3 * $Id: darray.c,v 1.2 1999/10/28 22:05:28 mdw Exp $
5 * Dynamically growing dense arrays
7 * (c) 1999 Straylight/Edgeware
10 /*----- Licensing notice --------------------------------------------------*
12 * This file is part of the mLib utilities library.
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.
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.
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,
30 /*----- Revision history --------------------------------------------------*
33 * Revision 1.2 1999/10/28 22:05:28 mdw
34 * Modify and debug allocation routines.
36 * Revision 1.1 1999/10/22 22:37:26 mdw
37 * New dynamic array implementation replaces `dynarray.h'.
41 /*----- Header files ------------------------------------------------------*/
50 /*----- Magic numbers -----------------------------------------------------*/
52 #define DA_INITSZ 16 /* Default size for new array */
53 #define DA_SLOTS 8 /* Number of preshifted slots */
55 /*----- Main code ---------------------------------------------------------*/
57 /* --- @da_ensure@ --- *
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
64 * Returns: Pointer to newly allocated or adjusted array vector.
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.
71 void *da_ensure(da_base *b, void *v, size_t sz, size_t n)
73 size_t rq = n + b->len;
78 /* --- Make sure there's something which needs doing --- *
80 * If there's enough space already then return immediately.
86 /* --- Compute a number of `unshift' slots --- *
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.
98 while (slots < b->unshift)
103 /* --- Maybe just shunt data around a bit --- *
105 * If the vector is large enough, then theoretically we could cope by
106 * moving the objects about in their existing storage.
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;
114 b->unshift = b->push = 0;
118 /* --- Reallocate the array --- */
120 nsz = v ? b->sz + b->off : (DA_INITSZ >> 1);
121 do nsz <<= 1; while (nsz < rq);
122 q = xmalloc(nsz * sz);
124 memcpy(q, p, b->len * sz);
126 free(p - b->off * sz);
129 b->unshift = b->push = 0;
133 /* --- @da_shunt@ --- *
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
140 * Returns: Pointer to appropriately bodged vector.
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.
147 void *da_shunt(da_base *b, void *v, size_t sz, size_t n)
154 /* --- Make sure there's something which needs doing --- *
156 * If there's enough space already then return immediately.
162 /* --- Compute a number of `push' slots --- *
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
176 while (slots < b->push)
182 /* --- Maybe just shunt data around a bit --- *
184 * If the vector is large enough, then theoretically we could cope by
185 * moving the objects about in their existing storage.
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;
193 b->unshift = b->push = 0;
197 /* --- Reallocate the array --- */
199 nsz = v ? b->sz + b->off : (DA_INITSZ >> 1);
200 do nsz <<= 1; while (nsz < rq);
201 q = xmalloc(nsz * sz);
202 q += (nsz - slots) * sz;
203 memcpy(q, p, b->len * sz);
205 free(p - b->off * sz);
206 b->off = nsz - slots;
208 b->unshift = b->push = 0;
212 /* --- @da_tidy@ --- *
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
218 * Returns: Newly allocated vector.
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
225 void *da_tidy(da_base *b, void *v, size_t sz)
229 b->unshift = b->push = 0;
233 if (b->sz == b->len && b->off == 0)
237 free(p - b->off * sz);
241 q = xmalloc(b->len * sz);
242 memcpy(q, p, b->len * sz);
243 free(p - b->off * sz);
249 /* --- Note about testing --- *
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.
263 /*----- That's all, folks -------------------------------------------------*/