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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: darray.c,v 1.2 1999/10/28 22:05:28 mdw Exp $ |
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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 $ |
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33 | * Revision 1.2 1999/10/28 22:05:28 mdw |
34 | * Modify and debug allocation routines. |
35 | * |
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36 | * Revision 1.1 1999/10/22 22:37:26 mdw |
37 | * New dynamic array implementation replaces `dynarray.h'. |
38 | * |
39 | */ |
40 | |
41 | /*----- Header files ------------------------------------------------------*/ |
42 | |
43 | #include <stdio.h> |
44 | #include <string.h> |
45 | #include <stdlib.h> |
46 | |
47 | #include "alloc.h" |
48 | #include "darray.h" |
49 | |
50 | /*----- Magic numbers -----------------------------------------------------*/ |
51 | |
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52 | #define DA_INITSZ 16 /* Default size for new array */ |
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53 | #define DA_SLOTS 8 /* Number of preshifted slots */ |
54 | |
55 | /*----- Main code ---------------------------------------------------------*/ |
56 | |
57 | /* --- @da_ensure@ --- * |
58 | * |
59 | * Arguments: @da_base *b@ = pointer to array base structure |
60 | * @void *v@ = pointer to array vector |
61 | * @size_t sz@ = size of individual array elements |
62 | * @size_t n@ = number of items required at the end |
63 | * |
64 | * Returns: Pointer to newly allocated or adjusted array vector. |
65 | * |
66 | * Use: Extends a dynamic array to accommodate a number of new items |
67 | * at its end. This function is a helper for the @DA_ENSURE@ |
68 | * macro, which should be used by preference. |
69 | */ |
70 | |
71 | void *da_ensure(da_base *b, void *v, size_t sz, size_t n) |
72 | { |
73 | size_t rq = n + b->len; |
74 | char *p = v, *q; |
75 | size_t nsz; |
76 | size_t slots; |
77 | |
78 | /* --- Make sure there's something which needs doing --- * |
79 | * |
80 | * If there's enough space already then return immediately. |
81 | */ |
82 | |
83 | if (rq < b->sz) |
84 | return (p); |
85 | |
86 | /* --- Compute a number of `unshift' slots --- * |
87 | * |
88 | * When returning from this function, the offset will be set to @slots@. |
89 | * If @unshift@ is zero, there's no point in reserving slots. Otherwise |
90 | * choose a power of two greater than @unshift@, with a minimum of |
91 | * @DA_SLOTS@. Then add the number of slots to the requirement. |
92 | */ |
93 | |
94 | if (!b->unshift) |
95 | slots = 0; |
96 | else { |
97 | slots = DA_SLOTS; |
98 | while (slots < b->unshift) |
99 | slots <<= 1; |
100 | } |
101 | rq += slots; |
102 | |
103 | /* --- Maybe just shunt data around a bit --- * |
104 | * |
105 | * If the vector is large enough, then theoretically we could cope by |
106 | * moving the objects about in their existing storage. |
107 | */ |
108 | |
109 | if (rq < b->sz + b->off) { |
110 | q = p - (b->off - slots) * sz; |
111 | memmove(q, p, b->len * sz); |
112 | b->sz += b->off - slots; |
113 | b->off = slots; |
114 | b->unshift = b->push = 0; |
115 | return (q); |
116 | } |
117 | |
118 | /* --- Reallocate the array --- */ |
119 | |
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120 | nsz = v ? b->sz + b->off : (DA_INITSZ >> 1); |
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121 | do nsz <<= 1; while (nsz < rq); |
122 | q = xmalloc(nsz * sz); |
123 | q += slots * sz; |
124 | memcpy(q, p, b->len * sz); |
125 | if (p) |
126 | free(p - b->off * sz); |
127 | b->off = slots; |
128 | b->sz = nsz - slots; |
129 | b->unshift = b->push = 0; |
130 | return (q); |
131 | } |
132 | |
133 | /* --- @da_shunt@ --- * |
134 | * |
135 | * Arguments: @da_base *b@ = pointer to array base structure |
136 | * @void *v@ = pointer to array vector |
137 | * @size_t sz@ = size of the array elements |
138 | * @size_t n@ = number of items required at the start |
139 | * |
140 | * Returns: Pointer to appropriately bodged vector. |
141 | * |
