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IABSD.fr/src/lib/libc/stdlib/qsort.c
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- lib/libc/stdlib/qsort.c
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/* $OpenBSD: qsort.c,v 1.18 2017/05/30 14:54:09 millert 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 <sys/types.h> #include <stdlib.h> static __inline char *med3(char *, char *, char *, int (*)(const void *, const void *)); static __inline void swapfunc(char *, char *, size_t, int); #define min(a, b) (a) < (b) ? a : b /* * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function". * * This version differs from Bentley & McIlroy in the following ways: * 1. The partition value is swapped into a[0] instead of being * stored out of line. * * 2. The swap function can swap 32-bit aligned elements on 64-bit * platforms instead of swapping them as byte-aligned. * * 3. It uses David Musser's introsort algorithm to fall back to * heapsort(3) when the recursion depth reaches 2*lg(n + 1). * This avoids quicksort's quadratic behavior for pathological * input without appreciably changing the average run time. * * 4. Tail recursion is eliminated when sorting the larger of two * subpartitions to save stack space. */ #define SWAPTYPE_BYTEV 1 #define SWAPTYPE_INTV 2 #define SWAPTYPE_LONGV 3 #define SWAPTYPE_INT 4 #define SWAPTYPE_LONG 5 #define TYPE_ALIGNED(TYPE, a, es) \ (((char *)a - (char *)0) % sizeof(TYPE) == 0 && es % sizeof(TYPE) == 0) #define swapcode(TYPE, parmi, parmj, n) { \ size_t i = (n) / sizeof (TYPE); \ TYPE *pi = (TYPE *) (parmi); \ TYPE *pj = (TYPE *) (parmj); \ do { \ TYPE t = *pi; \ *pi++ = *pj; \ *pj++ = t; \ } while (--i > 0); \ } static __inline void swapfunc(char *a, char *b, size_t n, int swaptype) { switch (swaptype) { case SWAPTYPE_INT: case SWAPTYPE_INTV: swapcode(int, a, b, n); break; case SWAPTYPE_LONG: case SWAPTYPE_LONGV: swapcode(long, a, b, n); break; default: swapcode(char, a, b, n); break; } } #define swap(a, b) do { \ switch (swaptype) { \ case SWAPTYPE_INT: { \ int t = *(int *)(a); \ *(int *)(a) = *(int *)(b); \ *(int *)(b) = t; \ break; \ } \ case SWAPTYPE_LONG: { \ long t = *(long *)(a); \ *(long *)(a) = *(long *)(b); \ *(long *)(b) = t; \ break; \ } \ default: \ swapfunc(a, b, es, swaptype); \ } \ } while (0) #define vecswap(a, b, n) if ((n) > 0) swapfunc(a, b, n, swaptype) static __inline 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 )); } static void introsort(char *a, size_t n, size_t es, size_t maxdepth, int swaptype, int (*cmp)(const void *, const void *)) { char *pa, *pb, *pc, *pd, *pl, *pm, *pn; int cmp_result; size_t r, s; loop: if (n < 7) { for (pm = a + es; pm < a + n * es; pm += es) for (pl = pm; pl > a && cmp(pl - es, pl) > 0; pl -= es) swap(pl, pl - es); return; } if (maxdepth == 0) { if (heapsort(a, n, es, cmp) == 0) return; } maxdepth--; pm = a + (n / 2) * es; if (n > 7) { pl = a; pn = a + (n - 1) * es; if (n > 40) { s = (n / 8) * es; pl = med3(pl, pl + s, pl + 2 * s, cmp); pm = med3(pm - s, pm, pm + s, cmp); pn = med3(pn - 2 * s, pn - s, pn, cmp); } pm = med3(pl, pm, pn, cmp); } swap(a, pm); pa = pb = a + es; pc = pd = a + (n - 1) * es; for (;;) { while (pb <= pc && (cmp_result = cmp(pb, a)) <= 0) { if (cmp_result == 0) { swap(pa, pb); pa += es; } pb += es; } while (pb <= pc && (cmp_result = cmp(pc, a)) >= 0) { if (cmp_result == 0) { swap(pc, pd); pd -= es; } pc -= es; } if (pb > pc) break; swap(pb, pc); pb += es; pc -= es; } pn = a + n * es; r = min(pa - a, pb - pa); vecswap(a, pb - r, r); r = min(pd - pc, pn - pd - es); vecswap(pb, pn - r, r); /* * To save stack space we sort the smaller side of the partition first * using recursion and eliminate tail recursion for the larger side. */ r = pb - pa; s = pd - pc; if (r < s) { /* Recurse for 1st side, iterate for 2nd side. */ if (s > es) { if (r > es) { introsort(a, r / es, es, maxdepth, swaptype, cmp); } a = pn - s; n = s / es; goto loop; } } else { /* Recurse for 2nd side, iterate for 1st side. */ if (r > es) { if (s > es) { introsort(pn - s, s / es, es, maxdepth, swaptype, cmp); } n = r / es; goto loop; } } } void qsort(void *a, size_t n, size_t es, int (*cmp)(const void *, const void *)) { size_t i, maxdepth = 0; int swaptype; /* Approximate 2*ceil(lg(n + 1)) */ for (i = n; i > 0; i >>= 1) maxdepth++; maxdepth *= 2; if (TYPE_ALIGNED(long, a, es)) swaptype = es == sizeof(long) ? SWAPTYPE_LONG : SWAPTYPE_LONGV; else if (sizeof(int) != sizeof(long) && TYPE_ALIGNED(int, a, es)) swaptype = es == sizeof(int) ? SWAPTYPE_INT : SWAPTYPE_INTV; else swaptype = SWAPTYPE_BYTEV; introsort(a, n, es, maxdepth, swaptype, cmp); } DEF_STRONG(qsort);