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IABSD.fr/src/lib/libc/stdlib/merge.c
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- lib/libc/stdlib/merge.c
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/* $OpenBSD: merge.c,v 1.10 2015/06/21 03:20:56 millert Exp $ */ /*- * Copyright (c) 1992, 1993 * The Regents of the University of California. All rights reserved. * * This code is derived from software contributed to Berkeley by * Peter McIlroy. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ /* * Hybrid exponential search/linear search merge sort with hybrid * natural/pairwise first pass. Requires about .3% more comparisons * for random data than LSMS with pairwise first pass alone. * It works for objects as small as two bytes. */ #define NATURAL #define THRESHOLD 16 /* Best choice for natural merge cut-off. */ /* #define NATURAL to get hybrid natural merge. * (The default is pairwise merging.) */ #include <sys/types.h> #include <errno.h> #include <stdlib.h> #include <string.h> static void setup(u_char *, u_char *, size_t, size_t, int (*)()); static void insertionsort(u_char *, size_t, size_t, int (*)()); #define ISIZE sizeof(int) #define PSIZE sizeof(u_char *) #define ICOPY_LIST(src, dst, last) \ do \ *(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE; \ while(src < last) #define ICOPY_ELT(src, dst, i) \ do \ *(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE; \ while (i -= ISIZE) #define CCOPY_LIST(src, dst, last) \ do \ *dst++ = *src++; \ while (src < last) #define CCOPY_ELT(src, dst, i) \ do \ *dst++ = *src++; \ while (i -= 1) /* * Find the next possible pointer head. (Trickery for forcing an array * to do double duty as a linked list when objects do not align with word * boundaries. */ /* Assumption: PSIZE is a power of 2. */ #define EVAL(p) (u_char **) \ ((u_char *)0 + \ (((u_char *)p + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1))) /* * Arguments are as for qsort. */ int mergesort(void *base, size_t nmemb, size_t size, int (*cmp)(const void *, const void *)) { int i, sense; int big, iflag; u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2; u_char *list2, *list1, *p2, *p, *last, **p1; if (size < PSIZE / 2) { /* Pointers must fit into 2 * size. */ errno = EINVAL; return (-1); } if (nmemb == 0) return (0); /* * XXX * Stupid subtraction for the Cray. */ iflag = 0; if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE)) iflag = 1; if ((list2 = malloc(nmemb * size + PSIZE)) == NULL) return (-1); list1 = base; setup(list1, list2, nmemb, size, cmp); last = list2 + nmemb * size; i = big = 0; while (*EVAL(list2) != last) { l2 = list1; p1 = EVAL(list1); for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) { p2 = *EVAL(p2); f1 = l2; f2 = l1 = list1 + (p2 - list2); if (p2 != last) p2 = *EVAL(p2); l2 = list1 + (p2 - list2); while (f1 < l1 && f2 < l2) { if ((*cmp)(f1, f2) <= 0) { q = f2; b = f1, t = l1; sense = -1; } else { q = f1; b = f2, t = l2; sense = 0; } if (!big) { /* here i = 0 */ while ((b += size) < t && cmp(q, b) >sense) if (++i == 6) { big = 1; goto EXPONENTIAL; } } else { EXPONENTIAL: for (i = size; ; i <<= 1) if ((p = (b + i)) >= t) { if ((p = t - size) > b && (*cmp)(q, p) <= sense) t = p; else b = p; break; } else if ((*cmp)(q, p) <= sense) { t = p; if (i == size) big = 0; goto