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 * @(#)merge.c 8.2 (Berkeley) 2/14/94
33 * $FreeBSD: src/lib/libc/stdlib/merge.c,v 1.8 2007/01/09 00:28:10 imp Exp $
34 */
35
36 /*
37 * Hybrid exponential search/linear search merge sort with hybrid
38 * natural/pairwise first pass. Requires about .3% more comparisons
39 * for random data than LSMS with pairwise first pass alone.
40 * It works for objects as small as two bytes.
41 */
42
43 #define NATURAL
44 #define THRESHOLD 16 /* Best choice for natural merge cut-off. */
45
46 /* #define NATURAL to get hybrid natural merge.
47 * (The default is pairwise merging.)
48 */
49
50 #include <sys/param.h>
51
52 #include <errno.h>
53 #include <stdlib.h>
54 #include <string.h>
55
56 static void setup(u_char *, u_char *, size_t, size_t,
57 int (*)(const void *, const void *));
58 static void insertionsort(u_char *, size_t, size_t,
59 int (*)(const void *, const void *));
60
61 #define ISIZE sizeof(int)
62 #define PSIZE sizeof(u_char *)
63 #define ICOPY_LIST(src, dst, last) \
64 do \
65 *(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE; \
66 while(src < last)
67 #define ICOPY_ELT(src, dst, i) \
68 do \
69 *(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE; \
70 while (i -= ISIZE)
71
72 #define CCOPY_LIST(src, dst, last) \
73 do \
74 *dst++ = *src++; \
75 while (src < last)
76 #define CCOPY_ELT(src, dst, i) \
77 do \
78 *dst++ = *src++; \
79 while (i -= 1)
80
81 /*
82 * Find the next possible pointer head. (Trickery for forcing an array
83 * to do double duty as a linked list when objects do not align with word
84 * boundaries.
85 */
86 /* Assumption: PSIZE is a power of 2. */
87 #define EVAL(p) (u_char **) \
88 ((u_char *)0 + \
89 (rounddown2((u_char *)p + PSIZE - 1 - (u_char *)0, PSIZE)))
90
91 /*
92 * Arguments are as for qsort.
93 */
94 int
mergesort(void * base,size_t nmemb,size_t size,int (* cmp)(const void *,const void *))95 mergesort(void *base, size_t nmemb, size_t size,
96 int (*cmp)(const void *, const void *))
97 {
98 size_t i;
99 int sense;
100 int big, iflag;
101 u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
102 u_char *list2, *list1, *p2, *p, *last, **p1;
103
104 if (size < PSIZE / 2) { /* Pointers must fit into 2 * size. */
105 errno = EINVAL;
106 return (-1);
107 }
108
109 if (nmemb == 0)
110 return (0);
111
112 /*
113 * XXX
114 * Stupid subtraction for the Cray.
115 */
116 iflag = 0;
117 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
118 iflag = 1;
119
120 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
121 return (-1);
122
123 list1 = base;
124 setup(list1, list2, nmemb, size, cmp);
125 last = list2 + nmemb * size;
126 i = big = 0;
127 while (*EVAL(list2) != last) {
128 l2 = list1;
129 p1 = EVAL(list1);
130 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
131 p2 = *EVAL(p2);
132 f1 = l2;
133 f2 = l1 = list1 + (p2 - list2);
134 if (p2 != last)
135 p2 = *EVAL(p2);
136 l2 = list1 + (p2 - list2);
137 while (f1 < l1 && f2 < l2) {
138 if ((*cmp)(f1, f2) <= 0) {
139 q = f2;
140 b = f1, t = l1;
141 sense = -1;
142 } else {
143 q = f1;
144 b = f2, t = l2;
145 sense = 0;
146 }
147 if (!big) { /* here i = 0 */
148 while ((b += size) < t && cmp(q, b) >sense)
149 if (++i == 6) {
150 big = 1;
151 goto EXPONENTIAL;
152 }
153 } else {
154 EXPONENTIAL: for (i = size; ; i <<= 1)
155 if ((p = (b + i)) >= t) {
156 if ((p = t - size) > b &&
157 (*cmp)(q, p) <= sense)
158 t = p;
159 else
160 b = p;
161 break;
162 } else if ((*cmp)(q, p) <= sense) {
163 t = p;
164 if (i == size)
165 big = 0;
166 goto FASTCASE;
167 } else
168 b = p;
169 while (t > b+size) {
170 i = (((t - b) / size) >> 1) * size;
171 if ((*cmp)(q, p = b + i) <= sense)
172 t = p;
173 else
174 b = p;
175 }
176 goto COPY;
177 FASTCASE: while (i > size)
178 if ((*cmp)(q,
179 p = b + (i >>= 1)) <= sense)
180 t = p;
181 else
182 b = p;
183 COPY: b = t;
184 }
185 i = size;
186 if (q == f1) {
187 if (iflag) {
188 ICOPY_LIST(f2, tp2, b);
189 ICOPY_ELT(f1, tp2, i);
190 } else {
191 CCOPY_LIST(f2, tp2, b);
192 CCOPY_ELT(f1, tp2, i);
193 }
194 } else {
195 if (iflag) {
196 ICOPY_LIST(f1, tp2, b);
197 ICOPY_ELT(f2, tp2, i);
198 } else {
199 CCOPY_LIST(f1, tp2, b);
200 CCOPY_ELT(f2, tp2, i);
201 }
202 }
203 }
204 if (f2 < l2) {
205 if (iflag)
206 ICOPY_LIST(f2, tp2, l2);
207 else
208 CCOPY_LIST(f2, tp2, l2);
209 } else if (f1 < l1) {
210 if (iflag)
211 ICOPY_LIST(f1, tp2, l1);
212 else
213 CCOPY_LIST(f1, tp2, l1);
214 }
215 *p1 = l2;
216 }
217 tp2 = list1; /* swap list1, list2 */
218 list1 = list2;
219 list2 = tp2;
220 last = list2 + nmemb*size;
221 }
222 if (base == list2) {
223 memmove(list2, list1, nmemb*size);
224 list2 = list1;
225 }
226 free(list2);
227 return (0);
228 }
229
230 #define swap(a, b) { \
231 s = b; \
232 i = size; \
233 do { \
234 tmp = *a; *a++ = *s; *s++ = tmp; \
235 } while (--i); \
236 a -= size; \
237 }
238 #define reverse(bot, top) { \
239 s = top; \
240 do { \
241 i = size; \
242 do { \
243 tmp = *bot; *bot++ = *s; *s++ = tmp; \
244 } while (--i); \
245 s -= size2; \
246 } while(bot < s); \
247 }
248
249 /*
250 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of
251 * increasing order, list2 in a corresponding linked list. Checks for runs
252 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL
253 * is defined. Otherwise simple pairwise merging is used.)
254 */
255 static void
setup(u_char * list1,u_char * list2,size_t n,size_t size,int (* cmp)(const void *,const void *))256 setup(u_char *list1, u_char *list2, size_t n, size_t size,
257 int (*cmp)(const void *, const void *))
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 */
327 static void
insertionsort(u_char * a,size_t n,size_t size,int (* cmp)(const void *,const void *))328 insertionsort(u_char *a, size_t n, size_t size,
329 int (*cmp)(const void *, const void *))
330 {
331 u_char *ai, *s, *t, *u, tmp;
332 int i;
333
334 for (ai = a+size; --n >= 1; ai += size)
335 for (t = ai; t > a; t -= size) {
336 u = t - size;
337 if (cmp(u, t) <= 0)
338 break;
339 swap(u, t);
340 }
341 }
342