xref: /PHP-7.2/main/mergesort.c (revision bdeb220f)
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. All advertising materials mentioning features or use of this software
17  *    must display the following acknowledgement:
18  *	This product includes software developed by the University of
19  *	California, Berkeley and its contributors.
20  * 4. Neither the name of the University nor the names of its contributors
21  *    may be used to endorse or promote products derived from this software
22  *    without specific prior written permission.
23  *
24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34  * SUCH DAMAGE.
35  */
36 
37 /* $Id$ */
38 
39 #if defined(LIBC_SCCS) && !defined(lint)
40 static char sccsid[] = "@(#)merge.c	8.2 (Berkeley) 2/14/94";
41 #endif /* LIBC_SCCS and not lint */
42 
43 /*
44  * Hybrid exponential search/linear search merge sort with hybrid
45  * natural/pairwise first pass.  Requires about .3% more comparisons
46  * for random data than LSMS with pairwise first pass alone.
47  * It works for objects as small as two bytes.
48  */
49 
50 #define NATURAL
51 #define THRESHOLD 16	/* Best choice for natural merge cut-off. */
52 
53 /* #define NATURAL to get hybrid natural merge.
54  * (The default is pairwise merging.)
55  */
56 
57 #include <sys/types.h>
58 
59 #include <errno.h>
60 #include <stdlib.h>
61 #include <string.h>
62 
63 #include "php.h"
64 
65 #ifdef PHP_WIN32
66 #include <winsock2.h> /* Includes definition for u_char */
67 #endif
68 
69 static void setup(u_char *list1, u_char *list2, size_t n, size_t size, int (*cmp)(const void *, const void *));
70 static void insertionsort(u_char *a, size_t n, size_t size, int (*cmp)(const void *, const void *));
71 
72 #define ISIZE sizeof(int)
73 #define PSIZE sizeof(u_char *)
74 #define ICOPY_LIST(src, dst, last)				\
75 	do							\
76 	*(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE;	\
77 	while(src < last)
78 #define ICOPY_ELT(src, dst, i)					\
79 	do							\
80 	*(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE;	\
81 	while (i -= ISIZE)
82 
83 #define CCOPY_LIST(src, dst, last)		\
84 	do					\
85 		*dst++ = *src++;		\
86 	while (src < last)
87 #define CCOPY_ELT(src, dst, i)			\
88 	do					\
89 		*dst++ = *src++;		\
90 	while (i -= 1)
91 
92 /*
93  * Find the next possible pointer head.  (Trickery for forcing an array
94  * to do double duty as a linked list when objects do not align with word
95  * boundaries.
96  */
97 /* Assumption: PSIZE is a power of 2. */
98 #define EVAL(p) (u_char **)						\
99        	((u_char *)0 +							\
100 	    (((u_char *)p + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1)))
101 
102 /* {{{ php_mergesort
103  * Arguments are as for qsort.
104  */
php_mergesort(void * base,size_t nmemb,size_t size,int (* cmp)(const void *,const void *))105 PHPAPI int php_mergesort(void *base, size_t nmemb, size_t size, int (*cmp)(const void *, const void *))
106 {
107 	register size_t i;
108 	register int sense;
109 	int big, iflag;
110 	register u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
111 	u_char *list2, *list1, *p2, *p, *last, **p1;
112 
113 	if (size < PSIZE / 2) {		/* Pointers must fit into 2 * size. */
114 		errno = EINVAL;
115 		return (-1);
116 	}
117 
118 	if (nmemb == 0)
119 		return (0);
120 
121 	/*
122 	 * XXX
123 	 * Stupid subtraction for the Cray.
