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Update qsort implementation

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Aikawa Yataro 2024-06-19 00:09:45 +00:00 • committed by Ozkan Sezer
parent 02597cdc56
commit 0fe9f5da54
1 changed files with 20 additions and 12 deletions
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32
src/stdlib/SDL_qsort.c
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@ -48,7 +48,7 @@
/* /*
This code came from Gareth McCaughan, under the zlib license. This code came from Gareth McCaughan, under the zlib license.
Specifically this: https://www.mccaughan.org.uk/software/qsort.c-1.15 Specifically this: https://www.mccaughan.org.uk/software/qsort.c-1.16
Everything below this comment until the HAVE_QSORT #endif was from Gareth Everything below this comment until the HAVE_QSORT #endif was from Gareth
(any minor changes will be noted inline). (any minor changes will be noted inline).
@ -97,7 +97,7 @@ Update for SDL3: we have modified this from a qsort function to qsort_r.
* Gareth McCaughan * Gareth McCaughan
*/ */
/* Copyright (c) 1998-2016 Gareth McCaughan /* Copyright (c) 1998-2021 Gareth McCaughan
* *
* This software is provided 'as-is', without any express or implied * This software is provided 'as-is', without any express or implied
* warranty. In no event will the authors be held liable for any * warranty. In no event will the authors be held liable for any
@ -133,17 +133,23 @@ Update for SDL3: we have modified this from a qsort function to qsort_r.
* (pre-insertion-sort messed up). * (pre-insertion-sort messed up).
* Disable DEBUG_QSORT by default. * Disable DEBUG_QSORT by default.
* Tweak comments very slightly. * Tweak comments very slightly.
* 2021-02-20 v1.16 Fix bug kindly reported by Ray Gardner
* (error in recursion leading to possible
* stack overflow).
* When checking alignment, avoid casting
* pointer to possibly-smaller integer.
*/ */
/* BEGIN SDL CHANGE ... commented this out with an #if 0 block. --ryan. */ /* BEGIN SDL CHANGE ... commented this out with an #if 0 block. --ryan. */
#if 0 #if 0
#include <assert.h> #include <assert.h>
#include <stdint.h>
#include <stdlib.h> #include <stdlib.h>
#include <string.h> #include <string.h>
#undef DEBUG_QSORT #undef DEBUG_QSORT
static char _ID[]="<qsort.c gjm WITH CHANGES FOR SDL3 1.15 2016-03-10>"; static char _ID[]="<qsort.c gjm WITH CHANGES FOR SDL3 1.16 2021-02-20>";
#endif #endif
/* END SDL CHANGE ... commented this out with an #if 0 block. --ryan. */ /* END SDL CHANGE ... commented this out with an #if 0 block. --ryan. */
@ -153,7 +159,8 @@ static char _ID[]="<qsort.c gjm WITH CHANGES FOR SDL3 1.15 2016-03-10>";
#define WORD_BYTES sizeof(int) #define WORD_BYTES sizeof(int)
/* How big does our stack need to be? Answer: one entry per /* How big does our stack need to be? Answer: one entry per
* bit in a |size_t|. * bit in a |size_t|. (Actually, a bit less because we don't
* recurse all the way down to size-1 subarrays.)
*/ */
#define STACK_SIZE (8*sizeof(size_t)) #define STACK_SIZE (8*sizeof(size_t))
@ -192,11 +199,12 @@ typedef struct { char * first; char * last; } stack_entry;
* on large datasets for locality-of-reference reasons, * on large datasets for locality-of-reference reasons,
* but it makes the code much nastier and increases * but it makes the code much nastier and increases
* bookkeeping overhead. * bookkeeping overhead.
* 2. We always save the shorter and get to work on the * 2. We always save the longer and get to work on the
* longer. This guarantees that every time we push * shorter. This guarantees that whenever we push
* an item onto the stack its size is <= 1/2 of that * a k'th entry onto the stack we are about to get
* of its parent; so the stack can't need more than * working on something of size <= N/2^k where N is
* log_2(max-array-size) entries. * the original array size; 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 * 3. We choose a pivot by looking at the first, last
* and middle elements. We arrange them into order * and middle elements. We arrange them into order
* because it's easy to do that in conjunction with * because it's easy to do that in conjunction with
@ -258,8 +266,8 @@ typedef struct { char * first; char * last; } stack_entry;
if (r>=Trunc) doRight \ if (r>=Trunc) doRight \
else pop \ else pop \
} \ } \
else if (l<=r) { pushLeft; doRight } \ else if (l<=r) { pushRight; doLeft } \
else if (r>=Trunc) { pushRight; doLeft }\ else if (r>=Trunc) { pushLeft; doRight }\
else doLeft \ else doLeft \
} }
@ -511,7 +519,7 @@ void SDL_qsort_r(void *base, size_t nmemb, size_t size,
SDL_CompareCallback_r compare, void *userdata) { SDL_CompareCallback_r compare, void *userdata) {
if (nmemb<=1) return; if (nmemb<=1) return;
if (((size_t)base|size)&(WORD_BYTES-1)) if (((uintptr_t)base|size)&(WORD_BYTES-1))
qsort_r_nonaligned(base,nmemb,size,compare,userdata); qsort_r_nonaligned(base,nmemb,size,compare,userdata);
else if (size!=WORD_BYTES) else if (size!=WORD_BYTES)
qsort_r_aligned(base,nmemb,size,compare,userdata); qsort_r_aligned(base,nmemb,size,compare,userdata);