1.2 stdlib: Updated qsort with licensing resolved (thanks, Gareth!). SDL-1.2
authorRyan C. Gordon <icculus@icculus.org>
Sun, 21 Feb 2016 13:19:33 -0500
branchSDL-1.2
changeset 10086 2e3396e62aa6
parent 9900 453dce726f24
child 10118 2f1eb5fa26ea
1.2 stdlib: Updated qsort with licensing resolved (thanks, Gareth!).
src/stdlib/SDL_qsort.c
--- a/src/stdlib/SDL_qsort.c	Sun Nov 01 08:41:08 2015 +0100
+++ b/src/stdlib/SDL_qsort.c	Sun Feb 21 13:19:33 2016 -0500
@@ -1,54 +1,25 @@
-/* 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
- */
-#include "SDL_config.h"
+/*
+  Simple DirectMedia Layer
+  Copyright (C) 1997-2016 Sam Lantinga <slouken@libsdl.org>
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
 
-/*
-#include <assert.h>
-#include <stdlib.h>
-#include <string.h>
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.
 */
-#include "SDL_stdinc.h"
+
+#ifndef HAVE_QSORT
 
 #ifdef assert
 #undef assert
@@ -57,28 +28,118 @@
 #ifdef malloc
 #undef malloc
 #endif
-#define malloc	SDL_malloc
+#define malloc SDL_malloc
 #ifdef free
 #undef free
 #endif
-#define free	SDL_free
+#define free SDL_free
 #ifdef memcpy
 #undef memcpy
 #endif
-#define memcpy	SDL_memcpy
+#define memcpy SDL_memcpy
 #ifdef memmove
 #undef memmove
 #endif
-#define memmove	SDL_memmove
-#ifdef qsort
-#undef qsort
+#define memmove SDL_memmove
+#ifdef qsortG
+#undef qsortG
 #endif
-#define qsort	SDL_qsort
+#define qsortG SDL_qsort
+
+/*
+This code came from Gareth McCaughan, under the zlib license.
+Specifically this: https://www.mccaughan.org.uk/software/qsort.c-1.14
 
+Everything below this comment until the HAVE_QSORT #endif was from Gareth
+(any minor changes will be noted inline).
+
+Thank you to Gareth for relicensing this code under the zlib license for our
+benefit!
+
+--ryan.
+*/
 
-#ifndef HAVE_QSORT
+/* This is a drop-in replacement for the C library's |qsort()| routine.
+ *
+ * It is intended for use where you know or suspect that your
+ * platform's qsort is bad. If that isn't the case, then you
+ * should probably use the qsort your system gives you in preference
+ * to mine -- it will likely have been tested and tuned better.
+ *
+ * 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()|.
+ *     (For the avoidance of doubt, no code was stolen, only
+ *     broad ideas.)
+ *   - separate code for non-aligned / aligned / word-size objects
+ *
+ * Earlier releases of this code used an idiosyncratic licence
+ * I wrote myself, because I'm an idiot. The code is now released
+ * under the "zlib/libpng licence"; you will find the actual
+ * terms in the next comment. I request (but do not require)
+ * that if you make any changes beyond the name of the exported
+ * routine and reasonable tweaks to the TRUNC_* and
+ * PIVOT_THRESHOLD values, you modify the _ID string so as
+ * to make it clear that you have changed the code.
+ *
+ * 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 2016 and for the
+ * foreseeable future, is
+ *    gareth.mccaughan@pobox.com
+ * Thanks!
+ *
+ * Gareth McCaughan
+ */
 
