qsort.c
1 /*- 2 * Copyright (c) 1992, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 */ 29 30 #if defined(LIBC_SCCS) && !defined(lint) 31 static char sccsid[] = "@(#)qsort.c 8.1 (Berkeley) 6/4/93"; 32 #endif /* LIBC_SCCS and not lint */ 33 #include <sys/cdefs.h> 34 __FBSDID("$FreeBSD$"); 35 36 #include <stdbool.h> 37 #include <stdlib.h> 38 #include <string.h> 39 40 #ifdef I_AM_QSORT_R 41 typedef int cmp_t(void *, const void *, const void *); 42 #else 43 typedef int cmp_t(const void *, const void *); 44 #endif 45 static inline char *med3(char *, char *, char *, cmp_t *, void *); 46 static inline void swapfunc(char *, char *, size_t, int, int); 47 48 #define MIN(a, b) ((a) < (b) ? a : b) 49 50 /* 51 * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function". 52 */ 53 #define swapcode(TYPE, parmi, parmj, n) { \ 54 size_t i = (n) / sizeof (TYPE); \ 55 TYPE *pi = (TYPE *) (parmi); \ 56 TYPE *pj = (TYPE *) (parmj); \ 57 do { \ 58 TYPE t = *pi; \ 59 *pi++ = *pj; \ 60 *pj++ = t; \ 61 } while (--i > 0); \ 62 } 63 64 #define SWAPINIT(TYPE, a, es) swaptype_ ## TYPE = \ 65 ((char *)a - (char *)0) % sizeof(TYPE) || \ 66 es % sizeof(TYPE) ? 2 : es == sizeof(TYPE) ? 0 : 1; 67 68 static inline void 69 swapfunc(char *a, char *b, size_t n, int swaptype_long, int swaptype_int) 70 { 71 if (swaptype_long <= 1) 72 swapcode(long, a, b, n) 73 else if (swaptype_int <= 1) 74 swapcode(int, a, b, n) 75 else 76 swapcode(char, a, b, n) 77 } 78 79 #define swap(a, b) \ 80 if (swaptype_long == 0) { \ 81 long t = *(long *)(a); \ 82 *(long *)(a) = *(long *)(b); \ 83 *(long *)(b) = t; \ 84 } else if (swaptype_int == 0) { \ 85 int t = *(int *)(a); \ 86 *(int *)(a) = *(int *)(b); \ 87 *(int *)(b) = t; \ 88 } else \ 89 swapfunc(a, b, es, swaptype_long, swaptype_int) 90 91 #define vecswap(a, b, n) \ 92 if ((n) > 0) swapfunc(a, b, n, swaptype_long, swaptype_int) 93 94 #ifdef I_AM_QSORT_R 95 #define CMP(t, x, y) (cmp((t), (x), (y))) 96 #else 97 #define CMP(t, x, y) (cmp((x), (y))) 98 #endif 99 100 /* 101 * Find the median of 3 elements 102 */ 103 static inline char * 104 med3(char *a, char *b, char *c, cmp_t *cmp, void *thunk 105 #ifndef I_AM_QSORT_R 106 __unused 107 #endif 108 ) 109 { 110 return CMP(thunk, a, b) < 0 ? 111 (CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a )) 112 :(CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c )); 113 } 114 115 #ifdef __LP64__ 116 #define DEPTH(x) (2 * (flsl((long)(x)) - 1)) 117 #else /* !__LP64__ */ 118 #define DEPTH(x) (2 * (fls((int)(x)) - 1)) 119 #endif /* __LP64__ */ 120 121 #ifdef I_AM_QSORT_R 122 int __heapsort_r(void *, size_t, size_t, void *, int (*)(void *, const void *, const void *)); 123 #endif 124 125 /* 126 * Simple insertion sort routine. 127 */ 128 static bool 129 _isort(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp, int swap_limit, int swaptype_long, int swaptype_int) 130 { 131 int swap_cnt = 0; 132 for (char *pm = (char *)a + es; pm < (char *)a + n * es; pm += es) { 133 for (char *pl = pm; pl > (char *)a && CMP(thunk, pl - es, pl) > 0; 134 pl -= es) { 135 swap(pl, pl - es); 136 if (swap_limit && ++swap_cnt > swap_limit) return false; 137 } 138 } 139 return true; 140 } 141 142 #ifdef I_AM_QSORT_R 143 static void 144 _qsort(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp, int depth_limit) 145 #else 146 #define thunk NULL 147 static void 148 _qsort(void *a, size_t n, size_t es, cmp_t *cmp, int depth_limit) 149 #endif 150 { 151 char *pa, *pb, *pc, *pd, *pl, *pm, *pn; 152 size_t d1, d2; 153 int cmp_result; 154 int swaptype_long, swaptype_int, swap_cnt; 155 156 loop: 157 SWAPINIT(long, a, es); 158 SWAPINIT(int, a, es); 159 swap_cnt = 0; 160 161 if (depth_limit-- <= 0) { 162 /* 163 * We've hit our recursion limit, switch to heapsort 164 */ 165 #ifdef I_AM_QSORT_R 166 __heapsort_r(a, n, es, thunk, cmp); 167 #else 168 heapsort(a, n, es, cmp); 169 #endif 170 return; 171 } 172 173 if (n <= 7) { 174 /* 175 * For sufficiently small inputs, we'll just insertion sort. 176 * 177 * Pass 0 as swap limit, since this must complete. 