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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. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#if defined(LIBC_SCCS) && !defined(lint)
34static char *rcsid = "$OpenBSD: merge.c,v 1.6 2003/06/02 20:18:38 millert Exp $";
35#endif /* LIBC_SCCS and not lint */
36
37/*
38 * Hybrid exponential search/linear search merge sort with hybrid
39 * natural/pairwise first pass. Requires about .3% more comparisons
40 * for random data than LSMS with pairwise first pass alone.
41 * It works for objects as small as two bytes.
42 */
43
44#define NATURAL
45#define THRESHOLD 16 /* Best choice for natural merge cut-off. */
46
47/* #define NATURAL to get hybrid natural merge.
48 * (The default is pairwise merging.)
49 */
50
51#include <sys/types.h>
52
53#include <errno.h>
54#include <stdlib.h>
55#include <string.h>
56
57static void setup(u_char *, u_char *, size_t, size_t, int (*)());
58static void insertionsort(u_char *, size_t, size_t, int (*)());
59
60#define ISIZE sizeof(int)
61#define PSIZE sizeof(u_char *)
62#define ICOPY_LIST(src, dst, last) \
63 do \
64 *(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE; \
65 while(src < last)
66#define ICOPY_ELT(src, dst, i) \
67 do \
68 *(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE; \
69 while (i -= ISIZE)
70
71#define CCOPY_LIST(src, dst, last) \
72 do \
73 *dst++ = *src++; \
74 while (src < last)
75#define CCOPY_ELT(src, dst, i) \
76 do \
77 *dst++ = *src++; \
78 while (i -= 1)
79
80/*
81 * Find the next possible pointer head. (Trickery for forcing an array
82 * to do double duty as a linked list when objects do not align with word
83 * boundaries.
84 */
85/* Assumption: PSIZE is a power of 2. */
86#define EVAL(p) (u_char **) \
87 ((u_char *)0 + \
88 (((u_char *)p + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1)))
89
90/*
91 * Arguments are as for qsort.
92 */
93int
94mergesort(base, nmemb, size, cmp)
95 void *base;
96 size_t nmemb;
97 register size_t size;
98 int (*cmp)(const void *, const void *);
99{
100 register int i, sense;
101 int big, iflag;
102 register u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
103 u_char *list2, *list1, *p2, *p, *last, **p1;
104
105 if (size < PSIZE / 2) { /* Pointers must fit into 2 * size. */
106 errno = EINVAL;
107 return (-1);
108 }
109
110 /*
111 * XXX
112 * Stupid subtraction for the Cray.
113 */
114 iflag = 0;
115 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
116 iflag = 1;
117
118 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
119 return (-1);
120
121 list1 = base;
122 setup(list1, list2, nmemb, size, cmp);
123 last = list2 + nmemb * size;
124 i = big = 0;
125 while (*EVAL(list2) != last) {
126 l2 = list1;
127 p1 = EVAL(list1);
128 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
129 p2 = *EVAL(p2);
130 f1 = l2;
131 f2 = l1 = list1 + (p2 - list2);
132 if (p2 != last)
133 p2 = *EVAL(p2);
134 l2 = list1 + (p2 - list2);
135 while (f1 < l1 && f2 < l2) {
136 if ((*cmp)(f1, f2) <= 0) {
137 q = f2;
138 b = f1, t = l1;
139 sense = -1;
140 } else {
141 q = f1;
142 b = f2, t = l2;
143 sense = 0;
144 }
145 if (!big) { /* here i = 0 */
146 while ((b += size) < t && cmp(q, b) >sense)
147 if (++i == 6) {
148 big = 1;
149 goto EXPONENTIAL;
150 }
151 } else {
152EXPONENTIAL: for (i = size; ; i <<= 1)
153 if ((p = (b + i)) >= t) {
154 if ((p = t - size) > b &&
155 (*cmp)(q, p) <= sense)
156 t = p;
157 else
158 b = p;
159 break;
160 } else if ((*cmp)(q, p) <= sense) {
161 t = p;
162 if (i == size)
163 big = 0;
164 goto FASTCASE;
165 } else
166 b = p;
167 while (t > b+size) {
168 i = (((t - b) / size) >> 1) * size;
169 if ((*cmp)(q, p = b + i) <= sense)
170 t = p;
171 else
172 b = p;
173 }
174 goto COPY;
175FASTCASE: while (i > size)
176 if ((*cmp)(q,
177 p = b + (i >>= 1)) <= sense)
