1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1992, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 *    may be used to endorse or promote products derived from this software
17 *    without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32#include <errno.h>
33#include <stdint.h>
34#include <stdlib.h>
35#include <string.h>
36#include "libc_private.h"
37
38#if defined(I_AM_QSORT_R)
39typedef int		 cmp_t(const void *, const void *, void *);
40#elif defined(I_AM_QSORT_R_COMPAT)
41typedef int		 cmp_t(void *, const void *, const void *);
42#elif defined(I_AM_QSORT_S)
43typedef int		 cmp_t(const void *, const void *, void *);
44#else
45typedef int		 cmp_t(const void *, const void *);
46#endif
47static inline char	*med3(char *, char *, char *, cmp_t *, void *);
48
49#define	MIN(a, b)	((a) < (b) ? a : b)
50
51/*
52 * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
53 */
54
55static inline void
56swapfunc(char *a, char *b, size_t es)
57{
58	char t;
59
60	do {
61		t = *a;
62		*a++ = *b;
63		*b++ = t;
64	} while (--es > 0);
65}
66
67#define	vecswap(a, b, n)				\
68	if ((n) > 0) swapfunc(a, b, n)
69
70#if defined(I_AM_QSORT_R)
71#define	CMP(t, x, y) (cmp((x), (y), (t)))
72#elif defined(I_AM_QSORT_R_COMPAT)
73#define	CMP(t, x, y) (cmp((t), (x), (y)))
74#elif defined(I_AM_QSORT_S)
75#define	CMP(t, x, y) (cmp((x), (y), (t)))
76#else
77#define	CMP(t, x, y) (cmp((x), (y)))
78#endif
79
80static inline char *
81med3(char *a, char *b, char *c, cmp_t *cmp, void *thunk
82#if !defined(I_AM_QSORT_R) && !defined(I_AM_QSORT_R_COMPAT) && !defined(I_AM_QSORT_S)
83__unused
84#endif
85)
86{
87	return CMP(thunk, a, b) < 0 ?
88	       (CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a ))
89	      :(CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c ));
90}
91
92/*
93 * The actual qsort() implementation is static to avoid preemptible calls when
94 * recursing. Also give them different names for improved debugging.
95 */
96#if defined(I_AM_QSORT_R)
97#define local_qsort local_qsort_r
98#elif defined(I_AM_QSORT_R_COMPAT)
99#define local_qsort local_qsort_r_compat
100#elif defined(I_AM_QSORT_S)
101#define local_qsort local_qsort_s
102#endif
103static void
104local_qsort(void *a, size_t n, size_t es, cmp_t *cmp, void *thunk)
105{
106	char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
107	size_t d1, d2;
108	int cmp_result;
109	int swap_cnt;
110
111	/* if there are less than 2 elements, then sorting is not needed */
112	if (__predict_false(n < 2))
113		return;
114loop:
115	swap_cnt = 0;
116	if (n < 7) {
117		for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
118			for (pl = pm;
119			     pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
120			     pl -= es)
121				swapfunc(pl, pl - es, es);
122		return;
123	}
124	pm = (char *)a + (n / 2) * es;
125	if (n > 7) {
126		pl = a;
127		pn = (char *)a + (n - 1) * es;
128		if (n > 40) {
129			size_t d = (n / 8) * es;
130
131			pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk);
132			pm = med3(pm - d, pm, pm + d, cmp, thunk);
133			pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk);
134		}
135		pm = med3(pl, pm, pn, cmp, thunk);
136	}
137	swapfunc(a, pm, es);
138	pa = pb = (char *)a + es;
139
140	pc = pd = (char *)a + (n - 1) * es;
141	for (;;) {
142		while (pb <= pc && (cmp_result = CMP(thunk, pb, a)) <= 0) {
143			if (cmp_result == 0) {
144				swap_cnt = 1;
145				swapfunc(pa, pb, es);
146				pa += es;
147			}
148			pb += es;
149		}
150		while (pb <= pc && (cmp_result = CMP(thunk, pc, a)) >= 0) {
151			if (cmp_result == 0) {
152				swap_cnt = 1;
153				swapfunc(pc, pd, es);
154				pd -= es;
155			}
156			pc -= es;
157		}
158		if (pb > pc)
159			break;
160		swapfunc(pb, pc, es);
161		swap_cnt = 1;
162		pb += es;
163		pc -= es;
164	}
165	if (swap_cnt == 0) {  /* Switch to insertion sort */
166		for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
167			for (pl = pm;
168			     pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
169			     pl -= es)
170				swapfunc(pl, pl - es, es);
171		return;
172	}
173
174	pn = (char *)a + n * es;
175	d1 = MIN(pa - (char *)a, pb - pa);
176	vecswap(a, pb - d1, d1);
177	/*
178	 * Cast es to preserve signedness of right-hand side of MIN()
179	 * expression, to avoid sign ambiguity in the implied comparison.  es
180	 * is safely within [0, SSIZE_MAX].
