SDL_qsort.c
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#include "../SDL_internal.h"
#include "SDL_stdinc.h"
#include "SDL_assert.h"
#if defined(HAVE_QSORT)
void
SDL_qsort(void *base, size_t nmemb, size_t size, int (*compare) (const void *, const void *))
{
qsort(base, nmemb, size, compare);
}
#else
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#ifdef REGTEST
#undef REGTEST
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#ifdef TEST
#undef TEST
#endif
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#ifndef _PDCLIB_memswp
#define _PDCLIB_memswp( i, j, size ) char tmp; do { tmp = *i; *i++ = *j; *j++ = tmp; } while ( --size );
#endif
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#ifndef _PDCLIB_size_t
#define _PDCLIB_size_t size_t
#endif
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#define qsort SDL_qsort
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#define inline SDL_INLINE
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/*
This code came from PDCLib, under the public domain. Specifically this:
https://bitbucket.org/pdclib/pdclib/raw/a82b02d0c7d4ed633b97f2a7639d9a10b1c92ec8/functions/stdlib/qsort.c
The _PDCLIB_memswp macro was from
https://bitbucket.org/pdclib/pdclib/src/a82b02d0c7d4ed633b97f2a7639d9a10b1c92ec8/platform/posix/internals/_PDCLIB_config.h?at=default&fileviewer=file-view-default#_PDCLIB_config.h-28
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Everything below this comment until the HAVE_QSORT #endif was from PDCLib.
--ryan.
*/
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/* qsort( void *, size_t, size_t, int(*)( const void *, const void * ) )
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This file is part of the Public Domain C Library (PDCLib).
Permission is granted to use, modify, and / or redistribute at will.
*/
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#include <stdlib.h>
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#ifndef REGTEST
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/* This implementation is taken from Paul Edward's PDPCLIB.
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Original code is credited to Raymond Gardner, Englewood CO.
Minor mods are credited to Paul Edwards.
Some reformatting and simplification done by Martin Baute.
All code is still Public Domain.
*/
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/* Wrapper for _PDCLIB_memswp protects against multiple argument evaluation. */
static inline void memswp( char * i, char * j, size_t size )
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_PDCLIB_memswp( i, j, size );
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/* For small sets, insertion sort is faster than quicksort.
T is the threshold below which insertion sort will be used.
Must be 3 or larger.
*/
#define T 7
/* Macros for handling the QSort stack */
#define PREPARE_STACK char * stack[STACKSIZE]; char * * stackptr = stack
#define PUSH( base, limit ) stackptr[0] = base; stackptr[1] = limit; stackptr += 2
#define POP( base, limit ) stackptr -= 2; base = stackptr[0]; limit = stackptr[1]
/* TODO: Stack usage is log2( nmemb ) (minus what T shaves off the worst case).
Worst-case nmemb is platform dependent and should probably be
configured through _PDCLIB_config.h.
*/
#define STACKSIZE 64
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void qsort( void * base, size_t nmemb, size_t size, int (*compar)( const void *, const void * ) )
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char * i;
char * j;
_PDCLIB_size_t thresh = T * size;
char * base_ = (char *)base;
char * limit = base_ + nmemb * size;
PREPARE_STACK;
for ( ;; )
{
if ( (size_t)( limit - base_ ) > thresh ) /* QSort for more than T elements. */
{
/* We work from second to last - first will be pivot element. */
i = base_ + size;
j = limit - size;
/* We swap first with middle element, then sort that with second
and last element so that eventually first element is the median
of the three - avoiding pathological pivots.
TODO: Instead of middle element, chose one randomly.
*/
memswp( ( ( ( (size_t)( limit - base_ ) ) / size ) / 2 ) * size + base_, base_, size );
if ( compar( i, j ) > 0 ) memswp( i, j, size );
if ( compar( base_, j ) > 0 ) memswp( base_, j, size );
if ( compar( i, base_ ) > 0 ) memswp( i, base_, size );
/* Now we have the median for pivot element, entering main Quicksort. */
for ( ;; )
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do
{
/* move i right until *i >= pivot */
i += size;
} while ( compar( i, base_ ) < 0 );
do
{
/* move j left until *j <= pivot */
j -= size;
} while ( compar( j, base_ ) > 0 );
if ( i > j )
{
/* break loop if pointers crossed */
break;
}
/* else swap elements, keep scanning */
memswp( i, j, size );
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/* move pivot into correct place */
memswp( base_, j, size );
/* larger subfile base / limit to stack, sort smaller */
if ( j - base_ > limit - i )
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/* left is larger */
PUSH( base_, j );
base_ = i;
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/* right is larger */
PUSH( i, limit );
limit = j;
}
}
else /* insertion sort for less than T elements */
{
for ( j = base_, i = j + size; i < limit; j = i, i += size )
{
for ( ; compar( j, j + size ) > 0; j -= size )
{
memswp( j, j + size, size );
if ( j == base_ )
{
break;
}
}
}
if ( stackptr != stack ) /* if any entries on stack */
{
POP( base_, limit );
}
else /* else stack empty, done */
{
break;
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}
}
}
}
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#ifdef TEST
#include <_PDCLIB_test.h>
#include <string.h>
#include <limits.h>
static int compare( const void * left, const void * right )
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return *( (unsigned char *)left ) - *( (unsigned char *)right );
}
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int main( void )
{
char presort[] = { "shreicnyjqpvozxmbt" };
char sorted1[] = { "bcehijmnopqrstvxyz" };
char sorted2[] = { "bticjqnyozpvreshxm" };
char s[19];
strcpy( s, presort );
qsort( s, 18, 1, compare );
TESTCASE( strcmp( s, sorted1 ) == 0 );
strcpy( s, presort );
qsort( s, 9, 2, compare );
TESTCASE( strcmp( s, sorted2 ) == 0 );
strcpy( s, presort );
qsort( s, 1, 1, compare );
TESTCASE( strcmp( s, presort ) == 0 );
#if defined(REGTEST) && (__BSD_VISIBLE || __APPLE__)
puts( "qsort.c: Skipping test #4 for BSD as it goes into endless loop here." );
#else
qsort( s, 100, 0, compare );
TESTCASE( strcmp( s, presort ) == 0 );
#endif
return TEST_RESULTS;
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#endif
#endif /* HAVE_QSORT */
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/* vi: set ts=4 sw=4 expandtab: */