1 /* $OpenBSD: merge.c,v 1.10 2015/06/21 03:20:56 millert Exp $ */
2 /*-
3 * Copyright (c) 1992, 1993
4 * The Regents of the University of California. All rights reserved.
5 *
6 * This code is derived from software contributed to Berkeley by
7 * Peter McIlroy.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 3. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34 /*
35 * Hybrid exponential search/linear search merge sort with hybrid
36 * natural/pairwise first pass. Requires about .3% more comparisons
37 * for random data than LSMS with pairwise first pass alone.
38 * It works for objects as small as two bytes.
39 */
40
41 #define NATURAL
42 #define THRESHOLD 16 /* Best choice for natural merge cut-off. */
43
44 /* #define NATURAL to get hybrid natural merge.
45 * (The default is pairwise merging.)
46 */
47
48 #include <sys/types.h>
49
50 #include <errno.h>
51 #include <stdlib.h>
52 #include <string.h>
53
54 static void setup(u_char *list1, u_char *list2, size_t n, size_t size,
55 int (*cmp)(const void *, const void *));
56 static void insertionsort(u_char *a, size_t n, size_t size,
57 int (*cmp)(const void *, const void *));
58
59 #define ISIZE sizeof(int)
60 #define PSIZE sizeof(u_char *)
61 #define ICOPY_LIST(src, dst, last) \
62 do \
63 *(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE; \
64 while(src < last)
65 #define ICOPY_ELT(src, dst, i) \
66 do \
67 *(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE; \
68 while (i -= ISIZE)
69
70 #define CCOPY_LIST(src, dst, last) \
71 do \
72 *dst++ = *src++; \
73 while (src < last)
74 #define CCOPY_ELT(src, dst, i) \
75 do \
76 *dst++ = *src++; \
77 while (i -= 1)
78
79 /*
80 * Find the next possible pointer head. (Trickery for forcing an array
81 * to do double duty as a linked list when objects do not align with word
82 * boundaries.
83 */
84 /* Assumption: PSIZE is a power of 2. */
85 #define EVAL(p) (u_char **) \
86 ((u_char *)0 + \
87 (((u_char *)p + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1)))
88
89 /*
90 * Arguments are as for qsort.
91 */
92 int
mergesort(void * base,size_t nmemb,size_t size,int (* cmp)(const void *,const void *))93 mergesort(void *base, size_t nmemb, size_t size,
94 int (*cmp)(const void *, const void *))
95 {
96 int i, sense;
97 int big, iflag;
98 u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
99 u_char *list2, *list1, *p2, *p, *last, **p1;
100
101 if (size < PSIZE / 2) { /* Pointers must fit into 2 * size. */
102 errno = EINVAL;
103 return (-1);
104 }
105
106 if (nmemb == 0)
107 return (0);
108
109 /*
110 * XXX
111 * Stupid subtraction for the Cray.
112 */
113 iflag = 0;
114 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
115 iflag = 1;
116
117 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
118 return (-1);
119
120 list1 = base;
121 setup(list1, list2, nmemb, size, cmp);
122 last = list2 + nmemb * size;
123 i = big = 0;
124 while (*EVAL(list2) != last) {
125 l2 = list1;
126 p1 = EVAL(list1);
127 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
128 p2 = *EVAL(p2);
129 f1 = l2;
130 f2 = l1 = list1 + (p2 - list2);
131 if (p2 != last)
132 p2 = *EVAL(p2);
133 l2 = list1 + (p2 - list2);
134 while (f1 < l1 && f2 < l2) {
135 if ((*cmp)(f1, f2) <= 0) {
136 q = f2;
137 b = f1, t = l1;
138 sense = -1;
139 } else {
140 q = f1;
141 b = f2, t = l2;
142 sense = 0;
143 }
144 if (!big) { /* here i = 0 */
145 while ((b += size) < t && cmp(q, b) >sense)
146 if (++i == 6) {
147 big = 1;
148 goto EXPONENTIAL;
149 }
150 } else {
151 EXPONENTIAL: for (i = size; ; i <<= 1)
152 if ((p = (b + i)) >= t) {
153 if ((p = t - size) > b &&
154 (*cmp)(q, p) <= sense)
155 t = p;
156 else
157 b = p;
158 break;
159 } else if ((*cmp)(q, p) <= sense) {
160 t = p;
161 if (i == size)
162 big = 0;
163 goto FASTCASE;
164 } else
165 b = p;
166 while (t > b+size) {
167 i = (((t - b) / size) >> 1) * size;
168 if ((*cmp)(q, p = b + i) <= sense)
169 t = p;
170 else
171 b = p;
172 }
173 goto COPY;
174 FASTCASE: while (i > size)
