Line data Source code
1 : /*
2 : * qsort_arg.c: qsort with a passthrough "void *" argument
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.c, gen_qsort_tuple.pl
12 : *
13 : * src/port/qsort_arg.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 : qsort_arg_comparator cmp, void *arg);
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 4168487 : swapfunc(char *a, char *b, size_t n, int swaptype)
87 : {
88 4168487 : if (swaptype <= 1)
89 4168487 : swapcode(long, a, b, n);
90 : else
91 0 : swapcode(char, a, b, n);
92 4168487 : }
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 399970 : med3(char *a, char *b, char *c, qsort_arg_comparator cmp, void *arg)
106 : {
107 799940 : return cmp(a, b, arg) < 0 ?
108 187425 : (cmp(b, c, arg) < 0 ? b : (cmp(a, c, arg) < 0 ? c : a))
109 587395 : : (cmp(b, c, arg) > 0 ? b : (cmp(a, c, arg) < 0 ? a : c));
110 : }
111 :
112 : void
113 533471 : qsort_arg(void *a, size_t n, size_t es, qsort_arg_comparator cmp, void *arg)
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 533471 : loop:SWAPINIT(a, es);
129 533471 : if (n < 7)
130 : {
131 943628 : for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
132 2112983 : for (pl = pm; pl > (char *) a && cmp(pl - es, pl, arg) > 0;
133 708099 : pl -= es)
134 708099 : swap(pl, pl - es);
135 241186 : return;
136 : }
137 292285 : presorted = 1;
138 2003506 : for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
139 : {
140 1996367 : if (cmp(pm - es, pm, arg) > 0)
141 : {
142 285146 : presorted = 0;
143 285146 : break;
144 : }
145 : }
146 292285 : if (presorted)
147 7139 : return;
148 285146 : pm = (char *) a + (n / 2) * es;
149 285146 : if (n > 7)
150 : {
151 258022 : pl = (char *) a;
152 258022 : pn = (char *) a + (n - 1) * es;
153 258022 : if (n > 40)
154 : {
155 47316 : size_t d = (n / 8) * es;
156 :
157 47316 : pl = med3(pl, pl + d, pl + 2 * d, cmp, arg);
158 47316 : pm = med3(pm - d, pm, pm + d, cmp, arg);
159 47316 : pn = med3(pn - 2 * d, pn - d, pn, cmp, arg);
160 : }
161 258022 : pm = med3(pl, pm, pn, cmp, arg);
162 : }
163 285146 : swap(a, pm);
164 285146 : pa = pb = (char *) a + es;
165 285146 : pc = pd = (char *) a + (n - 1) * es;
166 : for (;;)
167 : {
168 10824440 : while (pb <= pc && (r = cmp(pb, a, arg)) <= 0)
169 : {
170 4710494 : if (r == 0)
171 : {
172 63717 : swap(pa, pb);
173 63717 : pa += es;
174 : }
175 4710494 : pb += es;
176 : }
177 10547204 : while (pb <= pc && (r = cmp(pc, a, arg)) >= 0)
178 : {
179 4433258 : if (r == 0)
180 : {
181 58501 : swap(pc, pd);
182 58501 : pd -= es;
183 : }
184 4433258 : pc -= es;
185 : }
186 3056973 : if (pb > pc)
187 285146 : break;
188 2771827 : swap(pb, pc);
189 2771827 : pb += es;
190 2771827 : pc -= es;
191 2771827 : }
192 285146 : pn = (char *) a + n * es;
193 285146 : d1 = Min(pa - (char *) a, pb - pa);
194 285146 : vecswap(a, pb - d1, d1);
195 285146 : d1 = Min(pd - pc, pn - pd - es);
196 285146 : vecswap(pb, pn - d1, d1);
197 285146 : d1 = pb - pa;
198 285146 : d2 = pd - pc;
199 285146 : if (d1 <= d2)
200 : {
201 : /* Recurse on left partition, then iterate on right partition */
202 134543 : if (d1 > es)
203 111565 : qsort_arg(a, d1 / es, es, cmp, arg);
204 134543 : if (d2 > es)
205 : {
206 : /* Iterate rather than recurse to save stack space */
207 : /* qsort_arg(pn - d2, d2 / es, es, cmp, arg); */
208 134543 : a = pn - d2;
209 134543 : n = d2 / es;
210 134543 : goto loop;
211 : }
212 : }
213 : else
214 : {
215 : /* Recurse on right partition, then iterate on left partition */
216 150603 : if (d2 > es)
217 96346 : qsort_arg(pn - d2, d2 / es, es, cmp, arg);
218 150603 : if (d1 > es)
219 : {
220 : /* Iterate rather than recurse to save stack space */
221 : /* qsort_arg(a, d1 / es, es, cmp, arg); */
222 150603 : n = d1 / es;
223 150603 : goto loop;
224 : }
225 : }
226 : }
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