-static char _ID[]="<qsort.c gjm 1.12 1998-03-19>";
+/* Copyright (c) 1998-2016 Gareth McCaughan
+ *
+ * This software is provided 'as-is', without any express or implied
+ * warranty. In no event will the authors be held liable for any
+ * damages arising from the use of this software.
+ *
+ * Permission is granted to anyone to use this software for any purpose,
+ * including commercial applications, and to alter it and redistribute it
+ * freely, subject to the following restrictions:
+ *
+ * 1. The origin of this software must not be misrepresented;
+ *    you must not claim that you wrote the original software.
+ *    If you use this software in a product, an acknowledgment
+ *    in the product documentation would be appreciated but
+ *    is not required.
+ *
+ * 2. Altered source versions must be plainly marked as such,
+ *    and must not be misrepresented as being the original software.
+ *
+ * 3. This notice may not be removed or altered from any source
+ *    distribution.
+ */
+
+/* Revision history since release:
+ *   1998-03-19 v1.12 First release I have any records of.
+ *   2007-09-02 v1.13 Fix bug kindly reported by Dan Bodoh
+ *                    (premature termination of recursion).
+ *                    Add a few clarifying comments.
+ *                    Minor improvements to debug output.
+ *   2016-02-21 v1.14 Replace licence with 2-clause BSD,
+ *                    and clarify a couple of things in
+ *                    comments. No code changes.
+ */
+
+/* BEGIN SDL CHANGE ... commented this out with an #if 0 block. --ryan. */
+#if 0
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define DEBUG_QSORT
+
+static char _ID[]="<qsort.c gjm 1.14 2016-02-21>";
+#endif
+/* END SDL CHANGE ... commented this out with an #if 0 block. --ryan. */
 
 /* How many bytes are there per word? (Must be a power of 2,
  * and must in fact equal sizeof(int).)
@@ -182,7 +243,9 @@
  *        16-bit |int|s and 4096-bit |size_t|s. :-)
  */
 
-/* The recursion logic is the same in each case: */
+/* The recursion logic is the same in each case.
+ * We keep chopping up until we reach subarrays of size
+ * strictly less than Trunc; we leave these unsorted. */
 #define Recurse(Trunc)				\
       { size_t l=last-ffirst,r=llast-first;	\
         if (l<Trunc) {				\
@@ -194,9 +257,9 @@
         else doLeft				\
       }
 
-/* and so is the pivoting logic: */
+/* and so is the pivoting logic (note: last is inclusive): */
 #define Pivot(swapper,sz)			\
-  if ((size_t)(last-first)>PIVOT_THRESHOLD*sz) mid=pivot_big(first,mid,last,sz,compare);\
+  if (last-first>PIVOT_THRESHOLD*sz) mid=pivot_big(first,mid,last,sz,compare);\
   else {	\
     if (compare(first,mid)<0) {			\
       if (compare(mid,last)>0) {		\
@@ -220,26 +283,28 @@
 
 /* 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;		\
+      swapper(first,last);			\
       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().
+ * We find the smallest element from the first |nmemb|,
+ * or the first |limit|, whichever is smaller;
+ * therefore we must have ensured that the globally smallest
+ * element is in the first |limit|.
  */
 #define PreInsertion(swapper,limit,sz)		\
   first=base;					\
-  last=first + (nmemb>limit ? limit : nmemb-1)*sz;\
+  last=first + ((nmemb>limit ? limit : nmemb)-1)*sz;\
   while (last!=base) {				\
     if (compare(first,last)>0) first=last;	\
     last-=sz; }					\
@@ -281,11 +346,14 @@
 
 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;
+  int d=(((last-first)/size)>>3)*size;
+#ifdef DEBUG_QSORT
+fprintf(stderr, "pivot_big: first=%p last=%p size=%lu n=%lu\n", first, (unsigned long)last, size, (unsigned long)((last-first+1)/size));
+#endif
   char *m1,*m2,*m3;
   { 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);
+fprintf(stderr,"< %d %d %d @ %p %p %p\n",*(int*)a,*(int*)b,*(int*)c, a,b,c);
 #endif
     m1 = compare(a,b)<0 ?
            (compare(b,c)<0 ? b : (compare(a,c)<0 ? c : a))
@@ -293,7 +361,7 @@
   }
   { char *a=mid-d, *b=mid, *c=mid+d;
 #ifdef DEBUG_QSORT
-fprintf(stderr,". %d %d %d\n",*(int*)a,*(int*)b,*(int*)c);
+fprintf(stderr,". %d %d %d @ %p %p %p\n",*(int*)a,*(int*)b,*(int*)c, a,b,c);
 #endif
     m2 = compare(a,b)<0 ?
            (compare(b,c)<0 ? b : (compare(a,c)<0 ? c : a))
@@ -301,14 +369,14 @@
   }
   { 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);
+fprintf(stderr,"> %d %d %d @ %p %p %p\n",*(int*)a,*(int*)b,*(int*)c, a,b,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);
+fprintf(stderr,"-> %d %d %d @ %p %p %p\n",*(int*)m1,*(int*)m2,*(int*)m3, m1,m2,m3);
 #endif
   return compare(m1,m2)<0 ?
            (compare(m2,m3)<0 ? m2 : (compare(m1,m3)<0 ? m3 : m1))
@@ -329,7 +397,7 @@
 
