Fix xslt_process() to ensure that it inserts a NULL terminator after the
[PostgreSQL.git] / src / port / qsort.c
blob7d50fb87661323e7b3b6cf0eb6902a02bcc557c1
1 /*
2 * qsort.c: standard quicksort algorithm
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.
10 * CAUTION: if you change this file, see also qsort_arg.c
12 * $PostgreSQL$
15 /* $NetBSD$ */
17 /*-
18 * Copyright (c) 1992, 1993
19 * The Regents of the University of California. All rights reserved.
21 * Redistribution and use in source and binary forms, with or without
22 * modification, are permitted provided that the following conditions
23 * are met:
24 * 1. Redistributions of source code must retain the above copyright
25 * notice, this list of conditions and the following disclaimer.
26 * 2. Redistributions in binary form must reproduce the above copyright
27 * notice, this list of conditions and the following disclaimer in the
28 * documentation and/or other materials provided with the distribution.
29 * 3. Neither the name of the University nor the names of its contributors
30 * may be used to endorse or promote products derived from this software
31 * without specific prior written permission.
33 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
34 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
35 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
36 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
37 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
38 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
39 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
40 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
41 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
42 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
43 * SUCH DAMAGE.
46 #include "c.h"
49 static char *med3(char *a, char *b, char *c,
50 int (*cmp) (const void *, const void *));
51 static void swapfunc(char *, char *, size_t, int);
54 * Qsort routine based on J. L. Bentley and M. D. McIlroy,
55 * "Engineering a sort function",
56 * Software--Practice and Experience 23 (1993) 1249-1265.
57 * We have modified their original by adding a check for already-sorted input,
58 * which seems to be a win per discussions on pgsql-hackers around 2006-03-21.
60 #define swapcode(TYPE, parmi, parmj, n) \
61 do { \
62 size_t i = (n) / sizeof (TYPE); \
63 TYPE *pi = (TYPE *)(void *)(parmi); \
64 TYPE *pj = (TYPE *)(void *)(parmj); \
65 do { \
66 TYPE t = *pi; \
67 *pi++ = *pj; \
68 *pj++ = t; \
69 } while (--i > 0); \
70 } while (0)
72 #define SWAPINIT(a, es) swaptype = ((char *)(a) - (char *)0) % sizeof(long) || \
73 (es) % sizeof(long) ? 2 : (es) == sizeof(long)? 0 : 1;
75 static void
76 swapfunc(char *a, char *b, size_t n, int swaptype)
78 if (swaptype <= 1)
79 swapcode(long, a, b, n);
80 else
81 swapcode(char, a, b, n);
84 #define swap(a, b) \
85 if (swaptype == 0) { \
86 long t = *(long *)(void *)(a); \
87 *(long *)(void *)(a) = *(long *)(void *)(b); \
88 *(long *)(void *)(b) = t; \
89 } else \
90 swapfunc(a, b, es, swaptype)
92 #define vecswap(a, b, n) if ((n) > 0) swapfunc((a), (b), (size_t)(n), swaptype)
94 static char *
95 med3(char *a, char *b, char *c, int (*cmp) (const void *, const void *))
97 return cmp(a, b) < 0 ?
98 (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a))
99 : (cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c));
102 void
103 pg_qsort(void *a, size_t n, size_t es, int (*cmp) (const void *, const void *))
105 char *pa,
106 *pb,
107 *pc,
108 *pd,
109 *pl,
110 *pm,
111 *pn;
112 int d,
114 swaptype,
115 presorted;
117 loop:SWAPINIT(a, es);
118 if (n < 7)
120 for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
121 for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
122 pl -= es)
123 swap(pl, pl - es);
124 return;
126 presorted = 1;
127 for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
129 if (cmp(pm - es, pm) > 0)
131 presorted = 0;
132 break;
135 if (presorted)
136 return;
137 pm = (char *) a + (n / 2) * es;
138 if (n > 7)
140 pl = (char *) a;
141 pn = (char *) a + (n - 1) * es;
142 if (n > 40)
144 d = (n / 8) * es;
145 pl = med3(pl, pl + d, pl + 2 * d, cmp);
146 pm = med3(pm - d, pm, pm + d, cmp);
147 pn = med3(pn - 2 * d, pn - d, pn, cmp);
149 pm = med3(pl, pm, pn, cmp);
151 swap(a, pm);
152 pa = pb = (char *) a + es;
153 pc = pd = (char *) a + (n - 1) * es;
154 for (;;)
156 while (pb <= pc && (r = cmp(pb, a)) <= 0)
158 if (r == 0)
160 swap(pa, pb);
161 pa += es;
163 pb += es;
165 while (pb <= pc && (r = cmp(pc, a)) >= 0)
167 if (r == 0)
169 swap(pc, pd);
170 pd -= es;
172 pc -= es;
174 if (pb > pc)
175 break;
176 swap(pb, pc);
177 pb += es;
178 pc -= es;
180 pn = (char *) a + n * es;
181 r = Min(pa - (char *) a, pb - pa);
182 vecswap(a, pb - r, r);
183 r = Min(pd - pc, pn - pd - es);
184 vecswap(pb, pn - r, r);
185 if ((r = pb - pa) > es)
186 qsort(a, r / es, es, cmp);
187 if ((r = pd - pc) > es)
189 /* Iterate rather than recurse to save stack space */
190 a = pn - r;
191 n = r / es;
192 goto loop;
194 /* qsort(pn - r, r / es, es, cmp);*/