libc-top-half/musl/src/stdlib/qsort.c

   1 /* Copyright (C) 2011 by Valentin Ochs
   2  *
   3  * Permission is hereby granted, free of charge, to any person obtaining a copy
   4  * of this software and associated documentation files (the "Software"), to
   5  * deal in the Software without restriction, including without limitation the
   6  * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
   7  * sell copies of the Software, and to permit persons to whom the Software is
   8  * furnished to do so, subject to the following conditions:
   9  *
  10  * The above copyright notice and this permission notice shall be included in
  11  * all copies or substantial portions of the Software.
  12  *
  13  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  14  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  15  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  16  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  17  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  18  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  19  * IN THE SOFTWARE.
  20  */
  21
  22 /* Minor changes by Rich Felker for integration in musl, 2011-04-27. */
  23
  24 /* Smoothsort, an adaptive variant of Heapsort.  Memory usage: O(1).
  25    Run time: Worst case O(n log n), close to O(n) in the mostly-sorted case. */
  26
  27 #define _BSD_SOURCE
  28 #include <stdint.h>
  29 #include <stdlib.h>
  30 #include <string.h>
  31
  32 #include "atomic.h"
  33 #define ntz(x) a_ctz_l((x))
  34
  35 typedef int (*cmpfun)(const void *, const void *, void *);
  36
  37 static inline int pntz(size_t p[2]) {
  38         int r = ntz(p[0] - 1);
  39         if(r != 0 || (r = 8*sizeof(size_t) + ntz(p[1])) != 8*sizeof(size_t)) {
  40                 return r;
  41         }
  42         return 0;
  43 }
  44
  45 static void cycle(size_t width, unsigned char* ar[], int n)
  46 {
  47         unsigned char tmp[256];
  48         size_t l;
  49         int i;
  50
  51         if(n < 2) {
  52                 return;
  53         }
  54
  55         ar[n] = tmp;
  56         while(width) {
  57                 l = sizeof(tmp) < width ? sizeof(tmp) : width;
  58                 memcpy(ar[n], ar[0], l);
  59                 for(i = 0; i < n; i++) {
  60                         memcpy(ar[i], ar[i + 1], l);
  61                         ar[i] += l;
  62                 }
  63                 width -= l;
  64         }
  65 }
  66
  67 /* shl() and shr() need n > 0 */
  68 static inline void shl(size_t p[2], int n)
  69 {
  70         if(n >= 8 * sizeof(size_t)) {
  71                 n -= 8 * sizeof(size_t);
  72                 p[1] = p[0];
  73                 p[0] = 0;
  74         }
  75         p[1] <<= n;
  76         p[1] |= p[0] >> (sizeof(size_t) * 8 - n);
  77         p[0] <<= n;
  78 }
  79
  80 static inline void shr(size_t p[2], int n)
  81 {
  82         if(n >= 8 * sizeof(size_t)) {
  83                 n -= 8 * sizeof(size_t);
  84                 p[0] = p[1];
  85                 p[1] = 0;
  86         }
  87         p[0] >>= n;
  88         p[0] |= p[1] << (sizeof(size_t) * 8 - n);
  89         p[1] >>= n;
  90 }
  91
  92 static void sift(unsigned char *head, size_t width, cmpfun cmp, void *arg, int pshift, size_t lp[])
  93 {
  94         unsigned char *rt, *lf;
  95         unsigned char *ar[14 * sizeof(size_t) + 1];
  96         int i = 1;
  97
  98         ar[0] = head;
  99         while(pshift > 1) {
 100                 rt = head - width;
 101                 lf = head - width - lp[pshift - 2];
 102
 103                 if(cmp(ar[0], lf, arg) >= 0 && cmp(ar[0], rt, arg) >= 0) {
 104                         break;
 105                 }
 106                 if(cmp(lf, rt, arg) >= 0) {
 107                         ar[i++] = lf;
 108                         head = lf;
 109                         pshift -= 1;
 110                 } else {
 111                         ar[i++] = rt;
 112                         head = rt;
