Subversion Repositories scarts

/* 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, 51 Franklin Street - Fifth Floor,

Boston, MA 02110-1301, USA.  */

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include "libiberty.h"

#include "sort.h"

#ifdef HAVE_LIMITS_H

#include <limits.h>

#endif

#ifdef HAVE_SYS_PARAM_H

#include <sys/param.h>

#endif

#ifdef HAVE_STDLIB_H

#include <stdlib.h>

#endif

#ifdef HAVE_STRING_H

#include <string.h>

#endif

#ifndef UCHAR_MAX

#define UCHAR_MAX ((unsigned char)(-1))

#endif

/* POINTERS and WORK are both arrays of N pointers.  When this

   function returns POINTERS will be sorted in ascending order.  */

void sort_pointers (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, j = 0; i < sizeof (size_t); ++i)

    {

      j *= (UCHAR_MAX + 1);

      j += 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) + j;

      top = ((digit_t *) (pointers + n)) + j;

      /* 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)[j]]] = *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 (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 = XNEWVEC (void*, k);

  work = XNEWVEC (void*, k);

  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