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Replaced SDL_qsort with public domain code from PDCLib: http://pdclib.e43.eu/

This commit is contained in:
Ryan C. Gordon 2016-02-15 03:16:46 -05:00
parent 33af421d7b
commit 014956ac1d
2 changed files with 167 additions and 446 deletions
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11
debian/copyright vendored
View File

@ -31,10 +31,6 @@ Copyright: 1995 Erik Corry
1995 Brown University
License: BrownUn_UnCalifornia_ErikCorry
Files: src/stdlib/SDL_qsort.c
Copyright: 1998 Gareth McCaughan
License: Gareth_McCaughan
Files: src/test/SDL_test_md5.c
Copyright: 1997-2016 Sam Lantinga <slouken@libsdl.org>
1990 RSA Data Security, Inc.
@ -270,13 +266,6 @@ License: BrownUn_UnCalifornia_ErikCorry
* SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
*/
License: Gareth_McCaughan
You may use it in anything you like; you may make money
out of it; you may distribute it in object form or as
part of an executable without including source code;
you don't have to credit me. (But it would be nice if
you did.)
License: Johnson_M._Hart
Permission is granted for any and all use providing that this
copyright is properly acknowledged.

612
src/stdlib/SDL_qsort.c
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@ -1,58 +1,5 @@
/* qsort.c
* (c) 1998 Gareth McCaughan
*
* This is a drop-in replacement for the C library's |qsort()| routine.
*
* Features:
* - Median-of-three pivoting (and more)
* - Truncation and final polishing by a single insertion sort
* - Early truncation when no swaps needed in pivoting step
* - Explicit recursion, guaranteed not to overflow
* - A few little wrinkles stolen from the GNU |qsort()|.
* - separate code for non-aligned / aligned / word-size objects
*
* This code may be reproduced freely provided
* - this file is retained unaltered apart from minor
* changes for portability and efficiency
* - no changes are made to this comment
* - any changes that *are* made are clearly flagged
* - the _ID string below is altered by inserting, after
* the date, the string " altered" followed at your option
* by other material. (Exceptions: you may change the name
* of the exported routine without changing the ID string.
* You may change the values of the macros TRUNC_* and
* PIVOT_THRESHOLD without changing the ID string, provided
* they remain constants with TRUNC_nonaligned, TRUNC_aligned
* and TRUNC_words/WORD_BYTES between 8 and 24, and
* PIVOT_THRESHOLD between 32 and 200.)
*
* You may use it in anything you like; you may make money
* out of it; you may distribute it in object form or as
* part of an executable without including source code;
* you don't have to credit me. (But it would be nice if
* you did.)
*
* If you find problems with this code, or find ways of
* making it significantly faster, please let me know!
* My e-mail address, valid as of early 1998 and certainly
* OK for at least the next 18 months, is
* gjm11@dpmms.cam.ac.uk
* Thanks!
*
* Gareth McCaughan Peterhouse Cambridge 1998
*/
#if defined(__clang_analyzer__) && !defined(SDL_DISABLE_ANALYZE_MACROS)
#define SDL_DISABLE_ANALYZE_MACROS 1
#endif
#include "../SDL_internal.h"
/*
#include <assert.h>
#include <stdlib.h>
#include <string.h>
*/
#include "SDL_stdinc.h"
#include "SDL_assert.h"
@ -64,418 +11,203 @@ SDL_qsort(void *base, size_t nmemb, size_t size, int (*compare) (const void *, c
}
#else
#ifdef assert
#undef assert
#ifdef REGTEST
#undef REGTEST
#endif
#define assert(X) SDL_assert(X)
#ifdef malloc
#undef malloc
#ifdef TEST
#undef TEST
#endif
#define malloc SDL_malloc
#ifdef free
#undef free
#ifndef _PDCLIB_memswp
#define _PDCLIB_memswp( i, j, size ) char tmp; do { tmp = *i; *i++ = *j; *j++ = tmp; } while ( --size );
#endif
#define free SDL_free
#ifdef memcpy
#undef memcpy
#endif
#define memcpy SDL_memcpy
#ifdef memmove
#undef memmove
#endif
#define memmove SDL_memmove
#ifdef qsort
#undef qsort
#ifndef _PDCLIB_size_t
#define _PDCLIB_size_t size_t
#endif
#define qsort SDL_qsort
static const char _ID[] = "<qsort.c gjm 1.12 1998-03-19>";
#define inline SDL_INLINE
/* How many bytes are there per word? (Must be a power of 2,
* and must in fact equal sizeof(int).)
