1 /* $NetBSD: merge.c,v 1.16 2018/05/23 21:21:27 joerg 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 1.16 2018/05/23 21:21:27 joerg 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 *)(void *)(p) + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1)))
105
106 /*
107 * Arguments are as for qsort.
108 */
109 int
mergesort(void * base,size_t nmemb,size_t size,int (* cmp)(const void *,const void *))110 mergesort(void *base, size_t nmemb, size_t size,
111 int (*cmp)(const void *, const void *))
112 {
113 size_t i;
114 int sense;
115 int big, iflag;
116 u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
117 u_char *list2, *list1, *p2, *p, *last, **p1;
118
119 _DIAGASSERT(base != NULL);
120 _DIAGASSERT(cmp != NULL);
121
122 if (size < PSIZE / 2) { /* Pointers must fit into 2 * size. */
123 errno = EINVAL;
124 return (-1);
125 }
126
127 if (nmemb == 0)
128 return (0);
129
130 /*
131 * XXX
132 * Stupid subtraction for the Cray.
133 */
134 iflag = 0;
135 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
136 iflag = 1;
137
138 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
139 return (-1);
140
141 list1 = base;
142 setup(list1, list2, nmemb, size, cmp);
143 last = list2 + nmemb * size;
144 i = big = 0;
145 while (*EVAL(list2) != last) {
146 l2 = list1;
147 p1 = EVAL(list1);
148 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
149 p2 = *EVAL(p2);
150 f1 = l2;
151 f2 = l1 = list1 + (p2 - list2);
152 if (p2 != last)
153 p2 = *EVAL(p2);
154 l2 = list1 + (p2 - list2);
155 while (f1 < l1 && f2 < l2) {
156 if ((*cmp)(f1, f2) <= 0) {
157 q = f2;
158 b = f1, t = l1;
159 sense = -1;
160 } else {
161 q = f1;
162 b = f2, t = l2;
163 sense = 0;
164 }
165 if (!big) { /* here i = 0 */
166 #if 0
167 LINEAR:
168 #endif
169 while ((b += size) < t && cmp(q, b) >sense)
170 if (++i == 6) {
171 big = 1;
172 goto EXPONENTIAL;
173 }
174 } else {
175 EXPONENTIAL: for (i = size; ; i <<= 1)
176 if ((p = (b + i)) >= t) {
177 if ((p = t - size) > b &&
178 (*cmp)(q, p) <= sense)
179 t = p;
180 else
181 b = p;
182 break;
183 } else if ((*cmp)(q, p) <= sense) {
184 t = p;
185 if (i == size)
186 big = 0;
187 goto FASTCASE;
188 } else
189 b = p;
190 #if 0
191 SLOWCASE:
192 #endif
193 while (t > b+size) {
194 i = (((t - b) / size) >> 1) * size;
195 if ((*cmp)(q, p = b + i) <= sense)
196 t = p;
197 else
198 b = p;
199 }
200 goto COPY;
201 FASTCASE: while (i > size)
202 if ((*cmp)(q,
203 p = b +
204 (i = (unsigned int) i >> 1)) <= sense)
205 t = p;
206 else
207 b = p;
208 COPY: b = t;
209 }
210 i = size;
211 if (q == f1) {
212 if (iflag) {
213 ICOPY_LIST(f2, tp2, b);
214 ICOPY_ELT(f1, tp2, i);
215 } else {
216 CCOPY_LIST(f2, tp2, b);
217 CCOPY_ELT(f1, tp2, i);
218 }
219 } else {
220 if (iflag) {
221 ICOPY_LIST(f1, tp2, b);
222 ICOPY_ELT(f2, tp2, i);
223 } else {
224 CCOPY_LIST(f1, tp2, b);
225 CCOPY_ELT(f2, tp2, i);
226 }
227 }
228 }
229 if (f2 < l2) {
230 if (iflag)
231 ICOPY_LIST(f2, tp2, l2);
232 else
233 CCOPY_LIST(f2, tp2, l2);
234 } else if (f1 < l1) {
235 if (iflag)
236 ICOPY_LIST(f1, tp2, l1);
237 else
238 CCOPY_LIST(f1, tp2, l1);
239 }
240 *p1 = l2;
241 }
242 tp2 = list1; /* swap list1, list2 */
243 list1 = list2;
244 list2 = tp2;
245 last = list2 + nmemb*size;
246 }
247 if (base == list2) {
248 memmove(list2, list1, nmemb*size);
249 list2 = list1;
250 }
251 free(list2);
252 return (0);
253 }
254
255 #define swap(a, b) { \
256 s = b; \
257 i = size; \
258 do { \
259 tmp = *a; *a++ = *s; *s++ = tmp; \
260 } while (--i); \
261 a -= size; \
262 }
263 #define reverse(bot, top) { \
264 s = top; \
265 do { \
266 i = size; \
267 do { \
268 tmp = *bot; *bot++ = *s; *s++ = tmp; \
269 } while (--i); \
270 s -= size2; \
271 } while(bot < s); \
272 }
273
274 /*
275 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of
276 * increasing order, list2 in a corresponding linked list. Checks for runs
277 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL
278 * is defined. Otherwise simple pairwise merging is used.)
