lib/libc/stdlib/radixsort.c

   1 /*-
   2  * Copyright (c) 1990, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Peter McIlroy and by Dan Bernstein at New York University,
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  * $DragonFly: src/lib/libc/stdlib/radixsort.c,v 1.5 2005/11/20 12:37:49 swildner Exp $
  37  *
  38  * @(#)radixsort.c      8.2 (Berkeley) 4/28/95
  39  */
  40
  41 /*
  42  * Radixsort routines.
  43  *
  44  * Program r_sort_a() is unstable but uses O(logN) extra memory for a stack.
  45  * Use radixsort(a, n, trace, endchar) for this case.
  46  *
  47  * For stable sorting (using N extra pointers) use sradixsort(), which calls
  48  * r_sort_b().
  49  *
  50  * For a description of this code, see D. McIlroy, P. McIlroy, K. Bostic,
  51  * "Engineering Radix Sort".
  52  */
  53
  54 #include <sys/types.h>
  55 #include <stdlib.h>
  56 #include <stddef.h>
  57 #include <errno.h>
  58
  59 typedef struct {
  60         const u_char **sa;
  61         int sn, si;
  62 } stack;
  63
  64 static inline void simplesort
  65             (const u_char **, int, int, const u_char *, u_int);
  66 static void r_sort_a (const u_char **, int, int, const u_char *, u_int);
  67 static void r_sort_b (const u_char **,
  68             const u_char **, int, int, const u_char *, u_int);
  69
  70 #define THRESHOLD       20              /* Divert to simplesort(). */
  71 #define SIZE            512             /* Default stack size. */
  72
  73 #define SETUP {                                                         \
  74         if (tab == NULL) {                                              \
  75                 tr = tr0;                                               \
  76                 for (c = 0; c < endch; c++)                             \
  77                         tr0[c] = c + 1;                                 \
  78                 tr0[c] = 0;                                             \
  79                 for (c++; c < 256; c++)                                 \
  80                         tr0[c] = c;                                     \
  81                 endch = 0;                                              \
  82         } else {                                                        \
  83                 endch = tab[endch];                                     \
  84                 tr = tab;                                               \
  85                 if (endch != 0 && endch != 255) {                       \
  86                         errno = EINVAL;                                 \
  87                         return (-1);                                    \
  88                 }                                                       \
  89         }                                                               \
  90 }
  91
  92 int
  93 radixsort(const u_char **a, int n, const u_char *tab, u_int endch)
  94 {
  95         const u_char *tr;
  96         int c;
  97         u_char tr0[256];
  98
  99         SETUP;
 100         r_sort_a(a, n, 0, tr, endch);
 101         return (0);
 102 }
 103
 104 int
 105 sradixsort(const u_char **a, int n, const u_char *tab, u_int endch)
 106 {
 107         const u_char *tr, **ta;
 108         int c;
 109         u_char tr0[256];
 110
 111         SETUP;
 112         if (n < THRESHOLD)
 113                 simplesort(a, n, 0, tr, endch);
 114         else {
 115                 if ((ta = malloc(n * sizeof(a))) == NULL)
 116                         return (-1);
 117                 r_sort_b(a, ta, n, 0, tr, endch);
 118                 free(ta);
 119         }
 120         return (0);
 121 }
 122
 123 #define empty(s)        (s >= sp)
 124 #define pop(a, n, i)    a = (--sp)->sa, n = sp->sn, i = sp->si
 125 #define push(a, n, i)   sp->sa = a, sp->sn = n, (sp++)->si = i
 126 #define swap(a, b, t)   t = a, a = b, b = t
 127
 128 /* Unstable, in-place sort. */
 129 static void
 130 r_sort_a(const u_char **a, int n, int i, const u_char *tr, u_int endch)
 131 {
 132         static int count[256], nc, bmin;
 133         int c;
 134         const u_char **ak, *r;
 135         stack s[SIZE], *sp, *sp0, *sp1, temp;
 136         int *cp, bigc;
 137         const u_char **an, *t, **aj, **top[256];
 138
 139         /* Set up stack. */
 140         sp = s;
 141         push(a, n, i);
 142         while (!empty(s)) {
 143                 pop(a, n, i);
 144                 if (n < THRESHOLD) {
 145                         simplesort(a, n, i, tr, endch);
 146                         continue;
 147                 }
 148                 an = a + n;
 149
 150                 /* Make character histogram. */
 151                 if (nc == 0) {
 152                         bmin = 255;     /* First occupied bin, excluding eos. */
 153                         for (ak = a; ak < an;) {
 154                                 c = tr[(*ak++)[i]];
 155                                 if (++count[c] == 1 && c != endch) {
 156                                         if (c < bmin)
 157                                                 bmin = c;
 158                                         nc++;
 159                                 }
 160                         }
 161                         if (sp + nc > s + SIZE) {       /* Get more stack. */
 162                                 r_sort_a(a, n, i, tr, endch);
 163                                 continue;
 164                         }
 165                 }
 166
 167                 /*
 168                  * Set top[]; push incompletely sorted bins onto stack.
 169                  * top[] = pointers to last out-of-place element in bins.
