1 /* Simple 'n' stupid dynamic-array module.
2 Copyright (C) 1993 Sun Microsystems, Inc.
4 This file is part of XEmacs.
6 XEmacs is free software; you can redistribute it and/or modify it
7 under the terms of the GNU General Public License as published by the
8 Free Software Foundation; either version 2, or (at your option) any
11 XEmacs is distributed in the hope that it will be useful, but WITHOUT
12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 You should have received a copy of the GNU General Public License
17 along with XEmacs; see the file COPYING. If not, write to
18 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
21 /* Synched up with: Not in FSF. */
23 /* Written by Ben Wing, December 1993. */
27 A "dynamic array" is a contiguous array of fixed-size elements where there
28 is no upper limit (except available memory) on the number of elements in the
29 array. Because the elements are maintained contiguously, space is used
30 efficiently (no per-element pointers necessary) and random access to a
31 particular element is in constant time. At any one point, the block of memory
32 that holds the array has an upper limit; if this limit is exceeded, the
33 memory is realloc()ed into a new array that is twice as big. Assuming that
34 the time to grow the array is on the order of the new size of the array
35 block, this scheme has a provably constant amortized time (i.e. average
36 time over all additions).
38 When you add elements or retrieve elements, pointers are used. Note that
39 the element itself (of whatever size it is), and not the pointer to it,
40 is stored in the array; thus you do not have to allocate any heap memory
41 on your own. Also, returned pointers are only guaranteed to be valid
42 until the next operation that changes the length of the array.
44 This is a container object. Declare a dynamic array of a specific type
49 Dynarr_declare (mytype);
52 Use the following functions/macros:
54 void *Dynarr_new(type)
55 [MACRO] Create a new dynamic-array object, with each element of the
56 specified type. The return value is cast to (type##_dynarr).
57 This requires following the convention that types are declared in
58 such a way that this type concatenation works. In particular, TYPE
59 must be a symbol, not an arbitrary C type.
62 [MACRO] Add an element to the end of a dynamic array. EL is a pointer
63 to the element; the element itself is stored in the array, however.
64 No function call is performed unless the array needs to be resized.
66 Dynarr_add_many(d, base, len)
67 [MACRO] Add LEN elements to the end of the dynamic array. The elements
68 should be contiguous in memory, starting at BASE.
70 Dynarr_insert_many_at_start(d, base, len)
71 [MACRO] Append LEN elements to the beginning of the dynamic array.
72 The elements should be contiguous in memory, starting at BASE.
74 Dynarr_insert_many(d, base, len, start)
75 Insert LEN elements to the dynamic array starting at position
76 START. The elements should be contiguous in memory, starting at BASE.
79 [MACRO] Return the number of elements currently in a dynamic array.
82 [MACRO] Return the maximum value that Dynarr_length(d) would
86 [MACRO] Return the element at the specified index (no bounds checking
87 done on the index). The element itself is returned, not a pointer
90 type *Dynarr_atp(d, i)
91 [MACRO] Return a pointer to the element at the specified index (no
92 bounds checking done on the index). The pointer may not be valid
93 after an element is added to or removed from the array.
96 [MACRO] Reset the length of a dynamic array to 0.
99 Destroy a dynamic array and the memory allocated to it.
101 Use the following global variable:
104 Minimum allowable size for a dynamic array when it is resized. The
105 default is 32 and does not normally need to be changed.
112 int Dynarr_min_size = 1;
115 Dynarr_newf (int elsize)
117 Dynarr *d = xnew_and_zero (Dynarr);
124 Dynarr_resize (void *d, int size)
128 Dynarr *dy = (Dynarr *) d;
135 for (newsize = dy->max; newsize < size;)
136 newsize = max (Dynarr_min_size, (int) (multiplier * newsize));
138 /* Don't do anything if the array is already big enough. */
139 if (newsize > dy->max)
141 dy->base = xrealloc (dy->base, newsize*dy->elsize);
146 /* Add a number of contiguous elements to the array starting at START. */
148 Dynarr_insert_many (void *d, CONST void *el, int len, int start)
150 Dynarr *dy = (Dynarr *) d;
152 Dynarr_resize (dy, dy->cur+len);
153 /* Silently adjust start to be valid. */
159 if (start != dy->cur)
161 memmove ((char *) dy->base + (start + len)*dy->elsize,
162 (char *) dy->base + start*dy->elsize,
163 (dy->cur - start)*dy->elsize);
165 memcpy ((char *) dy->base + start*dy->elsize, el, len*dy->elsize);
168 if (dy->cur > dy->largest)
169 dy->largest = dy->cur;
173 Dynarr_delete_many (void *d, int start, int len)
175 Dynarr *dy = (Dynarr *) d;
177 assert (start >= 0 && len >= 0 && start + len <= dy->cur);
178 memmove ((char *) dy->base + start*dy->elsize,
179 (char *) dy->base + (start + len)*dy->elsize,
180 (dy->cur - start - len)*dy->elsize);
185 Dynarr_free (void *d)
187 Dynarr *dy = (Dynarr *) d;
194 #ifdef MEMORY_USAGE_STATS
196 /* Return memory usage for Dynarr D. The returned value is the total
197 amount of bytes actually being used for the Dynarr, including all
198 overhead. The extra amount of space in the Dynarr that is
199 allocated beyond what was requested is returned in DYNARR_OVERHEAD
200 in STATS. The extra amount of space that malloc() allocates beyond
201 what was requested of it is returned in MALLOC_OVERHEAD in STATS.
202 See the comment above the definition of this structure. */
205 Dynarr_memory_usage (void *d, struct overhead_stats *stats)
208 Dynarr *dy = (Dynarr *) d;
210 /* We have to be a bit tricky here because not all of the
211 memory that malloc() will claim as "requested" was actually
216 size_t malloc_used = malloced_storage_size (dy->base,
217 dy->elsize * dy->max, 0);
218 /* #### This may or may not be correct. Some Dynarrs would
219 prefer that we use dy->cur instead of dy->largest here. */
220 int was_requested = dy->elsize * dy->largest;
221 int dynarr_overhead = dy->elsize * (dy->max - dy->largest);
223 total += malloc_used;
224 stats->was_requested += was_requested;
225 stats->dynarr_overhead += dynarr_overhead;
226 /* And the remainder must be malloc overhead. */
227 stats->malloc_overhead +=
228 malloc_used - was_requested - dynarr_overhead;
231 total += malloced_storage_size (d, sizeof (*dy), stats);
236 #endif /* MEMORY_USAGE_STATS */