text: /* 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
  /* !kawai! */
  #include "../include/libiberty.h"
  #include "../include/sort.h"
  /* end of !kawai! */
  #ifdef HAVE_LIMITS_H
  #include "../include/limits.h"
  #endif
  #ifdef HAVE_STDLIB_H
  #include "../include/stdlib.h"
  #endif
  #ifdef HAVE_STRING_H
  #include "../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 (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, 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 (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
  