1 /* $OpenBSD: merge.c,v 1.8 2005/08/08 08:05:37 espie 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 *, u_char *, size_t, size_t,
55 int (*)(const void *, const void *));
56 static void insertionsort(u_char *, size_t, size_t,
57 int (*)(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 /*
107 * XXX
108 * Stupid subtraction for the Cray.
109 */
110 iflag = 0;
111 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
112 iflag = 1;
113
114 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
115 return (-1);
116
117 list1 = base;
118 setup(list1, list2, nmemb, size, cmp);
119 last = list2 + nmemb * size;
120 i = big = 0;
121 while (*EVAL(list2) != last) {
122 l2 = list1;
123 p1 = EVAL(list1);
124 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
125 p2 = *EVAL(p2);
126 f1 = l2;
127 f2 = l1 = list1 + (p2 - list2);
128 if (p2 != last)
129 p2 = *EVAL(p2);
130 l2 = list1 + (p2 - list2);
131 while (f1 < l1 && f2 < l2) {
132 if ((*cmp)(f1, f2) <= 0) {
133 q = f2;
134 b = f1, t = l1;
135 sense = -1;
136 } else {
137 q = f1;
138 b = f2, t = l2;
139 sense = 0;
140 }
141 if (!big) { /* here i = 0 */
142 while ((b += size) < t && cmp(q, b) >sense)
143 if (++i == 6) {
144 big = 1;
145 goto EXPONENTIAL;
146 }
147 } else {
148 EXPONENTIAL: for (i = size; ; i <<= 1)
149 if ((p = (b + i)) >= t) {
150 if ((p = t - size) > b &&
151 (*cmp)(q, p) <= sense)
152 t = p;
153 else
154 b = p;
155 break;
156 } else if ((*cmp)(q, p) <= sense) {
157 t = p;
158 if ((size_t)i == size)
159 big = 0;
160 goto FASTCASE;
161 } else
162 b = p;
163 while (t > b+size) {
164 i = (((t - b) / size) >> 1) * size;
165 if ((*cmp)(q, p = b + i) <= sense)
166 t = p;
167 else
168 b = p;
169 }
170 goto COPY;
171 FASTCASE: while ((size_t)i > size)
172 if ((*cmp)(q,
173 p = b + (i >>= 1)) <= sense)
174 t = p;
175 else
176 b = p;
177 COPY: b = t;
178 }
179 i = size;
180 if (q == f1) {
181 if (iflag) {
182 ICOPY_LIST(f2, tp2, b);
183 ICOPY_ELT(f1, tp2, i);
184 } else {
185 CCOPY_LIST(f2, tp2, b);
186 CCOPY_ELT(f1, tp2, i);
187 }
188 } else {
189 if (iflag) {
190 ICOPY_LIST(f1, tp2, b);
191 ICOPY_ELT(f2, tp2, i);
192 } else {
193 CCOPY_LIST(f1, tp2, b);
194 CCOPY_ELT(f2, tp2, i);
195 }
196 }
197 }
198 if (f2 < l2) {
199 if (iflag)
200 ICOPY_LIST(f2, tp2, l2);
201 else
202 CCOPY_LIST(f2, tp2, l2);
203 } else if (f1 < l1) {
204 if (iflag)
205 ICOPY_LIST(f1, tp2, l1);
206 else
207 CCOPY_LIST(f1, tp2, l1);
208 }
209 *p1 = l2;
210 }
211 tp2 = list1; /* swap list1, list2 */
212 list1 = list2;
213 list2 = tp2;
214 last = list2 + nmemb*size;
215 }
216 if (base == list2) {
217 memmove(list2, list1, nmemb*size);
218 list2 = list1;
219 }
220 free(list2);
221 return (0);
222 }
223
224 #define swap(a, b) { \
225 s = b; \
226 i = size; \
227 do { \
228 tmp = *a; *a++ = *s; *s++ = tmp; \
229 } while (--i); \
230 a -= size; \
231 }
232 #define reverse(bot, top) { \
233 s = top; \
234 do { \
235 i = size; \
236 do { \
237 tmp = *bot; *bot++ = *s; *s++ = tmp; \
238 } while (--i); \
239 s -= size2; \
240 } while(bot < s); \
241 }
242
243 /*
244 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of
245 * increasing order, list2 in a corresponding linked list. Checks for runs
246 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL
247 * is defined. Otherwise simple pairwise merging is used.)
248 */
249 void
setup(u_char * list1,u_char * list2,size_t n,size_t size,int (* cmp)(const void *,const void *))250 setup(u_char *list1, u_char *list2, size_t n, size_t size,
251 int (*cmp)(const void *, const void *))
252 {
253 int i, length, size2, tmp, sense;
254 u_char *f1, *f2, *s, *l2, *last, *p2;
255
256 size2 = size*2;
257 if (n <= 5) {
258 insertionsort(list1, n, size, cmp);
259 *EVAL(list2) = (u_char*) list2 + n*size;
260 return;
261 }
262 /*
263 * Avoid running pointers out of bounds; limit n to evens
264 * for simplicity.
265 */
266 i = 4 + (n & 1);
267 insertionsort(list1 + (n - i) * size, i, size, cmp);
268 last = list1 + size * (n - i);
269 *EVAL(list2 + (last - list1)) = list2 + n * size;
270
271 #ifdef NATURAL
272 p2 = list2;
273 f1 = list1;
274 sense = (cmp(f1, f1 + size) > 0);
275 for (; f1 < last; sense = !sense) {
276 length = 2;
277 /* Find pairs with same sense. */
278 for (f2 = f1 + size2; f2 < last; f2 += size2) {
279 if ((cmp(f2, f2+ size) > 0) != sense)
280 break;
281 length += 2;
282 }
283 if (length < THRESHOLD) { /* Pairwise merge */
284 do {
285 p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
286 if (sense > 0)
287 swap (f1, f1 + size);
288 } while ((f1 += size2) < f2);
289 } else { /* Natural merge */
290 l2 = f2;
291 for (f2 = f1 + size2; f2 < l2; f2 += size2) {
292 if ((cmp(f2-size, f2) > 0) != sense) {
293 p2 = *EVAL(p2) = f2 - list1 + list2;
294 if (sense > 0)
295 reverse(f1, f2-size);
296 f1 = f2;
297 }
298 }
299 if (sense > 0)
300 reverse (f1, f2-size);
301 f1 = f2;
302 if (f2 < last || cmp(f2 - size, f2) > 0)
303 p2 = *EVAL(p2) = f2 - list1 + list2;
304 else
305 p2 = *EVAL(p2) = list2 + n*size;
306 }
307 }
308 #else /* pairwise merge only. */
309 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
310 p2 = *EVAL(p2) = p2 + size2;
311 if (cmp (f1, f1 + size) > 0)
312 swap(f1, f1 + size);
313 }
314 #endif /* NATURAL */
315 }
316
317 /*
318 * This is to avoid out-of-bounds addresses in sorting the
319 * last 4 elements.
320 */
321 static void
insertionsort(u_char * a,size_t n,size_t size,int (* cmp)(const void *,const void *))322 insertionsort(u_char *a, size_t n, size_t size,
323 int (*cmp)(const void *, const void *))
324 {
325 u_char *ai, *s, *t, *u, tmp;
326 int i;
327
328 for (ai = a+size; --n >= 1; ai += size)
329 for (t = ai; t > a; t -= size) {
330 u = t - size;
331 if (cmp(u, t) <= 0)
332 break;
333 swap(u, t);
334 }
335 }
336