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1/* $OpenBSD: merge.c,v 1.9 2011/03/06 00:55:38 deraadt 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
54static void setup(u_char *, u_char *, size_t, size_t, int (*)());
55static void insertionsort(u_char *, size_t, size_t, int (*)());
56
57#define ISIZE sizeof(int)
58#define PSIZE sizeof(u_char *)
59#define ICOPY_LIST(src, dst, last) \
60 do \
61 *(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE; \
62 while(src < last)
63#define ICOPY_ELT(src, dst, i) \
64 do \
65 *(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE; \
66 while (i -= ISIZE)
67
68#define CCOPY_LIST(src, dst, last) \
69 do \
70 *dst++ = *src++; \
71 while (src < last)
72#define CCOPY_ELT(src, dst, i) \
73 do \
74 *dst++ = *src++; \
75 while (i -= 1)
76
77/*
78 * Find the next possible pointer head. (Trickery for forcing an array
79 * to do double duty as a linked list when objects do not align with word
80 * boundaries.
81 */
82/* Assumption: PSIZE is a power of 2. */
83#define EVAL(p) (u_char **) \
84 ((u_char *)0 + \
85 (((u_char *)p + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1)))
86
87/*
88 * Arguments are as for qsort.
89 */
90int
91mergesort(void *base, size_t nmemb, size_t size,
92 int (*cmp)(const void *, const void *))
93{
94 int i, sense;
95 int big, iflag;
96 u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
97 u_char *list2, *list1, *p2, *p, *last, **p1;
98
99 if (size < PSIZE / 2) { /* Pointers must fit into 2 * size. */
100 errno = EINVAL;
101 return (-1);
102 }
103
104 /*
105 * XXX
106 * Stupid subtraction for the Cray.
107 */
108 iflag = 0;
109 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
110 iflag = 1;
111
112 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
113 return (-1);
114
115 list1 = base;
116 setup(list1, list2, nmemb, size, cmp);
117 last = list2 + nmemb * size;
118 i = big = 0;
119 while (*EVAL(list2) != last) {
120 l2 = list1;
121 p1 = EVAL(list1);
122 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
123 p2 = *EVAL(p2);
124 f1 = l2;
125 f2 = l1 = list1 + (p2 - list2);
126 if (p2 != last)
127 p2 = *EVAL(p2);
128 l2 = list1 + (p2 - list2);
129 while (f1 < l1 && f2 < l2) {
130 if ((*cmp)(f1, f2) <= 0) {
131 q = f2;
132 b = f1, t = l1;
133 sense = -1;
134 } else {
135 q = f1;
136 b = f2, t = l2;
137 sense = 0;
138 }
139 if (!big) { /* here i = 0 */
140 while ((b += size) < t && cmp(q, b) >sense)
141 if (++i == 6) {
142 big = 1;
143 goto EXPONENTIAL;
144 }
145 } else {
146EXPONENTIAL: for (i = size; ; i <<= 1)
147 if ((p = (b + i)) >= t) {
148 if ((p = t - size) > b &&
149 (*cmp)(q, p) <= sense)
150 t = p;
151 else
152 b = p;
153 break;
154 } else if ((*cmp)(q, p) <= sense) {
155 t = p;
156 if (i == size)
157 big = 0;
158 goto FASTCASE;
159 } else
160 b = p;
161 while (t > b+size) {
162 i = (((t - b) / size) >> 1) * size;
163 if ((*cmp)(q, p = b + i) <= sense)
164 t = p;
165 else
166 b = p;
167 }
168 goto COPY;
169FASTCASE: while (i > size)
170 if ((*cmp)(q,
171 p = b + (i >>= 1)) <= sense)
172 t = p;
173 else
174 b = p;
175COPY: b = t;
176 }
177 i = size;
178 if (q == f1) {
179 if (iflag) {
180 ICOPY_LIST(f2, tp2, b);
181 ICOPY_ELT(f1, tp2, i);
182 } else {
183 CCOPY_LIST(f2, tp2, b);
184 CCOPY_ELT(f1, tp2, i);
185 }
186 } else {
187 if (iflag) {
188 ICOPY_LIST(f1, tp2, b);
189 ICOPY_ELT(f2, tp2, i);
190 } else {
191 CCOPY_LIST(f1, tp2, b);
