PATCH: New libiberty sorting routine

[Mark Mitchell <mark at codesourcery dot com>]

This patch adds a routine to libiberty to do linear-time sorting of
pointers, using radix sort with counting sort as the subordinate
stable sorting algorithm.

Unfortunately, it turns out not to be useful for the thing I thought
it would be useful for in GCC (at least not yet!), but it's still
likely to be useful to somebody else at some point.

--
Mark Mitchell                   mark@codesourcery.com
CodeSourcery, LLC               http://www.codesourcery.com

2000-04-23  Mark Mitchell  <mark@codesourcery.com>

	* sort.h: New file.

2000-04-23  Mark Mitchell  <mark@codesourcery.com>

	* sort.c: New file.
	* Makefile.in (CFILES): Add sort.c
	(REQUIRED_OFILES): Add sort.o.
	(sort.o): New target.

Index: sort.h
===================================================================
RCS file: sort.h
diff -N sort.h
*** /dev/null	Tue May  5 13:32:27 1998
--- sort.h	Sun Apr 23 17:47:16 2000
***************
*** 0 ****
--- 1,45 ----
+ /* Sorting algorithms.
+    Copyright (C) 2000 Free Software Foundation, Inc.
+    Contributed by Mark Mitchell <mark@codesourcery.com>.
+ 
+ This file is part of GNU CC.
+    
+ GNU CC is free software; you can redistribute it and/or modify it
+ under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2, or (at your option)
+ any later version.
+ 
+ GNU CC is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ General Public License for more details.
+ 
+ You should have received a copy of the GNU General Public License
+ along with GNU CC; see the file COPYING.  If not, write to
+ the Free Software Foundation, 59 Temple Place - Suite 330,
+ Boston, MA 02111-1307, USA.  */
+ 
+ #ifndef SORT_H
+ #define SORT_H
+ 
+ #include <stddef.h>
+ 
+ #ifdef __cplusplus
+ extern "C" {
+ #endif /* __cplusplus */
+ 
+ #include <ansidecl.h>
+ 
+ /* Sort an array of pointers.  */
+ 
+ extern void sort_pointers PARAMS ((size_t, void **, void **));
+ 
+ #ifdef __cplusplus
+ }
+ #endif /* __cplusplus */
+ 
+ #endif /* SORT_H */
+ 
+ 
+    
+    
Index: Makefile.in
===================================================================
RCS file: /cvs/gcc/egcs/libiberty/Makefile.in,v
retrieving revision 1.39
diff -c -p -r1.39 Makefile.in
*** Makefile.in	2000/03/24 21:32:08	1.39
--- Makefile.in	2000/04/24 00:47:23
*************** CFILES = asprintf.c alloca.c argv.c atex
*** 129,135 ****
  	getruntime.c floatformat.c hashtab.c hex.c index.c insque.c memchr.c  \
  	memcmp.c memcpy.c memmove.c memset.c mkstemps.c objalloc.c obstack.c  \
  	partition.c pexecute.c putenv.c random.c rename.c rindex.c	      \
! 	setenv.c sigsetmask.c spaces.c splay-tree.c strcasecmp.c	      \
  	strncasecmp.c strchr.c strdup.c strerror.c strrchr.c		      \
  	strsignal.c strstr.c strtod.c strtol.c strtoul.c tmpnam.c	      \
  	vasprintf.c vfork.c vfprintf.c vprintf.c vsprintf.c waitpid.c	      \
--- 129,135 ----
  	getruntime.c floatformat.c hashtab.c hex.c index.c insque.c memchr.c  \
  	memcmp.c memcpy.c memmove.c memset.c mkstemps.c objalloc.c obstack.c  \
  	partition.c pexecute.c putenv.c random.c rename.c rindex.c	      \
! 	setenv.c sigsetmask.c sort.c spaces.c splay-tree.c strcasecmp.c	      \
  	strncasecmp.c strchr.c strdup.c strerror.c strrchr.c		      \
  	strsignal.c strstr.c strtod.c strtol.c strtoul.c tmpnam.c	      \
  	vasprintf.c vfork.c vfprintf.c vprintf.c vsprintf.c waitpid.c	      \
*************** CFILES = asprintf.c alloca.c argv.c atex
*** 138,145 ****
  # These are always included in the library.
  REQUIRED_OFILES = argv.o choose-temp.o concat.o cplus-dem.o \
    fdmatch.o fnmatch.o getopt.o getopt1.o getpwd.o getruntime.o hashtab.o \
!   hex.o floatformat.o objalloc.o obstack.o partition.o pexecute.o spaces.o \
!   splay-tree.o strerror.o strsignal.o xatexit.o xexit.o xmalloc.o \
    xmemdup.o xstrdup.o xstrerror.o
  
