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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.

598
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))
/* 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 */
/* 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
typedef struct
{
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. :-)
Everything below this comment until the HAVE_QSORT #endif was from PDCLib.
--ryan.
*/
/* 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 \
}
/* $Id$ */
/* 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; \
}
/* qsort( void *, size_t, size_t, int(*)( const void *, const void * ) )
#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 \
}
/* 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().
This file is part of the Public Domain C Library (PDCLib).
Permission is granted to use, modify, and / or redistribute at will.
*/
#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); \
} \
}
#include <stdlib.h>
#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); }
#ifndef REGTEST
#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); }
/* This implementation is taken from Paul Edward's PDPCLIB.
#define SWAP_words(a,b) { \
register int t=*((int*)a); *((int*)a)=*((int*)b); *((int*)b)=t; }
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.
*/
/* ---------------------------------------------------------------------- */
static char *
pivot_big(char *first, char *mid, char *last, size_t size,
int compare(const void *, const void *))
/* Wrapper for _PDCLIB_memswp protects against multiple argument evaluation. */
static inline void memswp( char * i, char * j, size_t size )
{
size_t d = (((last - first) / size) >> 3) * size;
char *m1, *m2, *m3;
_PDCLIB_memswp( i, j, size );
}
/* 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 *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));
}
char * i;
char * j;
_PDCLIB_size_t thresh = T * size;
char * base_ = (char *)base;
char * limit = base_ + nmemb * size;
PREPARE_STACK;
for ( ;; )
{
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));
}
if ( (size_t)( limit - base_ ) > thresh ) /* QSort for more than T elements. */
{
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 *))
/* 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 ( ;; )
{
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 */
do
{
char *mid = first + size * ((last - first) / size >> 1);
Pivot(SWAP_nonaligned, size);
memcpy(pivot, mid, size);
}
/* Partition. */
Partition(SWAP_nonaligned, size);
/* Prepare to recurse/iterate. */
Recurse(trunc)}
}
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 *))
/* move i right until *i >= pivot */
i += size;
} while ( compar( i, base_ ) < 0 );
do
{
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 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_aligned, size);
memcpy(pivot, mid, size);
/* break loop if pointers crossed */
break;
}
/* Partition. */
Partition(SWAP_aligned, size);
/* Prepare to recurse/iterate. */
Recurse(trunc)}
/* else swap elements, keep scanning */
memswp( i, j, size );
}
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 *))
/* move pivot into correct place */
memswp( base_, j, size );
/* larger subfile base / limit to stack, sort smaller */
if ( j - base_ > limit - i )
{
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;
/* left is larger */
PUSH( base_, j );
base_ = i;
}
#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: */