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# rpmdb/merge.c

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    00001 /*@-bounds -mustmod -sizeoftype @*/
    00002 /*-
    00003  * Copyright (c) 1992, 1993
    00004  *      The Regents of the University of California.  All rights reserved.
    00005  *
    00006  * This code is derived from software contributed to Berkeley by
    00007  * Peter McIlroy.
    00008  *
    00009  * Redistribution and use in source and binary forms, with or without
    00010  * modification, are permitted provided that the following conditions
    00011  * are met:
    00012  * 1. Redistributions of source code must retain the above copyright
    00013  *    notice, this list of conditions and the following disclaimer.
    00014  * 2. Redistributions in binary form must reproduce the above copyright
    00015  *    notice, this list of conditions and the following disclaimer in the
    00016  *    documentation and/or other materials provided with the distribution.
    00017  * 3. All advertising materials mentioning features or use of this software
    00018  *    must display the following acknowledgement:
    00019  *      This product includes software developed by the University of
    00020  *      California, Berkeley and its contributors.
    00021  * 4. Neither the name of the University nor the names of its contributors
    00022  *    may be used to endorse or promote products derived from this software
    00023  *    without specific prior written permission.
    00024  *
    00025  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
    00026  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    00027  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    00028  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
    00029  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
    00030  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
    00031  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
    00032  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
    00033  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
    00034  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    00035  * SUCH DAMAGE.
    00036  */
    00037
    00038 #if defined(LIBC_SCCS) && !defined(lint)
    00039 static char sccsid[] = "@(#)merge.c     8.2 (Berkeley) 2/14/94";
    00040 #endif /* LIBC_SCCS and not lint */
    00041
    00042 /*
    00043  * Hybrid exponential search/linear search merge sort with hybrid
    00044  * natural/pairwise first pass.  Requires about .3% more comparisons
    00045  * for random data than LSMS with pairwise first pass alone.
    00046  * It works for objects as small as two bytes.
    00047  */
    00048
    00049 #define NATURAL
    00050 #define THRESHOLD 16    /* Best choice for natural merge cut-off. */
    00051
    00052 /* #define NATURAL to get hybrid natural merge.
    00053  * (The default is pairwise merging.)
    00054  */
    00055
    00056 #include "system.h"
    00057
    00058 #define ISIZE sizeof(int)
    00059 #define PSIZE sizeof(unsigned char *)
    00060 #define ICOPY_LIST(src, dst, last)                              \
    00061         do                                                      \
    00062         *(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE;    \
    00063         while(src < last)
    00064 #define ICOPY_ELT(src, dst, i)                                  \
    00065         do                                                      \
    00066         *(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE;  \
    00067         while (i -= ISIZE)
    00068
    00069 #define CCOPY_LIST(src, dst, last)              \
    00070         do                                      \
    00071                 *dst++ = *src++;                \
    00072         while (src < last)
    00073 #define CCOPY_ELT(src, dst, i)                  \
    00074         do                                      \
    00075                 *dst++ = *src++;                \
    00076         while (i -= 1)
    00077
    00078 /*
    00079  * Find the next possible pointer head.  (Trickery for forcing an array
    00080  * to do double duty as a linked list when objects do not align with word
    00081  * boundaries.
    00082  */
    00083 /* Assumption: PSIZE is a power of 2. */
    00084 #define EVAL(p) (unsigned char **)                                      \
    00085     ((unsigned char *)0 +                                               \
    00086         (((unsigned char *)p + PSIZE - 1 - (unsigned char *) 0) & ~(PSIZE - 1)))
    00087
    00088 #define swap(a, b) {                                    \
    00089                 s = b;                                  \
    00090                 i = size;                               \
    00091                 do {                                    \
    00092                         tmp = *a; *a++ = *s; *s++ = tmp; \
    00093                 } while (--i);                          \
    00094                 a -= size;                              \
    00095         }
    00096 #define reverse(bot, top) {                             \
    00097         s = top;                                        \
    00098         do {                                            \
    00099                 i = size;                               \
    00100                 do {                                    \
    00101                         tmp = *bot; *bot++ = *s; *s++ = tmp; \
    00102                 } while (--i);                          \
    00103                 s -= size2;                             \
    00104         } while(bot < s);                               \
    00105 }
    00106
    00107 /*
    00108  * This is to avoid out-of-bounds addresses in sorting the
    00109  * last 4 elements.
