297 lines
9.1 KiB
C
297 lines
9.1 KiB
C
/****************************************************************************
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* libs/libc/stdlib/lib_qsort.c
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*
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* Copyright (C) 2007, 2009, 2011 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Leveraged from:
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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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*
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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. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. 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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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <sys/param.h>
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#include <stdlib.h>
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#define swapcode(TYPE, parmi, parmj, n) \
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{ \
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long i = (n) / sizeof (TYPE); \
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register TYPE *pi = (TYPE *)(parmi); \
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register TYPE *pj = (TYPE *)(parmj); \
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do { \
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register 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, width) \
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swaptype = ((FAR char *)a - (FAR char *)0) % sizeof(long) || \
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width % sizeof(long) ? 2 : width == sizeof(long)? 0 : 1;
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#define swap(a, b) \
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if (swaptype == 0) \
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{ \
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long t = *(long *)(a); \
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*(long *)(a) = *(long *)(b); \
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*(long *)(b) = t; \
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} \
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else \
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{ \
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swapfunc(a, b, width, swaptype); \
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}
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#define vecswap(a, b, n) if ((n) > 0) swapfunc(a, b, n, swaptype)
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/****************************************************************************
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* Private Function Prototypes
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****************************************************************************/
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static inline void swapfunc(FAR char *a, FAR char *b, int n, int swaptype);
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static inline FAR char *med3(FAR char *a, FAR char *b, FAR char *c,
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CODE int (*compar)(FAR const void *,
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FAR const void *));
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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static inline void swapfunc(FAR char *a, FAR char *b, int n, int swaptype)
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{
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if (swaptype <= 1)
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{
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swapcode(long, a, b, n)
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}
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else
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{
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swapcode(char, a, b, n)
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}
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}
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static inline FAR char *med3(FAR char *a, FAR char *b, FAR char *c,
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CODE int (*compar)(FAR const void *,
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FAR const void *))
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{
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return compar(a, b) < 0 ?
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(compar(b, c) < 0 ? b : (compar(a, c) < 0 ? c : a)) :
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(compar(b, c) > 0 ? b : (compar(a, c) < 0 ? a : c));
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}
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/****************************************************************************
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* Public Function
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****************************************************************************/
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/****************************************************************************
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* Name: qsort
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*
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* Description:
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* The qsort() function will sort an array of 'nel' objects, the initial
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* element of which is pointed to by 'base'. The size of each object, in
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* bytes, is specified by the 'width" argument. If the 'nel' argument has
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* the value zero, the comparison function pointed to by 'compar' will not
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* be called and no rearrangement will take place.
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*
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* The application will ensure that the comparison function pointed to by
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* 'compar' does not alter the contents of the array. The implementation
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* may reorder elements of the array between calls to the comparison
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* function, but will not alter the contents of any individual element.
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*
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* When the same objects (consisting of 'width" bytes, irrespective of
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* their current positions in the array) are passed more than once to
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* the comparison function, the results will be consistent with one
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* another. That is, they will define a total ordering on the array.
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*
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* The contents of the array will be sorted in ascending order according
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* to a comparison function. The 'compar' argument is a pointer to the
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* comparison function, which is called with two arguments that point to
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* the elements being compared. The application will ensure that the
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* function returns an integer less than, equal to, or greater than 0,
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* if the first argument is considered respectively less than, equal to,
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* or greater than the second. If two members compare as equal, their
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* order in the sorted array is unspecified.
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*
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* (Based on description from OpenGroup.org).
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*
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* Returned Value:
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* The qsort() function will not return a value.
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*
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* Notes from the original BSD version:
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* Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
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*
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****************************************************************************/
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void qsort(FAR void *base, size_t nel, size_t width,
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CODE int(*compar)(FAR const void *, FAR const void *))
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{
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FAR char *pa;
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FAR char *pb;
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FAR char *pc;
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FAR char *pd;
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FAR char *pl;
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FAR char *pm;
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FAR char *pn;
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int swaptype;
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int swap_cnt;
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int d;
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int r;
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loop:
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SWAPINIT(base, width);
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swap_cnt = 0;
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if (nel < 7)
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{
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for (pm = (FAR char *)base + width;
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pm < (FAR char *)base + nel * width;
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pm += width)
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{
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for (pl = pm;
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pl > (FAR char *)base && compar(pl - width, pl) > 0;
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pl -= width)
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{
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swap(pl, pl - width);
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}
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}
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return;
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}
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pm = (FAR char *)base + (nel / 2) * width;
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if (nel > 7)
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{
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pl = base;
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pn = (FAR char *)base + (nel - 1) * width;
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if (nel > 40)
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{
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d = (nel / 8) * width;
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pl = med3(pl, pl + d, pl + 2 * d, compar);
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pm = med3(pm - d, pm, pm + d, compar);
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pn = med3(pn - 2 * d, pn - d, pn, compar);
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}
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pm = med3(pl, pm, pn, compar);
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}
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swap(base, pm);
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pa = pb = (FAR char *)base + width;
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pc = pd = (FAR char *)base + (nel - 1) * width;
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for (; ; )
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{
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while (pb <= pc && (r = compar(pb, base)) <= 0)
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{
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if (r == 0)
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{
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swap_cnt = 1;
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swap(pa, pb);
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pa += width;
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}
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pb += width;
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}
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while (pb <= pc && (r = compar(pc, base)) >= 0)
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{
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if (r == 0)
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{
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swap_cnt = 1;
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swap(pc, pd);
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pd -= width;
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}
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pc -= width;
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}
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if (pb > pc)
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{
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break;
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}
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swap(pb, pc);
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swap_cnt = 1;
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pb += width;
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pc -= width;
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}
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if (swap_cnt == 0)
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{
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/* Switch to insertion sort */
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for (pm = (FAR char *)base + width;
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pm < (FAR char *)base + nel * width;
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pm += width)
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{
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for (pl = pm;
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pl > (FAR char *)base && compar(pl - width, pl) > 0;
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pl -= width)
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{
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swap(pl, pl - width);
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}
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}
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return;
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}
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pn = (FAR char *)base + nel * width;
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r = MIN(pa - (FAR char *)base, pb - pa);
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vecswap(base, pb - r, r);
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r = MIN(pd - pc, pn - pd - width);
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vecswap(pb, pn - r, r);
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if ((r = pb - pa) > width)
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{
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qsort(base, r / width, width, compar);
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}
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if ((r = pd - pc) > width)
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{
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/* Iterate rather than recurse to save stack space */
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base = pn - r;
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nel = r / width;
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goto loop;
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}
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}
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