175 if ((*cmp)(q,
176 p = b + (i >>= 1)) <= sense)
177 t = p;
178 else
179 b = p;
180 COPY: b = t;
181 }
182 i = size;
183 if (q == f1) {
184 if (iflag) {
185 ICOPY_LIST(f2, tp2, b);
186 ICOPY_ELT(f1, tp2, i);
187 } else {
188 CCOPY_LIST(f2, tp2, b);
189 CCOPY_ELT(f1, tp2, i);
190 }
191 } else {
192 if (iflag) {
193 ICOPY_LIST(f1, tp2, b);
194 ICOPY_ELT(f2, tp2, i);
195 } else {
196 CCOPY_LIST(f1, tp2, b);
197 CCOPY_ELT(f2, tp2, i);
198 }
199 }
200 }
201 if (f2 < l2) {
202 if (iflag)
203 ICOPY_LIST(f2, tp2, l2);
204 else
205 CCOPY_LIST(f2, tp2, l2);
206 } else if (f1 < l1) {
207 if (iflag)
208 ICOPY_LIST(f1, tp2, l1);
209 else
210 CCOPY_LIST(f1, tp2, l1);
211 }
212 *p1 = l2;
213 }
214 tp2 = list1; /* swap list1, list2 */
215 list1 = list2;
216 list2 = tp2;
217 last = list2 + nmemb*size;
218 }
219 if (base == list2) {
220 memmove(list2, list1, nmemb*size);
221 list2 = list1;
222 }
223 free(list2);
224 return (0);
225 }
226
227 #define swap(a, b) { \
228 s = b; \
229 i = size; \
230 do { \
231 tmp = *a; *a++ = *s; *s++ = tmp; \
232 } while (--i); \
233 a -= size; \
234 }
235 #define reverse(bot, top) { \
236 s = top; \
237 do { \
238 i = size; \
239 do { \
240 tmp = *bot; *bot++ = *s; *s++ = tmp; \
241 } while (--i); \
242 s -= size2; \
243 } while(bot < s); \
244 }
245
246 /*
247 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of
248 * increasing order, list2 in a corresponding linked list. Checks for runs
249 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL
250 * is defined. Otherwise simple pairwise merging is used.)
251 */
252 void
setup(u_char * list1,u_char * list2,size_t n,size_t size,int (* cmp)(const void *,const void *))253 setup(u_char *list1, u_char *list2, size_t n, size_t size,
254 int (*cmp)(const void *, const void *))
255 {
256 int i, length, size2, sense;
257 u_char tmp, *f1, *f2, *s, *l2, *last, *p2;
258
259 size2 = size*2;
260 if (n <= 5) {
261 insertionsort(list1, n, size, cmp);
262 *EVAL(list2) = (u_char*) list2 + n*size;
263 return;
264 }
265 /*
266 * Avoid running pointers out of bounds; limit n to evens
267 * for simplicity.
268 */
269 i = 4 + (n & 1);
270 insertionsort(list1 + (n - i) * size, i, size, cmp);
271 last = list1 + size * (n - i);
272 *EVAL(list2 + (last - list1)) = list2 + n * size;
273
274 #ifdef NATURAL
275 p2 = list2;
276 f1 = list1;
277 sense = (cmp(f1, f1 + size) > 0);
278 for (; f1 < last; sense = !sense) {
279 length = 2;
280 /* Find pairs with same sense. */
281 for (f2 = f1 + size2; f2 < last; f2 += size2) {
282 if ((cmp(f2, f2+ size) > 0) != sense)
283 break;
284 length += 2;
285 }
286 if (length < THRESHOLD) { /* Pairwise merge */
287 do {
288 p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
289 if (sense > 0)
290 swap (f1, f1 + size);
291 } while ((f1 += size2) < f2);
292 } else { /* Natural merge */
293 l2 = f2;
294 for (f2 = f1 + size2; f2 < l2; f2 += size2) {
295 if ((cmp(f2-size, f2) > 0) != sense) {
296 p2 = *EVAL(p2) = f2 - list1 + list2;
297 if (sense > 0)
298 reverse(f1, f2-size);
299 f1 = f2;
300 }
301 }
302 if (sense > 0)
303 reverse (f1, f2-size);
304 f1 = f2;
305 if (f2 < last || cmp(f2 - size, f2) > 0)
306 p2 = *EVAL(p2) = f2 - list1 + list2;
307 else
308 p2 = *EVAL(p2) = list2 + n*size;
309 }
310 }
311 #else /* pairwise merge only. */
312 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
313 p2 = *EVAL(p2) = p2 + size2;
314 if (cmp (f1, f1 + size) > 0)
315 swap(f1, f1 + size);
316 }
317 #endif /* NATURAL */
318 }
319
320 /*
321 * This is to avoid out-of-bounds addresses in sorting the
322 * last 4 elements.
323 */
324 static void
insertionsort(u_char * a,size_t n,size_t size,int (* cmp)(const void *,const void *))325 insertionsort(u_char *a, size_t n, size_t size,
326 int (*cmp)(const void *, const void *))
327 {
328 u_char *ai, *s, *t, *u, tmp;
329 int i;
330
331 for (ai = a+size; --n >= 1; ai += size)
332 for (t = ai; t > a; t -= size) {
333 u = t - size;
334 if (cmp(u, t) <= 0)
335 break;
336 swap(u, t);
337 }
338 }
339