    00110  */
    00111 static void
    00112 insertionsort(unsigned char *a, size_t n, size_t size,
    00113                 int (*cmp) (const void *, const void *))
    00114         /*@modifies *a @*/
    00115 {
    00116         u_char *ai, *s, *t, *u, tmp;
    00117         int i;
    00118
    00119         for (ai = a+size; --n >= 1; ai += size)
    00120                 for (t = ai; t > a; t -= size) {
    00121                         u = t - size;
    00122                         if (cmp(u, t) <= 0)
    00123                                 /*@innerbreak@*/ break;
    00124                         swap(u, t);
    00125                 }
    00126 }
    00127
    00128 /*
    00129  * Optional hybrid natural/pairwise first pass.  Eats up list1 in runs of
    00130  * increasing order, list2 in a corresponding linked list.  Checks for runs
    00131  * when THRESHOLD/2 pairs compare with same sense.  (Only used when NATURAL
    00132  * is defined.  Otherwise simple pairwise merging is used.)
    00133  */
    00134 static void
    00135 setup(unsigned char *list1, /*@out@*/ unsigned char *list2,
    00136                 size_t n, size_t size, int (*cmp) (const void *, const void *))
    00137         /*@modifies list1, list2 @*/
    00138 {
    00139         int i, length, size2, tmp, sense;
    00140         unsigned char *f1, *f2, *s, *l2, *last, *p2;
    00141
    00142         size2 = size*2;
    00143         if (n <= 5) {
    00144                 insertionsort(list1, n, size, cmp);
    00145                 *EVAL(list2) = (unsigned char*) list2 + n*size;
    00146                 return;
    00147         }
    00148         /*
    00149          * Avoid running pointers out of bounds; limit n to evens
    00150          * for simplicity.
    00151          */
    00152         i = 4 + (n & 1);
    00153         insertionsort(list1 + (n - i) * size, i, size, cmp);
    00154         last = list1 + size * (n - i);
    00155         *EVAL(list2 + (last - list1)) = list2 + n * size;
    00156
    00157 #ifdef NATURAL
    00158         p2 = list2;
    00159         f1 = list1;
    00160         sense = (cmp(f1, f1 + size) > 0);
    00161         for (; f1 < last; sense = !sense) {
    00162                 length = 2;
    00163                                         /* Find pairs with same sense. */
    00164                 for (f2 = f1 + size2; f2 < last; f2 += size2) {
    00165                         if ((cmp(f2, f2+ size) > 0) != sense)
    00166                                 /*@innerbreak@*/ break;
    00167                         length += 2;
    00168                 }
    00169                 if (length < THRESHOLD) {               /* Pairwise merge */
    00170                         do {
    00171                                 p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
    00172                                 if (sense > 0)
    00173                                         swap (f1, f1 + size);
    00174                         } while ((f1 += size2) < f2);
    00175                 } else {                                /* Natural merge */
    00176                         l2 = f2;
    00177                         for (f2 = f1 + size2; f2 < l2; f2 += size2) {
    00178                                 if ((cmp(f2-size, f2) > 0) != sense) {
    00179                                         p2 = *EVAL(p2) = f2 - list1 + list2;
    00180                                         if (sense > 0)
    00181                                                 reverse(f1, f2-size);
    00182                                         f1 = f2;
    00183                                 }
    00184                         }
    00185                         if (sense > 0)
    00186                                 reverse (f1, f2-size);
    00187                         f1 = f2;
    00188                         if (f2 < last || cmp(f2 - size, f2) > 0)
    00189                                 p2 = *EVAL(p2) = f2 - list1 + list2;
    00190                         else
    00191                                 p2 = *EVAL(p2) = list2 + n*size;
    00192                 }
    00193         }
    00194 #else           /* pairwise merge only. */
    00195         for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
    00196                 p2 = *EVAL(p2) = p2 + size2;
    00197                 if (cmp (f1, f1 + size) > 0)
    00198                         swap(f1, f1 + size);
    00199         }
    00200 #endif /* NATURAL */
    00201 }
    00202
    00203 /*
    00204  * Arguments are as for qsort.
    00205  */
    00206 int
    00207 mergesort(void *base, size_t nmemb, size_t size,
    00208                 int (*cmp) (const void *, const void *))
    00209 {
    00210         register int i, sense;
    00211         int big, iflag;
    00212         register unsigned char *f1, *f2, *t, *b, *q, *l1, *l2;
    00213         /*@dependent@*/
    00214         register unsigned char *tp2;
    00215         /*@owned@*/
    00216         unsigned char *list2;
    00217         /*@dependent@*/
    00218         unsigned char *list1;
    00219         unsigned char *p2, *p, *last, **p1;
    00220
    00221         if (size < PSIZE / 2) {         /* Pointers must fit into 2 * size. */
    00222                 errno = EINVAL;
    00223                 return (-1);
    00224         }
    00225
    00226         if (nmemb == 0)
    00227                 return (0);
    00228
    00229         /*
    00230          * XXX
    00231          * Stupid subtraction for the Cray.
