1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1992, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Peter McIlroy.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 #if defined(LIBC_SCCS) && !defined(lint)
36 static char sccsid[] = "@(#)merge.c 8.2 (Berkeley) 2/14/94";
37 #endif /* LIBC_SCCS and not lint */
38
39 /*
40 * Hybrid exponential search/linear search merge sort with hybrid
41 * natural/pairwise first pass. Requires about .3% more comparisons
42 * for random data than LSMS with pairwise first pass alone.
43 * It works for objects as small as two bytes.
44 */
45
46 #define NATURAL
47 #define THRESHOLD 16 /* Best choice for natural merge cut-off. */
48
49 /* #define NATURAL to get hybrid natural merge.
50 * (The default is pairwise merging.)
51 */
52
53 #include <sys/types.h>
54 #include <stdint.h>
55
56 #include <errno.h>
57 #include <stdlib.h>
58 #include <string.h>
59
60 typedef int (*cmp_t)(const void *, const void *);
61 #define CMP(x, y) cmp(x, y)
62
63 static void setup(u_char *, u_char *, size_t, size_t, cmp_t);
64 static void insertionsort(u_char *, size_t, size_t, cmp_t);
65
66 #define ISIZE sizeof(int)
67 #define PSIZE sizeof(u_char *)
68 #define ICOPY_LIST(src, dst, last) \
69 do \
70 *(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE; \
71 while(src < last)
72 #define ICOPY_ELT(src, dst, i) \
73 do \
74 *(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE; \
75 while (i -= ISIZE)
76
77 #define CCOPY_LIST(src, dst, last) \
78 do \
79 *dst++ = *src++; \
80 while (src < last)
81 #define CCOPY_ELT(src, dst, i) \
82 do \
83 *dst++ = *src++; \
84 while (i -= 1)
85
86 /*
87 * Find the next possible pointer head. (Trickery for forcing an array
88 * to do double duty as a linked list when objects do not align with word
89 * boundaries.
90 */
91 /* Assumption: PSIZE is a power of 2. */
92 #define roundup2(x, y) (((x) + ((y) - 1)) & (~((y) - 1)))
93 #define EVAL(p) (u_char **)roundup2((uintptr_t)p, PSIZE)
94
95 /*
96 * Arguments are as for qsort.
97 */
98 int
mergesort(void * base,size_t nmemb,size_t size,cmp_t cmp)99 mergesort(void *base, size_t nmemb, size_t size, cmp_t cmp)
100 {
101 size_t i;
102 int sense;
103 int big, iflag;
104 u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
105 u_char *list2, *list1, *p2, *p, *last, **p1;
106
107 if (size < PSIZE / 2) { /* Pointers must fit into 2 * size. */
108 errno = EINVAL;
109 return (-1);
110 }
111
112 if (nmemb == 0)
113 return (0);
114
115 iflag = 0;
116 if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
117 iflag = 1;
118
119 if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
120 return (-1);
121
122 list1 = base;
123 setup(list1, list2, nmemb, size, cmp);
124 last = list2 + nmemb * size;
125 i = big = 0;
126 while (*EVAL(list2) != last) {
127 l2 = list1;
128 p1 = EVAL(list1);
129 for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
130 p2 = *EVAL(p2);
131 f1 = l2;
132 f2 = l1 = list1 + (p2 - list2);
133 if (p2 != last)
134 p2 = *EVAL(p2);
135 l2 = list1 + (p2 - list2);
136 while (f1 < l1 && f2 < l2) {
137 if (CMP(f1, f2) <= 0) {
138 q = f2;
139 b = f1, t = l1;
140 sense = -1;
141 } else {
142 q = f1;
143 b = f2, t = l2;
144 sense = 0;
145 }
146 if (!big) { /* here i = 0 */
147 while ((b += size) < t && CMP(q, b) >sense)
148 if (++i == 6) {
149 big = 1;
150 goto EXPONENTIAL;
151 }
152 } else {
153 EXPONENTIAL: for (i = size; ; i <<= 1)
154 if ((p = (b + i)) >= t) {
155 if ((p = t - size) > b &&
156 CMP(q, p) <= sense)
157 t = p;
158 else
159 b = p;
160 break;
161 } else if (CMP(q, p) <= sense) {
162 t = p;
163 if (i == size)
164 big = 0;
165 goto FASTCASE;
166 } else
167 b = p;
168 while (t > b+size) {
169 i = (((t - b) / size) >> 1) * size;
170 if (CMP(q, p = b + i) <= sense)
171 t = p;
172 else
173 b = p;
174 }
175 goto COPY;
176 FASTCASE: while (i > size)
177 if (CMP(q,
178 p = b + (i >>= 1)) <= sense)
