Line data Source code
1 : /*
2 : * qsort.c: standard quicksort algorithm
3 : *
4 : * Modifications from vanilla NetBSD source:
5 : * Add do ... while() macro fix
6 : * Remove __inline, _DIAGASSERTs, __P
7 : * Remove ill-considered "swap_cnt" switch to insertion sort,
8 : * in favor of a simple check for presorted input.
9 : * Take care to recurse on the smaller partition, to bound stack usage.
10 : *
11 : * CAUTION: if you change this file, see also qsort_arg.c, gen_qsort_tuple.pl
12 : *
13 : * src/port/qsort.c
14 : */
15 :
16 : /* $NetBSD: qsort.c,v 1.13 2003/08/07 16:43:42 agc Exp $ */
17 :
18 : /*-
19 : * Copyright (c) 1992, 1993
20 : * The Regents of the University of California. All rights reserved.
21 : *
22 : * Redistribution and use in source and binary forms, with or without
23 : * modification, are permitted provided that the following conditions
24 : * are met:
25 : * 1. Redistributions of source code must retain the above copyright
26 : * notice, this list of conditions and the following disclaimer.
27 : * 2. Redistributions in binary form must reproduce the above copyright
28 : * notice, this list of conditions and the following disclaimer in the
29 : * documentation and/or other materials provided with the distribution.
30 : * 3. Neither the name of the University nor the names of its contributors
31 : * may be used to endorse or promote products derived from this software
32 : * without specific prior written permission.
33 : *
34 : * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
35 : * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
36 : * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
37 : * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
38 : * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
39 : * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
40 : * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
41 : * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
42 : * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
43 : * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
44 : * SUCH DAMAGE.
45 : */
46 :
47 : #include "c.h"
48 :
49 :
50 : static char *med3(char *a, char *b, char *c,
51 : int (*cmp) (const void *, const void *));
52 : static void swapfunc(char *, char *, size_t, int);
53 :
54 : /*
55 : * Qsort routine based on J. L. Bentley and M. D. McIlroy,
56 : * "Engineering a sort function",
57 : * Software--Practice and Experience 23 (1993) 1249-1265.
58 : *
59 : * We have modified their original by adding a check for already-sorted input,
60 : * which seems to be a win per discussions on pgsql-hackers around 2006-03-21.
61 : *
62 : * Also, we recurse on the smaller partition and iterate on the larger one,
63 : * which ensures we cannot recurse more than log(N) levels (since the
64 : * partition recursed to is surely no more than half of the input). Bentley
65 : * and McIlroy explicitly rejected doing this on the grounds that it's "not
66 : * worth the effort", but we have seen crashes in the field due to stack
67 : * overrun, so that judgment seems wrong.
68 : */
69 :
70 : #define swapcode(TYPE, parmi, parmj, n) \
71 : do { \
72 : size_t i = (n) / sizeof (TYPE); \
73 : TYPE *pi = (TYPE *)(void *)(parmi); \
74 : TYPE *pj = (TYPE *)(void *)(parmj); \
75 : do { \
76 : TYPE t = *pi; \
77 : *pi++ = *pj; \
78 : *pj++ = t; \
79 : } while (--i > 0); \
80 : } while (0)
81 :
82 : #define SWAPINIT(a, es) swaptype = ((char *)(a) - (char *)0) % sizeof(long) || \
83 : (es) % sizeof(long) ? 2 : (es) == sizeof(long)? 0 : 1;
84 :
85 : static void
86 994550 : swapfunc(char *a, char *b, size_t n, int swaptype)
87 : {
88 994550 : if (swaptype <= 1)
89 636271 : swapcode(long, a, b, n);
90 : else
91 358279 : swapcode(char, a, b, n);
92 994550 : }
93 :
94 : #define swap(a, b) \
95 : if (swaptype == 0) { \
96 : long t = *(long *)(void *)(a); \
97 : *(long *)(void *)(a) = *(long *)(void *)(b); \
98 : *(long *)(void *)(b) = t; \
99 : } else \
100 : swapfunc(a, b, es, swaptype)
101 :
102 : #define vecswap(a, b, n) if ((n) > 0) swapfunc(a, b, n, swaptype)
103 :
104 : static char *
105 265353 : med3(char *a, char *b, char *c, int (*cmp) (const void *, const void *))
106 : {
107 530706 : return cmp(a, b) < 0 ?
