redis qsort源码阅读

心已赠人 2023-06-06 03:47 4阅读 0赞

/* The following is the NetBSD libc qsort implementation modified in order to
     * support partial sorting of ranges for Redis.
     *
     * Copyright(C) 2009-2012 Salvatore Sanfilippo. All rights reserved.
     *
     * The original copyright notice follows. */
    
    
    /*	$NetBSD: qsort.c,v 1.19 2009/01/30 23:38:44 lukem Exp $	*/
    
    /*-
     * Copyright (c) 1992, 1993
     *	The Regents of the University of California.  All rights reserved.
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     */
    
    #include <sys/types.h>
    
    #include <errno.h>
    #include <stdlib.h>
    
    static inline char	*med3 (char *, char *, char *,
        int (*)(const void *, const void *));
    static inline void	 swapfunc (char *, char *, size_t, int);
    
    #define min(a, b)	(a) < (b) ? a : b
    
    /*
     * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
     */
    #define swapcode(TYPE, parmi, parmj, n) { 		\
    	size_t i = (n) / sizeof (TYPE); 		\
    	TYPE *pi = (TYPE *)(void *)(parmi); 		\
    	TYPE *pj = (TYPE *)(void *)(parmj); 		\
    	do { 						\
    		TYPE	t = *pi;			\
    		*pi++ = *pj;				\
    		*pj++ = t;				\
            } while (--i > 0);				\
    }
    
    #define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
    	es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
    
    static inline void
    swapfunc(char *a, char *b, size_t n, int swaptype)
    {
    
    	if (swaptype <= 1) 
    		swapcode(long, a, b, n)
    	else
    		swapcode(char, a, b, n)
    }
    
    #define swap(a, b)						\
    	if (swaptype == 0) {					\
    		long t = *(long *)(void *)(a);			\
    		*(long *)(void *)(a) = *(long *)(void *)(b);	\
    		*(long *)(void *)(b) = t;			\
    	} else							\
    		swapfunc(a, b, es, swaptype)
    
    #define vecswap(a, b, n) if ((n) > 0) swapfunc((a), (b), (size_t)(n), swaptype)
    
    static inline char *
    med3(char *a, char *b, char *c,
        int (*cmp) (const void *, const void *))
    {
    
    	return cmp(a, b) < 0 ?
    	       (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
                  :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
    }
    
    static void
    _pqsort(void *a, size_t n, size_t es,
        int (*cmp) (const void *, const void *), void *lrange, void *rrange)
    {
    	char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
    	size_t d, r;
    	int swaptype, cmp_result;
    
    loop:	SWAPINIT(a, es);
    	if (n < 7) {
    		for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
    			for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
    			     pl -= es)
    				swap(pl, pl - es);
    		return;
    	}
    	pm = (char *) a + (n / 2) * es;
    	if (n > 7) {
    		pl = (char *) a;
    		pn = (char *) a + (n - 1) * es;
    		if (n > 40) {
    			d = (n / 8) * es;
    			pl = med3(pl, pl + d, pl + 2 * d, cmp);
    			pm = med3(pm - d, pm, pm + d, cmp);
    			pn = med3(pn - 2 * d, pn - d, pn, cmp);
    		}
    		pm = med3(pl, pm, pn, cmp);
    	}
    	swap(a, pm);
    	pa = pb = (char *) a + es;
    
    	pc = pd = (char *) a + (n - 1) * es;
    	for (;;) {
    		while (pb <= pc && (cmp_result = cmp(pb, a)) <= 0) {
    			if (cmp_result == 0) {
    				swap(pa, pb);
    				pa += es;
    			}
    			pb += es;
    		}
    		while (pb <= pc && (cmp_result = cmp(pc, a)) >= 0) {
    			if (cmp_result == 0) {
    				swap(pc, pd);
    				pd -= es;
    			}
    			pc -= es;
    		}
    		if (pb > pc)
    			break;
    		swap(pb, pc);
    		pb += es;
    		pc -= es;
    	}
    
    	pn = (char *) a + n * es;
    	r = min(pa - (char *) a, pb - pa);
    	vecswap(a, pb - r, r);
    	r = min((size_t)(pd - pc), pn - pd - es);
    	vecswap(pb, pn - r, r);
    	if ((r = pb - pa) > es) {
                    void *_l = a, *_r = ((unsigned char*)a)+r-1;
                    if (!((lrange < _l && rrange < _l) ||
                        (lrange > _r && rrange > _r)))
    		    _pqsort(a, r / es, es, cmp, lrange, rrange);
            }
    	if ((r = pd - pc) > es) { 
                    void *_l, *_r;
                    
    		/* Iterate rather than recurse to save stack space */
    		a = pn - r;
    		n = r / es;
    
                    _l = a;
                    _r = ((unsigned char*)a)+r-1;
                    if (!((lrange < _l && rrange < _l) ||
                        (lrange > _r && rrange > _r)))
    		    goto loop;
    	}
    /*		qsort(pn - r, r / es, es, cmp);*/
    }
    
    void
    pqsort(void *a, size_t n, size_t es,
        int (*cmp) (const void *, const void *), size_t lrange, size_t rrange)
    {
        _pqsort(a,n,es,cmp,((unsigned char*)a)+(lrange*es),
                           ((unsigned char*)a)+((rrange+1)*es)-1);
    }