1 /* $NetBSD: qsort.c,v 1.23 2017/05/19 19:48:19 christos Exp $ */ 2 /*- 3 * Copyright (c) 1992, 1993 4 * The Regents of the University of California. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. Neither the name of the University nor the names of its contributors 15 * may be used to endorse or promote products derived from this software 16 * without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 */ 30 31 #include <sys/cdefs.h> 32 #if defined(LIBC_SCCS) && !defined(lint) 33 #if 0 34 static char sccsid[] = "@(#)qsort.c 8.1 (Berkeley) 6/4/93"; 35 #else 36 __RCSID("$NetBSD: qsort.c,v 1.23 2017/05/19 19:48:19 christos Exp $"); 37 #endif 38 #endif /* LIBC_SCCS and not lint */ 39 40 #include <sys/types.h> 41 42 #include <assert.h> 43 #include <errno.h> 44 #include <stdlib.h> 45 46 static inline char *med3(char *, char *, char *, 47 int (*)(const void *, const void *)); 48 static inline void swapfunc(char *, char *, size_t, int); 49 50 #define min(a, b) (a) < (b) ? a : b 51 52 /* 53 * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function". 54 */ 55 #define swapcode(TYPE, parmi, parmj, n) { \ 56 size_t i = (n) / sizeof (TYPE); \ 57 TYPE *pi = (TYPE *)(void *)(parmi); \ 58 TYPE *pj = (TYPE *)(void *)(parmj); \ 59 do { \ 60 TYPE t = *pi; \ 61 *pi++ = *pj; \ 62 *pj++ = t; \ 63 } while (--i > 0); \ 64 } 65 66 #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \ 67 es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1; 68 69 static inline void 70 swapfunc(char *a, char *b, size_t n, int swaptype) 71 { 72 73 if (swaptype <= 1) 74 swapcode(long, a, b, n) 75 else 76 swapcode(char, a, b, n) 77 } 78 79 #define swap(a, b) \ 80 if (swaptype == 0) { \ 81 long t = *(long *)(void *)(a); \ 82 *(long *)(void *)(a) = *(long *)(void *)(b); \ 83 *(long *)(void *)(b) = t; \ 84 } else \ 85 swapfunc(a, b, es, swaptype) 86 87 #define vecswap(a, b, n) if ((n) > 0) swapfunc((a), (b), (size_t)(n), swaptype) 88 89 static inline char * 90 med3(char *a, char *b, char *c, 91 int (*cmp)(const void *, const void *)) 92 { 93 94 return cmp(a, b) < 0 ? 95 (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a )) 96 :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c )); 97 } 98 99 void 100 qsort(void *a, size_t n, size_t es, 101 int (*cmp)(const void *, const void *)) 102 { 103 char *pa, *pb, *pc, *pd, *pl, *pm, *pn; 104 size_t d, r, s; 105 int swaptype, cmp_result; 106 107 _DIAGASSERT(a != NULL || n == 0 || es == 0); 108 _DIAGASSERT(cmp != NULL); 109 110 loop: SWAPINIT(a, es); 111 if (n < 7) { 112 for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es) 113 for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0; 114 pl -= es) 115 swap(pl, pl - es); 116 return; 117 } 118 pm = (char *) a + (n / 2) * es; 119 if (n > 7) { 120 pl = (char *) a; 121 pn = (char *) a + (n - 1) * es; 122 if (n > 40) { 123 d = (n / 8) * es; 124 pl = med3(pl, pl + d, pl + 2 * d, cmp); 125 pm = med3(pm - d, pm, pm + d, cmp); 126 pn = med3(pn - 2 * d, pn - d, pn, cmp); 127 } 128 pm = med3(pl, pm, pn, cmp); 129 } 130 swap(a, pm); 131 pa = pb = (char *) a + es; 132 133 pc = pd = (char *) a + (n - 1) * es; 134 for (;;) { 135 while (pb <= pc && (cmp_result = cmp(pb, a)) <= 0) { 136 if (cmp_result == 0) { 137 swap(pa, pb); 138 pa += es; 139 } 140 pb += es; 141 } 142 while (pb <= pc && (cmp_result = cmp(pc, a)) >= 0) { 143 if (cmp_result == 0) { 144 swap(pc, pd); 145 pd -= es; 146 } 147 pc -= es; 148 } 149 if (pb > pc) 150 break; 151 swap(pb, pc); 152 pb += es; 153 pc -= es; 154 } 155 156 pn = (char *) a + n * es; 157 r = min(pa - (char *) a, pb - pa); 158 vecswap(a, pb - r, r); 159 r = min((size_t)(pd - pc), pn - pd - es); 160 vecswap(pb, pn - r, r); 161 /* 162 * To save stack space we sort the smaller side of the partition first 163 * using recursion and eliminate tail recursion for the larger side. 164 */ 165 r = pb - pa; 166 s = pd - pc; 167 if (r < s) { 168 /* Recurse for 1st side, iterate for 2nd side. */ 169 if (s > es) { 170 if (r > es) 171 qsort(a, r / es, es, cmp); 172 a = pn - s; 173 n = s / es; 174 goto loop; 175 } 176 } else { 177 /* Recurse for 2nd side, iterate for 1st side. */ 178 if (r > es) { 179 if (s > es) 180 qsort(pn - s, s / es, es, cmp); 181 n = r / es; 182 goto loop; 183 } 184 } 185 } 186