 170                  * count[] = counts of elements in bins.
 171                  * Before permuting: top[c-1] + count[c] = top[c];
 172                  * during deal: top[c] counts down to top[c-1].
 173                  */
 174                 sp0 = sp1 = sp;         /* Stack position of biggest bin. */
 175                 bigc = 2;               /* Size of biggest bin. */
 176                 if (endch == 0)         /* Special case: set top[eos]. */
 177                         top[0] = ak = a + count[0];
 178                 else {
 179                         ak = a;
 180                         top[255] = an;
 181                 }
 182                 for (cp = count + bmin; nc > 0; cp++) {
 183                         while (*cp == 0)        /* Find next non-empty pile. */
 184                                 cp++;
 185                         if (*cp > 1) {
 186                                 if (*cp > bigc) {
 187                                         bigc = *cp;
 188                                         sp1 = sp;
 189                                 }
 190                                 push(ak, *cp, i+1);
 191                         }
 192                         top[cp-count] = ak += *cp;
 193                         nc--;
 194                 }
 195                 swap(*sp0, *sp1, temp); /* Play it safe -- biggest bin last. */
 196
 197                 /*
 198                  * Permute misplacements home.  Already home: everything
 199                  * before aj, and in bin[c], items from top[c] on.
 200                  * Inner loop:
 201                  *      r = next element to put in place;
 202                  *      ak = top[r[i]] = location to put the next element.
 203                  *      aj = bottom of 1st disordered bin.
 204                  * Outer loop:
 205                  *      Once the 1st disordered bin is done, ie. aj >= ak,
 206                  *      aj<-aj + count[c] connects the bins in a linked list;
 207                  *      reset count[c].
 208                  */
 209                 for (aj = a; aj < an;  *aj = r, aj += count[c], count[c] = 0)
 210                         for (r = *aj;  aj < (ak = --top[c = tr[r[i]]]);)
 211                                 swap(*ak, r, t);
 212         }
 213 }
 214
 215 /* Stable sort, requiring additional memory. */
 216 static void
 217 r_sort_b(const u_char **a, const u_char **ta, int n, int i, const u_char *tr,
 218          u_int endch)
 219 {
 220         static int count[256], nc, bmin;
 221         int c;
 222         const u_char **ak, **ai;
 223         stack s[512], *sp, *sp0, *sp1, temp;
 224         const u_char **top[256];
 225         int *cp, bigc;
 226
 227         sp = s;
 228         push(a, n, i);
 229         while (!empty(s)) {
 230                 pop(a, n, i);
 231                 if (n < THRESHOLD) {
 232                         simplesort(a, n, i, tr, endch);
 233                         continue;
 234                 }
 235
 236                 if (nc == 0) {
 237                         bmin = 255;
 238                         for (ak = a + n; --ak >= a;) {
 239                                 c = tr[(*ak)[i]];
 240                                 if (++count[c] == 1 && c != endch) {
 241                                         if (c < bmin)
 242                                                 bmin = c;
 243                                         nc++;
 244                                 }
 245                         }
 246                         if (sp + nc > s + SIZE) {
 247                                 r_sort_b(a, ta, n, i, tr, endch);
 248                                 continue;
 249                         }
 250                 }
 251
 252                 sp0 = sp1 = sp;
 253                 bigc = 2;
 254                 if (endch == 0) {
 255                         top[0] = ak = a + count[0];
 256                         count[0] = 0;
 257                 } else {
 258                         ak = a;
 259                         top[255] = a + n;
 260                         count[255] = 0;
 261                 }
 262                 for (cp = count + bmin; nc > 0; cp++) {
 263                         while (*cp == 0)
 264                                 cp++;
 265                         if ((c = *cp) > 1) {
 266                                 if (c > bigc) {
 267                                         bigc = c;
 268                                         sp1 = sp;
 269                                 }
 270                                 push(ak, c, i+1);
 271                         }
 272                         top[cp-count] = ak += c;
 273                         *cp = 0;                        /* Reset count[]. */
 274                         nc--;
 275                 }
 276                 swap(*sp0, *sp1, temp);
 277
 278                 for (ak = ta + n, ai = a+n; ak > ta;)   /* Copy to temp. */
 279                         *--ak = *--ai;
 280                 for (ak = ta+n; --ak >= ta;)            /* Deal to piles. */
 281                         *--top[tr[(*ak)[i]]] = *ak;
 282         }
 283 }
 284
 285 /* insertion sort */
 286 static inline void
 287 simplesort(const u_char **a, int n, int b, const u_char *tr, u_int endch)
 288 {
 289         u_char ch;
 290         const u_char  **ak, **ai, *s, *t;
 291
 292         for (ak = a+1; --n >= 1; ak++)
 293                 for (ai = ak; ai > a; ai--) {
 294                         for (s = ai[0] + b, t = ai[-1] + b;
 295                             (ch = tr[*s]) != endch; s++, t++)
 296                                 if (ch != tr[*t])
 297                                         break;
 298                         if (ch >= tr[*t])
 299                                 break;
 300                         swap(ai[0], ai[-1], s);
 301                 }
 302 }