/* Sorting algorithms.   Copyright (C) 2000-2026 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 itunder the terms of the GNU General Public License as published bythe 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, butWITHOUT ANY WARRANTY; without even the implied warranty ofMERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNUGeneral Public License for more details. You should have received a copy of the GNU General Public Licensealong with GNU CC; see the file COPYING.  If not, write tothe 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