1 /* $NetBSD: merge.c,v 1.14 2012/03/13 21:13:48 christos 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 1.14 2012/03/13 21:13:48 christos 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 #endif
69
70 static void setup(u_char *, u_char *, size_t, size_t,
71 int (*)(const void *, const void *));
72 static void insertionsort(u_char *, size_t, size_t,
73 int (*)(const void *, const void *));
74
75 #define ISIZE sizeof(int)
76 #define PSIZE sizeof(u_char *)
77 #define ICOPY_LIST(src, dst, last) \
78 do \
79 *(int*)(void *)dst = *(int*)(void *)src, \
80 src += ISIZE, dst += ISIZE; \
81 while(src < last)
82 #define ICOPY_ELT(src, dst, i) \
83 do \
84 *(int*)(void *)dst = *(int*)(void *)src, \
85 src += ISIZE, dst += ISIZE; \
86 while (i -= ISIZE)
87
88 #define CCOPY_LIST(src, dst, last) \
89 do \
90 *dst++ = *src++; \
91 while (src < last)
92 #define CCOPY_ELT(src, dst, i) \
93 do \
94 *dst++ = *src++; \
95 while (i -= 1)
96
97 /*
98 * Find the next possible pointer head. (Trickery for forcing an array
99 * to do double duty as a linked list when objects do not align with word
100 * boundaries.
101 */
102 /* Assumption: PSIZE is a power of 2. */
103 #define EVAL(p) ((u_char **)(void *) \
104 ((u_char *)0 + \
105 (((u_char *)(void *)(p) + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1))))
106
107 /*
108 * Arguments are as for qsort.
109 */
110 int
mergesort(void * base,size_t nmemb,size_t size,int (* cmp)(const void *,const void *))111 mergesort(void *base, size_t nmemb, size_t size,
112 int (*cmp)(const void *, const void *))
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 /*
129 * XXX
130 * Stupid subtraction for the Cray.
131 */
132 iflag = 0;
133 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
134 iflag = 1;
135
136 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
137 return (-1);
138
139 list1 = base;
140 setup(list1, list2, nmemb, size, cmp);
141 last = list2 + nmemb * size;
142 i = big = 0;
143 while (*EVAL(list2) != last) {
144 l2 = list1;
145 p1 = EVAL(list1);
146 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
147 p2 = *EVAL(p2);
148 f1 = l2;
149 f2 = l1 = list1 + (p2 - list2);
150 if (p2 != last)
151 p2 = *EVAL(p2);
152 l2 = list1 + (p2 - list2);
153 while (f1 < l1 && f2 < l2) {
154 if ((*cmp)(f1, f2) <= 0) {
155 q = f2;
156 b = f1, t = l1;
157 sense = -1;
158 } else {
159 q = f1;
160 b = f2, t = l2;
161 sense = 0;
162 }
163 if (!big) { /* here i = 0 */
164 #if 0
165 LINEAR:
166 #endif
167 while ((b += size) < t && cmp(q, b) >sense)
168 if (++i == 6) {
169 big = 1;
170 goto EXPONENTIAL;
171 }
172 } else {
173 EXPONENTIAL: for (i = size; ; i <<= 1)
174 if ((p = (b + i)) >= t) {
175 if ((p = t - size) > b &&
176 (*cmp)(q, p) <= sense)
177 t = p;
178 else
179 b = p;
180 break;
181 } else if ((*cmp)(q, p) <= sense) {
182 t = p;
183 if (i == size)
184 big = 0;
185 goto FASTCASE;
186 } else
187 b = p;
188 #if 0
189 SLOWCASE:
190 #endif
191 while (t > b+size) {
192 i = (((t - b) / size) >> 1) * size;
193 if ((*cmp)(q, p = b + i) <= sense)
194 t = p;
195 else
196 b = p;
197 }
198 goto COPY;
199 FASTCASE: while (i > size)
200 if ((*cmp)(q,
201 p = b +
202 (i = (unsigned int) i >> 1)) <= sense)
203 t = p;
204 else
205 b = p;
206 COPY: b = t;
207 }
208 i = size;
209 if (q == f1) {
210 if (iflag) {
211 ICOPY_LIST(f2, tp2, b);
212 ICOPY_ELT(f1, tp2, i);
213 } else {
214 CCOPY_LIST(f2, tp2, b);
215 CCOPY_ELT(f1, tp2, i);
216 }
217 } else {
218 if (iflag) {
219 ICOPY_LIST(f1, tp2, b);
220 ICOPY_ELT(f2, tp2, i);
221 } else {
222 CCOPY_LIST(f1, tp2, b);
223 CCOPY_ELT(f2, tp2, i);
224 }
225 }
226 }
227 if (f2 < l2) {
228 if (iflag)
229 ICOPY_LIST(f2, tp2, l2);
230 else
231 CCOPY_LIST(f2, tp2, l2);
232 } else if (f1 < l1) {
233 if (iflag)
234 ICOPY_LIST(f1, tp2, l1);
235 else
236 CCOPY_LIST(f1, tp2, l1);
237 }
238 *p1 = l2;
239 }
240 tp2 = list1; /* swap list1, list2 */
241 list1 = list2;
242 list2 = tp2;
243 last = list2 + nmemb*size;
244 }
245 if (base == list2) {
246 memmove(list2, list1, nmemb*size);
247 list2 = list1;
248 }
249 free(list2);
250 return (0);
251 }
252
253 #define swap(a, b) { \
254 s = b; \
255 i = size; \
256 do { \
257 tmp = *a; *a++ = *s; *s++ = tmp; \
258 } while (--i); \
259 a -= size; \
260 }
261 #define reverse(bot, top) { \
262 s = top; \
263 do { \
264 i = size; \
265 do { \
266 tmp = *bot; *bot++ = *s; *s++ = tmp; \
267 } while (--i); \
268 s -= size2; \
269 } while(bot < s); \
270 }
271
272 /*
273 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of
274 * increasing order, list2 in a corresponding linked list. Checks for runs
275 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL
276 * is defined. Otherwise simple pairwise merging is used.)
