = 0; |
265 | |
266 | if (!p) |
267 | return (0); |
268 | if (b->sz == b->len && b->off == 0) |
269 | return (p); |
270 | |
271 | if (!b->len) { |
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272 | xfree(p - b->off * sz); |
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273 | return (0); |
274 | } |
275 | |
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276 | q = x_alloc(b->a, b->len * sz); |
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277 | memcpy(q, p, b->len * sz); |
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278 | x_free(b->a, p - b->off * sz); |
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279 | b->sz = b->len; |
280 | b->off = 0; |
281 | return (q); |
282 | } |
283 | |
284 | /* --- Note about testing --- * |
285 | * |
286 | * The test rig for this code is split into three parts. There's `da-gtest', |
287 | * which is a Perl script which generates a list of commands. The `da-ref' |
288 | * Perl script interprets these commands as operations on a Perl array. It's |
289 | * relatively conservatively written and believed to be reliable. The |
290 | * `da-test.c' file implements a command reader for the same syntax and |
291 | * performs the operations on an integer darray, producing output in the same |
292 | * format. To test darray, generate a command script with `da-gtest', pass |
293 | * it through both `da-ref' and `da-test' (the result of compiling |
294 | * da-test.c'), and compare the results. If they're not byte-for-byte |
295 | * identical, there's something wrong. |
296 | */ |
297 | |
298 | /*----- That's all, folks -------------------------------------------------*/ |