1 /* $NetBSD: merge.c,v 1.17 2025/03/02 16:35:41 riastradh Exp $ */
2
3 /*-
4 * Copyright (c) 1992, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Peter McIlroy.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 #include <sys/cdefs.h>
36 #if defined(LIBC_SCCS) && !defined(lint)
37 #if 0
38 static char sccsid[] = "from: @(#)merge.c 8.2 (Berkeley) 2/14/94";
39 #else
40 __RCSID("$NetBSD: merge.c,v 1.17 2025/03/02 16:35:41 riastradh Exp $");
41 #endif
42 #endif /* LIBC_SCCS and not lint */
43
44 /*
45 * Hybrid exponential search/linear search merge sort with hybrid
46 * natural/pairwise first pass. Requires about .3% more comparisons
47 * for random data than LSMS with pairwise first pass alone.
48 * It works for objects as small as two bytes.
49 */
50
51 #define NATURAL
52 #define THRESHOLD 16 /* Best choice for natural merge cut-off. */
53
54 /* #define NATURAL to get hybrid natural merge.
55 * (The default is pairwise merging.)
56 */
57
58 #include "namespace.h"
59 #include <sys/types.h>
60
61 #include <assert.h>
62 #include <errno.h>
63 #include <stdlib.h>
64 #include <string.h>
65
66 #ifdef __weak_alias
67 __weak_alias(mergesort,_mergesort)
68 __weak_alias(mergesort_r,_mergesort_r)
69 #endif
70
71 static void setup(u_char *, u_char *, size_t, size_t,
72 int (*)(const void *, const void *, void *), void *);
73 static void insertionsort(u_char *, size_t, size_t,
74 int (*)(const void *, const void *, void *), void *);
75
76 #define ISIZE sizeof(int)
77 #define PSIZE sizeof(u_char *)
78 #define ICOPY_LIST(src, dst, last) \
79 do \
80 *(int*)(void *)dst = *(int*)(void *)src, \
81 src += ISIZE, dst += ISIZE; \
82 while(src < last)
83 #define ICOPY_ELT(src, dst, i) \
84 do \
85 *(int*)(void *)dst = *(int*)(void *)src, \
86 src += ISIZE, dst += ISIZE; \
87 while (i -= ISIZE)
88
89 #define CCOPY_LIST(src, dst, last) \
90 do \
91 *dst++ = *src++; \
92 while (src < last)
93 #define CCOPY_ELT(src, dst, i) \
94 do \
95 *dst++ = *src++; \
96 while (i -= 1)
97
98 /*
99 * Find the next possible pointer head. (Trickery for forcing an array
100 * to do double duty as a linked list when objects do not align with word
101 * boundaries.
102 */
103 /* Assumption: PSIZE is a power of 2. */
104 #define EVAL(p) ((u_char **)(void *) \
105 (((u_char *)(void *)(p) + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1)))
106
107 /*
108 * Arguments are as for qsort.
109 */
110 int
mergesort_r(void * base,size_t nmemb,size_t size,int (* cmp)(const void *,const void *,void *),void * cookie)111 mergesort_r(void *base, size_t nmemb, size_t size,
112 int (*cmp)(const void *, const void *, void *), void *cookie)
113 {
114 size_t i;
115 int sense;
116 int big, iflag;
117 u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
118 u_char *list2, *list1, *p2, *p, *last, **p1;
119
120 _DIAGASSERT(base != NULL);
121 _DIAGASSERT(cmp != NULL);
122
123 if (size < PSIZE / 2) { /* Pointers must fit into 2 * size. */
124 errno = EINVAL;
125 return (-1);
126 }
127
128 if (nmemb == 0)
129 return (0);
130
131 /*
132 * XXX
133 * Stupid subtraction for the Cray.