277 */
278
279 /* XXX: shouldn't this function be static? - lukem 990810 */
280 void
setup(u_char * list1,u_char * list2,size_t n,size_t size,int (* cmp)(const void *,const void *))281 setup(u_char *list1, u_char *list2, size_t n, size_t size,
282 int (*cmp)(const void *, const void *))
283 {
284 int length, tmp, sense;
285 u_char *f1, *f2, *s, *l2, *last, *p2;
286 size_t size2, i;
287
288 _DIAGASSERT(cmp != NULL);
289 _DIAGASSERT(list1 != NULL);
290 _DIAGASSERT(list2 != NULL);
291
292 size2 = size*2;
293 if (n <= 5) {
294 insertionsort(list1, n, size, cmp);
295 *EVAL(list2) = list2 + n*size;
296 return;
297 }
298 /*
299 * Avoid running pointers out of bounds; limit n to evens
300 * for simplicity.
301 */
302 i = 4 + (n & 1);
303 insertionsort(list1 + (n - i) * size, i, size, cmp);
304 last = list1 + size * (n - i);
305 *EVAL(list2 + (last - list1)) = list2 + n * size;
306
307 #ifdef NATURAL
308 p2 = list2;
309 f1 = list1;
310 sense = (cmp(f1, f1 + size) > 0);
311 for (; f1 < last; sense = !sense) {
312 length = 2;
313 /* Find pairs with same sense. */
314 for (f2 = f1 + size2; f2 < last; f2 += size2) {
315 if ((cmp(f2, f2+ size) > 0) != sense)
316 break;
317 length += 2;
318 }
319 if (length < THRESHOLD) { /* Pairwise merge */
320 do {
321 p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
322 if (sense > 0)
323 swap (f1, f1 + size);
324 } while ((f1 += size2) < f2);
325 } else { /* Natural merge */
326 l2 = f2;
327 for (f2 = f1 + size2; f2 < l2; f2 += size2) {
328 if ((cmp(f2-size, f2) > 0) != sense) {
329 p2 = *EVAL(p2) = f2 - list1 + list2;
330 if (sense > 0)
331 reverse(f1, f2 - size);
332 f1 = f2;
333 }
334 }
335 if (sense > 0)
336 reverse(f1, f2 - size);
337 f1 = f2;
338 if (f2 < last || cmp(f2 - size, f2) > 0)
339 p2 = *EVAL(p2) = f2 - list1 + list2;
340 else
341 p2 = *EVAL(p2) = list2 + n*size;
342 }
343 }
344 #else /* pairwise merge only. */
345 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
346 p2 = *EVAL(p2) = p2 + size2;
347 if (cmp (f1, f1 + size) > 0)
348 swap(f1, f1 + size);
349 }
350 #endif /* NATURAL */
351 }
352
353 /*
354 * This is to avoid out-of-bounds addresses in sorting the
355 * last 4 elements.
356 */
357 static void
insertionsort(u_char * a,size_t n,size_t size,int (* cmp)(const void *,const void *))358 insertionsort(u_char *a, size_t n, size_t size,
359 int (*cmp)(const void *, const void *))
360 {
361 u_char *ai, *s, *t, *u, tmp;
362 size_t i;
363
364 _DIAGASSERT(a != NULL);
365 _DIAGASSERT(cmp != NULL);
366
367 for (ai = a+size; --n >= 1; ai += size)
368 for (t = ai; t > a; t -= size) {
369 u = t - size;
370 if (cmp(u, t) <= 0)
371 break;
372 swap(u, t);
373 }
374 }
375