124 	 */
125 	iflag = 0;
126 	if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
127 		iflag = 1;
128 
129 	if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
130 		return (-1);
131 
132 	list1 = base;
133 	setup(list1, list2, nmemb, size, cmp);
134 	last = list2 + nmemb * size;
135 	i = big = 0;
136 	while (*EVAL(list2) != last) {
137 	    l2 = list1;
138 	    p1 = EVAL(list1);
139 	    for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
140 	    	p2 = *EVAL(p2);
141 	    	f1 = l2;
142 	    	f2 = l1 = list1 + (p2 - list2);
143 	    	if (p2 != last)
144 	    		p2 = *EVAL(p2);
145 	    	l2 = list1 + (p2 - list2);
146 	    	while (f1 < l1 && f2 < l2) {
147 	    		if ((*cmp)(f1, f2) <= 0) {
148 	    			q = f2;
149 	    			b = f1, t = l1;
150 	    			sense = -1;
151 	    		} else {
152 	    			q = f1;
153 	    			b = f2, t = l2;
154 	    			sense = 0;
155 	    		}
156 	    		if (!big) {	/* here i = 0 */
157 				while ((b += size) < t && cmp(q, b) >sense)
158 	    				if (++i == 6) {
159 	    					big = 1;
160 	    					goto EXPONENTIAL;
161 	    				}
162 	    		} else {
163 EXPONENTIAL:	    		for (i = size; ; i <<= 1)
164 	    				if ((p = (b + i)) >= t) {
165 	    					if ((p = t - size) > b &&
166 						    (*cmp)(q, p) <= sense)
167 	    						t = p;
168 	    					else
169 	    						b = p;
170 	    					break;
171 	    				} else if ((*cmp)(q, p) <= sense) {
172 	    					t = p;
173 	    					if (i == size)
174 	    						big = 0;
175 	    					goto FASTCASE;
176 	    				} else
177 	    					b = p;
178 				while (t > b+size) {
179 	    				i = (((t - b) / size) >> 1) * size;
180 	    				if ((*cmp)(q, p = b + i) <= sense)
181 	    					t = p;
182 	    				else
183 	    					b = p;
184 	    			}
185 	    			goto COPY;
186 FASTCASE:	    		while (i > size)
187 	    				if ((*cmp)(q,
188 	    					p = b + (i >>= 1)) <= sense)
189 	    					t = p;
190 	    				else
191 	    					b = p;
192 COPY:	    			b = t;
193 	    		}
194 	    		i = size;
195 	    		if (q == f1) {
196 	    			if (iflag) {
197 	    				ICOPY_LIST(f2, tp2, b);
198 	    				ICOPY_ELT(f1, tp2, i);
199 	    			} else {
200 	    				CCOPY_LIST(f2, tp2, b);
201 	    				CCOPY_ELT(f1, tp2, i);
202 	    			}
203 	    		} else {
204 	    			if (iflag) {
205 	    				ICOPY_LIST(f1, tp2, b);
206 	    				ICOPY_ELT(f2, tp2, i);
207 	    			} else {
208 	    				CCOPY_LIST(f1, tp2, b);
209 	    				CCOPY_ELT(f2, tp2, i);
210 	    			}
211 	    		}
212 	    	}
213 	    	if (f2 < l2) {
214 	    		if (iflag)
215 	    			ICOPY_LIST(f2, tp2, l2);
216 	    		else
217 	    			CCOPY_LIST(f2, tp2, l2);
218 	    	} else if (f1 < l1) {
219 	    		if (iflag)
220 	    			ICOPY_LIST(f1, tp2, l1);
221 	    		else
222 	    			CCOPY_LIST(f1, tp2, l1);
223 	    	}
224 	    	*p1 = l2;
225 	    }
226 	    tp2 = list1;	/* swap list1, list2 */
227 	    list1 = list2;
228 	    list2 = tp2;
229 	    last = list2 + nmemb*size;
230 	}
231 	if (base == list2) {
232 		memmove(list2, list1, nmemb*size);
233 		list2 = list1;
234 	}
235 	free(list2);
236 	return (0);
237 }
238 /* }}} */
239 
240 #define	swap(a, b) {					\
241 		s = b;					\
242 		i = size;				\
243 		do {					\
244 			tmp = *a; *a++ = *s; *s++ = tmp; \
245 		} while (--i);				\
246 		a -= size;				\
247 	}
248 #define reverse(bot, top) {				\
249 	s = top;					\
250 	do {						\
251 		i = size;				\
252 		do {					\
253 			tmp = *bot; *bot++ = *s; *s++ = tmp; \
254 		} while (--i);				\
255 		s -= size2;				\
256 	} while(bot < s);				\
257 }
258 
259 /* {{{ setup
260  * Optional hybrid natural/pairwise first pass.  Eats up list1 in runs of
261  * increasing order, list2 in a corresponding linked list.  Checks for runs
262  * when THRESHOLD/2 pairs compare with same sense.  (Only used when NATURAL
263  * is defined.  Otherwise simple pairwise merging is used.)