FASTCASE; } else b = p; while (t > b+size) { i = (((t - b) / size) >> 1) * size; if ((*cmp)(q, p = b + i) <= sense) t = p; else b = p; } goto COPY; FASTCASE: while (i > size) if ((*cmp)(q, p = b + (i >>= 1)) <= sense) t = p; else b = p; COPY: b = t; } i = size; if (q == f1) { if (iflag) { ICOPY_LIST(f2, tp2, b); ICOPY_ELT(f1, tp2, i); } else { CCOPY_LIST(f2, tp2, b); CCOPY_ELT(f1, tp2, i); } } else { if (iflag) { ICOPY_LIST(f1, tp2, b); ICOPY_ELT(f2, tp2, i); } else { CCOPY_LIST(f1, tp2, b); CCOPY_ELT(f2, tp2, i); } } } if (f2 < l2) { if (iflag) ICOPY_LIST(f2, tp2, l2); else CCOPY_LIST(f2, tp2, l2); } else if (f1 < l1) { if (iflag) ICOPY_LIST(f1, tp2, l1); else CCOPY_LIST(f1, tp2, l1); } *p1 = l2; } tp2 = list1; /* swap list1, list2 */ list1 = list2; list2 = tp2; last = list2 + nmemb*size; } if (base == list2) { memmove(list2, list1, nmemb*size); list2 = list1; } free(list2); return (0); } #define swap(a, b) { \ s = b; \ i = size; \ do { \ tmp = *a; *a++ = *s; *s++ = tmp; \ } while (--i); \ a -= size; \ } #define reverse(bot, top) { \ s = top; \ do { \ i = size; \ do { \ tmp = *bot; *bot++ = *s; *s++ = tmp; \ } while (--i); \ s -= size2; \ } while(bot < s); \ } /* * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of * increasing order, list2 in a corresponding linked list. Checks for runs * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL * is defined. Otherwise simple pairwise merging is used.) */ void setup(u_char *list1, u_char *list2, size_t n, size_t size, int (*cmp)(const void *, const void *)) { int i, length, size2, sense; u_char tmp, *f1, *f2, *s, *l2, *last, *p2; size2 = size*2; if (n <= 5) { insertionsort(list1, n, size, cmp); *EVAL(list2) = (u_char*) list2 + n*size; return; } /* * Avoid running pointers out of bounds; limit n to evens * for simplicity. */ i = 4 + (n & 1); insertionsort(list1 + (n - i) * size, i, size, cmp); last = list1 + size * (n - i); *EVAL(list2 + (last - list1)) = list2 + n * size; #ifdef NATURAL p2 = list2; f1 = list1; sense = (cmp(f1, f1 + size) > 0); for (; f1 < last; sense = !sense) { length = 2; /* Find pairs with same sense. */ for (f2 = f1 + size2; f2 < last; f2 += size2) { if ((cmp(f2, f2+ size) > 0) != sense) break; length += 2; } if (length < THRESHOLD) { /* Pairwise merge */ do { p2 = *EVAL(p2) = f1 + size2 - list1 + list2; if (sense > 0) swap (f1, f1 + size); } while ((f1 += size2) < f2); } else { /* Natural merge */ l2 = f2; for (f2 = f1 + size2; f2 < l2; f2 += size2) { if ((cmp(f2-size, f2) > 0) != sense) { p2 = *EVAL(p2) = f2 - list1 + list2; if (sense > 0) reverse(f1, f2-size); f1 = f2; } } if (sense > 0) reverse (f1, f2-size); f1 = f2; if (f2 < last || cmp(f2 - size, f2) > 0) p2 = *EVAL(p2) = f2 - list1 + list2; else p2 = *EVAL(p2) = list2 + n*size; } } #else /* pairwise merge only. */ for (f1 = list1, p2 = list2; f1 < last; f1 += size2) { p2 = *EVAL(p2) = p2 + size2; if (cmp (f1, f1 + size) > 0) swap(f1, f1 + size); } #endif /* NATURAL */ } /* * This is to avoid out-of-bounds addresses in sorting the * last 4 elements. */ static void insertionsort(u_char *a, size_t n, size_t size, int (*cmp)(const void *, const void *)) { u_char *ai, *s, *t, *u, tmp; int i; for (ai = a+size; --n >= 1; ai += size) for (t = ai; t > a; t -= size) { u = t - size; if (cmp(u, t) <= 0) break; swap(u, t); } }