346 lines
10 KiB
C
346 lines
10 KiB
C
/*
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FUNCTION
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<<qsort>>---sort an array
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INDEX
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qsort
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SYNOPSIS
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#include <stdlib.h>
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void qsort(void *<[base]>, size_t <[nmemb]>, size_t <[size]>,
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int (*<[compar]>)(const void *, const void *) );
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DESCRIPTION
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<<qsort>> sorts an array (beginning at <[base]>) of <[nmemb]> objects.
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<[size]> describes the size of each element of the array.
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You must supply a pointer to a comparison function, using the argument
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shown as <[compar]>. (This permits sorting objects of unknown
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properties.) Define the comparison function to accept two arguments,
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each a pointer to an element of the array starting at <[base]>. The
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result of <<(*<[compar]>)>> must be negative if the first argument is
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less than the second, zero if the two arguments match, and positive if
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the first argument is greater than the second (where ``less than'' and
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``greater than'' refer to whatever arbitrary ordering is appropriate).
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The array is sorted in place; that is, when <<qsort>> returns, the
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array elements beginning at <[base]> have been reordered.
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RETURNS
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<<qsort>> does not return a result.
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PORTABILITY
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<<qsort>> is required by ANSI (without specifying the sorting algorithm).
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*/
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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 <_ansi.h>
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#include <sys/cdefs.h>
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#include <stdlib.h>
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#ifndef __GNUC__
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#define inline
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#endif
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#if defined(I_AM_QSORT_R)
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typedef int cmp_t(void *, const void *, const void *);
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#elif defined(I_AM_GNU_QSORT_R)
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typedef int cmp_t(const void *, const void *, void *);
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#else
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typedef int cmp_t(const void *, const void *);
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#endif
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static inline char *med3 (char *, char *, char *, cmp_t *, void *);
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static inline void swapfunc (char *, char *, int, 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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long i = (n) / sizeof (TYPE); \
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TYPE *pi = (TYPE *) (parmi); \
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TYPE *pj = (TYPE *) (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,
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char *b,
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int n,
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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 *)(a); \
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*(long *)(a) = *(long *)(b); \
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*(long *)(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, n, swaptype)
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#if defined(I_AM_QSORT_R)
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#define CMP(t, x, y) (cmp((t), (x), (y)))
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#elif defined(I_AM_GNU_QSORT_R)
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#define CMP(t, x, y) (cmp((x), (y), (t)))
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#else
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#define CMP(t, x, y) (cmp((x), (y)))
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#endif
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static inline char *
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med3 (char *a,
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char *b,
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char *c,
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cmp_t *cmp,
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void *thunk
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#if !defined(I_AM_QSORT_R) && !defined(I_AM_GNU_QSORT_R)
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__unused
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#endif
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)
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{
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return CMP(thunk, a, b) < 0 ?
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(CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a ))
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:(CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c ));
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}
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/*
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* Classical function call recursion wastes a lot of stack space. Each
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* recursion level requires a full stack frame comprising all local variables
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* and additional space as dictated by the processor calling convention.
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*
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* This implementation instead stores the variables that are unique for each
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* recursion level in a parameter stack array, and uses iteration to emulate
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* recursion. Function call recursion is not used until the array is full.
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*
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* To ensure the stack consumption isn't worsened by this design, the size of
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* the parameter stack array is chosen to be similar to the stack frame
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* excluding the array. Each function call recursion level can handle this
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* number of iterative recursion levels.