264  */
setup(u_char * list1,u_char * list2,size_t n,size_t size,int (* cmp)(const void *,const void *))265 static void setup(u_char *list1, u_char *list2, size_t n, size_t size, int (*cmp)(const void *, const void *))
266 {
267 	size_t i, length, size2, sense;
268 	u_char *f1, *f2, *s, *l2, *last, *p2, tmp;
269 
270 	size2 = size*2;
271 	if (n <= 5) {
272 		insertionsort(list1, n, size, cmp);
273 		*EVAL(list2) = (u_char*) list2 + n*size;
274 		return;
275 	}
276 	/*
277 	 * Avoid running pointers out of bounds; limit n to evens
278 	 * for simplicity.
279 	 */
280 	i = 4 + (n & 1);
281 	insertionsort(list1 + (n - i) * size, i, size, cmp);
282 	last = list1 + size * (n - i);
283 	*EVAL(list2 + (last - list1)) = list2 + n * size;
284 
285 #ifdef NATURAL
286 	p2 = list2;
287 	f1 = list1;
288 	sense = (cmp(f1, f1 + size) > 0);
289 	for (; f1 < last; sense = !sense) {
290 		length = 2;
291 					/* Find pairs with same sense. */
292 		for (f2 = f1 + size2; f2 < last; f2 += size2) {
293 			if ((cmp(f2, f2+ size) > 0) != sense)
294 				break;
295 			length += 2;
296 		}
297 		if (length < THRESHOLD) {		/* Pairwise merge */
298 			do {
299 				p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
300 				if (sense > 0)
301 					swap (f1, f1 + size);
302 			} while ((f1 += size2) < f2);
303 		} else {				/* Natural merge */
304 			l2 = f2;
305 			for (f2 = f1 + size2; f2 < l2; f2 += size2) {
306 				if ((cmp(f2-size, f2) > 0) != sense) {
307 					p2 = *EVAL(p2) = f2 - list1 + list2;
308 					if (sense > 0)
309 						reverse(f1, f2-size);
310 					f1 = f2;
311 				}
312 			}
313 			if (sense > 0)
314 				reverse (f1, f2-size);
315 			f1 = f2;
316 			if (f2 < last || cmp(f2 - size, f2) > 0)
317 				p2 = *EVAL(p2) = f2 - list1 + list2;
318 			else
319 				p2 = *EVAL(p2) = list2 + n*size;
320 		}
321 	}
322 #else		/* pairwise merge only. */
323 	for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
324 		p2 = *EVAL(p2) = p2 + size2;
325 		if (cmp (f1, f1 + size) > 0)
326 			swap(f1, f1 + size);
327 	}
328 #endif /* NATURAL */
329 }
330 /* }}} */
331 
332 /* {{{ insertionsort
333  * This is to avoid out-of-bounds addresses in sorting the
334  * last 4 elements.
335  */
insertionsort(u_char * a,size_t n,size_t size,int (* cmp)(const void *,const void *))336 static void insertionsort(u_char *a, size_t n, size_t size, int (*cmp)(const void *, const void *))
337 {
338 	u_char *ai, *s, *t, *u, tmp;
339 	size_t i;
340 
341 	for (ai = a+size; --n >= 1; ai += size)
342 		for (t = ai; t > a; t -= size) {
343 			u = t - size;
344 			if (cmp(u, t) <= 0)
345 				break;
346 			swap(u, t);
347 		}
348 }
349 /* }}} */
350 
351 /*
352  * Local variables:
353  * tab-width: 4
354  * c-basic-offset: 4
355  * End:
356  * vim600: fdm=marker
357  * vim: noet sw=4 ts=4
358  */
359