142 | * Use: Extends an array to accommodate items inserted at its front. |
143 | * This function is a helper for the @DA_SHUNT@ macro, which |
144 | * should be used by preference. |
145 | */ |
146 | |
147 | void *da_shunt(da_base *b, void *v, size_t sz, size_t n) |
148 | { |
149 | size_t rq; |
150 | char *p = v, *q; |
151 | size_t nsz; |
152 | size_t slots; |
153 | |
154 | /* --- Make sure there's something which needs doing --- * |
155 | * |
156 | * If there's enough space already then return immediately. |
157 | */ |
158 | |
159 | if (n < b->off) |
160 | return (p); |
161 | |
162 | /* --- Compute a number of `push' slots --- * |
163 | * |
164 | * When returning from this function, there will be @slots@ free spaces at |
165 | * the end of the array. If @push@ is zero, there's no point in reserving |
166 | * slots. Otherwise choose a power of two greater than @push@, with a |
167 | * minimum of @DA_SLOTS@. To simplify matters, add the number of items |
168 | * already in the array to @slots@, and then add the number of slots to the |
169 | * requirement. |
170 | */ |
171 | |
172 | if (!b->push) |
173 | slots = 0; |
174 | else { |
175 | slots = DA_SLOTS; |
176 | while (slots < b->push) |
177 | slots <<= 1; |
178 | } |
179 | slots += b->len; |
180 | rq = n + slots; |
181 | |
182 | /* --- Maybe just shunt data around a bit --- * |
183 | * |
184 | * If the vector is large enough, then theoretically we could cope by |
185 | * moving the objects about in their existing storage. |
186 | */ |
187 | |
188 | if (rq < b->sz + b->off) { |
189 | q = p + (b->sz - slots) * sz; |
190 | memmove(q, p, b->len * sz); |
191 | b->off += b->sz - slots; |
192 | b->sz = slots; |
193 | b->unshift = b->push = 0; |
194 | return (q); |
195 | } |
196 | |
197 | /* --- Reallocate the array --- */ |
198 | |
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199 | nsz = v ? b->sz + b->off : (DA_INITSZ >> 1); |
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200 | do nsz <<= 1; while (nsz < rq); |
201 | q = xmalloc(nsz * sz); |
202 | q += (nsz - slots) * sz; |
203 | memcpy(q, p, b->len * sz); |
204 | if (p) |
205 | free(p - b->off * sz); |
206 | b->off = nsz - slots; |
207 | b->sz = slots; |
208 | b->unshift = b->push = 0; |
209 | return (q); |
210 | } |
211 | |
212 | /* --- @da_tidy@ --- * |
213 | * |
214 | * Arguments: @da_base *b@ = pointer to array base structure |
215 | * @void *v@ = pointer to vector |
216 | * @size_t sz@ = size of the array elements |
217 | * |
218 | * Returns: Newly allocated vector. |
219 | * |
220 | * Use: Minimizes the space occupied by an array. This function is a |
221 | * helper for the @DA_TIDY@ macro, which should be used by |
222 | * preference. |
223 | */ |
224 | |
225 | void *da_tidy(da_base *b, void *v, size_t sz) |
226 | { |
227 | char *p = v, *q; |
228 | |
229 | b->unshift = b->push = 0; |
230 | |
231 | if (!p) |
232 | return (0); |
233 | if (b->sz == b->len && b->off == 0) |
234 | return (p); |
235 | |
236 | if (!b->len) { |
237 | free(p - b->off * sz); |
238 | return (0); |
239 | } |
240 | |
241 | q = xmalloc(b->len * sz); |
242 | memcpy(q, p, b->len * sz); |
243 | free(p - b->off * sz); |
244 | b->sz = b->len; |
245 | b->off = 0; |
246 | return (q); |
247 | } |
248 | |
249 | /* --- Note about testing --- * |
250 | * |
251 | * The test rig for this code is split into three parts. There's `da-gtest', |
252 | * which is a Perl script which generates a list of commands. The `da-ref' |
253 | * Perl script interprets these commands as operations on a Perl array. It's |
254 | * relatively conservatively written and believed to be reliable. The |
255 | * `da-test.c' file implements a command reader for the same syntax and |
256 | * performs the operations on an integer darray, producing output in the same |
257 | * format. To test darray, generate a command script with `da-gtest', pass |
258 | * it through both `da-ref' and `da-test' (the result of compiling |
259 | * da-test.c'), and compare the results. If they're not byte-for-byte |
260 | * identical, there's something wrong. |
261 | */ |
262 | |
263 | /*----- That's all, folks -------------------------------------------------*/ |