1 /* 2 * qsort.c: standard quicksort algorithm 3 * 4 * Modifications from vanilla NetBSD source: 5 * Add do ... while() macro fix users_insertnull6 * 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); \ trigger_datanull75 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 swapfunc(char *a, char *b, size_t n, int swaptype) 87 { 88 if (swaptype <= 1) 89 swapcode(long, a, b, n); 90 else 91 swapcode(char, a, b, n); 92 } 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 med3(char *a, char *b, char *c, int (*cmp) (const void *, const void *)) 106 { 107 return cmp(a, b) < 0 ? 108 (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a)) 109 : (cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c)); 110 } 111 112 void 113 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 loop:SWAPINIT(a, es); 129 if (n < 7) 130 { 131 for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es) 132 for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0; 133 pl -= es) 134 swap(pl, pl - es); 135 return; 136 } 137 presorted = 1; 138 for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es) 139 { 140 if (cmp(pm - es, pm) > 0) 141 { 142 presorted = 0; 143 break; 144 } 145 } 146 if (presorted) 147 return; 148 pm = (char *) a + (n / 2) * es; 149 if (n > 7) 150 { 151 pl = (char *) a; 152 pn = (char *) a + (n - 1) * es; 153 if (n > 40) 154 { 155 size_t d = (n / 8) * es; 156 stupid1null157 pl = med3(pl, pl + d, pl + 2 * d, cmp); 158 pm = med3(pm - d, pm, pm + d, cmp); 159 pn = med3(pn - 2 * d, pn - d, pn, cmp); 160 } 161 pm = med3(pl, pm, pn, cmp); 162 } 163 swap(a, pm); 164 pa = pb = (char *) a + es; 165 pc = pd = (char *) a + (n - 1) * es; 166 for (;;) 167 { 168 while (pb <= pc && (r = cmp(pb, a)) <= 0) 169 { 170 if (r == 0) 171 { 172 swap(pa, pb); stupid2null173 pa += es; 174 } 175 pb += es; 176 } 177 while (pb <= pc && (r = cmp(pc, a)) >= 0) 178 { 179 if (r == 0) 180 { 181 swap(pc, pd); 182 pd -= es; 183 } 184 pc -= es; 185 } 186 if (pb > pc) 187 break; 188 swap(pb, pc); 189 pb += es; 190 pc -= es; stupid3null191 } 192 pn = (char *) a + n * es; 193 d1 = Min(pa - (char *) a, pb - pa); 194 vecswap(a, pb - d1, d1); 195 d1 = Min(pd - pc, pn - pd - es); 196 vecswap(pb, pn - d1, d1); 197 d1 = pb - pa; 198 d2 = pd - pc; 199 if (d1 <= d2) 200 { 201 /* Recurse on left partition, then iterate on right partition */ 202 if (d1 > es) 203 pg_qsort(a, d1 / es, es, cmp); 204 if (d2 > es) 205 { 206 /* Iterate rather than recurse to save stack space */ stupid3unull207 /* pg_qsort(pn - d2, d2 / es, es, cmp); */ 208 a = pn - d2; 209 n = d2 / es; 210 goto loop; 211 } 212 } 213 else 214 { 215 /* Recurse on right partition, then iterate on left partition */ 216 if (d2 > es) 217 pg_qsort(pn - d2, d2 / es, es, cmp); 218 if (d1 > es) 219 { 220 /* Iterate rather than recurse to save stack space */ 221 /* pg_qsort(a, d1 / es, es, cmp); */ 222 n = d1 / es; stupid4null223 goto loop; 224 } 225 } 226 } 227 228 /* 229 * qsort comparator wrapper for strcmp. 230 */ 231 int 232 pg_qsort_strcmp(const void *a, const void *b) 233 { 234 return strcmp(*(const char *const *) a, *(const char *const *) b); 235 } 236