GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: lib/libc/stdlib/merge.c Lines: 0 102 0.0 %
Date: 2017-11-13 Branches: 0 132 0.0 %

Line Branch Exec Source
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/*	$OpenBSD: merge.c,v 1.10 2015/06/21 03:20:56 millert Exp $ */
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/*-
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 * Copyright (c) 1992, 1993
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 *	The Regents of the University of California.  All rights reserved.
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 *
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 * This code is derived from software contributed to Berkeley by
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 * Peter McIlroy.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 * 1. Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer.
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
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 *    documentation and/or other materials provided with the distribution.
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 * 3. Neither the name of the University nor the names of its contributors
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 *    may be used to endorse or promote products derived from this software
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 *    without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 * SUCH DAMAGE.
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 */
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/*
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 * Hybrid exponential search/linear search merge sort with hybrid
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 * natural/pairwise first pass.  Requires about .3% more comparisons
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 * for random data than LSMS with pairwise first pass alone.
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 * It works for objects as small as two bytes.
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 */
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#define NATURAL
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#define THRESHOLD 16	/* Best choice for natural merge cut-off. */
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/* #define NATURAL to get hybrid natural merge.
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 * (The default is pairwise merging.)
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 */
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#include <sys/types.h>
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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static void setup(u_char *, u_char *, size_t, size_t, int (*)());
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static void insertionsort(u_char *, size_t, size_t, int (*)());
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#define ISIZE sizeof(int)
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#define PSIZE sizeof(u_char *)
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#define ICOPY_LIST(src, dst, last)				\
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	do							\
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	*(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE;	\
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	while(src < last)
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#define ICOPY_ELT(src, dst, i)					\
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	do							\
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	*(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE;	\
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	while (i -= ISIZE)
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#define CCOPY_LIST(src, dst, last)		\
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	do					\
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		*dst++ = *src++;		\
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	while (src < last)
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#define CCOPY_ELT(src, dst, i)			\
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	do					\
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		*dst++ = *src++;		\
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	while (i -= 1)
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/*
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 * Find the next possible pointer head.  (Trickery for forcing an array
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 * to do double duty as a linked list when objects do not align with word
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 * boundaries.
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 */
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/* Assumption: PSIZE is a power of 2. */
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#define EVAL(p) (u_char **)						\
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	((u_char *)0 +							\
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	    (((u_char *)p + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1)))
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/*
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 * Arguments are as for qsort.
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 */
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int
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mergesort(void *base, size_t nmemb, size_t size,
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    int (*cmp)(const void *, const void *))
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{
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	int i, sense;
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	int big, iflag;
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	u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
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	u_char *list2, *list1, *p2, *p, *last, **p1;
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	if (size < PSIZE / 2) {		/* Pointers must fit into 2 * size. */
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		errno = EINVAL;
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		return (-1);
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	}
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	if (nmemb == 0)
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		return (0);
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	/*
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	 * XXX
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	 * Stupid subtraction for the Cray.
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	 */
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	iflag = 0;
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	if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
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		iflag = 1;
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	if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
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		return (-1);
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	list1 = base;
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	setup(list1, list2, nmemb, size, cmp);
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	last = list2 + nmemb * size;
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	i = big = 0;
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	while (*EVAL(list2) != last) {
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	    l2 = list1;
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	    p1 = EVAL(list1);
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	    for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
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	    	p2 = *EVAL(p2);
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	    	f1 = l2;
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	    	f2 = l1 = list1 + (p2 - list2);
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	    	if (p2 != last)
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	    		p2 = *EVAL(p2);
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	    	l2 = list1 + (p2 - list2);
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	    	while (f1 < l1 && f2 < l2) {
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	    		if ((*cmp)(f1, f2) <= 0) {
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	    			q = f2;
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	    			b = f1, t = l1;
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	    			sense = -1;
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	    		} else {
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	    			q = f1;
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	    			b = f2, t = l2;
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	    			sense = 0;
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	    		}
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	    		if (!big) {	/* here i = 0 */
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	    			while ((b += size) < t && cmp(q, b) >sense)
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	    				if (++i == 6) {
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	    					big = 1;
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	    					goto EXPONENTIAL;
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	    				}
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	    		} else {
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EXPONENTIAL:	    		for (i = size; ; i <<= 1)
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	    				if ((p = (b + i)) >= t) {
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	    					if ((p = t - size) > b &&
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						    (*cmp)(q, p) <= sense)
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	    						t = p;
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	    					else
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	    						b = p;
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	    					break;
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	    				} else if ((*cmp)(q, p) <= sense) {
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	    					t = p;
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	    					if (i == size)
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	    						big = 0;
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	    					goto FASTCASE;
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	    				} else
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	    					b = p;
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		    		while (t > b+size) {
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	    				i = (((t - b) / size) >> 1) * size;
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	    				if ((*cmp)(q, p = b + i) <= sense)
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	    					t = p;
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	    				else
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	    					b = p;
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	    			}
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	    			goto COPY;