  $(TARGETLIB): $(REQUIRED_OFILES) $(EXTRA_OFILES) $(LIBOBJS) $(ALLOCA)
--- 138,145 ----
  # These are always included in the library.
  REQUIRED_OFILES = argv.o choose-temp.o concat.o cplus-dem.o \
    fdmatch.o fnmatch.o getopt.o getopt1.o getpwd.o getruntime.o hashtab.o \
!   hex.o floatformat.o objalloc.o obstack.o partition.o pexecute.o sort.o \
!   spaces.o splay-tree.o strerror.o strsignal.o xatexit.o xexit.o xmalloc.o \
    xmemdup.o xstrdup.o xstrerror.o
  
  $(TARGETLIB): $(REQUIRED_OFILES) $(EXTRA_OFILES) $(LIBOBJS) $(ALLOCA)
*************** obstack.o: config.h $(INCDIR)/obstack.h
*** 275,280 ****
--- 275,281 ----
  partition.o: config.h $(INCDIR)/partition.h
  pexecute.o: config.h $(INCDIR)/libiberty.h
  setenv.o: config.h
+ sort.o: config.h $(INCDIR)/sort.h $(INCDIR)/ansidecl.h
  spaces.o: $(INCDIR)/libiberty.h
  splay-tree.o: config.h $(INCDIR)/libiberty.h $(INCDIR)/splay-tree.h $(INCDIR)/ansidecl.h
  strerror.o: config.h $(INCDIR)/libiberty.h
Index: sort.c
===================================================================
RCS file: sort.c
diff -N sort.c
*** /dev/null	Tue May  5 13:32:27 1998
--- sort.c	Sun Apr 23 17:47:25 2000
***************
*** 0 ****
--- 1,176 ----
+ /* Sorting algorithms.
+    Copyright (C) 2000 Free Software Foundation, Inc.
+    Contributed by Mark Mitchell <mark@codesourcery.com>.
+ 
+ This file is part of GNU CC.
+    
+ GNU CC is free software; you can redistribute it and/or modify it
+ under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2, or (at your option)
+ any later version.
+ 
+ GNU CC is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ General Public License for more details.
+ 
+ You should have received a copy of the GNU General Public License
+ along with GNU CC; see the file COPYING.  If not, write to
+ the Free Software Foundation, 59 Temple Place - Suite 330,
+ Boston, MA 02111-1307, USA.  */
+ 
+ #ifdef HAVE_CONFIG_H
+ #include "config.h"
+ #endif
+ #include "libiberty.h"
+ #include "sort.h"
+ #include <limits.h>
+ #ifdef HAVE_STDLIB_H
+ #include <stdlib.h>
+ #endif
+ 
+ /* POINTERSP and WORKP both point to arrays of N pointers.  When
+    this function returns POINTERSP will point to a sorted version of
+    the original array pointed to by POINTERSP.  */
+ 
+ void sort_pointers (n, pointers, work)
+      size_t n;
+      void **pointers;
+      void **work;
+ {
+   /* The type of a single digit.  This can be any unsigned integral
+      type.  When changing this, DIGIT_MAX should be changed as 
+      well.  */
+   typedef unsigned char digit_t;
+ 
+   /* The maximum value a single digit can have.  */
+ #define DIGIT_MAX (UCHAR_MAX + 1)
+ 
+   /* The Ith entry is the number of elements in *POINTERSP that have I
+      in the digit on which we are currently sorting.  */
+   unsigned int count[DIGIT_MAX];
+   /* Nonzero if we are running on a big-endian machine.  */
+   int big_endian_p;
+   size_t i;
+   size_t j;
+ 
+   /* The algorithm used here is radix sort which takes time linear in
+      the number of elements in the array.  */
+ 
