1 /* $OpenBSD: qsort.c,v 1.18 2017/05/30 14:54:09 millert 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/types.h> 32 #include <stdlib.h> 33 34 static __inline char *med3(char *, char *, char *, int (*)(const void *, const void *)); 35 static __inline void swapfunc(char *, char *, size_t, int); 36 37 #define min(a, b) (a) < (b) ? a : b 38 39 /* 40 * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function". 41 * 42 * This version differs from Bentley & McIlroy in the following ways: 43 * 1. The partition value is swapped into a[0] instead of being 44 * stored out of line. 45 * 46 * 2. The swap function can swap 32-bit aligned elements on 64-bit 47 * platforms instead of swapping them as byte-aligned. 48 * 49 * 3. It uses David Musser's introsort algorithm to fall back to 50 * heapsort(3) when the recursion depth reaches 2*lg(n + 1). 51 * This avoids quicksort's quadratic behavior for pathological 52 * input without appreciably changing the average run time. 53 * 54 * 4. Tail recursion is eliminated when sorting the larger of two 55 * subpartitions to save stack space. 56 */ 57 #define SWAPTYPE_BYTEV 1 58 #define SWAPTYPE_INTV 2 59 #define SWAPTYPE_LONGV 3 60 #define SWAPTYPE_INT 4 61 #define SWAPTYPE_LONG 5 62 63 #define TYPE_ALIGNED(TYPE, a, es) \ 64 (((char *)a - (char *)0) % sizeof(TYPE) == 0 && es % sizeof(TYPE) == 0) 65 66 #define swapcode(TYPE, parmi, parmj, n) { \ 67 size_t i = (n) / sizeof (TYPE); \ 68 TYPE *pi = (TYPE *) (parmi); \ 69 TYPE *pj = (TYPE *) (parmj); \ 70 do { \ 71 TYPE t = *pi; \ 72 *pi++ = *pj; \ 73 *pj++ = t; \ 74 } while (--i > 0); \ 75 } 76 77 static __inline void 78 swapfunc(char *a, char *b, size_t n, int swaptype) 79 { 80 switch (swaptype) { 81 case SWAPTYPE_INT: 82 case SWAPTYPE_INTV: 83 swapcode(int, a, b, n); 84 break; 85 case SWAPTYPE_LONG: 86 case SWAPTYPE_LONGV: 87 swapcode(long, a, b, n); 88 break; 89 default: 90 swapcode(char, a, b, n); 91 break; 92 } 93 } 94 95 #define swap(a, b) do { \ 96 switch (swaptype) { \ 97 case SWAPTYPE_INT: { \ 98 int t = *(int *)(a); \ 99 *(int *)(a) = *(int *)(b); \ 100 *(int *)(b) = t; \ 101 break; \ 102 } \ 103 case SWAPTYPE_LONG: { \ 104 long t = *(long *)(a); \ 105 *(long *)(a) = *(long *)(b); \ 106 *(long *)(b) = t; \ 107 break; \ 108 } \ 109 default: \ 110 swapfunc(a, b, es, swaptype); \ 111 } \ 112 } while (0) 113 114 #define vecswap(a, b, n) if ((n) > 0) swapfunc(a, b, n, swaptype) 115 116 static __inline char * 117 med3(char *a, char *b, char *c, int (*cmp)(const void *, const void *)) 118 { 119 return cmp(a, b) < 0 ? 120 (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a )) 121 :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c )); 122 } 123 124 static void 125 introsort(char *a, size_t n, size_t es, size_t maxdepth, int swaptype, 126 int (*cmp)(const void *, const void *)) 127 { 128 char *pa, *pb, *pc, *pd, *pl, *pm, *pn; 129 int cmp_result; 130 size_t r, s; 131 132 loop: if (n < 7) { 133 for (pm = a + es; pm < a + n * es; pm += es) 134 for (pl = pm; pl > a && cmp(pl - es, pl) > 0; 135 pl -= es) 136 swap(pl, pl - es); 137 return; 138 } 139 if (maxdepth == 0) { 140 if (heapsort(a, n, es, cmp) == 0) 141 return; 142 } 143 maxdepth--; 144 pm = a + (n / 2) * es; 145 if (n > 7) { 146 pl = a; 147 pn = a + (n - 1) * es; 148 if (n > 40) { 149 s = (n / 8) * es; 150 pl = med3(pl, pl + s, pl + 2 * s, cmp); 151 pm = med3(pm - s, pm, pm + s, cmp); 152 pn = med3(pn - 2 * s, pn - s, pn, cmp); 153 } 154 pm = med3(pl, pm, pn, cmp); 155 } 156 swap(a, pm); 157 pa = pb = a + es; 158 pc = pd = a + (n - 1) * es; 159 for (;;) { 160 while (pb <= pc && (cmp_result = cmp(pb, a)) <= 0) { 161 if (cmp_result == 0) { 162 swap(pa, pb); 163 pa += es; 164 } 165 pb += es; 166 } 167 while (pb <= pc && (cmp_result = cmp(pc, a)) >= 0) { 168 if (cmp_result == 0) { 169 swap(pc, pd); 170 pd -= es; 171 } 172 pc -= es; 173 } 174 if (pb > pc) 175 break; 176 swap(pb, pc); 177 pb += es; 178 pc -= es; 179 } 180 181 pn = a + n * es; 182 r = min(pa - a, pb - pa); 183 vecswap(a, pb - r, r); 184 r = min(pd - pc, pn - pd - es); 185 vecswap(pb, pn - r, r); 186 /* 187 * To save stack space we sort the smaller side of the partition first 188 * using recursion and eliminate tail recursion for the larger side. 189 */ 190 r = pb - pa; 191 s = pd - pc; 192 if (r < s) { 193 /* Recurse for 1st side, iterate for 2nd side. */ 194 if (s > es) { 195 if (r > es) { 196 introsort(a, r / es, es, maxdepth, 197 swaptype, cmp); 198 } 199 a = pn - s; 200 n = s / es; 201 goto loop; 202 } 203 } else { 204 /* Recurse for 2nd side, iterate for 1st side. */ 205 if (r > es) { 206 if (s > es) { 207 introsort(pn - s, s / es, es, maxdepth, 208 swaptype, cmp); 209 } 210 n = r / es; 211 goto loop; 212 } 213 } 214 } 215 216 void 217 qsort(void *a, size_t n, size_t es, int (*cmp)(const void *, const void *)) 218 { 219 size_t i, maxdepth = 0; 220 int swaptype; 221 222 /* Approximate 2*ceil(lg(n + 1)) */ 223 for (i = n; i > 0; i >>= 1) 224 maxdepth++; 225 maxdepth *= 2; 226 227 if (TYPE_ALIGNED(long, a, es)) 228 swaptype = es == sizeof(long) ? SWAPTYPE_LONG : SWAPTYPE_LONGV; 229 else if (sizeof(int) != sizeof(long) && TYPE_ALIGNED(int, a, es)) 230 swaptype = es == sizeof(int) ? SWAPTYPE_INT : SWAPTYPE_INTV; 231 else 232 swaptype = SWAPTYPE_BYTEV; 233 234 introsort(a, n, es, maxdepth, swaptype, cmp); 235 236 } 237 238 DEF_STRONG(qsort); 239