*/
#define WORD_BYTES sizeof(int)
/*
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
/* How big does our stack need to be? Answer: one entry per
* bit in a |size_t|.
*/
#define STACK_SIZE (8*sizeof(size_t))
Everything below this comment until the HAVE_QSORT #endif was from PDCLib.
--ryan.
*/
/* Different situations have slightly different requirements,
* and we make life epsilon easier by using different truncation
* points for the three different cases.
* So far, I have tuned TRUNC_words and guessed that the same
* value might work well for the other two cases. Of course
* what works well on my machine might work badly on yours.
*/
#define TRUNC_nonaligned 12
#define TRUNC_aligned 12
#define TRUNC_words 12*WORD_BYTES /* nb different meaning */
/* $Id$ */
/* We use a simple pivoting algorithm for shortish sub-arrays
* and a more complicated one for larger ones. The threshold
* is PIVOT_THRESHOLD.
*/
#define PIVOT_THRESHOLD 40
/* qsort( void *, size_t, size_t, int(*)( const void *, const void * ) )
typedef struct
This file is part of the Public Domain C Library (PDCLib).
Permission is granted to use, modify, and / or redistribute at will.
*/
#include <stdlib.h>
#ifndef REGTEST
/* This implementation is taken from Paul Edward's PDPCLIB.
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.
*/
/* Wrapper for _PDCLIB_memswp protects against multiple argument evaluation. */
static inline void memswp( char * i, char * j, size_t size )
{
char *first;
char *last;
} stack_entry;
#define pushLeft {stack[stacktop].first=ffirst;stack[stacktop++].last=last;}
#define pushRight {stack[stacktop].first=first;stack[stacktop++].last=llast;}
#define doLeft {first=ffirst;llast=last;continue;}
#define doRight {ffirst=first;last=llast;continue;}
#define pop {if (--stacktop<0) break;\
first=ffirst=stack[stacktop].first;\
last=llast=stack[stacktop].last;\
continue;}
/* Some comments on the implementation.
* 1. When we finish partitioning the array into "low"
* and "high", we forget entirely about short subarrays,
* because they'll be done later by insertion sort.
* Doing lots of little insertion sorts might be a win
* on large datasets for locality-of-reference reasons,
* but it makes the code much nastier and increases
* bookkeeping overhead.
* 2. We always save the shorter and get to work on the
* longer. This guarantees that every time we push
* an item onto the stack its size is <= 1/2 of that
* of its parent; so the stack can't need more than
* log_2(max-array-size) entries.
* 3. We choose a pivot by looking at the first, last
* and middle elements. We arrange them into order
* because it's easy to do that in conjunction with
* choosing the pivot, and it makes things a little
* easier in the partitioning step. Anyway, the pivot
* is the middle of these three. It's still possible
* to construct datasets where the algorithm takes
* time of order n^2, but it simply never happens in
* practice.
* 3' Newsflash: On further investigation I find that
* it's easy to construct datasets where median-of-3
* simply isn't good enough. So on large-ish subarrays
* we do a more sophisticated pivoting: we take three
* sets of 3 elements, find their medians, and then
* take the median of those.
* 4. We copy the pivot element to a separate place
* because that way we can always do our comparisons
* directly against a pointer to that separate place,
* and don't have to wonder "did we move the pivot
* element?". This makes the inner loop better.