+   /* The algorithm here depends on being able to swap the two arrays
+      an even number of times.  */
+   if ((sizeof (void *) / sizeof (digit_t)) % 2 != 0)
+     abort ();
+ 
+   /* Figure out the endianness of the machine.  */
+   for (i = 0; i < sizeof (size_t); ++i)
+     ((char *)&j)[i] = i;
+   big_endian_p = (((char *)&j)[0] == 0);
+ 
+   /* Move through the pointer values from least significant to most
+      significant digits.  */
+   for (i = 0; i < sizeof (void *) / sizeof (digit_t); ++i)
+     {
+       digit_t *digit;
+       digit_t *bias;
+       digit_t *top;
+       unsigned int *countp;
+       void **pointerp;
+ 
+       /* The offset from the start of the pointer will depend on the
+ 	 endianness of the machine.  */
+       if (big_endian_p)
+ 	j = sizeof (void *) / sizeof (digit_t) - i;
+       else
+ 	j = i;
+ 	
+       /* Now, perform a stable sort on this digit.  We use counting
+ 	 sort.  */
+       memset (count, 0, DIGIT_MAX * sizeof (unsigned int));
+ 
+       /* Compute the address of the appropriate digit in the first and
+ 	 one-past-the-end elements of the array.  On a little-endian
+ 	 machine, the least-significant digit is closest to the front.  */
+       bias = ((digit_t *) pointers) + i;
+       top = ((digit_t *) (pointers + n)) + i;
+ 
+       /* Count how many there are of each value.  At the end of this
+ 	 loop, COUNT[K] will contain the number of pointers whose Ith
+ 	 digit is K.  */
+       for (digit = bias; 
+ 	   digit < top; 
+ 	   digit += sizeof (void *) / sizeof (digit_t))
+ 	++count[*digit];
+ 
+       /* Now, make COUNT[K] contain the number of pointers whose Ith
+ 	 digit is less than or equal to K.  */
+       for (countp = count + 1; countp < count + DIGIT_MAX; ++countp)
+ 	*countp += countp[-1];
+ 
+       /* Now, drop the pointers into their correct locations.  */
+       for (pointerp = pointers + n - 1; pointerp >= pointers; --pointerp)
+ 	work[--count[((digit_t *) pointerp)[i]]] = *pointerp;
+ 
+       /* Swap WORK and POINTERS so that POINTERS contains the sorted
+ 	 array.  */
+       pointerp = pointers;
+       pointers = work;
+       work = pointerp;
+     }
+ }
+ 
+ /* Everything below here is a unit test for the routines in this
+    file.  */
+ 
+ #ifdef UNIT_TEST
+ 
+ #include <stdio.h>
+ 
+ void *xmalloc (n)
+      size_t n;
+ {
+   return malloc (n);
+ }
+ 
+ int main (int argc, char **argv)
+ {
+   int k;
+   int result;
+   size_t i;
+   void **pointers;
+   void **work;
+ 
+   if (argc > 1)
+     k = atoi (argv[1]);
+   else
+     k = 10;
+ 
+   pointers = xmalloc (k * sizeof (void *));
+   work = xmalloc (k * sizeof (void *));
+ 
+   for (i = 0; i < k; ++i)
+     {
+       pointers[i] = (void *) random ();
+       printf ("%x\n", pointers[i]);
+     }
+ 
+   sort_pointers (k, pointers, work);
+ 
+   printf ("\nSorted\n\n");
+ 
+   result = 0;
+ 
+   for (i = 0; i < k; ++i)
+     {
+       printf ("%x\n", pointers[i]);
+       if (i > 0 && (char*) pointers[i] < (char*) pointers[i - 1])
+ 	result = 1;
+     }
+ 
+   free (pointers);
+   free (work);
+ 
+   return result;
+ }
+ 
+ #endif