FreeBSD kernel libkern code
qsort.c
Go to the documentation of this file.
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 <sys/cdefs.h>
33 __FBSDID("$FreeBSD: head/sys/libkern/qsort.c 326023 2017-11-20 19:43:44Z pfg $");
34 
35 #include <sys/param.h>
36 #include <sys/libkern.h>
37 
38 #ifdef I_AM_QSORT_R
39 typedef int cmp_t(void *, const void *, const void *);
40 #else
41 typedef int cmp_t(const void *, const void *);
42 #endif
43 static inline char *med3(char *, char *, char *, cmp_t *, void *);
44 static inline void swapfunc(char *, char *, size_t, int, int);
45 
46 /*
47  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
48  */
49 #define swapcode(TYPE, parmi, parmj, n) { \
50  size_t i = (n) / sizeof (TYPE); \
51  TYPE *pi = (TYPE *) (parmi); \
52  TYPE *pj = (TYPE *) (parmj); \
53  do { \
54  TYPE t = *pi; \
55  *pi++ = *pj; \
56  *pj++ = t; \
57  } while (--i > 0); \
58 }
59 
60 #define SWAPINIT(TYPE, a, es) swaptype_ ## TYPE = \
61  ((char *)a - (char *)0) % sizeof(TYPE) || \
62  es % sizeof(TYPE) ? 2 : es == sizeof(TYPE) ? 0 : 1;
63 
64 static inline void
65 swapfunc(char *a, char *b, size_t n, int swaptype_long, int swaptype_int)
66 {
67  if (swaptype_long <= 1)
68  swapcode(long, a, b, n)
69  else if (swaptype_int <= 1)
70  swapcode(int, a, b, n)
71  else
72  swapcode(char, a, b, n)
73 }
74 
75 #define swap(a, b) \
76  if (swaptype_long == 0) { \
77  long t = *(long *)(a); \
78  *(long *)(a) = *(long *)(b); \
79  *(long *)(b) = t; \
80  } else if (swaptype_int == 0) { \
81  int t = *(int *)(a); \
82  *(int *)(a) = *(int *)(b); \
83  *(int *)(b) = t; \
84  } else \
85  swapfunc(a, b, es, swaptype_long, swaptype_int)
86 
87 #define vecswap(a, b, n) \
88  if ((n) > 0) swapfunc(a, b, n, swaptype_long, swaptype_int)
89 
90 #ifdef I_AM_QSORT_R
91 #define CMP(t, x, y) (cmp((t), (x), (y)))
92 #else
93 #define CMP(t, x, y) (cmp((x), (y)))
94 #endif
95 
96 static inline char *
97 med3(char *a, char *b, char *c, cmp_t *cmp, void *thunk
98 #ifndef I_AM_QSORT_R
99 __unused
100 #endif
101 )
102 {
103  return CMP(thunk, a, b) < 0 ?
104  (CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a ))
105  :(CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c ));
106 }
107 
108 #ifdef I_AM_QSORT_R
109 void
110 qsort_r(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp)
111 #else
112 #define thunk NULL
113 void
114 qsort(void *a, size_t n, size_t es, cmp_t *cmp)
115 #endif
116 {
117  char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
118  size_t d1, d2;
119  int cmp_result;
120  int swaptype_long, swaptype_int, swap_cnt;
121 
122 loop: SWAPINIT(long, a, es);
123  SWAPINIT(int, a, es);
124  swap_cnt = 0;
125  if (n < 7) {
126  for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
127  for (pl = pm;
128  pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
129  pl -= es)
130  swap(pl, pl - es);
131  return;
132  }
133  pm = (char *)a + (n / 2) * es;
134  if (n > 7) {
135  pl = a;
136  pn = (char *)a + (n - 1) * es;
137  if (n > 40) {
138  size_t d = (n / 8) * es;
139 
140  pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk);
141  pm = med3(pm - d, pm, pm + d, cmp, thunk);
142  pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk);
143  }
144  pm = med3(pl, pm, pn, cmp, thunk);
145  }
146  swap(a, pm);
147  pa = pb = (char *)a + es;
148 
149  pc = pd = (char *)a + (n - 1) * es;
150  for (;;) {
151  while (pb <= pc && (cmp_result = CMP(thunk, pb, a)) <= 0) {
152  if (cmp_result == 0) {
153  swap_cnt = 1;
154  swap(pa, pb);
155  pa += es;
156  }
157  pb += es;
158  }
159  while (pb <= pc && (cmp_result = CMP(thunk, pc, a)) >= 0) {
160  if (cmp_result == 0) {
161  swap_cnt = 1;
162  swap(pc, pd);
163  pd -= es;
164  }
165  pc -= es;
166  }
167  if (pb > pc)
168  break;
169  swap(pb, pc);
170  swap_cnt = 1;
171  pb += es;
172  pc -= es;
173  }
174  if (swap_cnt == 0) { /* Switch to insertion sort */
175  for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
176  for (pl = pm;
177  pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
178  pl -= es)
179  swap(pl, pl - es);
180  return;
181  }
182 
183  pn = (char *)a + n * es;
184  d1 = MIN(pa - (char *)a, pb - pa);
185  vecswap(a, pb - d1, d1);
186  d1 = MIN(pd - pc, pn - pd - es);
187  vecswap(pb, pn - d1, d1);
188 
189  d1 = pb - pa;
190  d2 = pd - pc;
191  if (d1 <= d2) {
192  /* Recurse on left partition, then iterate on right partition */
193  if (d1 > es) {
194 #ifdef I_AM_QSORT_R
195  qsort_r(a, d1 / es, es, thunk, cmp);
196 #else
197  qsort(a, d1 / es, es, cmp);
198 #endif
199  }
200  if (d2 > es) {
201  /* Iterate rather than recurse to save stack space */
202  /* qsort(pn - d2, d2 / es, es, cmp); */
203  a = pn - d2;
204  n = d2 / es;
205  goto loop;
206  }
207  } else {
208  /* Recurse on right partition, then iterate on left partition */
209  if (d2 > es) {
210 #ifdef I_AM_QSORT_R
211  qsort_r(pn - d2, d2 / es, es, thunk, cmp);
212 #else
213  qsort(pn - d2, d2 / es, es, cmp);
214 #endif
215  }
216  if (d1 > es) {
217  /* Iterate rather than recurse to save stack space */
218  /* qsort(a, d1 / es, es, cmp); */
219  n = d1 / es;
220  goto loop;
221  }
222  }
223 }
#define swap(a, b)
Definition: qsort.c:75
int c
void qsort(void *a, size_t n, size_t es, cmp_t *cmp)
Definition: qsort.c:114
#define I_AM_QSORT_R
Definition: qsort_r.c:7
int cmp_t(const void *, const void *)
Definition: qsort.c:41
#define swapcode(TYPE, parmi, parmj, n)
Definition: qsort.c:49
#define CMP(t, x, y)
Definition: qsort.c:93
__FBSDID("$FreeBSD: head/sys/libkern/qsort.c 326023 2017-11-20 19:43:44Z pfg $")
#define SWAPINIT(TYPE, a, es)
Definition: qsort.c:60
static char * med3(char *, char *, char *, cmp_t *, void *)
#define vecswap(a, b, n)
Definition: qsort.c:87
static void swapfunc(char *, char *, size_t, int, int)
Definition: qsort.c:65
#define thunk
Definition: qsort.c:112