* 5. It's possible to make the pivoting even more
* reliable by looking at more candidates when n
* is larger. (Taking this to its logical conclusion
* results in a variant of quicksort that doesn't
* have that n^2 worst case.) However, the overhead
* from the extra bookkeeping means that it's just
* not worth while.
* 6. This is pretty clean and portable code. Here are
* all the potential portability pitfalls and problems
* I know of:
* - In one place (the insertion sort) I construct
* a pointer that points just past the end of the
* supplied array, and assume that (a) it won't
* compare equal to any pointer within the array,
* and (b) it will compare equal to a pointer
* obtained by stepping off the end of the array.
* These might fail on some segmented architectures.
* - I assume that there are 8 bits in a |char| when
* computing the size of stack needed. This would
* fail on machines with 9-bit or 16-bit bytes.
* - I assume that if |((int)base&(sizeof(int)-1))==0|
* and |(size&(sizeof(int)-1))==0| then it's safe to
* get at array elements via |int*|s, and that if
* actually |size==sizeof(int)| as well then it's
* safe to treat the elements as |int|s. This might
* fail on systems that convert pointers to integers
* in non-standard ways.
* - I assume that |8*sizeof(size_t)<=INT_MAX|. This
* would be false on a machine with 8-bit |char|s,
* 16-bit |int|s and 4096-bit |size_t|s. :-)
*/
/* The recursion logic is the same in each case: */
#define Recurse(Trunc) \
{ size_t l=last-ffirst,r=llast-first; \
if (l<Trunc) { \
if (r>=Trunc) doRight \
else pop \
} \
else if (l<=r) { pushLeft; doRight } \
else if (r>=Trunc) { pushRight; doLeft }\
else doLeft \
}
/* and so is the pivoting logic: */
#define Pivot(swapper,sz) \
if ((size_t)(last-first)>PIVOT_THRESHOLD*sz) mid=pivot_big(first,mid,last,sz,compare);\
else { \
if (compare(first,mid)<0) { \
if (compare(mid,last)>0) { \
swapper(mid,last); \
if (compare(first,mid)>0) swapper(first,mid);\
} \
} \
else { \
if (compare(mid,last)>0) swapper(first,last)\
else { \
swapper(first,mid); \
if (compare(mid,last)>0) swapper(mid,last);\
} \
} \
first+=sz; last-=sz; \
}
#ifdef DEBUG_QSORT
#include <stdio.h>
#endif
/* and so is the partitioning logic: */
#define Partition(swapper,sz) { \
int swapped=0; \
do { \
while (compare(first,pivot)<0) first+=sz; \
while (compare(pivot,last)<0) last-=sz; \
if (first<last) { \
swapper(first,last); swapped=1; \
first+=sz; last-=sz; } \
else if (first==last) { first+=sz; last-=sz; break; }\
} while (first<=last); \
if (!swapped) pop \
_PDCLIB_memswp( i, j, size );
}
/* and so is the pre-insertion-sort operation of putting
* the smallest element into place as a sentinel.
* Doing this makes the inner loop nicer. I got this
* idea from the GNU implementation of qsort().
/* 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
void qsort( void * base, size_t nmemb, size_t size, int (*compar)( const void *, const void * ) )
{
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.
