newlib-cygwin/newlib/libc/search/qsort.c

346 lines
10 KiB
C

/*
FUNCTION
<<qsort>>---sort an array
INDEX
qsort
SYNOPSIS
#include <stdlib.h>
void qsort(void *<[base]>, size_t <[nmemb]>, size_t <[size]>,
int (*<[compar]>)(const void *, const void *) );
DESCRIPTION
<<qsort>> sorts an array (beginning at <[base]>) of <[nmemb]> objects.
<[size]> describes the size of each element of the array.
You must supply a pointer to a comparison function, using the argument
shown as <[compar]>. (This permits sorting objects of unknown
properties.) Define the comparison function to accept two arguments,
each a pointer to an element of the array starting at <[base]>. The
result of <<(*<[compar]>)>> must be negative if the first argument is
less than the second, zero if the two arguments match, and positive if
the first argument is greater than the second (where ``less than'' and
``greater than'' refer to whatever arbitrary ordering is appropriate).
The array is sorted in place; that is, when <<qsort>> returns, the
array elements beginning at <[base]> have been reordered.
RETURNS
<<qsort>> does not return a result.
PORTABILITY
<<qsort>> is required by ANSI (without specifying the sorting algorithm).
*/
/*-
* 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 <_ansi.h>
#include <sys/cdefs.h>
#include <stdlib.h>
#ifndef __GNUC__
#define inline
#endif
#if defined(I_AM_QSORT_R)
typedef int cmp_t(void *, const void *, const void *);
#elif defined(I_AM_GNU_QSORT_R)
typedef int cmp_t(const void *, const void *, void *);
#else
typedef int cmp_t(const void *, const void *);
#endif
static inline char *med3 (char *, char *, char *, cmp_t *, void *);
static inline void swapfunc (char *, char *, int, 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) { \
long i = (n) / sizeof (TYPE); \
TYPE *pi = (TYPE *) (parmi); \
TYPE *pj = (TYPE *) (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,
int 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 *)(a); \
*(long *)(a) = *(long *)(b); \
*(long *)(b) = t; \
} else \
swapfunc(a, b, es, swaptype)
#define vecswap(a, b, n) if ((n) > 0) swapfunc(a, b, n, swaptype)
#if defined(I_AM_QSORT_R)
#define CMP(t, x, y) (cmp((t), (x), (y)))
#elif defined(I_AM_GNU_QSORT_R)
#define CMP(t, x, y) (cmp((x), (y), (t)))
#else
#define CMP(t, x, y) (cmp((x), (y)))
#endif
static inline char *
med3 (char *a,
char *b,
char *c,
cmp_t *cmp,
void *thunk
#if !defined(I_AM_QSORT_R) && !defined(I_AM_GNU_QSORT_R)
__unused
#endif
)
{
return CMP(thunk, a, b) < 0 ?
(CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a ))
:(CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c ));
}
/*
* Classical function call recursion wastes a lot of stack space. Each
* recursion level requires a full stack frame comprising all local variables
* and additional space as dictated by the processor calling convention.
*
* This implementation instead stores the variables that are unique for each
* recursion level in a parameter stack array, and uses iteration to emulate
* recursion. Function call recursion is not used until the array is full.
*
* To ensure the stack consumption isn't worsened by this design, the size of
* the parameter stack array is chosen to be similar to the stack frame
* excluding the array. Each function call recursion level can handle this
* number of iterative recursion levels.