178 t = p;
179 else
180 b = p;
181COPY: b = t;
182 }
183 i = size;
184 if (q == f1) {
185 if (iflag) {
186 ICOPY_LIST(f2, tp2, b);
187 ICOPY_ELT(f1, tp2, i);
188 } else {
189 CCOPY_LIST(f2, tp2, b);
190 CCOPY_ELT(f1, tp2, i);
191 }
192 } else {
193 if (iflag) {
194 ICOPY_LIST(f1, tp2, b);
195 ICOPY_ELT(f2, tp2, i);
196 } else {
197 CCOPY_LIST(f1, tp2, b);
198 CCOPY_ELT(f2, tp2, i);
199 }
200 }
201 }
202 if (f2 < l2) {
203 if (iflag)
204 ICOPY_LIST(f2, tp2, l2);
205 else
206 CCOPY_LIST(f2, tp2, l2);
207 } else if (f1 < l1) {
208 if (iflag)
209 ICOPY_LIST(f1, tp2, l1);
210 else
211 CCOPY_LIST(f1, tp2, l1);
212 }
213 *p1 = l2;
214 }
215 tp2 = list1; /* swap list1, list2 */
216 list1 = list2;
217 list2 = tp2;
218 last = list2 + nmemb*size;
219 }
220 if (base == list2) {
221 memmove(list2, list1, nmemb*size);
222 list2 = list1;
223 }
224 free(list2);
225 return (0);
226}
227
228#define swap(a, b) { \
229 s = b; \
230 i = size; \
231 do { \
232 tmp = *a; *a++ = *s; *s++ = tmp; \
233 } while (--i); \
234 a -= size; \
235 }
236#define reverse(bot, top) { \
237 s = top; \
238 do { \
239 i = size; \
240 do { \
241 tmp = *bot; *bot++ = *s; *s++ = tmp; \
242 } while (--i); \
243 s -= size2; \
244 } while(bot < s); \
245}
246
247/*
248 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of
249 * increasing order, list2 in a corresponding linked list. Checks for runs
250 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL
251 * is defined. Otherwise simple pairwise merging is used.)
252 */
253void
254setup(list1, list2, n, size, cmp)
255 size_t n, size;
256 int (*cmp)(const void *, const void *);
257 u_char *list1, *list2;
258{
259 int i, length, size2, tmp, sense;
260 u_char *f1, *f2, *s, *l2, *last, *p2;
261
262 size2 = size*2;
263 if (n <= 5) {
264 insertionsort(list1, n, size, cmp);
265 *EVAL(list2) = (u_char*) list2 + n*size;
266 return;
267 }
268 /*
269 * Avoid running pointers out of bounds; limit n to evens
270 * for simplicity.
271 */
272 i = 4 + (n & 1);
273 insertionsort(list1 + (n - i) * size, i, size, cmp);
274 last = list1 + size * (n - i);
275 *EVAL(list2 + (last - list1)) = list2 + n * size;
276
277#ifdef NATURAL
278 p2 = list2;
279 f1 = list1;
280 sense = (cmp(f1, f1 + size) > 0);
281 for (; f1 < last; sense = !sense) {
282 length = 2;
283 /* Find pairs with same sense. */
284 for (f2 = f1 + size2; f2 < last; f2 += size2) {
285 if ((cmp(f2, f2+ size) > 0) != sense)
286 break;
287 length += 2;
288 }
289 if (length < THRESHOLD) { /* Pairwise merge */
290 do {
291 p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
292 if (sense > 0)
293 swap (f1, f1 + size);
294 } while ((f1 += size2) < f2);
295 } else { /* Natural merge */
296 l2 = f2;
297 for (f2 = f1 + size2; f2 < l2; f2 += size2) {
298 if ((cmp(f2-size, f2) > 0) != sense) {
299 p2 = *EVAL(p2) = f2 - list1 + list2;
300 if (sense > 0)
301 reverse(f1, f2-size);
302 f1 = f2;
303 }
304 }
305 if (sense > 0)
306 reverse (f1, f2-size);
307 f1 = f2;
308 if (f2 < last || cmp(f2 - size, f2) > 0)
309 p2 = *EVAL(p2) = f2 - list1 + list2;
310 else
311 p2 = *EVAL(p2) = list2 + n*size;
312 }
313 }
314#else /* pairwise merge only. */
315 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
316 p2 = *EVAL(p2) = p2 + size2;
317 if (cmp (f1, f1 + size) > 0)
318 swap(f1, f1 + size);
319 }
320#endif /* NATURAL */
321}
322
323/*
324 * This is to avoid out-of-bounds addresses in sorting the
325 * last 4 elements.
326 */
327static void
328insertionsort(a, n, size, cmp)
329 u_char *a;
330 size_t n, size;
331 int (*cmp)(const void *, const void *);
332{
333 u_char *ai, *s, *t, *u, tmp;
334 int i;
335
336 for (ai = a+size; --n >= 1; ai += size)
337 for (t = ai; t > a; t -= size) {
338 u = t - size;
339 if (cmp(u, t) <= 0)
340 break;
341 swap(u, t);
342 }
343}
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