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-rw-r--r--src/lib/libc/stdlib/merge.c336
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diff --git a/src/lib/libc/stdlib/merge.c b/src/lib/libc/stdlib/merge.c
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1/* $OpenBSD: merge.c,v 1.10 2015/06/21 03:20:56 millert 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 if (nmemb == 0)
105 return (0);
106
107 /*
108 * XXX
109 * Stupid subtraction for the Cray.
110 */
111 iflag = 0;
112 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
113 iflag = 1;
114
115 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
116 return (-1);
117
118 list1 = base;
119 setup(list1, list2, nmemb, size, cmp);
120 last = list2 + nmemb * size;
121 i = big = 0;
122 while (*EVAL(list2) != last) {
123 l2 = list1;
124 p1 = EVAL(list1);
125 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
126 p2 = *EVAL(p2);
127 f1 = l2;
128 f2 = l1 = list1 + (p2 - list2);
129 if (p2 != last)
130 p2 = *EVAL(p2);
131 l2 = list1 + (p2 - list2);
132 while (f1 < l1 && f2 < l2) {
133 if ((*cmp)(f1, f2) <= 0) {
134 q = f2;
135 b = f1, t = l1;
136 sense = -1;
137 } else {
138 q = f1;
139 b = f2, t = l2;
140 sense = 0;
141 }
142 if (!big) { /* here i = 0 */
143 while ((b += size) < t && cmp(q, b) >sense)
144 if (++i == 6) {
145 big = 1;
146 goto EXPONENTIAL;
147 }
148 } else {
149EXPONENTIAL: for (i = size; ; i <<= 1)
150 if ((p = (b + i)) >= t) {
151 if ((p = t - size) > b &&
152 (*cmp)(q, p) <= sense)
153 t = p;
154 else
155 b = p;
156 break;
157 } else if ((*cmp)(q, p) <= sense) {
158 t = p;
159 if (i == size)
160 big = 0;
161 goto FASTCASE;
162 } else
163 b = p;
164 while (t > b+size) {
165 i = (((t - b) / size) >> 1) * size;
166 if ((*cmp)(q, p = b + i) <= sense)
167 t = p;
168 else
169 b = p;
170 }
171 goto COPY;
172FASTCASE: while (i > size)
173 if ((*cmp)(q,
174 p = b + (i >>= 1)) <= sense)
175 t = p;
176 else
177 b = p;
178COPY: b = t;
179 }
180 i = size;
181 if (q == f1) {
182 if (iflag) {
183 ICOPY_LIST(f2, tp2, b);
184 ICOPY_ELT(f1, tp2, i);
185 } else {
186 CCOPY_LIST(f2, tp2, b);
187 CCOPY_ELT(f1, tp2, i);
188 }
189 } else {
190 if (iflag) {
191 ICOPY_LIST(f1, tp2, b);
192 ICOPY_ELT(f2, tp2, i);
193 } else {
194 CCOPY_LIST(f1, tp2, b);
195 CCOPY_ELT(f2, tp2, i);
196 }
197 }
198 }
199 if (f2 < l2) {
200 if (iflag)
201 ICOPY_LIST(f2, tp2, l2);
202 else
203 CCOPY_LIST(f2, tp2, l2);
204 } else if (f1 < l1) {
205 if (iflag)
206 ICOPY_LIST(f1, tp2, l1);
207 else
208 CCOPY_LIST(f1, tp2, l1);
209 }
210 *p1 = l2;
211 }
212 tp2 = list1; /* swap list1, list2 */
213 list1 = list2;
214 list2 = tp2;
215 last = list2 + nmemb*size;
216 }
217 if (base == list2) {
218 memmove(list2, list1, nmemb*size);
219 list2 = list1;
220 }
221 free(list2);
222 return (0);
223}
224
225#define swap(a, b) { \
226 s = b; \
227 i = size; \
228 do { \
229 tmp = *a; *a++ = *s; *s++ = tmp; \
230 } while (--i); \
231 a -= size; \
232 }
233#define reverse(bot, top) { \
234 s = top; \
235 do { \
236 i = size; \
237 do { \
238 tmp = *bot; *bot++ = *s; *s++ = tmp; \
239 } while (--i); \
240 s -= size2; \
241 } while(bot < s); \
242}
243
244/*
245 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of
246 * increasing order, list2 in a corresponding linked list. Checks for runs
247 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL
248 * is defined. Otherwise simple pairwise merging is used.)
249 */
250void
251setup(u_char *list1, u_char *list2, size_t n, size_t size,
252 int (*cmp)(const void *, const void *))
253{
254 int i, length, size2, sense;
255 u_char tmp, *f1, *f2, *s, *l2, *last, *p2;
256
257 size2 = size*2;
258 if (n <= 5) {
259 insertionsort(list1, n, size, cmp);
260 *EVAL(list2) = (u_char*) list2 + n*size;
261 return;
262 }
263 /*
264 * Avoid running pointers out of bounds; limit n to evens
265 * for simplicity.
266 */
267 i = 4 + (n & 1);
268 insertionsort(list1 + (n - i) * size, i, size, cmp);
269 last = list1 + size * (n - i);
270 *EVAL(list2 + (last - list1)) = list2 + n * size;
271
272#ifdef NATURAL
273 p2 = list2;
274 f1 = list1;
275 sense = (cmp(f1, f1 + size) > 0);
276 for (; f1 < last; sense = !sense) {
277 length = 2;
278 /* Find pairs with same sense. */
279 for (f2 = f1 + size2; f2 < last; f2 += size2) {
280 if ((cmp(f2, f2+ size) > 0) != sense)
281 break;
282 length += 2;
283 }
284 if (length < THRESHOLD) { /* Pairwise merge */
285 do {
286 p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
287 if (sense > 0)
288 swap (f1, f1 + size);
289 } while ((f1 += size2) < f2);
290 } else { /* Natural merge */
291 l2 = f2;
292 for (f2 = f1 + size2; f2 < l2; f2 += size2) {
293 if ((cmp(f2-size, f2) > 0) != sense) {
294 p2 = *EVAL(p2) = f2 - list1 + list2;
295 if (sense > 0)
296 reverse(f1, f2-size);
297 f1 = f2;
298 }
299 }
300 if (sense > 0)
301 reverse (f1, f2-size);
302 f1 = f2;
303 if (f2 < last || cmp(f2 - size, f2) > 0)
304 p2 = *EVAL(p2) = f2 - list1 + list2;
305 else
306 p2 = *EVAL(p2) = list2 + n*size;
307 }
308 }
309#else /* pairwise merge only. */
310 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
311 p2 = *EVAL(p2) = p2 + size2;
312 if (cmp (f1, f1 + size) > 0)
313 swap(f1, f1 + size);
314 }
315#endif /* NATURAL */
316}
317
318/*
319 * This is to avoid out-of-bounds addresses in sorting the
320 * last 4 elements.
321 */
322static void
323insertionsort(u_char *a, size_t n, size_t size,
324 int (*cmp)(const void *, const void *))
325{
326 u_char *ai, *s, *t, *u, tmp;
327 int i;
328
329 for (ai = a+size; --n >= 1; ai += size)
330 for (t = ai; t > a; t -= size) {
331 u = t - size;
332 if (cmp(u, t) <= 0)
333 break;
334 swap(u, t);
335 }
336}
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