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*/
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#define PARAMETER_STACK_LEVELS 8u
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#if defined(I_AM_QSORT_R)
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void
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__bsd_qsort_r (void *a,
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size_t n,
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size_t es,
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void *thunk,
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cmp_t *cmp)
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#elif defined(I_AM_GNU_QSORT_R)
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void
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qsort_r (void *a,
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size_t n,
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size_t es,
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cmp_t *cmp,
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void *thunk)
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#else
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#define thunk NULL
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void
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qsort (void *a,
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size_t n,
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size_t es,
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cmp_t *cmp)
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#endif
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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 cmp_result;
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int swaptype, swap_cnt;
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size_t recursion_level = 0;
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struct { void *a; size_t n; } parameter_stack[PARAMETER_STACK_LEVELS];
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SWAPINIT(a, es);
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loop: swap_cnt = 0;
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if (n < 7) {
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/* Short arrays are insertion sorted. */
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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(thunk, pl - es, pl) > 0;
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pl -= es)
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swap(pl, pl - es);
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goto pop;
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}
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/* Select a pivot element, move it to the left. */
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pm = (char *) a + (n / 2) * es;
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if (n > 7) {
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pl = 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, thunk);
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pm = med3(pm - d, pm, pm + d, cmp, thunk);
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pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk);
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}
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pm = med3(pl, pm, pn, cmp, thunk);
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}
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swap(a, pm);
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/*
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* Sort the array relative the pivot in four ranges as follows:
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* { elems == pivot, elems < pivot, elems > pivot, elems == pivot }
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*/
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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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/* Scan left to right stopping at first element > pivot. */
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while (pb <= pc && (cmp_result = CMP(thunk, pb, a)) <= 0) {
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/* Move elements == pivot to the left (to pa) */
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if (cmp_result == 0) {
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swap_cnt = 1;
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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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/* Scan right to left stopping at first element < pivot. */
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while (pb <= pc && (cmp_result = CMP(thunk, pc, a)) >= 0) {
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/* Move elements == pivot to the right (to pd) */
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if (cmp_result == 0) {
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swap_cnt = 1;
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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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/* The scan has found two elements to swap with each other. */
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swap(pb, pc);
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swap_cnt = 1;
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pb += es;
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pc -= es;
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}
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if (swap_cnt == 0) { /* Switch to insertion sort */
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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(thunk, pl - es, pl) > 0;
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pl -= es)
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swap(pl, pl - es);
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goto pop;
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}
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/*
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* Rearrange the array in three parts sorted like this:
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* { elements < pivot, elements == pivot, elements > pivot }
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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(pd - pc, pn - pd - es);
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vecswap(pb, pn - r, r);
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d = pb - pa; /* d = Size of left part. */
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r = pd - pc; /* r = Size of right part. */
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pn -= r; /* pn = Base of right part. */
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/*
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* Check which of the left and right parts are larger.
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* Set (a, n) to (base, size) of the larger part.
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* Set (pa, r) to (base, size) of the smaller part.
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*/
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if (r > d) { /* Right part is the larger part */
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pa = a;
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a = pn;
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n = r;
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r = d;
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}
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else { /* Left part is the larger part, or both are equal. */
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pa = pn;
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n = d;
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}
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/*
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* The left and right parts each need further sorting if they
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* contain two elements or more. If both need sorting we use
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* recursion to sort the smaller part and save the larger part
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* to be sorted by iteration after the recursion.
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* Using recursion only for the smaller part guarantees a
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* recursion depth that is bounded to be less than (log2(n)).
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*/
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if (r > es) { /* Smaller part > 1 element. Both parts need sorting. */
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if (recursion_level < PARAMETER_STACK_LEVELS) {
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/*
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* The smaller part needs to be recursively sorted
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* before the larger part is sorted. To avoid function
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* call recursion the parameters for the larger part
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* are pushed on the parameter_stack array. The smaller
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* part is sorted using iteration and the larger part
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* will be sorted when the parameter_stack is popped
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* after the smaller part has been sorted.
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*/
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parameter_stack[recursion_level].a = a;
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parameter_stack[recursion_level].n = n / es;
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recursion_level++;
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a = pa;
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n = r / es;
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goto loop;
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}
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else {
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/*
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* The parameter_stack array is full. The smaller part
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* is sorted using function call recursion. The larger
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* part will be sorted after the function call returns.
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*/
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#if defined(I_AM_QSORT_R)
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__bsd_qsort_r(pa, r / es, es, thunk, cmp);
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#elif defined(I_AM_GNU_QSORT_R)
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qsort_r(pa, r / es, es, cmp, thunk);
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#else
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qsort(pa, r / es, es, cmp);
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#endif
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}
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}
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if (n > es) { /* The larger part needs sorting. Iterate to sort. */
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n = n / es;
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goto loop;
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}
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/* Both left and right parts are one element or less - level done. */
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pop:
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if (recursion_level != 0) {
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recursion_level--;
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a = parameter_stack[recursion_level].a;
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n = parameter_stack[recursion_level].n;
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goto loop;
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}
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}
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