*/
#define PreInsertion(swapper,limit,sz) \
first=base; \
last=first + (nmemb>limit ? limit : nmemb-1)*sz;\
while (last!=base) { \
if (compare(first,last)>0) first=last; \
last-=sz; } \
if (first!=base) swapper(first,(char*)base);
/* and so is the insertion sort, in the first two cases: */
#define Insertion(swapper) \
last=((char*)base)+nmemb*size; \
for (first=((char*)base)+size;first!=last;first+=size) { \
char *test; \
/* Find the right place for |first|. \
* My apologies for var reuse. */ \
for (test=first-size;compare(test,first)>0;test-=size) ; \
test+=size; \
if (test!=first) { \
/* Shift everything in [test,first) \
* up by one, and place |first| \
* where |test| is. */ \
memcpy(pivot,first,size); \
memmove(test+size,test,first-test); \
memcpy(test,pivot,size); \
} \
}
#define SWAP_nonaligned(a,b) { \
register char *aa=(a),*bb=(b); \
register size_t sz=size; \
do { register char t=*aa; *aa++=*bb; *bb++=t; } while (--sz); }
#define SWAP_aligned(a,b) { \
register int *aa=(int*)(a),*bb=(int*)(b); \
register size_t sz=size; \
do { register int t=*aa;*aa++=*bb; *bb++=t; } while (sz-=WORD_BYTES); }
#define SWAP_words(a,b) { \
register int t=*((int*)a); *((int*)a)=*((int*)b); *((int*)b)=t; }
/* ---------------------------------------------------------------------- */
static char *
pivot_big(char *first, char *mid, char *last, size_t size,
int compare(const void *, const void *))
{
size_t d = (((last - first) / size) >> 3) * size;
char *m1, *m2, *m3;
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 ( ;; )
{
char *a = first, *b = first + d, *c = first + 2 * d;
#ifdef DEBUG_QSORT
fprintf(stderr, "< %d %d %d\n", *(int *) a, *(int *) b, *(int *) c);
#endif
m1 = compare(a, b) < 0 ?
(compare(b, c) < 0 ? b : (compare(a, c) < 0 ? c : a))
: (compare(a, c) < 0 ? a : (compare(b, c) < 0 ? c : b));
}
do
{
char *a = mid - d, *b = mid, *c = mid + d;
#ifdef DEBUG_QSORT
fprintf(stderr, ". %d %d %d\n", *(int *) a, *(int *) b, *(int *) c);
#endif
m2 = compare(a, b) < 0 ?
(compare(b, c) < 0 ? b : (compare(a, c) < 0 ? c : a))
: (compare(a, c) < 0 ? a : (compare(b, c) < 0 ? c : b));
}
/* move i right until *i >= pivot */
i += size;
} while ( compar( i, base_ ) < 0 );
do
{
char *a = last - 2 * d, *b = last - d, *c = last;
#ifdef DEBUG_QSORT
fprintf(stderr, "> %d %d %d\n", *(int *) a, *(int *) b, *(int *) c);
#endif
m3 = compare(a, b) < 0 ?
(compare(b, c) < 0 ? b : (compare(a, c) < 0 ? c : a))
: (compare(a, c) < 0 ? a : (compare(b, c) < 0 ? c : b));
}
#ifdef DEBUG_QSORT
fprintf(stderr, "-> %d %d %d\n", *(int *) m1, *(int *) m2, *(int *) m3);
#endif
return compare(m1, m2) < 0 ?
(compare(m2, m3) < 0 ? m2 : (compare(m1, m3) < 0 ? m3 : m1))
: (compare(m1, m3) < 0 ? m1 : (compare(m2, m3) < 0 ? m3 : m2));
}
/* ---------------------------------------------------------------------- */
static void
qsort_nonaligned(void *base, size_t nmemb, size_t size,
int (*compare) (const void *, const void *))
{
stack_entry stack[STACK_SIZE];
int stacktop = 0;
char *first, *last;
char *pivot = malloc(size);
size_t trunc = TRUNC_nonaligned * size;
assert(pivot != 0);
first = (char *) base;
last = first + (nmemb - 1) * size;
if ((size_t) (last - first) > trunc) {
char *ffirst = first, *llast = last;
while (1) {
/* Select pivot */
/* move j left until *j <= pivot */
j -= size;
} while ( compar( j, base_ ) > 0 );
if ( i > j )
{
char *mid = first + size * ((last - first) / size >> 1);
Pivot(SWAP_nonaligned, size);
