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Annotation of src/lib/libc/stdlib/qsort.c, Revision 1.23

1.23    ! christos    1: /*     $NetBSD: qsort.c,v 1.22 2012/05/26 21:47:05 christos Exp $      */
1.1       cgd         2: /*-
1.4       mycroft     3:  * Copyright (c) 1992, 1993
                      4:  *     The Regents of the University of California.  All rights reserved.
1.1       cgd         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.
1.13      agc        14:  * 3. Neither the name of the University nor the names of its contributors
1.1       cgd        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:
1.8       christos   31: #include <sys/cdefs.h>
1.1       cgd        32: #if defined(LIBC_SCCS) && !defined(lint)
1.5       thorpej    33: #if 0
1.7       mikel      34: static char sccsid[] = "@(#)qsort.c    8.1 (Berkeley) 6/4/93";
1.5       thorpej    35: #else
1.23    ! christos   36: __RCSID("$NetBSD: qsort.c,v 1.22 2012/05/26 21:47:05 christos Exp $");
1.5       thorpej    37: #endif
1.1       cgd        38: #endif /* LIBC_SCCS and not lint */
                     39:
                     40: #include <sys/types.h>
1.11      lukem      41:
                     42: #include <assert.h>
                     43: #include <errno.h>
1.1       cgd        44: #include <stdlib.h>
                     45:
1.21      dsl        46: static inline char     *med3(char *, char *, char *,
                     47:     int (*)(const void *, const void *));
                     48: static inline void      swapfunc(char *, char *, size_t, int);
1.4       mycroft    49:
                     50: #define min(a, b)      (a) < (b) ? a : b
                     51:
1.1       cgd        52: /*
1.4       mycroft    53:  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
1.1       cgd        54:  */
1.4       mycroft    55: #define swapcode(TYPE, parmi, parmj, n) {              \
1.10      christos   56:        size_t i = (n) / sizeof (TYPE);                 \
                     57:        TYPE *pi = (TYPE *)(void *)(parmi);             \
                     58:        TYPE *pj = (TYPE *)(void *)(parmj);             \
1.4       mycroft    59:        do {                                            \
1.10      christos   60:                TYPE    t = *pi;                        \
1.4       mycroft    61:                *pi++ = *pj;                            \
                     62:                *pj++ = t;                              \
                     63:         } while (--i > 0);                             \
                     64: }
1.1       cgd        65:
1.4       mycroft    66: #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
                     67:        es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
1.1       cgd        68:
1.14      perry      69: static inline void
1.15      rmind      70: swapfunc(char *a, char *b, size_t n, int swaptype)
1.1       cgd        71: {
1.15      rmind      72:
1.7       mikel      73:        if (swaptype <= 1)
1.4       mycroft    74:                swapcode(long, a, b, n)
1.1       cgd        75:        else
1.4       mycroft    76:                swapcode(char, a, b, n)
1.1       cgd        77: }
                     78:
1.10      christos   79: #define swap(a, b)                                             \
                     80:        if (swaptype == 0) {                                    \
                     81:                long t = *(long *)(void *)(a);                  \
                     82:                *(long *)(void *)(a) = *(long *)(void *)(b);    \
                     83:                *(long *)(void *)(b) = t;                       \
                     84:        } else                                                  \
1.4       mycroft    85:                swapfunc(a, b, es, swaptype)
                     86:
1.10      christos   87: #define vecswap(a, b, n) if ((n) > 0) swapfunc((a), (b), (size_t)(n), swaptype)
1.4       mycroft    88:
1.14      perry      89: static inline char *
1.15      rmind      90: med3(char *a, char *b, char *c,
1.21      dsl        91:     int (*cmp)(const void *, const void *))
1.4       mycroft    92: {
1.15      rmind      93:
1.4       mycroft    94:        return cmp(a, b) < 0 ?
