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d861d2787b
OpenBSD's qsort() function is more secure than the ones used by FreeBSD, NetBSD and MacOS. The best part is it goes faster too! This change also imports the OpenBSD mergesort() and heapsort()
292 lines
9.2 KiB
C
292 lines
9.2 KiB
C
/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8 -*-│
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│vi: set et ft=c ts=8 tw=8 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright (c) 1991, 1993 │
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│ The Regents of the University of California. All rights reserved. │
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│ │
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│ Redistribution and use in source and binary forms, with or without │
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│ modification, are permitted provided that the following conditions │
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│ are met: │
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│ 1. Redistributions of source code must retain the above copyright │
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│ notice, this list of conditions and the following disclaimer. │
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│ 2. Redistributions in binary form must reproduce the above copyright │
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│ notice, this list of conditions and the following disclaimer in the │
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│ documentation and/or other materials provided with the distribution. │
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│ 3. Neither the name of the University nor the names of its contributors │
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│ may be used to endorse or promote products derived from this software │
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│ without specific prior written permission. │
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│ │
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│ THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND │
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│ ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE │
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│ IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE │
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│ ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE │
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│ FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL │
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│ DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS │
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│ OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) │
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│ HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT │
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│ LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY │
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│ OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF │
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│ SUCH DAMAGE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/macros.internal.h"
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#include "libc/mem/alg.h"
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#include "libc/str/str.h"
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// clang-format off
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asm(".ident\t\"\\n\\n\
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OpenBSD Sorting (BSD-3)\\n\
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Copyright 1993 The Regents of the University of California\"");
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asm(".include \"libc/disclaimer.inc\"");
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#define CMPPAR int (*cmp)(const void *, const void *, void *),void *arg
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#define CMPARG cmp, arg
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#define CMP(a, b) cmp(a, b, arg)
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#define min(a, b) (a) < (b) ? a : b
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static inline char *med3(char *, char *, char *, CMPPAR);
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static inline void swapfunc(char *, char *, size_t, int);
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/*
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* Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
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*
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* This version differs from Bentley & McIlroy in the following ways:
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* 1. The partition value is swapped into a[0] instead of being
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* stored out of line.
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*
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* 2. The swap function can swap 32-bit aligned elements on 64-bit
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* platforms instead of swapping them as byte-aligned.
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*
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* 3. It uses David Musser's introsort algorithm to fall back to
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* heapsort(3) when the recursion depth reaches 2*lg(n + 1).
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* This avoids quicksort's quadratic behavior for pathological
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* input without appreciably changing the average run time.
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*
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* 4. Tail recursion is eliminated when sorting the larger of two
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* subpartitions to save stack space.
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*/
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#define SWAPTYPE_BYTEV 1
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#define SWAPTYPE_INTV 2
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#define SWAPTYPE_LONGV 3
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#define SWAPTYPE_INT 4
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#define SWAPTYPE_LONG 5
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#define TYPE_ALIGNED(TYPE, a, es) \
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(((char *)a - (char *)0) % sizeof(TYPE) == 0 && es % sizeof(TYPE) == 0)
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#define swapcode(TYPE, parmi, parmj, n) { \
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size_t i = (n) / sizeof (TYPE); \
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TYPE *pi = (TYPE *) (parmi); \
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TYPE *pj = (TYPE *) (parmj); \
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do { \
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TYPE t = *pi; \
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*pi++ = *pj; \
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*pj++ = t; \
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} while (--i > 0); \
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}
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static inline void
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swapfunc(char *a, char *b, size_t n, int swaptype)
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{
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switch (swaptype) {
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case SWAPTYPE_INT:
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case SWAPTYPE_INTV:
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swapcode(int, a, b, n);
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break;
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case SWAPTYPE_LONG:
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case SWAPTYPE_LONGV:
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swapcode(long, a, b, n);
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break;
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default:
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swapcode(char, a, b, n);
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break;
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}
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}
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#define swap(a, b) do { \
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switch (swaptype) { \
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case SWAPTYPE_INT: { \
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int t = *(int *)(a); \
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*(int *)(a) = *(int *)(b); \
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*(int *)(b) = t; \
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break; \
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} \
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case SWAPTYPE_LONG: { \
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long t = *(long *)(a); \
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*(long *)(a) = *(long *)(b); \
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*(long *)(b) = t; \
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break; \
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} \
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default: \
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swapfunc(a, b, es, swaptype); \
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} \
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} while (0)
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#define vecswap(a, b, n) if ((n) > 0) swapfunc(a, b, n, swaptype)
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static inline char *
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med3(char *a, char *b, char *c, CMPPAR)
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{
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return CMP(a, b) < 0 ?
