* sort.c: New file.

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


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@33364 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 176 insertions, 0 deletions

diff --git a/libiberty/sort.c b/libiberty/sort.c
new file mode 100644
index 00000000000..6dca09a9242
--- /dev/null
+++ b/libiberty/sort.c
@@ -0,0 +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