redis qsort源码阅读
【摘要】 /* 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 rese...
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/* The following is the NetBSD libc qsort implementation modified in order to
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* support partial sorting of ranges for Redis.
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*
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* Copyright(C) 2009-2012 Salvatore Sanfilippo. All rights reserved.
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*
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* The original copyright notice follows. */
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/* $NetBSD: qsort.c,v 1.19 2009/01/30 23:38:44 lukem 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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* 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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#include <sys/types.h>
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#include <errno.h>
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#include <stdlib.h>
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static inline char *med3 (char *, char *, char *,
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int (*)(const void *, const void *));
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static inline void swapfunc (char *, char *, size_t, int);
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#define min(a, b) (a) < (b) ? a : b
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/*
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* Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
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*/
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#define swapcode(TYPE, parmi, parmj, n) { \
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size_t i = (n) / sizeof (TYPE); \
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TYPE *pi = (TYPE *)(void *)(parmi); \
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TYPE *pj = (TYPE *)(void *)(parmj); \
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do { \
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TYPE t = *pi; \
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*pi++ = *pj; \
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*pj++ = t; \
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} while (--i > 0); \
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}
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#define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
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es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
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static inline void
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swapfunc(char *a, char *b, size_t n, int swaptype)
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{
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if (swaptype <= 1)
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swapcode(long, a, b, n)
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else
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swapcode(char, a, b, n)
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}
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#define swap(a, b) \
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if (swaptype == 0) { \
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long t = *(long *)(void *)(a); \
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*(long *)(void *)(a) = *(long *)(void *)(b); \
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*(long *)(void *)(b) = t; \
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} else \
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swapfunc(a, b, es, swaptype)
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#define vecswap(a, b, n) if ((n) > 0) swapfunc((a), (b), (size_t)(n), swaptype)
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static inline char *
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med3(char *a, char *b, char *c,
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int (*cmp) (const void *, const void *))
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{
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return cmp(a, b) < 0 ?
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(cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
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:(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
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}
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static void
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_pqsort(void *a, size_t n, size_t es,
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int (*cmp) (const void *, const void *), void *lrange, void *rrange)
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{
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char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
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size_t d, r;
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int swaptype, cmp_result;
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loop: SWAPINIT(a, es);
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if (n < 7) {
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for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
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for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0;
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pl -= es)
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swap(pl, pl - es);
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return;
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}
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pm = (char *) a + (n / 2) * es;
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if (n > 7) {
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pl = (char *) a;
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pn = (char *) a + (n - 1) * es;
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if (n > 40) {
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d = (n / 8) * es;
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pl = med3(pl, pl + d, pl + 2 * d, cmp);
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pm = med3(pm - d, pm, pm + d, cmp);
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pn = med3(pn - 2 * d, pn - d, pn, cmp);
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}
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pm = med3(pl, pm, pn, cmp);
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}
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swap(a, pm);
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pa = pb = (char *) a + es;
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pc = pd = (char *) a + (n - 1) * es;
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for (;;) {
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while (pb <= pc && (cmp_result = cmp(pb, a)) <= 0) {
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if (cmp_result == 0) {
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swap(pa, pb);
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pa += es;
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}
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pb += es;
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}
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while (pb <= pc && (cmp_result = cmp(pc, a)) >= 0) {
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if (cmp_result == 0) {
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swap(pc, pd);
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pd -= es;
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}
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pc -= es;
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}
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if (pb > pc)
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break;
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swap(pb, pc);
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pb += es;
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pc -= es;
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}
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pn = (char *) a + n * es;
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r = min(pa - (char *) a, pb - pa);
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vecswap(a, pb - r, r);
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r = min((size_t)(pd - pc), pn - pd - es);
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vecswap(pb, pn - r, r);
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if ((r = pb - pa) > es) {
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void *_l = a, *_r = ((unsigned char*)a)+r-1;
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if (!((lrange < _l && rrange < _l) ||
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(lrange > _r && rrange > _r)))
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_pqsort(a, r / es, es, cmp, lrange, rrange);
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}
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if ((r = pd - pc) > es) {
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void *_l, *_r;
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/* Iterate rather than recurse to save stack space */
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a = pn - r;
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n = r / es;
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_l = a;
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_r = ((unsigned char*)a)+r-1;
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if (!((lrange < _l && rrange < _l) ||
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(lrange > _r && rrange > _r)))
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goto loop;
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}
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/* qsort(pn - r, r / es, es, cmp);*/
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}
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void
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pqsort(void *a, size_t n, size_t es,
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int (*cmp) (const void *, const void *), size_t lrange, size_t rrange)
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{
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_pqsort(a,n,es,cmp,((unsigned char*)a)+(lrange*es),
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((unsigned char*)a)+((rrange+1)*es)-1);
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}
文章来源: fantianzuo.blog.csdn.net，作者：兔老大RabbitMQ，版权归原作者所有，如需转载，请联系作者。
原文链接：fantianzuo.blog.csdn.net/article/details/102470205
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