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1/*-
2 * Copyright (c) 1992, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Peter McIlroy.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. All advertising materials mentioning features or use of this software
17 * must display the following acknowledgement:
18 * This product includes software developed by the University of
19 * California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37#if defined(LIBC_SCCS) && !defined(lint)
38static char *rcsid = "$OpenBSD: merge.c,v 1.5 2002/02/17 19:42:24 millert Exp $";
39#endif /* LIBC_SCCS and not lint */
40
41/*
42 * Hybrid exponential search/linear search merge sort with hybrid
43 * natural/pairwise first pass. Requires about .3% more comparisons
44 * for random data than LSMS with pairwise first pass alone.
45 * It works for objects as small as two bytes.
46 */
47
48#define NATURAL
49#define THRESHOLD 16 /* Best choice for natural merge cut-off. */
50
51/* #define NATURAL to get hybrid natural merge.
52 * (The default is pairwise merging.)
53 */
54
55#include <sys/types.h>
56
57#include <errno.h>
58#include <stdlib.h>
59#include <string.h>
60
61static void setup(u_char *, u_char *, size_t, size_t, int (*)());
62static void insertionsort(u_char *, size_t, size_t, int (*)());
63
64#define ISIZE sizeof(int)
65#define PSIZE sizeof(u_char *)
66#define ICOPY_LIST(src, dst, last) \
67 do \
68 *(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE; \
69 while(src < last)
70#define ICOPY_ELT(src, dst, i) \
71 do \
72 *(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE; \
73 while (i -= ISIZE)
74
75#define CCOPY_LIST(src, dst, last) \
76 do \
77 *dst++ = *src++; \
78 while (src < last)
79#define CCOPY_ELT(src, dst, i) \
80 do \
81 *dst++ = *src++; \
82 while (i -= 1)
83
84/*
85 * Find the next possible pointer head. (Trickery for forcing an array
86 * to do double duty as a linked list when objects do not align with word
87 * boundaries.
88 */
89/* Assumption: PSIZE is a power of 2. */
90#define EVAL(p) (u_char **) \
91 ((u_char *)0 + \
92 (((u_char *)p + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1)))
93
94/*
95 * Arguments are as for qsort.
96 */
97int
98mergesort(base, nmemb, size, cmp)
99 void *base;
100 size_t nmemb;
101 register size_t size;
102 int (*cmp)(const void *, const void *);
103{
104 register int i, sense;
105 int big, iflag;
106 register u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
107 u_char *list2, *list1, *p2, *p, *last, **p1;
108
109 if (size < PSIZE / 2) { /* Pointers must fit into 2 * size. */
110 errno = EINVAL;
111 return (-1);
112 }
113
114 /*
115 * XXX
116 * Stupid subtraction for the Cray.
117 */
118 iflag = 0;
119 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
120 iflag = 1;
121
122 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
123 return (-1);
124
125 list1 = base;
126 setup(list1, list2, nmemb, size, cmp);
127 last = list2 + nmemb * size;
128 i = big = 0;
129 while (*EVAL(list2) != last) {
130 l2 = list1;
131 p1 = EVAL(list1);
132 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
133 p2 = *EVAL(p2);
134 f1 = l2;
135 f2 = l1 = list1 + (p2 - list2);
136 if (p2 != last)
137 p2 = *EVAL(p2);
138 l2 = list1 + (p2 - list2);
139 while (f1 < l1 && f2 < l2) {
140 if ((*cmp)(f1, f2) <= 0) {
141 q = f2;
142 b = f1, t = l1;
143 sense = -1;
144 } else {
145 q = f1;
146 b = f2, t = l2;
147 sense = 0;
148 }
149 if (!big) { /* here i = 0 */
150 while ((b += size) < t && cmp(q, b) >sense)
151 if (++i == 6) {
152 big = 1;
153 goto EXPONENTIAL;
154 }
155 } else {
156EXPONENTIAL: for (i = size; ; i <<= 1)
157 if ((p = (b + i)) >= t) {
158 if ((p = t - size) > b &&
159 (*cmp)(q, p) <= sense)
160 t = p;
161 else
162 b = p;
163 break;
164 } else if ((*cmp)(q, p) <= sense) {
165 t = p;
166 if (i == size)
167 big = 0;
168 goto FASTCASE;
169 } else
170 b = p;
171 while (t > b+size) {
172 i = (((t - b) / size) >> 1) * size;
173 if ((*cmp)(q, p = b + i) <= sense)
