/*-------------------------------------------------------------------- * Symbols referenced in this file: * - pg_qsort * - pg_qsort * - swapfunc * - med3 *-------------------------------------------------------------------- */ /* * qsort.c: standard quicksort algorithm * * Modifications from vanilla NetBSD source: * Add do ... while() macro fix * Remove __inline, _DIAGASSERTs, __P * Remove ill-considered "swap_cnt" switch to insertion sort, * in favor of a simple check for presorted input. * Take care to recurse on the smaller partition, to bound stack usage. * * CAUTION: if you change this file, see also qsort_arg.c, gen_qsort_tuple.pl * * src/port/qsort.c */ /* $NetBSD: qsort.c,v 1.13 2003/08/07 16:43:42 agc Exp $ */ /*- * Copyright (c) 1992, 1993 * The Regents of the University of California. All rights reserved. * * 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. */ #include "c.h" static char *med3(char *a, char *b, char *c, int (*cmp) (const void *, const void *)); static void swapfunc(char *, char *, size_t, int); /* * Qsort routine based on J. L. Bentley and M. D. McIlroy, * "Engineering a sort function", * Software--Practice and Experience 23 (1993) 1249-1265. * * We have modified their original by adding a check for already-sorted input, * which seems to be a win per discussions on pgsql-hackers around 2006-03-21. * * Also, we recurse on the smaller partition and iterate on the larger one, * which ensures we cannot recurse more than log(N) levels (since the * partition recursed to is surely no more than half of the input). Bentley * and McIlroy explicitly rejected doing this on the grounds that it's "not * worth the effort", but we have seen crashes in the field due to stack * overrun, so that judgment seems wrong. */ #define swapcode(TYPE, parmi, parmj, n) \ do { \ size_t i = (n) / sizeof (TYPE); \ TYPE *pi = (TYPE *)(void *)(parmi); \ TYPE *pj = (TYPE *)(void *)(parmj); \ do { \ TYPE t = *pi; \ *pi++ = *pj; \ *pj++ = t; \ } while (--i > 0); \ } while (0) #define SWAPINIT(a, es) swaptype = ((char *)(a) - (char *)0) % sizeof(long) || \ (es) % sizeof(long) ? 2 : (es) == sizeof(long)? 0 : 1; static void swapfunc(char *a, char *b, size_t n, int swaptype) { if (swaptype <= 1) swapcode(long, a, b, n); else swapcode(char, a, b, n); } #define swap(a, b) \ if (swaptype == 0) { \ long t = *(long *)(void *)(a); \ *(long *)(void *)(a) = *(long *)(void *)(b); \ *(long *)(void *)(b) = t; \ } else \ swapfunc(a, b, es, swaptype) #define vecswap(a, b, n) if ((n) > 0) swapfunc(a, b, n, swaptype) static char * med3(char *a, char *b, char *c, int (*cmp) (const void *, const void *)) { return cmp(a, b) < 0 ? (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a)) : (cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c)); } void pg_qsort(void *a, size_t n, size_t es, int (*cmp) (const void *, const void *)) { char *pa, *pb, *pc, *pd, *pl, *pm, *pn; size_t d1, d2; int r, swaptype, presorted; loop:SWAPINIT(a, es); if (n < 7) { for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es) for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0; pl -= es) swap(pl, pl - es); return; } presorted = 1; for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es) { if (cmp(pm - es, pm) > 0) { presorted = 0; break; } } if (presorted) return; pm = (char *) a + (n / 2) * es; if (n > 7) { pl = (char *) a; pn = (char *) a + (n - 1) * es; if (n > 40) { size_t d = (n / 8) * es; pl = med3(pl, pl + d, pl + 2 * d, cmp); pm = med3(pm - d, pm, pm + d, cmp); pn = med3(pn - 2 * d, pn - d, pn, cmp); } pm = med3(pl, pm, pn, cmp); } swap(a, pm); pa = pb = (char *) a + es; pc = pd = (char *) a + (n - 1) * es; for (;;) { while (pb <= pc && (r = cmp(pb, a)) <= 0) { if (r == 0) { swap(pa, pb); pa += es; } pb += es; } while (pb <= pc && (r = cmp(pc, a)) >= 0) { if (r == 0) { swap(pc, pd); pd -= es; } pc -= es; } if (pb > pc) break; swap(pb, pc); pb += es; pc -= es; } pn = (char *) a + n * es; d1 = Min(pa - (char *) a, pb - pa); vecswap(a, pb - d1, d1); d1 = Min(pd - pc, pn - pd - es); vecswap(pb, pn - d1, d1); d1 = pb - pa; d2 = pd - pc; if (d1 <= d2) { /* Recurse on left partition, then iterate on right partition */ if (d1 > es) pg_qsort(a, d1 / es, es, cmp); if (d2 > es) { /* Iterate rather than recurse to save stack space */ /* pg_qsort(pn - d2, d2 / es, es, cmp); */ a = pn - d2; n = d2 / es; goto loop; } } else { /* Recurse on right partition, then iterate on left partition */ if (d2 > es) pg_qsort(pn - d2, d2 / es, es, cmp); if (d1 > es) { /* Iterate rather than recurse to save stack space */ /* pg_qsort(a, d1 / es, es, cmp); */ n = d1 / es; goto loop; } } } /* * qsort comparator wrapper for strcmp. */