                     95:               (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
                     96:               :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
1.1       cgd        97: }
                     98:
1.4       mycroft    99: void
1.15      rmind     100: qsort(void *a, size_t n, size_t es,
1.21      dsl       101:     int (*cmp)(const void *, const void *))
1.4       mycroft   102: {
                    103:        char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
1.23    ! christos  104:        size_t d, r, s;
1.20      yamt      105:        int swaptype, cmp_result;
1.11      lukem     106:
1.22      christos  107:        _DIAGASSERT(a != NULL || n == 0 || es == 0);
1.11      lukem     108:        _DIAGASSERT(cmp != NULL);
1.1       cgd       109:
1.4       mycroft   110: loop:  SWAPINIT(a, es);
                    111:        if (n < 7) {
1.7       mikel     112:                for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
1.4       mycroft   113:                        for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
                    114:                             pl -= es)
                    115:                                swap(pl, pl - es);
                    116:                return;
                    117:        }
1.7       mikel     118:        pm = (char *) a + (n / 2) * es;
1.4       mycroft   119:        if (n > 7) {
1.7       mikel     120:                pl = (char *) a;
                    121:                pn = (char *) a + (n - 1) * es;
1.4       mycroft   122:                if (n > 40) {
                    123:                        d = (n / 8) * es;
                    124:                        pl = med3(pl, pl + d, pl + 2 * d, cmp);
                    125:                        pm = med3(pm - d, pm, pm + d, cmp);
                    126:                        pn = med3(pn - 2 * d, pn - d, pn, cmp);
1.1       cgd       127:                }
1.4       mycroft   128:                pm = med3(pl, pm, pn, cmp);
1.1       cgd       129:        }
1.4       mycroft   130:        swap(a, pm);
1.7       mikel     131:        pa = pb = (char *) a + es;
1.1       cgd       132:
1.7       mikel     133:        pc = pd = (char *) a + (n - 1) * es;
1.4       mycroft   134:        for (;;) {
1.15      rmind     135:                while (pb <= pc && (cmp_result = cmp(pb, a)) <= 0) {
                    136:                        if (cmp_result == 0) {
1.4       mycroft   137:                                swap(pa, pb);
                    138:                                pa += es;
1.1       cgd       139:                        }
1.4       mycroft   140:                        pb += es;
                    141:                }
1.15      rmind     142:                while (pb <= pc && (cmp_result = cmp(pc, a)) >= 0) {
                    143:                        if (cmp_result == 0) {
1.4       mycroft   144:                                swap(pc, pd);
                    145:                                pd -= es;
1.1       cgd       146:                        }
1.4       mycroft   147:                        pc -= es;
1.1       cgd       148:                }
1.4       mycroft   149:                if (pb > pc)
1.1       cgd       150:                        break;
1.4       mycroft   151:                swap(pb, pc);
                    152:                pb += es;
                    153:                pc -= es;
1.1       cgd       154:        }
                    155:
1.7       mikel     156:        pn = (char *) a + n * es;
                    157:        r = min(pa - (char *) a, pb - pa);
1.4       mycroft   158:        vecswap(a, pb - r, r);
1.19      lukem     159:        r = min((size_t)(pd - pc), pn - pd - es);
1.4       mycroft   160:        vecswap(pb, pn - r, r);
1.23    ! christos  161:        /*
        !           162:         * To save stack space we sort the smaller side of the partition first
        !           163:         * using recursion and eliminate tail recursion for the larger side.
        !           164:         */
        !           165:        r = pb - pa;
        !           166:        s = pd - pc;
        !           167:        if (r < s) {
        !           168:                /* Recurse for 1st side, iterate for 2nd side. */
        !           169:                if (s > es) {
        !           170:                        if (r > es)
        !           171:                                qsort(a, r / es, es, cmp);
        !           172:                        a = pn - s;
        !           173:                        n = s / es;
        !           174:                        goto loop;
        !           175:                }
        !           176:        } else {
        !           177:                /* Recurse for 2nd side, iterate for 1st side. */
        !           178:                if (r > es) {
        !           179:                        if (s > es)
        !           180:                                qsort(pn - s, s / es, es, cmp);
        !           181:                        n = r / es;
        !           182:                        goto loop;
        !           183:                }
1.1       cgd       184:        }
                    185: }

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