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 
54 static void setup(u_char *, u_char *, size_t, size_t, int (*)());
55 static 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  */
90 int
mergesort(void * base,size_t nmemb,size_t size,int (* cmp)(const void *,const void *))91 mergesort(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 {
149 EXPONENTIAL:	    		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;
172 FASTCASE:	    		while (i > size)
173 	    				if ((*cmp)(q,
174 	    					p = b + (i >>= 1)) <= sense)
175 	    					t = p;
176 	    				else
177 	    					b = p;
178 COPY:	    			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  */
250 void
setup(u_char * list1,u_char * list2,size_t n,size_t size,int (* cmp)(const void *,const void *))251 setup(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  */
322 static void
insertionsort(u_char * a,size_t n,size_t size,int (* cmp)(const void *,const void *))323 insertionsort(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 }
337