178 */ 179 _isort(a, n, es, thunk, cmp, 0, swaptype_long, swaptype_int); 180 return; 181 } 182 183 /* 184 * Compute the pseudomedian. Small arrays use 3 samples, large ones use 9. 185 */ 186 pl = a; 187 pm = (char *)a + (n / 2) * es; 188 pn = (char *)a + (n - 1) * es; 189 if (n > 40) { 190 size_t d = (n / 8) * es; 191 192 pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk); 193 pm = med3(pm - d, pm, pm + d, cmp, thunk); 194 pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk); 195 } 196 pm = med3(pl, pm, pn, cmp, thunk); 197 198 /* 199 * Pull the median to the front, starting us with: 200 * 201 * +-+-------------+ 202 * |=| ? | 203 * +-+-------------+ 204 * a pa,pb pc,pd 205 */ 206 swap(a, pm); 207 pa = pb = (char *)a + es; 208 pc = pd = (char *)a + (n - 1) * es; 209 210 for (;;) { 211 /* 212 * - Move b forward while it's less than the median 213 * - Move c backwards while it's greater than the median 214 * - When equal to the median, swap to the outside 215 */ 216 while (pb <= pc && (cmp_result = CMP(thunk, pb, a)) <= 0) { 217 if (cmp_result == 0) { 218 swap_cnt = 1; 219 swap(pa, pb); 220 pa += es; 221 } 222 pb += es; 223 } 224 while (pb <= pc && (cmp_result = CMP(thunk, pc, a)) >= 0) { 225 if (cmp_result == 0) { 226 swap_cnt = 1; 227 swap(pc, pd); 228 pd -= es; 229 } 230 pc -= es; 231 } 232 if (pb > pc) 233 break; 234 swap(pb, pc); 235 swap_cnt = 1; 236 pb += es; 237 pc -= es; 238 } 239 240 /* 241 * Now we've got: 242 * 243 * +---+-----+-----+---+ 244 * | = | < | > | = | 245 * +---+-----+-----+---+ 246 * a pa pc,pb pd pn 247 * 248 * So swap the '=' into the middle 249 */ 250 251 pn = (char *)a + n * es; 252 d1 = MIN(pa - (char *)a, pb - pa); 253 vecswap(a, pb - d1, d1); 254 d1 = MIN(pd - pc, pn - pd - es); 255 vecswap(pb, pn - d1, d1); 256 257 /* 258 * +-----+---+---+-----+ 259 * | < | = | > | 260 * +-----+---+---+-----+ 261 * a pn 262 */ 263 264 if (swap_cnt == 0) { /* Switch to insertion sort */ 265 int r = 1 + n / 4; /* n > 7, so r >= 2 */ 266 if (!_isort(a, n, es, thunk, cmp, r, swaptype_long, swaptype_int)) { 267 goto nevermind; 268 } 269 return; 270 } 271 nevermind: 272 273 d1 = pb - pa; 274 d2 = pd - pc; 275 if (d1 <= d2) { 276 /* Recurse on left partition, then iterate on right partition */ 277 if (d1 > es) { 278 #ifdef I_AM_QSORT_R 279 _qsort(a, d1 / es, es, thunk, cmp, depth_limit); 280 #else 281 _qsort(a, d1 / es, es, cmp, depth_limit); 282 #endif 283 } 284 if (d2 > es) { 285 /* Iterate rather than recurse to save stack space */ 286 /* qsort(pn - d2, d2 / es, es, cmp); */ 287 a = pn - d2; 288 n = d2 / es; 289 goto loop; 290 } 291 } else { 292 /* Recurse on right partition, then iterate on left partition */ 293 if (d2 > es) { 294 #ifdef I_AM_QSORT_R 295 _qsort(pn - d2, d2 / es, es, thunk, cmp, depth_limit); 296 #else 297 _qsort(pn - d2, d2 / es, es, cmp, depth_limit); 298 #endif 299 } 300 if (d1 > es) { 301 /* Iterate rather than recurse to save stack space */ 302 /* qsort(a, d1 / es, es, cmp); */ 303 n = d1 / es; 304 goto loop; 305 } 306 } 307 } 308 309 void 310 #ifdef I_AM_QSORT_R 311 qsort_r(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp) 312 #else 313 qsort(void *a, size_t n, size_t es, cmp_t *cmp) 314 #endif 315 { 316 _qsort(a, n, es, 317 #ifdef I_AM_QSORT_R 318 thunk, 319 #endif 320 cmp, DEPTH(n)); 321 }