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Annotation of src/lib/libc/stdlib/qsort.c, Revision 1.8

1.8     ! christos    1: /*     $NetBSD: qsort.c,v 1.7 1997/06/19 07:41:33 mikel 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
1.8     ! christos   41: __RCSID("$NetBSD$");
1.5       thorpej    42: #endif
1.1       cgd        43: #endif /* LIBC_SCCS and not lint */
                     44:
                     45: #include <sys/types.h>
                     46: #include <stdlib.h>
                     47:
1.8     ! christos   48: static __inline char   *med3 __P((char *, char *, char *,
        !            49:     int (*)(const void *, const void *)));
1.6       cgd        50: static __inline void    swapfunc __P((char *, char *, int, int));
1.4       mycroft    51:
                     52: #define min(a, b)      (a) < (b) ? a : b
                     53:
1.1       cgd        54: /*
1.4       mycroft    55:  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
1.1       cgd        56:  */
1.4       mycroft    57: #define swapcode(TYPE, parmi, parmj, n) {              \
                     58:        long i = (n) / sizeof (TYPE);                   \
                     59:        register TYPE *pi = (TYPE *) (parmi);           \
                     60:        register TYPE *pj = (TYPE *) (parmj);           \
                     61:        do {                                            \
                     62:                register TYPE   t = *pi;                \
                     63:                *pi++ = *pj;                            \
                     64:                *pj++ = t;                              \
                     65:         } while (--i > 0);                             \
                     66: }
1.1       cgd        67:
1.4       mycroft    68: #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
                     69:        es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
1.1       cgd        70:
1.6       cgd        71: static __inline void
1.4       mycroft    72: swapfunc(a, b, n, swaptype)
                     73:        char *a, *b;
                     74:        int n, swaptype;
1.1       cgd        75: {
1.7       mikel      76:        if (swaptype <= 1)
1.4       mycroft    77:                swapcode(long, a, b, n)
1.1       cgd        78:        else
1.4       mycroft    79:                swapcode(char, a, b, n)
1.1       cgd        80: }
                     81:
1.4       mycroft    82: #define swap(a, b)                                     \
                     83:        if (swaptype == 0) {                            \
                     84:                long t = *(long *)(a);                  \
                     85:                *(long *)(a) = *(long *)(b);            \
                     86:                *(long *)(b) = t;                       \
                     87:        } else                                          \
                     88:                swapfunc(a, b, es, swaptype)
                     89:
                     90: #define vecswap(a, b, n)       if ((n) > 0) swapfunc(a, b, n, swaptype)
                     91:
1.6       cgd        92: static __inline char *
1.4       mycroft    93: med3(a, b, c, cmp)
                     94:        char *a, *b, *c;
1.8     ! christos   95:        int (*cmp) __P((const void *, const void *));
1.4       mycroft    96: {
                     97:        return cmp(a, b) < 0 ?
                     98:               (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
                     99:               :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
1.1       cgd       100: }
                    101:
1.4       mycroft   102: void
                    103: qsort(a, n, es, cmp)
                    104:        void *a;
                    105:        size_t n, es;
1.8     ! christos  106:        int (*cmp) __P((const void *, const void *));
1.4       mycroft   107: {
                    108:        char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
                    109:        int d, r, swaptype, swap_cnt;
1.1       cgd       110:
1.4       mycroft   111: loop:  SWAPINIT(a, es);
                    112:        swap_cnt = 0;
                    113:        if (n < 7) {
1.7       mikel     114:                for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
1.4       mycroft   115:                        for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
                    116:                             pl -= es)
                    117:                                swap(pl, pl - es);
                    118:                return;
                    119:        }
1.7       mikel     120:        pm = (char *) a + (n / 2) * es;
1.4       mycroft   121:        if (n > 7) {
1.7       mikel     122:                pl = (char *) a;
                    123:                pn = (char *) a + (n - 1) * es;
1.4       mycroft   124:                if (n > 40) {
                    125:                        d = (n / 8) * es;
                    126:                        pl = med3(pl, pl + d, pl + 2 * d, cmp);
                    127:                        pm = med3(pm - d, pm, pm + d, cmp);
                    128:                        pn = med3(pn - 2 * d, pn - d, pn, cmp);
1.1       cgd       129:                }
1.4       mycroft   130:                pm = med3(pl, pm, pn, cmp);
1.1       cgd       131:        }
1.4       mycroft   132:        swap(a, pm);
1.7       mikel     133:        pa = pb = (char *) a + es;
1.1       cgd       134:
1.7       mikel     135:        pc = pd = (char *) a + (n - 1) * es;
1.4       mycroft   136:        for (;;) {
                    137:                while (pb <= pc && (r = cmp(pb, a)) <= 0) {
                    138:                        if (r == 0) {
                    139:                                swap_cnt = 1;
                    140:                                swap(pa, pb);
                    141:                                pa += es;
1.1       cgd       142:                        }
1.4       mycroft   143:                        pb += es;
                    144:                }
                    145:                while (pb <= pc && (r = cmp(pc, a)) >= 0) {
                    146:                        if (r == 0) {
                    147:                                swap_cnt = 1;
                    148:                                swap(pc, pd);
                    149:                                pd -= es;
1.1       cgd       150:                        }
1.4       mycroft   151:                        pc -= es;
1.1       cgd       152:                }
1.4       mycroft   153:                if (pb > pc)
1.1       cgd       154:                        break;
1.4       mycroft   155:                swap(pb, pc);
                    156:                swap_cnt = 1;
                    157:                pb += es;
                    158:                pc -= es;
1.1       cgd       159:        }
1.4       mycroft   160:        if (swap_cnt == 0) {  /* Switch to insertion sort */
1.7       mikel     161:                for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
1.4       mycroft   162:                        for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
                    163:                             pl -= es)
                    164:                                swap(pl, pl - es);
1.1       cgd       165:                return;
                    166:        }
                    167:
1.7       mikel     168:        pn = (char *) a + n * es;
                    169:        r = min(pa - (char *) a, pb - pa);
1.4       mycroft   170:        vecswap(a, pb - r, r);
                    171:        r = min(pd - pc, pn - pd - es);
                    172:        vecswap(pb, pn - r, r);
                    173:        if ((r = pb - pa) > es)
                    174:                qsort(a, r / es, es, cmp);
                    175:        if ((r = pd - pc) > es) {
                    176:                /* Iterate rather than recurse to save stack space */
                    177:                a = pn - r;
                    178:                n = r / es;
                    179:                goto loop;
1.1       cgd       180:        }
1.4       mycroft   181: /*             qsort(pn - r, r / es, es, cmp);*/
1.1       cgd       182: }

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