134 */
135 iflag = 0;
136 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
137 iflag = 1;
138
139 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
140 return (-1);
141
142 list1 = base;
143 setup(list1, list2, nmemb, size, cmp, cookie);
144 last = list2 + nmemb * size;
145 i = big = 0;
146 while (*EVAL(list2) != last) {
147 l2 = list1;
148 p1 = EVAL(list1);
149 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
150 p2 = *EVAL(p2);
151 f1 = l2;
152 f2 = l1 = list1 + (p2 - list2);
153 if (p2 != last)
154 p2 = *EVAL(p2);
155 l2 = list1 + (p2 - list2);
156 while (f1 < l1 && f2 < l2) {
157 if ((*cmp)(f1, f2, cookie) <= 0) {
158 q = f2;
159 b = f1, t = l1;
160 sense = -1;
161 } else {
162 q = f1;
163 b = f2, t = l2;
164 sense = 0;
165 }
166 if (!big) { /* here i = 0 */
167 #if 0
168 LINEAR:
169 #endif
170 while ((b += size) < t &&
171 cmp(q, b, cookie) >sense)
172 if (++i == 6) {
173 big = 1;
174 goto EXPONENTIAL;
175 }
176 } else {
177 EXPONENTIAL: for (i = size; ; i <<= 1)
178 if ((p = (b + i)) >= t) {
179 if ((p = t - size) > b &&
180 ((*cmp)(q, p, cookie) <=
181 sense))
182 t = p;
183 else
184 b = p;
185 break;
186 } else if ((*cmp)(q, p, cookie) <=
187 sense) {
188 t = p;
189 if (i == size)
190 big = 0;
191 goto FASTCASE;
192 } else
193 b = p;
194 #if 0
195 SLOWCASE:
196 #endif
197 while (t > b+size) {
198 i = (((t - b) / size) >> 1) * size;
199 if ((*cmp)(q, p = b + i, cookie) <=
200 sense)
201 t = p;
202 else
203 b = p;
204 }
205 goto COPY;
206 FASTCASE: while (i > size) {
207 i = (unsigned int)i >> 1;
208 p = b + i;
209 if ((*cmp)(q, p, cookie) <= sense)
210 t = p;
211 else
212 b = p;
213 }
214 COPY: b = t;
215 }
216 i = size;
217 if (q == f1) {
218 if (iflag) {
219 ICOPY_LIST(f2, tp2, b);
220 ICOPY_ELT(f1, tp2, i);
221 } else {
222 CCOPY_LIST(f2, tp2, b);
223 CCOPY_ELT(f1, tp2, i);
224 }
225 } else {
226 if (iflag) {
227 ICOPY_LIST(f1, tp2, b);
228 ICOPY_ELT(f2, tp2, i);
229 } else {
230 CCOPY_LIST(f1, tp2, b);
231 CCOPY_ELT(f2, tp2, i);
232 }
233 }
234 }
235 if (f2 < l2) {
236 if (iflag)
237 ICOPY_LIST(f2, tp2, l2);
238 else
239 CCOPY_LIST(f2, tp2, l2);
240 } else if (f1 < l1) {
241 if (iflag)
242 ICOPY_LIST(f1, tp2, l1);
243 else
244 CCOPY_LIST(f1, tp2, l1);
245 }
246 *p1 = l2;
247 }
248 tp2 = list1; /* swap list1, list2 */
249 list1 = list2;
250 list2 = tp2;
251 last = list2 + nmemb*size;
252 }
253 if (base == list2) {
254 memmove(list2, list1, nmemb*size);
255 list2 = list1;
256 }
257 free(list2);
258 return (0);
259 }
260
261 #define swap(a, b) { \
262 s = b; \
263 i = size; \
264 do { \
265 tmp = *a; *a++ = *s; *s++ = tmp; \
266 } while (--i); \
267 a -= size; \
268 }
269 #define reverse(bot, top) { \
270 s = top; \
271 do { \
272 i = size; \
273 do { \
274 tmp = *bot; *bot++ = *s; *s++ = tmp; \
275 } while (--i); \
276 s -= size2; \
277 } while(bot < s); \
278 }
279
280 /*
281 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of
282 * increasing order, list2 in a corresponding linked list. Checks for runs
283 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL
284 * is defined. Otherwise simple pairwise merging is used.)