174 t = p;
175 else
176 b = p;
177 }
178 goto COPY;
179FASTCASE: while (i > size)
180 if ((*cmp)(q,
181 p = b + (i >>= 1)) <= sense)
182 t = p;
183 else
184 b = p;
185COPY: b = t;
186 }
187 i = size;
188 if (q == f1) {
189 if (iflag) {
190 ICOPY_LIST(f2, tp2, b);
191 ICOPY_ELT(f1, tp2, i);
192 } else {
193 CCOPY_LIST(f2, tp2, b);
194 CCOPY_ELT(f1, tp2, i);
195 }
196 } else {
197 if (iflag) {
198 ICOPY_LIST(f1, tp2, b);
199 ICOPY_ELT(f2, tp2, i);
200 } else {
201 CCOPY_LIST(f1, tp2, b);
202 CCOPY_ELT(f2, tp2, i);
203 }
204 }
205 }
206 if (f2 < l2) {
207 if (iflag)
208 ICOPY_LIST(f2, tp2, l2);
209 else
210 CCOPY_LIST(f2, tp2, l2);
211 } else if (f1 < l1) {
212 if (iflag)
213 ICOPY_LIST(f1, tp2, l1);
214 else
215 CCOPY_LIST(f1, tp2, l1);
216 }
217 *p1 = l2;
218 }
219 tp2 = list1; /* swap list1, list2 */
220 list1 = list2;
221 list2 = tp2;
222 last = list2 + nmemb*size;
223 }
224 if (base == list2) {
225 memmove(list2, list1, nmemb*size);
226 list2 = list1;
227 }
228 free(list2);
229 return (0);
230}
231
232#define swap(a, b) { \
233 s = b; \
234 i = size; \
235 do { \
236 tmp = *a; *a++ = *s; *s++ = tmp; \
237 } while (--i); \
238 a -= size; \
239 }
240#define reverse(bot, top) { \
241 s = top; \
242 do { \
243 i = size; \
244 do { \
245 tmp = *bot; *bot++ = *s; *s++ = tmp; \
246 } while (--i); \
247 s -= size2; \
248 } while(bot < s); \
249}
250
251/*
252 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of
253 * increasing order, list2 in a corresponding linked list. Checks for runs
254 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL
255 * is defined. Otherwise simple pairwise merging is used.)
256 */
257void
258setup(list1, list2, n, size, cmp)
259 size_t n, size;
260 int (*cmp)(const void *, const void *);
261 u_char *list1, *list2;
262{
263 int i, length, size2, tmp, sense;
264 u_char *f1, *f2, *s, *l2, *last, *p2;
265
266 size2 = size*2;
267 if (n <= 5) {
268 insertionsort(list1, n, size, cmp);
269 *EVAL(list2) = (u_char*) list2 + n*size;
270 return;
271 }
272 /*
273 * Avoid running pointers out of bounds; limit n to evens
274 * for simplicity.
275 */
276 i = 4 + (n & 1);
277 insertionsort(list1 + (n - i) * size, i, size, cmp);
278 last = list1 + size * (n - i);
279 *EVAL(list2 + (last - list1)) = list2 + n * size;
280
281#ifdef NATURAL
282 p2 = list2;
283 f1 = list1;
284 sense = (cmp(f1, f1 + size) > 0);
285 for (; f1 < last; sense = !sense) {
286 length = 2;
287 /* Find pairs with same sense. */
288 for (f2 = f1 + size2; f2 < last; f2 += size2) {
289 if ((cmp(f2, f2+ size) > 0) != sense)
290 break;
291 length += 2;
292 }
293 if (length < THRESHOLD) { /* Pairwise merge */
294 do {
295 p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
296 if (sense > 0)
297 swap (f1, f1 + size);
298 } while ((f1 += size2) < f2);
299 } else { /* Natural merge */
300 l2 = f2;
301 for (f2 = f1 + size2; f2 < l2; f2 += size2) {
302 if ((cmp(f2-size, f2) > 0) != sense) {
303 p2 = *EVAL(p2) = f2 - list1 + list2;
304 if (sense > 0)
305 reverse(f1, f2-size);
306 f1 = f2;
307 }
308 }
309 if (sense > 0)
310 reverse (f1, f2-size);
311 f1 = f2;
312 if (f2 < last || cmp(f2 - size, f2) > 0)
313 p2 = *EVAL(p2) = f2 - list1 + list2;
314 else
315 p2 = *EVAL(p2) = list2 + n*size;
316 }
317 }
318#else /* pairwise merge only. */
319 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
320 p2 = *EVAL(p2) = p2 + size2;
321 if (cmp (f1, f1 + size) > 0)
322 swap(f1, f1 + size);
323 }
324#endif /* NATURAL */
325}
326
327/*
328 * This is to avoid out-of-bounds addresses in sorting the
329 * last 4 elements.
330 */
331static void
332insertionsort(a, n, size, cmp)
333 u_char *a;
334 size_t n, size;
335 int (*cmp)(const void *, const void *);
336{
337 u_char *ai, *s, *t, *u, tmp;
338 int i;
339
340 for (ai = a+size; --n >= 1; ai += size)
341 for (t = ai; t > a; t -= size) {
342 u = t - size;
343 if (cmp(u, t) <= 0)
344 break;
345 swap(u, t);
346 }
347}
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