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FASTCASE:	    		while (i > size)
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	    				if ((*cmp)(q,
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	    					p = b + (i >>= 1)) <= sense)
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	    					t = p;
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	    				else
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	    					b = p;
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COPY:	    			b = t;
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	    		}
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	    		i = size;
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	    		if (q == f1) {
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	    			if (iflag) {
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	    				ICOPY_LIST(f2, tp2, b);
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	    				ICOPY_ELT(f1, tp2, i);
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	    			} else {
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	    				CCOPY_LIST(f2, tp2, b);
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	    				CCOPY_ELT(f1, tp2, i);
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	    			}
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	    		} else {
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	    			if (iflag) {
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	    				ICOPY_LIST(f1, tp2, b);
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	    				ICOPY_ELT(f2, tp2, i);
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	    			} else {
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	    				CCOPY_LIST(f1, tp2, b);
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	    				CCOPY_ELT(f2, tp2, i);
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	    			}
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	    		}
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	    	}
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	    	if (f2 < l2) {
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	    		if (iflag)
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	    			ICOPY_LIST(f2, tp2, l2);
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	    		else
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	    			CCOPY_LIST(f2, tp2, l2);
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	    	} else if (f1 < l1) {
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	    		if (iflag)
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	    			ICOPY_LIST(f1, tp2, l1);
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	    		else
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	    			CCOPY_LIST(f1, tp2, l1);
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	    	}
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	    	*p1 = l2;
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	    }
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	    tp2 = list1;	/* swap list1, list2 */
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	    list1 = list2;
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	    list2 = tp2;
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	    last = list2 + nmemb*size;
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	}
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	if (base == list2) {
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		memmove(list2, list1, nmemb*size);
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		list2 = list1;
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	}
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	free(list2);
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	return (0);
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}
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#define	swap(a, b) {					\
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		s = b;					\
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		i = size;				\
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		do {					\
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			tmp = *a; *a++ = *s; *s++ = tmp; \
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		} while (--i);				\
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		a -= size;				\
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	}
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#define reverse(bot, top) {				\
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	s = top;					\
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	do {						\
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		i = size;				\
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		do {					\
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			tmp = *bot; *bot++ = *s; *s++ = tmp; \
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		} while (--i);				\
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		s -= size2;				\
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	} while(bot < s);				\
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}
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/*
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 * Optional hybrid natural/pairwise first pass.  Eats up list1 in runs of
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 * increasing order, list2 in a corresponding linked list.  Checks for runs
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 * when THRESHOLD/2 pairs compare with same sense.  (Only used when NATURAL
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 * is defined.  Otherwise simple pairwise merging is used.)
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 */
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void
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setup(u_char *list1, u_char *list2, size_t n, size_t size,
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    int (*cmp)(const void *, const void *))
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{
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	int i, length, size2, sense;
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	u_char tmp, *f1, *f2, *s, *l2, *last, *p2;
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	size2 = size*2;
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	if (n <= 5) {
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		insertionsort(list1, n, size, cmp);
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		*EVAL(list2) = (u_char*) list2 + n*size;
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		return;
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	}
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	/*
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	 * Avoid running pointers out of bounds; limit n to evens
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	 * for simplicity.
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	 */
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	i = 4 + (n & 1);
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	insertionsort(list1 + (n - i) * size, i, size, cmp);
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	last = list1 + size * (n - i);
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	*EVAL(list2 + (last - list1)) = list2 + n * size;
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#ifdef NATURAL
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	p2 = list2;
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	f1 = list1;
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	sense = (cmp(f1, f1 + size) > 0);
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	for (; f1 < last; sense = !sense) {
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		length = 2;
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					/* Find pairs with same sense. */
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		for (f2 = f1 + size2; f2 < last; f2 += size2) {
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			if ((cmp(f2, f2+ size) > 0) != sense)
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				break;
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			length += 2;
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		}
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		if (length < THRESHOLD) {		/* Pairwise merge */
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			do {
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				p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
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				if (sense > 0)
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					swap (f1, f1 + size);
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			} while ((f1 += size2) < f2);
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		} else {				/* Natural merge */
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			l2 = f2;
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			for (f2 = f1 + size2; f2 < l2; f2 += size2) {
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				if ((cmp(f2-size, f2) > 0) != sense) {
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					p2 = *EVAL(p2) = f2 - list1 + list2;
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					if (sense > 0)
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						reverse(f1, f2-size);
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					f1 = f2;
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				}
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			}
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			if (sense > 0)
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				reverse (f1, f2-size);
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			f1 = f2;
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			if (f2 < last || cmp(f2 - size, f2) > 0)
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				p2 = *EVAL(p2) = f2 - list1 + list2;
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			else
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				p2 = *EVAL(p2) = list2 + n*size;
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		}
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	}
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#else		/* pairwise merge only. */
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	for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
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		p2 = *EVAL(p2) = p2 + size2;
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		if (cmp (f1, f1 + size) > 0)
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			swap(f1, f1 + size);
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	}
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#endif /* NATURAL */
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}
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/*
319
 * This is to avoid out-of-bounds addresses in sorting the
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 * last 4 elements.
321
 */
322
static void
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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)
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				break;
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			swap(u, t);
335
		}
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}