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Annotation of src/lib/libc/stdlib/qsort.c, Revision 1.12

1.12    ! lukem       1: /*     $NetBSD: qsort.c,v 1.11 1999/09/16 11:45:35 lukem Exp $ */
1.5       thorpej     2:
1.1       cgd         3: /*-
1.4       mycroft     4:  * Copyright (c) 1992, 1993
                      5:  *     The Regents of the University of California.  All rights reserved.
1.1       cgd         6:  *
                      7:  * Redistribution and use in source and binary forms, with or without
                      8:  * modification, are permitted provided that the following conditions
                      9:  * are met:
                     10:  * 1. Redistributions of source code must retain the above copyright
                     11:  *    notice, this list of conditions and the following disclaimer.
                     12:  * 2. Redistributions in binary form must reproduce the above copyright
                     13:  *    notice, this list of conditions and the following disclaimer in the
                     14:  *    documentation and/or other materials provided with the distribution.
                     15:  * 3. All advertising materials mentioning features or use of this software
                     16:  *    must display the following acknowledgement:
                     17:  *     This product includes software developed by the University of
                     18:  *     California, Berkeley and its contributors.
                     19:  * 4. Neither the name of the University nor the names of its contributors
                     20:  *    may be used to endorse or promote products derived from this software
                     21:  *    without specific prior written permission.
                     22:  *
                     23:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
                     24:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
                     25:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
                     26:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
                     27:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
                     28:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
                     29:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                     30:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                     31:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                     32:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                     33:  * SUCH DAMAGE.
                     34:  */
                     35:
1.8       christos   36: #include <sys/cdefs.h>
1.1       cgd        37: #if defined(LIBC_SCCS) && !defined(lint)
1.5       thorpej    38: #if 0
1.7       mikel      39: static char sccsid[] = "@(#)qsort.c    8.1 (Berkeley) 6/4/93";
1.5       thorpej    40: #else
1.12    ! lukem      41: __RCSID("$NetBSD: qsort.c,v 1.11 1999/09/16 11:45:35 lukem Exp $");
1.5       thorpej    42: #endif
1.1       cgd        43: #endif /* LIBC_SCCS and not lint */
                     44:
                     45: #include <sys/types.h>
1.11      lukem      46:
                     47: #include <assert.h>
                     48: #include <errno.h>
1.1       cgd        49: #include <stdlib.h>
                     50:
1.8       christos   51: static __inline char   *med3 __P((char *, char *, char *,
                     52:     int (*)(const void *, const void *)));
1.10      christos   53: static __inline void    swapfunc __P((char *, char *, size_t, int));
1.4       mycroft    54:
                     55: #define min(a, b)      (a) < (b) ? a : b
                     56:
1.1       cgd        57: /*
1.4       mycroft    58:  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
1.1       cgd        59:  */
1.4       mycroft    60: #define swapcode(TYPE, parmi, parmj, n) {              \
1.10      christos   61:        size_t i = (n) / sizeof (TYPE);                 \
                     62:        TYPE *pi = (TYPE *)(void *)(parmi);             \
                     63:        TYPE *pj = (TYPE *)(void *)(parmj);             \
1.4       mycroft    64:        do {                                            \
1.10      christos   65:                TYPE    t = *pi;                        \
1.4       mycroft    66:                *pi++ = *pj;                            \
                     67:                *pj++ = t;                              \
                     68:         } while (--i > 0);                             \
                     69: }
1.1       cgd        70:
1.4       mycroft    71: #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
                     72:        es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
1.1       cgd        73:
1.6       cgd        74: static __inline void
1.4       mycroft    75: swapfunc(a, b, n, swaptype)
                     76:        char *a, *b;
1.10      christos   77:        size_t n;
                     78:        int swaptype;
1.1       cgd        79: {
1.7       mikel      80:        if (swaptype <= 1)
1.4       mycroft    81:                swapcode(long, a, b, n)
1.1       cgd        82:        else
1.4       mycroft    83:                swapcode(char, a, b, n)
1.1       cgd        84: }
                     85:
1.10      christos   86: #define swap(a, b)                                             \
                     87:        if (swaptype == 0) {                                    \
                     88:                long t = *(long *)(void *)(a);                  \
                     89:                *(long *)(void *)(a) = *(long *)(void *)(b);    \
                     90:                *(long *)(void *)(b) = t;                       \
                     91:        } else                                                  \
1.4       mycroft    92:                swapfunc(a, b, es, swaptype)
                     93:
1.10      christos   94: #define vecswap(a, b, n) if ((n) > 0) swapfunc((a), (b), (size_t)(n), swaptype)
1.4       mycroft    95:
1.6       cgd        96: static __inline char *
1.4       mycroft    97: med3(a, b, c, cmp)
                     98:        char *a, *b, *c;
1.8       christos   99:        int (*cmp) __P((const void *, const void *));
1.4       mycroft   100: {
                    101:        return cmp(a, b) < 0 ?