279 */
280
281 /* XXX: shouldn't this function be static? - lukem 990810 */
282 void
setup(u_char * list1,u_char * list2,size_t n,size_t size,int (* cmp)(const void *,const void *))283 setup(u_char *list1, u_char *list2, size_t n, size_t size,
284 int (*cmp)(const void *, const void *))
285 {
286 int length, tmp, sense;
287 u_char *f1, *f2, *s, *l2, *last, *p2;
288 size_t size2, i;
289
290 _DIAGASSERT(cmp != NULL);
291 _DIAGASSERT(list1 != NULL);
292 _DIAGASSERT(list2 != NULL);
293
294 size2 = size*2;
295 if (n <= 5) {
296 insertionsort(list1, n, size, cmp);
297 *EVAL(list2) = list2 + n*size;
298 return;
299 }
300 /*
301 * Avoid running pointers out of bounds; limit n to evens
302 * for simplicity.
303 */
304 i = 4 + (n & 1);
305 insertionsort(list1 + (n - i) * size, i, size, cmp);
306 last = list1 + size * (n - i);
307 *EVAL(list2 + (last - list1)) = list2 + n * size;
308
309 #ifdef NATURAL
310 p2 = list2;
311 f1 = list1;
312 sense = (cmp(f1, f1 + size) > 0);
313 for (; f1 < last; sense = !sense) {
314 length = 2;
315 /* Find pairs with same sense. */
316 for (f2 = f1 + size2; f2 < last; f2 += size2) {
317 if ((cmp(f2, f2+ size) > 0) != sense)
318 break;
319 length += 2;
320 }
321 if (length < THRESHOLD) { /* Pairwise merge */
322 do {
323 p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
324 if (sense > 0)
325 swap (f1, f1 + size);
326 } while ((f1 += size2) < f2);
327 } else { /* Natural merge */
328 l2 = f2;
329 for (f2 = f1 + size2; f2 < l2; f2 += size2) {
330 if ((cmp(f2-size, f2) > 0) != sense) {
331 p2 = *EVAL(p2) = f2 - list1 + list2;
332 if (sense > 0)
333 reverse(f1, f2 - size);
334 f1 = f2;
335 }
336 }
337 if (sense > 0)
338 reverse(f1, f2 - size);
339 f1 = f2;
340 if (f2 < last || cmp(f2 - size, f2) > 0)
341 p2 = *EVAL(p2) = f2 - list1 + list2;
342 else
343 p2 = *EVAL(p2) = list2 + n*size;
344 }
345 }
346 #else /* pairwise merge only. */
347 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
348 p2 = *EVAL(p2) = p2 + size2;
349 if (cmp (f1, f1 + size) > 0)
350 swap(f1, f1 + size);
351 }
352 #endif /* NATURAL */
353 }
354
355 /*
356 * This is to avoid out-of-bounds addresses in sorting the
357 * last 4 elements.
358 */
359 static void
insertionsort(u_char * a,size_t n,size_t size,int (* cmp)(const void *,const void *))360 insertionsort(u_char *a, size_t n, size_t size,
361 int (*cmp)(const void *, const void *))
362 {
363 u_char *ai, *s, *t, *u, tmp;
364 size_t i;
365
366 _DIAGASSERT(a != NULL);
367 _DIAGASSERT(cmp != NULL);
368
369 for (ai = a+size; --n >= 1; ai += size)
370 for (t = ai; t > a; t -= size) {
371 u = t - size;
372 if (cmp(u, t) <= 0)
373 break;
374 swap(u, t);
375 }
376 }
377