 113                         pshift -= 2;
 114                 }
 115         }
 116         cycle(width, ar, i);
 117 }
 118
 119 static void trinkle(unsigned char *head, size_t width, cmpfun cmp, void *arg, size_t pp[2], int pshift, int trusty, size_t lp[])
 120 {
 121         unsigned char *stepson,
 122                       *rt, *lf;
 123         size_t p[2];
 124         unsigned char *ar[14 * sizeof(size_t) + 1];
 125         int i = 1;
 126         int trail;
 127
 128         p[0] = pp[0];
 129         p[1] = pp[1];
 130
 131         ar[0] = head;
 132         while(p[0] != 1 || p[1] != 0) {
 133                 stepson = head - lp[pshift];
 134                 if(cmp(stepson, ar[0], arg) <= 0) {
 135                         break;
 136                 }
 137                 if(!trusty && pshift > 1) {
 138                         rt = head - width;
 139                         lf = head - width - lp[pshift - 2];
 140                         if(cmp(rt, stepson, arg) >= 0 || cmp(lf, stepson, arg) >= 0) {
 141                                 break;
 142                         }
 143                 }
 144
 145                 ar[i++] = stepson;
 146                 head = stepson;
 147                 trail = pntz(p);
 148                 shr(p, trail);
 149                 pshift += trail;
 150                 trusty = 0;
 151         }
 152         if(!trusty) {
 153                 cycle(width, ar, i);
 154                 sift(head, width, cmp, arg, pshift, lp);
 155         }
 156 }
 157
 158 void __qsort_r(void *base, size_t nel, size_t width, cmpfun cmp, void *arg)
 159 {
 160         size_t lp[12*sizeof(size_t)];
 161         size_t i, size = width * nel;
 162         unsigned char *head, *high;
 163         size_t p[2] = {1, 0};
 164         int pshift = 1;
 165         int trail;
 166
 167         if (!size) return;
 168
 169         head = base;
 170         high = head + size - width;
 171
 172         /* Precompute Leonardo numbers, scaled by element width */
 173         for(lp[0]=lp[1]=width, i=2; (lp[i]=lp[i-2]+lp[i-1]+width) < size; i++);
 174
 175         while(head < high) {
 176                 if((p[0] & 3) == 3) {
 177                         sift(head, width, cmp, arg, pshift, lp);
 178                         shr(p, 2);
 179                         pshift += 2;
 180                 } else {
 181                         if(lp[pshift - 1] >= high - head) {
 182                                 trinkle(head, width, cmp, arg, p, pshift, 0, lp);
 183                         } else {
 184                                 sift(head, width, cmp, arg, pshift, lp);
 185                         }
 186
 187                         if(pshift == 1) {
 188                                 shl(p, 1);
 189                                 pshift = 0;
 190                         } else {
 191                                 shl(p, pshift - 1);
 192                                 pshift = 1;
 193                         }
 194                 }
 195
 196                 p[0] |= 1;
 197                 head += width;
 198         }
 199
 200         trinkle(head, width, cmp, arg, p, pshift, 0, lp);
 201
 202         while(pshift != 1 || p[0] != 1 || p[1] != 0) {
 203                 if(pshift <= 1) {
 204                         trail = pntz(p);
 205                         shr(p, trail);
 206                         pshift += trail;
 207                 } else {
 208                         shl(p, 2);
 209                         pshift -= 2;
 210                         p[0] ^= 7;
 211                         shr(p, 1);
 212                         trinkle(head - lp[pshift] - width, width, cmp, arg, p, pshift + 1, 1, lp);
 213                         shl(p, 1);
 214                         p[0] |= 1;
 215                         trinkle(head - width, width, cmp, arg, p, pshift, 1, lp);
 216                 }
 217                 head -= width;
 218         }
 219 }
 220
 221 weak_alias(__qsort_r, qsort_r);