179 t = p;
180 else
181 b = p;
182 COPY: b = t;
183 }
184 i = size;
185 if (q == f1) {
186 if (iflag) {
187 ICOPY_LIST(f2, tp2, b);
188 ICOPY_ELT(f1, tp2, i);
189 } else {
190 CCOPY_LIST(f2, tp2, b);
191 CCOPY_ELT(f1, tp2, i);
192 }
193 } else {
194 if (iflag) {
195 ICOPY_LIST(f1, tp2, b);
196 ICOPY_ELT(f2, tp2, i);
197 } else {
198 CCOPY_LIST(f1, tp2, b);
199 CCOPY_ELT(f2, tp2, i);
200 }
201 }
202 }
203 if (f2 < l2) {
204 if (iflag)
205 ICOPY_LIST(f2, tp2, l2);
206 else
207 CCOPY_LIST(f2, tp2, l2);
208 } else if (f1 < l1) {
209 if (iflag)
210 ICOPY_LIST(f1, tp2, l1);
211 else
212 CCOPY_LIST(f1, tp2, l1);
213 }
214 *p1 = l2;
215 }
216 tp2 = list1; /* swap list1, list2 */
217 list1 = list2;
218 list2 = tp2;
219 last = list2 + nmemb*size;
220 }
221 if (base == list2) {
222 memmove(list2, list1, nmemb*size);
223 list2 = list1;
224 }
225 free(list2);
226 return (0);
227 }
228
229 #define swap(a, b) { \
230 s = b; \
231 i = size; \
232 do { \
233 tmp = *a; *a++ = *s; *s++ = tmp; \
234 } while (--i); \
235 a -= size; \
236 }
237 #define reverse(bot, top) { \
238 s = top; \
239 do { \
240 i = size; \
241 do { \
242 tmp = *bot; *bot++ = *s; *s++ = tmp; \
243 } while (--i); \
244 s -= size2; \
245 } while(bot < s); \
246 }
247
248 /*
249 * Optional hybrid natural/pairwise first pass. Eats up list1 in runs of
250 * increasing order, list2 in a corresponding linked list. Checks for runs
251 * when THRESHOLD/2 pairs compare with same sense. (Only used when NATURAL
252 * is defined. Otherwise simple pairwise merging is used.)
253 */
254 static
255 void
setup(u_char * list1,u_char * list2,size_t n,size_t size,cmp_t cmp)256 setup(u_char *list1, u_char *list2, size_t n, size_t size, cmp_t cmp)
257 {
258 int i, length, size2, tmp, sense;
259 u_char *f1, *f2, *s, *l2, *last, *p2;
260
261 size2 = size*2;
262 if (n <= 5) {
263 insertionsort(list1, n, size, cmp);
264 *EVAL(list2) = (u_char*) list2 + n*size;
265 return;
266 }
267 /*
268 * Avoid running pointers out of bounds; limit n to evens
269 * for simplicity.
270 */
271 i = 4 + (n & 1);
272 insertionsort(list1 + (n - i) * size, i, size, cmp);
273 last = list1 + size * (n - i);
274 *EVAL(list2 + (last - list1)) = list2 + n * size;
275
276 #ifdef NATURAL
277 p2 = list2;
278 f1 = list1;
279 sense = (CMP(f1, f1 + size) > 0);
280 for (; f1 < last; sense = !sense) {
281 length = 2;
282 /* Find pairs with same sense. */
283 for (f2 = f1 + size2; f2 < last; f2 += size2) {
284 if ((CMP(f2, f2+ size) > 0) != sense)
285 break;
286 length += 2;
287 }
288 if (length < THRESHOLD) { /* Pairwise merge */
289 do {
290 p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
291 if (sense > 0)
292 swap (f1, f1 + size);
293 } while ((f1 += size2) < f2);
294 } else { /* Natural merge */
295 l2 = f2;
296 for (f2 = f1 + size2; f2 < l2; f2 += size2) {
297 if ((CMP(f2-size, f2) > 0) != sense) {
298 p2 = *EVAL(p2) = f2 - list1 + list2;
299 if (sense > 0)
300 reverse(f1, f2-size);
301 f1 = f2;
302 }
303 }
304 if (sense > 0)
305 reverse (f1, f2-size);
306 f1 = f2;
307 if (f2 < last || CMP(f2 - size, f2) > 0)
308 p2 = *EVAL(p2) = f2 - list1 + list2;
309 else
310 p2 = *EVAL(p2) = list2 + n*size;
311 }
312 }
313 #else /* pairwise merge only. */
314 for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
315 p2 = *EVAL(p2) = p2 + size2;
316 if (CMP (f1, f1 + size) > 0)
317 swap(f1, f1 + size);
318 }
319 #endif /* NATURAL */
320 }
321
322 /*
323 * This is to avoid out-of-bounds addresses in sorting the
324 * last 4 elements.
325 */
326 static void
insertionsort(u_char * a,size_t n,size_t size,cmp_t cmp)327 insertionsort(u_char *a, size_t n, size_t size, cmp_t cmp)
328 {
329 u_char *ai, *s, *t, *u, tmp;
330 int i;
331
332 for (ai = a+size; --n >= 1; ai += size)
333 for (t = ai; t > a; t -= size) {
334 u = t - size;
335 if (CMP(u, t) <= 0)
336 break;
337 swap(u, t);
338 }
339 }
340