108 169182 : (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a))
109 434535 : : (cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c));
110 : }
111 :
112 : void
113 328316 : pg_qsort(void *a, size_t n, size_t es, int (*cmp) (const void *, const void *))
114 : {
115 : char *pa,
116 : *pb,
117 : *pc,
118 : *pd,
119 : *pl,
120 : *pm,
121 : *pn;
122 : size_t d1,
123 : d2;
124 : int r,
125 : swaptype,
126 : presorted;
127 :
128 328316 : loop:SWAPINIT(a, es);
129 328316 : if (n < 7)
130 : {
131 438082 : for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
132 993997 : for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
133 347595 : pl -= es)
134 347595 : swap(pl, pl - es);
135 114881 : return;
136 : }
137 213435 : presorted = 1;
138 4352864 : for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
139 : {
140 4329643 : if (cmp(pm - es, pm) > 0)
141 : {
142 190214 : presorted = 0;
143 190214 : break;
144 : }
145 : }
146 213435 : if (presorted)
147 23221 : return;
148 190214 : pm = (char *) a + (n / 2) * es;
149 190214 : if (n > 7)
150 : {
151 176289 : pl = (char *) a;
152 176289 : pn = (char *) a + (n - 1) * es;
153 176289 : if (n > 40)
154 : {
155 29688 : size_t d = (n / 8) * es;
156 :
157 29688 : pl = med3(pl, pl + d, pl + 2 * d, cmp);
158 29688 : pm = med3(pm - d, pm, pm + d, cmp);
159 29688 : pn = med3(pn - 2 * d, pn - d, pn, cmp);
160 : }
161 176289 : pm = med3(pl, pm, pn, cmp);
162 : }
163 190214 : swap(a, pm);
164 190214 : pa = pb = (char *) a + es;
165 190214 : pc = pd = (char *) a + (n - 1) * es;
166 : for (;;)
167 : {
168 4925166 : while (pb <= pc && (r = cmp(pb, a)) <= 0)
169 : {
170 3436806 : if (r == 0)
171 : {
172 25409 : swap(pa, pb);
173 25409 : pa += es;
174 : }
175 3436806 : pb += es;
176 : }
177 5261116 : while (pb <= pc && (r = cmp(pc, a)) >= 0)
178 : {
179 3772756 : if (r == 0)
180 : {
181 21862 : swap(pc, pd);
182 21862 : pd -= es;
183 : }
184 3772756 : pc -= es;
185 : }
186 744180 : if (pb > pc)
187 190214 : break;
188 553966 : swap(pb, pc);
189 553966 : pb += es;
190 553966 : pc -= es;
191 553966 : }
192 190214 : pn = (char *) a + n * es;
193 190214 : d1 = Min(pa - (char *) a, pb - pa);
194 190214 : vecswap(a, pb - d1, d1);
195 190214 : d1 = Min(pd - pc, pn - pd - es);
196 190214 : vecswap(pb, pn - d1, d1);
197 190214 : d1 = pb - pa;
198 190214 : d2 = pd - pc;
199 190214 : if (d1 <= d2)
200 : {
201 : /* Recurse on left partition, then iterate on right partition */
202 106297 : if (d1 > es)
203 55506 : pg_qsort(a, d1 / es, es, cmp);
204 106297 : if (d2 > es)
205 : {
206 : /* Iterate rather than recurse to save stack space */
207 : /* pg_qsort(pn - d2, d2 / es, es, cmp); */
208 106265 : a = pn - d2;
209 106265 : n = d2 / es;
210 106265 : goto loop;
211 : }
212 : }
213 : else
214 : {
215 : /* Recurse on right partition, then iterate on left partition */
216 83917 : if (d2 > es)
217 50221 : pg_qsort(pn - d2, d2 / es, es, cmp);
218 83917 : if (d1 > es)
219 : {
220 : /* Iterate rather than recurse to save stack space */
221 : /* pg_qsort(a, d1 / es, es, cmp); */
222 83884 : n = d1 / es;
223 83884 : goto loop;
224 : }
225 : }
226 : }
227 :
228 : /*
229 : * qsort comparator wrapper for strcmp.
230 : */
231 : int
232 13305 : pg_qsort_strcmp(const void *a, const void *b)
233 : {
234 13305 : return strcmp(*(const char *const *) a, *(const char *const *) b);
235 : }
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