1 /* GLIB - Library of useful routines for C programming
2 * Copyright (C) 1991, 1992, 1996, 1997,1999,2004 Free Software Foundation, Inc.
3 * Copyright (C) 2000 Eazel, Inc.
4 * Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
5 *
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2 of the License, or (at your option) any later version.
10 *
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; if not, write to the
18 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 * Boston, MA 02111-1307, USA.
20 */
21
22 /*
23 * This file was originally part of the GNU C Library, and was modified to allow
24 * user data to be passed in to the sorting function.
25 *
26 * Written by Douglas C. Schmidt (schmidt@ics.uci.edu).
27 * Modified by Maciej Stachowiak (mjs@eazel.com)
28 *
29 * Modified by the GLib Team and others 1997-2000. See the AUTHORS
30 * file for a list of people on the GLib Team. See the ChangeLog
31 * files for a list of changes. These files are distributed with GLib
32 * at ftp://ftp.gtk.org/pub/gtk/.
33 */
34
35 #include "config.h"
36
37 #include <limits.h>
38 #include <stdlib.h>
39 #include <string.h>
40
41 #include "glib.h"
42 #include "galias.h"
43
44 /* Byte-wise swap two items of size SIZE. */
45 #define SWAP(a, b, size) \
46 do \
47 { \
48 register size_t __size = (size); \
49 register char *__a = (a), *__b = (b); \
50 do \
51 { \
52 char __tmp = *__a; \
53 *__a++ = *__b; \
54 *__b++ = __tmp; \
55 } while (--__size > 0); \
56 } while (0)
57
58 /* Discontinue quicksort algorithm when partition gets below this size.
59 This particular magic number was chosen to work best on a Sun 4/260. */
60 #define MAX_THRESH 4
61
62 /* Stack node declarations used to store unfulfilled partition obligations. */
63 typedef struct
64 {
65 char *lo;
66 char *hi;
67 } stack_node;
68
69 /* The next 4 #defines implement a very fast in-line stack abstraction. */
70 /* The stack needs log (total_elements) entries (we could even subtract
71 log(MAX_THRESH)). Since total_elements has type size_t, we get as
72 upper bound for log (total_elements):
73 bits per byte (CHAR_BIT) * sizeof(size_t). */
74 #define STACK_SIZE (CHAR_BIT * sizeof(size_t))
75 #define PUSH(low, high) ((void) ((top->lo = (low)), (top->hi = (high)), ++top))
76 #define POP(low, high) ((void) (--top, (low = top->lo), (high = top->hi)))
77 #define STACK_NOT_EMPTY (stack < top)
78
79
80 /* Order size using quicksort. This implementation incorporates
81 four optimizations discussed in Sedgewick:
82
83 1. Non-recursive, using an explicit stack of pointer that store the
84 next array partition to sort. To save time, this maximum amount
85 of space required to store an array of SIZE_MAX is allocated on the
86 stack. Assuming a 32-bit (64 bit) integer for size_t, this needs
87 only 32 * sizeof(stack_node) == 256 bytes (for 64 bit: 1024 bytes).
88 Pretty cheap, actually.
89
90 2. Chose the pivot element using a median-of-three decision tree.
91 This reduces the probability of selecting a bad pivot value and
92 eliminates certain extraneous comparisons.
93
94 3. Only quicksorts TOTAL_ELEMS / MAX_THRESH partitions, leaving
95 insertion sort to order the MAX_THRESH items within each partition.
96 This is a big win, since insertion sort is faster for small, mostly
97 sorted array segments.
98
99 4. The larger of the two sub-partitions is always pushed onto the
100 stack first, with the algorithm then concentrating on the
101 smaller partition. This *guarantees* no more than log (total_elems)
102 stack size is needed (actually O(1) in this case)! */
103
104 /**
105 * g_qsort_with_data:
106 * @pbase: start of array to sort
107 * @total_elems: elements in the array
108 * @size: size of each element
109 * @compare_func: function to compare elements
110 * @user_data: data to pass to @compare_func
111 *
112 * This is just like the standard C qsort() function, but
113 * the comparison routine accepts a user data argument.
