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
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.
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.
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.
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.
26 * Written by Douglas C. Schmidt (schmidt@ics.uci.edu).
27 * Modified by Maciej Stachowiak (mjs@eazel.com)
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/.
44 #include "gtestutils.h"
50 * @pbase: start of array to sort
51 * @total_elems: elements in the array
52 * @size: size of each element
53 * @compare_func: function to compare elements
54 * @user_data: data to pass to @compare_func
56 * This is just like the standard C qsort() function, but
57 * the comparison routine accepts a user data argument.
60 g_qsort_with_data (gconstpointer pbase,
63 GCompareDataFunc compare_func,
66 qsort_r ((gpointer)pbase, total_elems, size, compare_func, user_data);
71 /* Byte-wise swap two items of size SIZE. */
72 #define SWAP(a, b, size) \
75 register size_t __size = (size); \
76 register char *__a = (a), *__b = (b); \
82 } while (--__size > 0); \
85 /* Discontinue quicksort algorithm when partition gets below this size.
86 This particular magic number was chosen to work best on a Sun 4/260. */
89 /* Stack node declarations used to store unfulfilled partition obligations. */
96 /* The next 4 #defines implement a very fast in-line stack abstraction. */
97 /* The stack needs log (total_elements) entries (we could even subtract
98 log(MAX_THRESH)). Since total_elements has type size_t, we get as
99 upper bound for log (total_elements):
100 bits per byte (CHAR_BIT) * sizeof(size_t). */
101 #define STACK_SIZE (CHAR_BIT * sizeof(size_t))
102 #define PUSH(low, high) ((void) ((top->lo = (low)), (top->hi = (high)), ++top))
103 #define POP(low, high) ((void) (--top, (low = top->lo), (high = top->hi)))
104 #define STACK_NOT_EMPTY (stack < top)
107 /* Order size using quicksort. This implementation incorporates
108 four optimizations discussed in Sedgewick:
110 1. Non-recursive, using an explicit stack of pointer that store the
111 next array partition to sort. To save time, this maximum amount
112 of space required to store an array of SIZE_MAX is allocated on the
113 stack. Assuming a 32-bit (64 bit) integer for size_t, this needs
114 only 32 * sizeof(stack_node) == 256 bytes (for 64 bit: 1024 bytes).
115 Pretty cheap, actually.
117 2. Chose the pivot element using a median-of-three decision tree.
118 This reduces the probability of selecting a bad pivot value and
119 eliminates certain extraneous comparisons.
121 3. Only quicksorts TOTAL_ELEMS / MAX_THRESH partitions, leaving
122 insertion sort to order the MAX_THRESH items within each partition.
123 This is a big win, since insertion sort is faster for small, mostly
124 sorted array segments.
126 4. The larger of the two sub-partitions is always pushed onto the
127 stack first, with the algorithm then concentrating on the
128 smaller partition. This *guarantees* no more than log (total_elems)
129 stack size is needed (actually O(1) in this case)! */
132 g_qsort_with_data (gconstpointer pbase,
135 GCompareDataFunc compare_func,
138 register char *base_ptr = (char *) pbase;
140 const size_t max_thresh = MAX_THRESH * size;
142 g_return_if_fail (total_elems >= 0);
143 g_return_if_fail (pbase != NULL || total_elems == 0);
144 g_return_if_fail (compare_func != NULL);
146 if (total_elems == 0)
147 /* Avoid lossage with unsigned arithmetic below. */
150 if (total_elems > MAX_THRESH)
153 char *hi = &lo[size * (total_elems - 1)];
154 stack_node stack[STACK_SIZE];
155 stack_node *top = stack;
159 while (STACK_NOT_EMPTY)
164 /* Select median value from among LO, MID, and HI. Rearrange
165 LO and HI so the three values are sorted. This lowers the
166 probability of picking a pathological pivot value and
167 skips a comparison for both the LEFT_PTR and RIGHT_PTR in
170 char *mid = lo + size * ((hi - lo) / size >> 1);
172 if ((*compare_func) ((void *) mid, (void *) lo, user_data) < 0)
173 SWAP (mid, lo, size);
174 if ((*compare_func) ((void *) hi, (void *) mid, user_data) < 0)
175 SWAP (mid, hi, size);
178 if ((*compare_func) ((void *) mid, (void *) lo, user_data) < 0)
179 SWAP (mid, lo, size);
182 left_ptr = lo + size;
183 right_ptr = hi - size;
185 /* Here's the famous ``collapse the walls'' section of quicksort.
186 Gotta like those tight inner loops! They are the main reason
187 that this algorithm runs much faster than others. */
190 while ((*compare_func) ((void *) left_ptr, (void *) mid, user_data) < 0)
193 while ((*compare_func) ((void *) mid, (void *) right_ptr, user_data) < 0)
196 if (left_ptr < right_ptr)
198 SWAP (left_ptr, right_ptr, size);
201 else if (mid == right_ptr)
206 else if (left_ptr == right_ptr)
213 while (left_ptr <= right_ptr);
215 /* Set up pointers for next iteration. First determine whether
216 left and right partitions are below the threshold size. If so,
217 ignore one or both. Otherwise, push the larger partition's
218 bounds on the stack and continue sorting the smaller one. */
220 if ((size_t) (right_ptr - lo) <= max_thresh)
222 if ((size_t) (hi - left_ptr) <= max_thresh)
223 /* Ignore both small partitions. */
226 /* Ignore small left partition. */
229 else if ((size_t) (hi - left_ptr) <= max_thresh)
230 /* Ignore small right partition. */
232 else if ((right_ptr - lo) > (hi - left_ptr))
234 /* Push larger left partition indices. */
235 PUSH (lo, right_ptr);
240 /* Push larger right partition indices. */
247 /* Once the BASE_PTR array is partially sorted by quicksort the rest
248 is completely sorted using insertion sort, since this is efficient
249 for partitions below MAX_THRESH size. BASE_PTR points to the beginning
250 of the array to sort, and END_PTR points at the very last element in
251 the array (*not* one beyond it!). */
253 #define min(x, y) ((x) < (y) ? (x) : (y))
256 char *const end_ptr = &base_ptr[size * (total_elems - 1)];
257 char *tmp_ptr = base_ptr;
258 char *thresh = min(end_ptr, base_ptr + max_thresh);
259 register char *run_ptr;
261 /* Find smallest element in first threshold and place it at the
262 array's beginning. This is the smallest array element,
263 and the operation speeds up insertion sort's inner loop. */
265 for (run_ptr = tmp_ptr + size; run_ptr <= thresh; run_ptr += size)
266 if ((*compare_func) ((void *) run_ptr, (void *) tmp_ptr, user_data) < 0)
269 if (tmp_ptr != base_ptr)
270 SWAP (tmp_ptr, base_ptr, size);
272 /* Insertion sort, running from left-hand-side up to right-hand-side. */
274 run_ptr = base_ptr + size;
275 while ((run_ptr += size) <= end_ptr)
277 tmp_ptr = run_ptr - size;
278 while ((*compare_func) ((void *) run_ptr, (void *) tmp_ptr, user_data) < 0)
282 if (tmp_ptr != run_ptr)
286 trav = run_ptr + size;
287 while (--trav >= run_ptr)
292 for (hi = lo = trav; (lo -= size) >= tmp_ptr; hi = lo)
301 #endif /* HAVE_QSORT_R */