192 CCOPY_ELT(f2, tp2, i);
193 }
194 }
195 }
196 if (f2 < l2) {
197 if (iflag)
198 ICOPY_LIST(f2, tp2, l2);
199 else
200 CCOPY_LIST(f2, tp2, l2);
201 } else if (f1 < l1) {
202 if (iflag)
203 ICOPY_LIST(f1, tp2, l1);
204 else
205 CCOPY_LIST(f1, tp2, l1);
206 }
207 *p1 = l2;
208 }
209 tp2 = list1; /* swap list1, list2 */
210 list1 = list2;
211 list2 = tp2;
212 last = list2 + nmemb*size;
213 }
214 if (base == list2) {
215 memmove(list2, list1, nmemb*size);
216 list2 = list1;
217 }
218 free(list2);
219 return (0);
220}
221
222#define swap(a, b) { \
223 s = b; \
224 i = size; \
225 do { \
226 tmp = *a; *a++ = *s; *s++ = tmp; \
227 } while (--i); \
228 a -= size; \
229 }
230#define reverse(bot, top) { \
231 s = top; \
232 do { \
233 i = size; \
234 do { \
235 tmp = *bot; *bot++ = *s; *s++ = tmp; \
236 } while (--i); \
237 s -= size2; \
238 } while(bot < s); \
239}
240
241/*
242 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of
243 * increasing order, list2 in a corresponding linked list. Checks for runs
244 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL
245 * is defined. Otherwise simple pairwise merging is used.)
246 */
247void
248setup(u_char *list1, u_char *list2, size_t n, size_t size,
249 int (*cmp)(const void *, const void *))
250{
251 int i, length, size2, sense;
252 u_char tmp, *f1, *f2, *s, *l2, *last, *p2;
253
254 size2 = size*2;
255 if (n <= 5) {
256 insertionsort(list1, n, size, cmp);
257 *EVAL(list2) = (u_char*) list2 + n*size;
258 return;
259 }
260 /*
261 * Avoid running pointers out of bounds; limit n to evens
262 * for simplicity.
263 */
264 i = 4 + (n & 1);
265 insertionsort(list1 + (n - i) * size, i, size, cmp);
266 last = list1 + size * (n - i);
267 *EVAL(list2 + (last - list1)) = list2 + n * size;
268
269#ifdef NATURAL
270 p2 = list2;
271 f1 = list1;
272 sense = (cmp(f1, f1 + size) > 0);
273 for (; f1 < last; sense = !sense) {
274 length = 2;
275 /* Find pairs with same sense. */
276 for (f2 = f1 + size2; f2 < last; f2 += size2) {
277 if ((cmp(f2, f2+ size) > 0) != sense)
278 break;
279 length += 2;
280 }
281 if (length < THRESHOLD) { /* Pairwise merge */
282 do {
283 p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
284 if (sense > 0)
285 swap (f1, f1 + size);
286 } while ((f1 += size2) < f2);
287 } else { /* Natural merge */
288 l2 = f2;
289 for (f2 = f1 + size2; f2 < l2; f2 += size2) {
290 if ((cmp(f2-size, f2) > 0) != sense) {
291 p2 = *EVAL(p2) = f2 - list1 + list2;
292 if (sense > 0)
293 reverse(f1, f2-size);
294 f1 = f2;
295 }
296 }
297 if (sense > 0)
298 reverse (f1, f2-size);
299 f1 = f2;
300 if (f2 < last || cmp(f2 - size, f2) > 0)
301 p2 = *EVAL(p2) = f2 - list1 + list2;
302 else
303 p2 = *EVAL(p2) = list2 + n*size;
304 }
305 }
306#else /* pairwise merge only. */
307 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
308 p2 = *EVAL(p2) = p2 + size2;
309 if (cmp (f1, f1 + size) > 0)
310 swap(f1, f1 + size);
311 }
312#endif /* NATURAL */
313}
314
315/*
316 * This is to avoid out-of-bounds addresses in sorting the
317 * last 4 elements.
318 */
319static void
320insertionsort(u_char *a, size_t n, size_t size,
321 int (*cmp)(const void *, const void *))
322{
323 u_char *ai, *s, *t, *u, tmp;
324 int i;
325
326 for (ai = a+size; --n >= 1; ai += size)
327 for (t = ai; t > a; t -= size) {
328 u = t - size;
329 if (cmp(u, t) <= 0)
330 break;
331 swap(u, t);
332 }
333}
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