114 *
115 **/
116 void
g_qsort_with_data(gconstpointer pbase,gint total_elems,gsize size,GCompareDataFunc compare_func,gpointer user_data)117 g_qsort_with_data (gconstpointer pbase,
118 gint total_elems,
119 gsize size,
120 GCompareDataFunc compare_func,
121 gpointer user_data)
122 {
123 register char *base_ptr = (char *) pbase;
124
125 const size_t max_thresh = MAX_THRESH * size;
126
127 g_return_if_fail (total_elems >= 0);
128 g_return_if_fail (pbase != NULL || total_elems == 0);
129 g_return_if_fail (compare_func != NULL);
130
131 if (total_elems == 0)
132 /* Avoid lossage with unsigned arithmetic below. */
133 return;
134
135 if (total_elems > MAX_THRESH)
136 {
137 char *lo = base_ptr;
138 char *hi = &lo[size * (total_elems - 1)];
139 stack_node stack[STACK_SIZE];
140 stack_node *top = stack;
141
142 PUSH (NULL, NULL);
143
144 while (STACK_NOT_EMPTY)
145 {
146 char *left_ptr;
147 char *right_ptr;
148
149 /* Select median value from among LO, MID, and HI. Rearrange
150 LO and HI so the three values are sorted. This lowers the
151 probability of picking a pathological pivot value and
152 skips a comparison for both the LEFT_PTR and RIGHT_PTR in
153 the while loops. */
154
155 char *mid = lo + size * ((hi - lo) / size >> 1);
156
157 if ((*compare_func) ((void *) mid, (void *) lo, user_data) < 0)
158 SWAP (mid, lo, size);
159 if ((*compare_func) ((void *) hi, (void *) mid, user_data) < 0)
160 SWAP (mid, hi, size);
161 else
162 goto jump_over;
163 if ((*compare_func) ((void *) mid, (void *) lo, user_data) < 0)
164 SWAP (mid, lo, size);
165 jump_over:;
166
167 left_ptr = lo + size;
168 right_ptr = hi - size;
169
170 /* Here's the famous ``collapse the walls'' section of quicksort.
171 Gotta like those tight inner loops! They are the main reason
172 that this algorithm runs much faster than others. */
173 do
174 {
175 while ((*compare_func) ((void *) left_ptr, (void *) mid, user_data) < 0)
176 left_ptr += size;
177
178 while ((*compare_func) ((void *) mid, (void *) right_ptr, user_data) < 0)
179 right_ptr -= size;
180
181 if (left_ptr < right_ptr)
182 {
183 SWAP (left_ptr, right_ptr, size);
184 if (mid == left_ptr)
185 mid = right_ptr;
186 else if (mid == right_ptr)
187 mid = left_ptr;
188 left_ptr += size;
189 right_ptr -= size;
190 }
191 else if (left_ptr == right_ptr)
192 {
193 left_ptr += size;
194 right_ptr -= size;
195 break;
196 }
197 }
198 while (left_ptr <= right_ptr);
199
200 /* Set up pointers for next iteration. First determine whether
201 left and right partitions are below the threshold size. If so,
202 ignore one or both. Otherwise, push the larger partition's
203 bounds on the stack and continue sorting the smaller one. */
204
205 if ((size_t) (right_ptr - lo) <= max_thresh)
206 {
207 if ((size_t) (hi - left_ptr) <= max_thresh)
208 /* Ignore both small partitions. */
209 POP (lo, hi);
210 else
211 /* Ignore small left partition. */
212 lo = left_ptr;
213 }
214 else if ((size_t) (hi - left_ptr) <= max_thresh)
215 /* Ignore small right partition. */
216 hi = right_ptr;
217 else if ((right_ptr - lo) > (hi - left_ptr))
218 {
219 /* Push larger left partition indices. */
220 PUSH (lo, right_ptr);
221 lo = left_ptr;
222 }
223 else
224 {
225 /* Push larger right partition indices. */
226 PUSH (left_ptr, hi);
227 hi = right_ptr;
228 }
229 }
230 }
231
232 /* Once the BASE_PTR array is partially sorted by quicksort the rest
233 is completely sorted using insertion sort, since this is efficient
234 for partitions below MAX_THRESH size. BASE_PTR points to the beginning
235 of the array to sort, and END_PTR points at the very last element in
236 the array (*not* one beyond it!). */
237
238 #define min(x, y) ((x) < (y) ? (x) : (y))
239
240 {
241 char *const end_ptr = &base_ptr[size * (total_elems - 1)];
242 char *tmp_ptr = base_ptr;
243 char *thresh = min(end_ptr, base_ptr + max_thresh);
244 register char *run_ptr;
245
246 /* Find smallest element in first threshold and place it at the
247 array's beginning. This is the smallest array element,
248 and the operation speeds up insertion sort's inner loop. */
249
250 for (run_ptr = tmp_ptr + size; run_ptr <= thresh; run_ptr += size)
251 if ((*compare_func) ((void *) run_ptr, (void *) tmp_ptr, user_data) < 0)
252 tmp_ptr = run_ptr;
253
254 if (tmp_ptr != base_ptr)
255 SWAP (tmp_ptr, base_ptr, size);
256
257 /* Insertion sort, running from left-hand-side up to right-hand-side. */
258
259 run_ptr = base_ptr + size;
260 while ((run_ptr += size) <= end_ptr)
261 {
262 tmp_ptr = run_ptr - size;
263 while ((*compare_func) ((void *) run_ptr, (void *) tmp_ptr, user_data) < 0)
264 tmp_ptr -= size;
265
266 tmp_ptr += size;
267 if (tmp_ptr != run_ptr)
268 {
269 char *trav;
270
271 trav = run_ptr + size;
272 while (--trav >= run_ptr)
273 {
274 char c = *trav;
275 char *hi, *lo;
276
277 for (hi = lo = trav; (lo -= size) >= tmp_ptr; hi = lo)
278 *hi = *lo;
279 *hi = c;
280 }
281 }
282 }
283 }
284 }
285
286 #define __G_QSORT_C__
287 #include "galiasdef.c"
288