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(CMP(b, c) < 0 ? b : (CMP(a, c) < 0 ? c : a ))
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:(CMP(b, c) > 0 ? b : (CMP(a, c) < 0 ? a : c ));
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}
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static void
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introsort(char *a, size_t n, size_t es, size_t maxdepth, int swaptype, CMPPAR)
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{
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char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
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int cmp_result;
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size_t r, s;
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loop: if (n < 7) {
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for (pm = a + es; pm < a + n * es; pm += es)
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for (pl = pm; pl > a && CMP(pl - es, pl) > 0;
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pl -= es)
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swap(pl, pl - es);
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return;
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}
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if (maxdepth == 0) {
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if (heapsort_r(a, n, es, CMPARG) == 0)
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return;
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}
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maxdepth--;
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pm = a + (n / 2) * es;
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if (n > 7) {
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pl = a;
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pn = a + (n - 1) * es;
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if (n > 40) {
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s = (n / 8) * es;
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pl = med3(pl, pl + s, pl + 2 * s, CMPARG);
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pm = med3(pm - s, pm, pm + s, CMPARG);
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pn = med3(pn - 2 * s, pn - s, pn, CMPARG);
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}
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pm = med3(pl, pm, pn, CMPARG);
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}
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swap(a, pm);
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pa = pb = a + es;
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pc = pd = a + (n - 1) * es;
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for (;;) {
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while (pb <= pc && (cmp_result = CMP(pb, a)) <= 0) {
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if (cmp_result == 0) {
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swap(pa, pb);
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pa += es;
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}
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pb += es;
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}
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while (pb <= pc && (cmp_result = CMP(pc, a)) >= 0) {
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if (cmp_result == 0) {
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swap(pc, pd);
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pd -= es;
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}
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pc -= es;
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}
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if (pb > pc)
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break;
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swap(pb, pc);
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pb += es;
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pc -= es;
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}
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pn = a + n * es;
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r = min(pa - a, pb - pa);
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vecswap(a, pb - r, r);
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r = min(pd - pc, pn - pd - es);
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vecswap(pb, pn - r, r);
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/*
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* To save stack space we sort the smaller side of the partition first
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* using recursion and eliminate tail recursion for the larger side.
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*/
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r = pb - pa;
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s = pd - pc;
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if (r < s) {
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/* Recurse for 1st side, iterate for 2nd side. */
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if (s > es) {
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if (r > es) {
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introsort(a, r / es, es, maxdepth,
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swaptype, CMPARG);
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}
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a = pn - s;
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n = s / es;
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goto loop;
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}
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} else {
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/* Recurse for 2nd side, iterate for 1st side. */
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if (r > es) {
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if (s > es) {
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introsort(pn - s, s / es, es, maxdepth,
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swaptype, CMPARG);
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}
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n = r / es;
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goto loop;
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}
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}
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}
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/**
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* Sorts array w/ optional callback parameter.
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*
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* @param a is base of array
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* @param n is item count
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* @param es is item width
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* @param cmp is a callback returning <0, 0, or >0
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* @param arg is passed to callback
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* @see qsort()
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*/
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void
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qsort_r(void *a, size_t n, size_t es,
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int (*cmp)(const void *, const void *, void *), void *arg)
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{
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size_t i, maxdepth = 0;
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int swaptype;
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/* Approximate 2*ceil(lg(n + 1)) */
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for (i = n; i > 0; i >>= 1)
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maxdepth++;
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maxdepth *= 2;
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if (TYPE_ALIGNED(long, a, es))
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swaptype = es == sizeof(long) ? SWAPTYPE_LONG : SWAPTYPE_LONGV;
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else if (sizeof(int) != sizeof(long) && TYPE_ALIGNED(int, a, es))
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swaptype = es == sizeof(int) ? SWAPTYPE_INT : SWAPTYPE_INTV;
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else
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swaptype = SWAPTYPE_BYTEV;
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introsort(a, n, es, maxdepth, swaptype, CMPARG);
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}
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/**
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* Sorts array.
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*
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* This implementation uses the Quicksort routine from Bentley &
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* McIlroy's "Engineering a Sort Function", 1992, Bell Labs.
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*
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* This version differs from Bentley & McIlroy in the following ways:
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*
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* 1. The partition value is swapped into a[0] instead of being stored
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* out of line.
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*
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* 2. The swap function can swap 32-bit aligned elements on 64-bit
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* platforms instead of swapping them as byte-aligned.
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*
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* 3. It uses David Musser's introsort algorithm to fall back to
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* heapsort(3) when the recursion depth reaches 2*lg(n + 1). This
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* avoids quicksort's quadratic behavior for pathological input
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* without appreciably changing the average run time.
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*
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* 4. Tail recursion is eliminated when sorting the larger of two
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* subpartitions to save stack space.
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*
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* @param a is base of array
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* @param n is item count
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* @param es is item width
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* @param cmp is a callback returning <0, 0, or >0
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* @see mergesort()
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* @see heapsort()
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* @see qsort_r()
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* @see djbsort()
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*/
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void
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qsort(void *a, size_t n, size_t es, int (*cmp)(const void *, const void *))
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{
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qsort_r(a, n, es, (void *)cmp, 0);
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}
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