1/*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1992, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 */ 31 32#if defined(LIBC_SCCS) && !defined(lint) 33static char sccsid[] = "@(#)qsort.c 8.1 (Berkeley) 6/4/93"; 34#endif /* LIBC_SCCS and not lint */ 35 36#include <errno.h> 37#include <stdint.h> 38#include <stdlib.h> 39#include <string.h> 40 41typedef int cmp_t(const void *, const void *); 42static inline char *med3(char *, char *, char *, cmp_t *, void *); 43 44#define MIN(a, b) ((a) < (b) ? a : b) 45 46/* 47 * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function". 48 */ 49 50static inline void 51swapfunc(char *a, char *b, size_t es) 52{ 53 char t; 54 55 do { 56 t = *a; 57 *a++ = *b; 58 *b++ = t; 59 } while (--es > 0); 60} 61 62#define vecswap(a, b, n) \ 63 if ((n) > 0) swapfunc(a, b, n) 64 65#define CMP(t, x, y) (cmp((x), (y))) 66 67static inline char * 68med3(char *a, char *b, char *c, cmp_t *cmp, void *thunk) 69{ 70 return CMP(thunk, a, b) < 0 ? 71 (CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a )) 72 :(CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c )); 73} 74 75/* 76 * The actual qsort() implementation is static to avoid preemptible calls when 77 * recursing. Also give them different names for improved debugging. 78 */ 79static void 80local_qsort(void *a, size_t n, size_t es, cmp_t *cmp, void *thunk) 81{ 82 char *pa, *pb, *pc, *pd, *pl, *pm, *pn; 83 size_t d1, d2; 84 int cmp_result; 85 int swap_cnt; 86 87 /* if there are less than 2 elements, then sorting is not needed */ 88 if (n < 2) 89 return; 90loop: 91 swap_cnt = 0; 92 if (n < 7) { 93 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es) 94 for (pl = pm; 95 pl > (char *)a && CMP(thunk, pl - es, pl) > 0; 96 pl -= es) 97 swapfunc(pl, pl - es, es); 98 return; 99 } 100 pm = (char *)a + (n / 2) * es; 101 if (n > 7) { 102 pl = a; 103 pn = (char *)a + (n - 1) * es; 104 if (n > 40) { 105 size_t d = (n / 8) * es; 106 107 pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk); 108 pm = med3(pm - d, pm, pm + d, cmp, thunk); 109 pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk); 110 } 111 pm = med3(pl, pm, pn, cmp, thunk); 112 } 113 swapfunc(a, pm, es); 114 pa = pb = (char *)a + es; 115 116 pc = pd = (char *)a + (n - 1) * es; 117 for (;;) { 118 while (pb <= pc && (cmp_result = CMP(thunk, pb, a)) <= 0) { 119 if (cmp_result == 0) { 120 swap_cnt = 1; 121 swapfunc(pa, pb, es); 122 pa += es; 123 } 124 pb += es; 125 } 126 while (pb <= pc && (cmp_result = CMP(thunk, pc, a)) >= 0) { 127 if (cmp_result == 0) { 128 swap_cnt = 1; 129 swapfunc(pc, pd, es); 130 pd -= es; 131 } 132 pc -= es; 133 } 134 if (pb > pc) 135 break; 136 swapfunc(pb, pc, es); 137 swap_cnt = 1; 138 pb += es; 139 pc -= es; 140 } 141 if (swap_cnt == 0) { /* Switch to insertion sort */ 142 for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es) 143 for (pl = pm; 144 pl > (char *)a && CMP(thunk, pl - es, pl) > 0; 145 pl -= es) 146 swapfunc(pl, pl - es, es); 147 return; 148 } 149 150 pn = (char *)a + n * es; 151 d1 = MIN(pa - (char *)a, pb - pa); 152 vecswap(a, pb - d1, d1); 153 /* 154 * Cast es to preserve signedness of right-hand side of MIN() 155 * expression, to avoid sign ambiguity in the implied comparison. es 156 * is safely within [0, SSIZE_MAX]. 157 */ 158 d1 = MIN(pd - pc, pn - pd - (ssize_t)es); 159 vecswap(pb, pn - d1, d1); 160 161 d1 = pb - pa; 162 d2 = pd - pc; 163 if (d1 <= d2) { 164 /* Recurse on left partition, then iterate on right partition */ 165 if (d1 > es) { 166 local_qsort(a, d1 / es, es, cmp, thunk); 167 } 168 if (d2 > es) { 169 /* Iterate rather than recurse to save stack space */ 170 /* qsort(pn - d2, d2 / es, es, cmp); */ 171 a = pn - d2; 172 n = d2 / es; 173 goto loop; 174 } 175 } else { 176 /* Recurse on right partition, then iterate on left partition */ 177 if (d2 > es) { 178 local_qsort(pn - d2, d2 / es, es, cmp, thunk); 179 } 180 if (d1 > es) { 181 /* Iterate rather than recurse to save stack space */ 182 /* qsort(a, d1 / es, es, cmp); */ 183 n = d1 / es; 184 goto loop; 185 } 186 } 187} 188 189void 190qsort(void *a, size_t n, size_t es, cmp_t *cmp) 191{ 192 local_qsort(a, n, es, cmp, NULL); 193} 194