memcpy(pivot, mid, size);
/* break loop if pointers crossed */
break;
}
/* Partition. */
Partition(SWAP_nonaligned, size);
/* Prepare to recurse/iterate. */
Recurse(trunc)}
/* else swap elements, keep scanning */
memswp( i, j, size );
}
PreInsertion(SWAP_nonaligned, TRUNC_nonaligned, size);
Insertion(SWAP_nonaligned);
free(pivot);
}
static void
qsort_aligned(void *base, size_t nmemb, size_t size,
int (*compare) (const void *, const void *))
{
stack_entry stack[STACK_SIZE];
int stacktop = 0;
char *first, *last;
char *pivot = malloc(size);
size_t trunc = TRUNC_aligned * size;
assert(pivot != 0);
first = (char *) base;
last = first + (nmemb - 1) * size;
if ((size_t) (last - first) > trunc) {
char *ffirst = first, *llast = last;
while (1) {
/* Select pivot */
/* move pivot into correct place */
memswp( base_, j, size );
/* larger subfile base / limit to stack, sort smaller */
if ( j - base_ > limit - i )
{
char *mid = first + size * ((last - first) / size >> 1);
Pivot(SWAP_aligned, size);
memcpy(pivot, mid, size);
/* left is larger */
PUSH( base_, j );
base_ = i;
}
/* Partition. */
Partition(SWAP_aligned, size);
/* Prepare to recurse/iterate. */
Recurse(trunc)}
}
PreInsertion(SWAP_aligned, TRUNC_aligned, size);
Insertion(SWAP_aligned);
free(pivot);
}
static void
qsort_words(void *base, size_t nmemb,
int (*compare) (const void *, const void *))
{
stack_entry stack[STACK_SIZE];
int stacktop = 0;
char *first, *last;
char *pivot = malloc(WORD_BYTES);
assert(pivot != 0);
first = (char *) base;
last = first + (nmemb - 1) * WORD_BYTES;
if (last - first > TRUNC_words) {
char *ffirst = first, *llast = last;
while (1) {
#ifdef DEBUG_QSORT
fprintf(stderr, "Doing %d:%d: ",
(first - (char *) base) / WORD_BYTES,
(last - (char *) base) / WORD_BYTES);
#endif
/* Select pivot */
{
char *mid =
first + WORD_BYTES * ((last - first) / (2 * WORD_BYTES));
Pivot(SWAP_words, WORD_BYTES);
*(int *) pivot = *(int *) mid;
}
#ifdef DEBUG_QSORT
fprintf(stderr, "pivot=%d\n", *(int *) pivot);
#endif
/* Partition. */
Partition(SWAP_words, WORD_BYTES);
/* Prepare to recurse/iterate. */
Recurse(TRUNC_words)}
}
PreInsertion(SWAP_words, (TRUNC_words / WORD_BYTES), WORD_BYTES);
/* Now do insertion sort. */
last = ((char *) base) + nmemb * WORD_BYTES;
for (first = ((char *) base) + WORD_BYTES; first != last;
first += WORD_BYTES) {
/* Find the right place for |first|. My apologies for var reuse */
int *pl = (int *) (first - WORD_BYTES), *pr = (int *) first;
*(int *) pivot = *(int *) first;
for (; compare(pl, pivot) > 0; pr = pl, --pl) {
*pr = *pl;
}
if (pr != (int *) first)
*pr = *(int *) pivot;
}
free(pivot);
}
/* ---------------------------------------------------------------------- */
void
qsort(void *base, size_t nmemb, size_t size,
int (*compare) (const void *, const void *))
{
if (nmemb <= 1)
return;
if (((uintptr_t) base | size) & (WORD_BYTES - 1))
qsort_nonaligned(base, nmemb, size, compare);
else if (size != WORD_BYTES)
qsort_aligned(base, nmemb, size, compare);
else
qsort_words(base, nmemb, compare);
{
/* 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;
}
}
}
}
#endif /* !SDL_qsort */
#endif
#ifdef TEST
#include <_PDCLIB_test.h>
#include <string.h>
#include <limits.h>
static int compare( const void * left, const void * right )
{
return *( (unsigned char *)left ) - *( (unsigned char *)right );
}
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;
}
#endif
#endif /* HAVE_QSORT */
/* vi: set ts=4 sw=4 expandtab: */