   first=(char*)base; last=first+(nmemb-1)*size;
 
-  if ((size_t)(last-first)>trunc) {
+  if (last-first>=trunc) {
     char *ffirst=first, *llast=last;
     while (1) {
       /* Select pivot */
@@ -343,7 +411,7 @@
       Recurse(trunc)
     }
   }
-  PreInsertion(SWAP_nonaligned,TRUNC_nonaligned,size);
+  PreInsertion(SWAP_nonaligned,TRUNC_nonaligned-1,size);
   Insertion(SWAP_nonaligned);
   free(pivot);
 }
@@ -360,7 +428,7 @@
 
   first=(char*)base; last=first+(nmemb-1)*size;
 
-  if ((size_t)(last-first)>trunc) {
+  if (last-first>=trunc) {
     char *ffirst=first,*llast=last;
     while (1) {
       /* Select pivot */
@@ -374,7 +442,7 @@
       Recurse(trunc)
     }
   }
-  PreInsertion(SWAP_aligned,TRUNC_aligned,size);
+  PreInsertion(SWAP_aligned,TRUNC_aligned-1,size);
   Insertion(SWAP_aligned);
   free(pivot);
 }
@@ -390,7 +458,7 @@
 
   first=(char*)base; last=first+(nmemb-1)*WORD_BYTES;
 
-  if (last-first>TRUNC_words) {
+  if (last-first>=TRUNC_words) {
     char *ffirst=first, *llast=last;
     while (1) {
 #ifdef DEBUG_QSORT
@@ -402,17 +470,20 @@
       { 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 = %p = #%lu = %d\n", mid, (unsigned long)(((int*)mid)-((int*)base)), *(int*)mid);
+#endif
       }
-#ifdef DEBUG_QSORT
-fprintf(stderr,"pivot=%d\n",*(int*)pivot);
-#endif
       /* Partition. */
       Partition(SWAP_words,WORD_BYTES);
+#ifdef DEBUG_QSORT
+fprintf(stderr, "after partitioning first=#%lu last=#%lu\n", (first-(char*)base)/4lu, (last-(char*)base)/4lu);
+#endif
       /* Prepare to recurse/iterate. */
       Recurse(TRUNC_words)
     }
   }
-  PreInsertion(SWAP_words,(TRUNC_words/WORD_BYTES),WORD_BYTES);
+  PreInsertion(SWAP_words,(TRUNC_words/WORD_BYTES)-1,WORD_BYTES);
   /* Now do insertion sort. */
   last=((char*)base)+nmemb*WORD_BYTES;
   for (first=((char*)base)+WORD_BYTES;first!=last;first+=WORD_BYTES) {
@@ -428,11 +499,11 @@
 
 /* ---------------------------------------------------------------------- */
 
-void qsort(void *base, size_t nmemb, size_t size,
+extern void qsortG(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))
+  if (((int)base|size)&(WORD_BYTES-1))
     qsort_nonaligned(base,nmemb,size,compare);
   else if (size!=WORD_BYTES)
     qsort_aligned(base,nmemb,size,compare);
@@ -440,4 +511,7 @@
     qsort_words(base,nmemb,compare);
 }
 
-#endif /* !HAVE_QSORT */
+#endif /* ifndef HAVE_QSORT */
+
+/* vi: set ts=4 sw=4 expandtab: */
+