181	 */
182	d1 = MIN(pd - pc, pn - pd - (ssize_t)es);
183	vecswap(pb, pn - d1, d1);
184
185	d1 = pb - pa;
186	d2 = pd - pc;
187	if (d1 <= d2) {
188		/* Recurse on left partition, then iterate on right partition */
189		if (d1 > es) {
190			local_qsort(a, d1 / es, es, cmp, thunk);
191		}
192		if (d2 > es) {
193			/* Iterate rather than recurse to save stack space */
194			/* qsort(pn - d2, d2 / es, es, cmp); */
195			a = pn - d2;
196			n = d2 / es;
197			goto loop;
198		}
199	} else {
200		/* Recurse on right partition, then iterate on left partition */
201		if (d2 > es) {
202			local_qsort(pn - d2, d2 / es, es, cmp, thunk);
203		}
204		if (d1 > es) {
205			/* Iterate rather than recurse to save stack space */
206			/* qsort(a, d1 / es, es, cmp); */
207			n = d1 / es;
208			goto loop;
209		}
210	}
211}
212
213#if defined(I_AM_QSORT_R)
214void
215(qsort_r)(void *a, size_t n, size_t es, cmp_t *cmp, void *thunk)
216{
217	local_qsort_r(a, n, es, cmp, thunk);
218}
219#elif defined(I_AM_QSORT_R_COMPAT)
220void
221__qsort_r_compat(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp)
222{
223	local_qsort_r_compat(a, n, es, cmp, thunk);
224}
225#elif defined(I_AM_QSORT_S)
226errno_t
227qsort_s(void *a, rsize_t n, rsize_t es, cmp_t *cmp, void *thunk)
228{
229	if (n > RSIZE_MAX) {
230		__throw_constraint_handler_s("qsort_s : n > RSIZE_MAX", EINVAL);
231		return (EINVAL);
232	} else if (es > RSIZE_MAX) {
233		__throw_constraint_handler_s("qsort_s : es > RSIZE_MAX",
234		    EINVAL);
235		return (EINVAL);
236	} else if (n != 0) {
237		if (a == NULL) {
238			__throw_constraint_handler_s("qsort_s : a == NULL",
239			    EINVAL);
240			return (EINVAL);
241		} else if (cmp == NULL) {
242			__throw_constraint_handler_s("qsort_s : cmp == NULL",
243			    EINVAL);
244			return (EINVAL);
245		} else if (es <= 0) {
246			__throw_constraint_handler_s("qsort_s : es <= 0",
247			    EINVAL);
248			return (EINVAL);
249		}
250	}
251
252	local_qsort_s(a, n, es, cmp, thunk);
253	return (0);
254}
255#else
256void
257qsort(void *a, size_t n, size_t es, cmp_t *cmp)
258{
259	local_qsort(a, n, es, cmp, NULL);
260}
261#endif
262