                    102:               (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
                    103:               :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
1.1       cgd       104: }
                    105:
1.4       mycroft   106: void
                    107: qsort(a, n, es, cmp)
                    108:        void *a;
                    109:        size_t n, es;
1.8       christos  110:        int (*cmp) __P((const void *, const void *));
1.4       mycroft   111: {
                    112:        char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
                    113:        int d, r, swaptype, swap_cnt;
1.11      lukem     114:
                    115:        _DIAGASSERT(a != NULL);
                    116:        _DIAGASSERT(cmp != NULL);
1.1       cgd       117:
1.4       mycroft   118: loop:  SWAPINIT(a, es);
                    119:        swap_cnt = 0;
                    120:        if (n < 7) {
1.7       mikel     121:                for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
1.4       mycroft   122:                        for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
                    123:                             pl -= es)
                    124:                                swap(pl, pl - es);
                    125:                return;
                    126:        }
1.7       mikel     127:        pm = (char *) a + (n / 2) * es;
1.4       mycroft   128:        if (n > 7) {
1.7       mikel     129:                pl = (char *) a;
                    130:                pn = (char *) a + (n - 1) * es;
1.4       mycroft   131:                if (n > 40) {
                    132:                        d = (n / 8) * es;
                    133:                        pl = med3(pl, pl + d, pl + 2 * d, cmp);
                    134:                        pm = med3(pm - d, pm, pm + d, cmp);
                    135:                        pn = med3(pn - 2 * d, pn - d, pn, cmp);
1.1       cgd       136:                }
1.4       mycroft   137:                pm = med3(pl, pm, pn, cmp);
1.1       cgd       138:        }
1.4       mycroft   139:        swap(a, pm);
1.7       mikel     140:        pa = pb = (char *) a + es;
1.1       cgd       141:
1.7       mikel     142:        pc = pd = (char *) a + (n - 1) * es;
1.4       mycroft   143:        for (;;) {
                    144:                while (pb <= pc && (r = cmp(pb, a)) <= 0) {
                    145:                        if (r == 0) {
                    146:                                swap_cnt = 1;
                    147:                                swap(pa, pb);
                    148:                                pa += es;
1.1       cgd       149:                        }
1.4       mycroft   150:                        pb += es;
                    151:                }
                    152:                while (pb <= pc && (r = cmp(pc, a)) >= 0) {
                    153:                        if (r == 0) {
                    154:                                swap_cnt = 1;
                    155:                                swap(pc, pd);
                    156:                                pd -= es;
1.1       cgd       157:                        }
1.4       mycroft   158:                        pc -= es;
1.1       cgd       159:                }
1.4       mycroft   160:                if (pb > pc)
1.1       cgd       161:                        break;
1.4       mycroft   162:                swap(pb, pc);
                    163:                swap_cnt = 1;
                    164:                pb += es;
                    165:                pc -= es;
1.1       cgd       166:        }
1.4       mycroft   167:        if (swap_cnt == 0) {  /* Switch to insertion sort */
1.7       mikel     168:                for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
1.4       mycroft   169:                        for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
                    170:                             pl -= es)
                    171:                                swap(pl, pl - es);
1.1       cgd       172:                return;
                    173:        }
                    174:
1.7       mikel     175:        pn = (char *) a + n * es;
                    176:        r = min(pa - (char *) a, pb - pa);
1.4       mycroft   177:        vecswap(a, pb - r, r);
                    178:        r = min(pd - pc, pn - pd - es);
                    179:        vecswap(pb, pn - r, r);
                    180:        if ((r = pb - pa) > es)
                    181:                qsort(a, r / es, es, cmp);
                    182:        if ((r = pd - pc) > es) {
                    183:                /* Iterate rather than recurse to save stack space */
                    184:                a = pn - r;
                    185:                n = r / es;
                    186:                goto loop;
1.1       cgd       187:        }
1.4       mycroft   188: /*             qsort(pn - r, r / es, es, cmp);*/
1.1       cgd       189: }

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