285 */
286 static void
setup(u_char * list1,u_char * list2,size_t n,size_t size,int (* cmp)(const void *,const void *,void *),void * cookie)287 setup(u_char *list1, u_char *list2, size_t n, size_t size,
288 int (*cmp)(const void *, const void *, void *), void *cookie)
289 {
290 int length, tmp, sense;
291 u_char *f1, *f2, *s, *l2, *last, *p2;
292 size_t size2, i;
293
294 _DIAGASSERT(cmp != NULL);
295 _DIAGASSERT(list1 != NULL);
296 _DIAGASSERT(list2 != NULL);
297
298 size2 = size*2;
299 if (n <= 5) {
300 insertionsort(list1, n, size, cmp, cookie);
301 *EVAL(list2) = list2 + n*size;
302 return;
303 }
304 /*
305 * Avoid running pointers out of bounds; limit n to evens
306 * for simplicity.
307 */
308 i = 4 + (n & 1);
309 insertionsort(list1 + (n - i) * size, i, size, cmp, cookie);
310 last = list1 + size * (n - i);
311 *EVAL(list2 + (last - list1)) = list2 + n * size;
312
313 #ifdef NATURAL
314 p2 = list2;
315 f1 = list1;
316 sense = (cmp(f1, f1 + size, cookie) > 0);
317 for (; f1 < last; sense = !sense) {
318 length = 2;
319 /* Find pairs with same sense. */
320 for (f2 = f1 + size2; f2 < last; f2 += size2) {
321 if ((cmp(f2, f2 + size, cookie) > 0) != sense)
322 break;
323 length += 2;
324 }
325 if (length < THRESHOLD) { /* Pairwise merge */
326 do {
327 p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
328 if (sense > 0)
329 swap (f1, f1 + size);
330 } while ((f1 += size2) < f2);
331 } else { /* Natural merge */
332 l2 = f2;
333 for (f2 = f1 + size2; f2 < l2; f2 += size2) {
334 if ((cmp(f2-size, f2, cookie) > 0) != sense) {
335 p2 = *EVAL(p2) = f2 - list1 + list2;
336 if (sense > 0)
337 reverse(f1, f2 - size);
338 f1 = f2;
339 }
340 }
341 if (sense > 0)
342 reverse(f1, f2 - size);
343 f1 = f2;
344 if (f2 < last || cmp(f2 - size, f2, cookie) > 0)
345 p2 = *EVAL(p2) = f2 - list1 + list2;
346 else
347 p2 = *EVAL(p2) = list2 + n*size;
348 }
349 }
350 #else /* pairwise merge only. */
351 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
352 p2 = *EVAL(p2) = p2 + size2;
353 if (cmp(f1, f1 + size, cookie) > 0)
354 swap(f1, f1 + size);
355 }
356 #endif /* NATURAL */
357 }
358
359 /*
360 * This is to avoid out-of-bounds addresses in sorting the
361 * last 4 elements.
362 */
363 static void
insertionsort(u_char * a,size_t n,size_t size,int (* cmp)(const void *,const void *,void *),void * cookie)364 insertionsort(u_char *a, size_t n, size_t size,
365 int (*cmp)(const void *, const void *, void *), void *cookie)
366 {
367 u_char *ai, *s, *t, *u, tmp;
368 size_t i;
369
370 _DIAGASSERT(a != NULL);
371 _DIAGASSERT(cmp != NULL);
372
373 for (ai = a+size; --n >= 1; ai += size)
374 for (t = ai; t > a; t -= size) {
375 u = t - size;
376 if (cmp(u, t, cookie) <= 0)
377 break;
378 swap(u, t);
379 }
380 }
381
382 static int
cmpnocookie(const void * a,const void * b,void * cookie)383 cmpnocookie(const void *a, const void *b, void *cookie)
384 {
385 int (*cmp)(const void *, const void *) = cookie;
386
387 return cmp(a, b);
388 }
389
390 int
mergesort(void * a,size_t n,size_t es,int (* cmp)(const void *,const void *))391 mergesort(void *a, size_t n, size_t es,
392 int (*cmp)(const void *, const void *))
393 {
394
395 return mergesort_r(a, n, es, cmpnocookie, cmp);
396 }
397