*/
#define PARAMETER_STACK_LEVELS 8u
#if defined(I_AM_QSORT_R)
void
__bsd_qsort_r (void *a,
size_t n,
size_t es,
void *thunk,
cmp_t *cmp)
#elif defined(I_AM_GNU_QSORT_R)
void
qsort_r (void *a,
size_t n,
size_t es,
cmp_t *cmp,
void *thunk)
#else
#define thunk NULL
void
qsort (void *a,
size_t n,
size_t es,
cmp_t *cmp)
#endif
{
char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
size_t d, r;
int cmp_result;
int swaptype, swap_cnt;
size_t recursion_level = 0;
struct { void *a; size_t n; } parameter_stack[PARAMETER_STACK_LEVELS];
SWAPINIT(a, es);
loop: swap_cnt = 0;
if (n < 7) {
/* Short arrays are insertion sorted. */
for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
for (pl = pm; pl > (char *) a && CMP(thunk, pl - es, pl) > 0;
pl -= es)
swap(pl, pl - es);
goto pop;
}
/* Select a pivot element, move it to the left. */
pm = (char *) a + (n / 2) * es;
if (n > 7) {
pl = a;
pn = (char *) a + (n - 1) * es;
if (n > 40) {
d = (n / 8) * es;
pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk);
pm = med3(pm - d, pm, pm + d, cmp, thunk);
pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk);
}
pm = med3(pl, pm, pn, cmp, thunk);
}
swap(a, pm);
/*
* Sort the array relative the pivot in four ranges as follows:
* { elems == pivot, elems < pivot, elems > pivot, elems == pivot }
*/
pa = pb = (char *) a + es;
pc = pd = (char *) a + (n - 1) * es;
for (;;) {
/* Scan left to right stopping at first element > pivot. */
while (pb <= pc && (cmp_result = CMP(thunk, pb, a)) <= 0) {
/* Move elements == pivot to the left (to pa) */
if (cmp_result == 0) {
swap_cnt = 1;
swap(pa, pb);
pa += es;
}
pb += es;
}
/* Scan right to left stopping at first element < pivot. */
while (pb <= pc && (cmp_result = CMP(thunk, pc, a)) >= 0) {
/* Move elements == pivot to the right (to pd) */
if (cmp_result == 0) {
swap_cnt = 1;
swap(pc, pd);
pd -= es;
}
pc -= es;
}
if (pb > pc)
break;
/* The scan has found two elements to swap with each other. */
swap(pb, pc);
swap_cnt = 1;
pb += es;
pc -= es;
}
if (swap_cnt == 0) { /* Switch to insertion sort */
for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
for (pl = pm; pl > (char *) a && CMP(thunk, pl - es, pl) > 0;
pl -= es)
swap(pl, pl - es);
goto pop;
}
/*
* Rearrange the array in three parts sorted like this:
* { elements < pivot, elements == pivot, elements > pivot }
*/
pn = (char *) a + n * es;
r = min(pa - (char *)a, pb - pa);
vecswap(a, pb - r, r);
r = min(pd - pc, pn - pd - es);
vecswap(pb, pn - r, r);
d = pb - pa; /* d = Size of left part. */
r = pd - pc; /* r = Size of right part. */
pn -= r; /* pn = Base of right part. */
/*
* Check which of the left and right parts are larger.
* Set (a, n) to (base, size) of the larger part.
* Set (pa, r) to (base, size) of the smaller part.
*/
if (r > d) { /* Right part is the larger part */
pa = a;
a = pn;
n = r;
r = d;
}
else { /* Left part is the larger part, or both are equal. */
pa = pn;
n = d;
}
/*
* The left and right parts each need further sorting if they
* contain two elements or more. If both need sorting we use
* recursion to sort the smaller part and save the larger part
* to be sorted by iteration after the recursion.
* Using recursion only for the smaller part guarantees a
* recursion depth that is bounded to be less than (log2(n)).
*/
if (r > es) { /* Smaller part > 1 element. Both parts need sorting. */
if (recursion_level < PARAMETER_STACK_LEVELS) {
/*
* The smaller part needs to be recursively sorted
* before the larger part is sorted. To avoid function
* call recursion the parameters for the larger part
* are pushed on the parameter_stack array. The smaller
* part is sorted using iteration and the larger part
* will be sorted when the parameter_stack is popped
* after the smaller part has been sorted.
*/
parameter_stack[recursion_level].a = a;
parameter_stack[recursion_level].n = n / es;
recursion_level++;
a = pa;
n = r / es;
goto loop;
}
else {
/*
* The parameter_stack array is full. The smaller part
* is sorted using function call recursion. The larger
* part will be sorted after the function call returns.
*/
#if defined(I_AM_QSORT_R)
__bsd_qsort_r(pa, r / es, es, thunk, cmp);
#elif defined(I_AM_GNU_QSORT_R)
qsort_r(pa, r / es, es, cmp, thunk);
#else
qsort(pa, r / es, es, cmp);
#endif
}
}
if (n > es) { /* The larger part needs sorting. Iterate to sort. */
n = n / es;
goto loop;
}
/* Both left and right parts are one element or less - level done. */
pop:
if (recursion_level != 0) {
recursion_level--;
a = parameter_stack[recursion_level].a;
n = parameter_stack[recursion_level].n;
goto loop;
}
}