    00232          */
    00233         iflag = 0;
    00234         if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
    00235                 iflag = 1;
    00236
    00237         if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
    00238                 return (-1);
    00239
    00240         list1 = base;
    00241         setup(list1, list2, nmemb, size, cmp);
    00242         last = list2 + nmemb * size;
    00243         i = big = 0;
    00244 /*@-branchstate@*/
    00245         while (*EVAL(list2) != last) {
    00246             l2 = list1;
    00247             p1 = EVAL(list1);
    00248             for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
    00249                 p2 = *EVAL(p2);
    00250                 f1 = l2;
    00251                 f2 = l1 = list1 + (p2 - list2);
    00252                 if (p2 != last)
    00253                         p2 = *EVAL(p2);
    00254                 l2 = list1 + (p2 - list2);
    00255                 while (f1 < l1 && f2 < l2) {
    00256                         if ((*cmp)(f1, f2) <= 0) {
    00257                                 q = f2;
    00258                                 b = f1, t = l1;
    00259                                 sense = -1;
    00260                         } else {
    00261                                 q = f1;
    00262                                 b = f2, t = l2;
    00263                                 sense = 0;
    00264                         }
    00265                         if (!big) {     /* here i = 0 */
    00266                                 while ((b += size) < t && cmp(q, b) >sense)
    00267                                         if (++i == 6) {
    00268                                                 big = 1;
    00269                                                 goto EXPONENTIAL;
    00270                                         }
    00271                         } else {
    00272 /*@-shiftimplementation@*/
    00273 EXPONENTIAL:                    for (i = size; ; i <<= 1)
    00274                                         if ((p = (b + i)) >= t) {
    00275                                                 if ((p = t - size) > b &&
    00276                                                     (*cmp)(q, p) <= sense)
    00277                                                         t = p;
    00278                                                 else
    00279                                                         b = p;
    00280                                                 /*@innerbreak@*/ break;
    00281                                         } else if ((*cmp)(q, p) <= sense) {
    00282                                                 t = p;
    00283                                                 if (i == size)
    00284                                                         big = 0;
    00285                                                 goto FASTCASE;
    00286                                         } else
    00287                                                 b = p;
    00288                                 /*@-infloopsuncon@*/
    00289                                 while (t > b+size) {
    00290                                         i = (((t - b) / size) >> 1) * size;
    00291                                         if ((*cmp)(q, p = b + i) <= sense)
    00292                                                 t = p;
    00293                                         else
    00294                                                 b = p;
    00295                                 }
    00296                                 goto COPY;
    00297 FASTCASE:                       while (i > size)
    00298                                         if ((*cmp)(q,
    00299                                                 p = b + (i >>= 1)) <= sense)
    00300                                                 t = p;
    00301                                         else
    00302                                                 b = p;
    00303                                 /*@=infloopsuncon@*/
    00304 /*@=shiftimplementation@*/
    00305 COPY:                           b = t;
    00306                         }
    00307                         i = size;
    00308                         if (q == f1) {
    00309                                 if (iflag) {
    00310                                         ICOPY_LIST(f2, tp2, b);
    00311                                         ICOPY_ELT(f1, tp2, i);
    00312                                 } else {
    00313                                         CCOPY_LIST(f2, tp2, b);
    00314                                         CCOPY_ELT(f1, tp2, i);
    00315                                 }
    00316                         } else {
    00317                                 if (iflag) {
    00318                                         ICOPY_LIST(f1, tp2, b);
    00319                                         ICOPY_ELT(f2, tp2, i);
    00320                                 } else {
    00321                                         CCOPY_LIST(f1, tp2, b);
    00322                                         CCOPY_ELT(f2, tp2, i);
    00323                                 }
    00324                         }
    00325                 }
    00326                 if (f2 < l2) {
    00327                         if (iflag)
    00328                                 ICOPY_LIST(f2, tp2, l2);
    00329                         else
    00330                                 CCOPY_LIST(f2, tp2, l2);
    00331                 } else if (f1 < l1) {
    00332                         if (iflag)
    00333                                 ICOPY_LIST(f1, tp2, l1);
    00334                         else
    00335                                 CCOPY_LIST(f1, tp2, l1);
    00336                 }
    00337                 *p1 = l2;
    00338             }
    00339 /*@-dependenttrans@*/
    00340             tp2 = list1;        /* swap list1, list2 */
    00341             list1 = list2;
    00342             list2 = tp2;
    00343 /*@=dependenttrans@*/
    00344             last = list2 + nmemb*size;
    00345         }
    00346 /*@=branchstate@*/
    00347         if (base == list2) {
    00348                 memmove(list2, list1, nmemb*size);
    00349                 list2 = list1;
    00350         }
    00351 /*@-usereleased@*/
    00352         free(list2);
    00353 /*@=usereleased@*/
    00354         return (0);
    00355 }
    00356 /*@=bounds =mustmod =sizeoftype @*/