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/* Sorting algorithms. |
Copyright (C) 2000 Free Software Foundation, Inc. |
Contributed by Mark Mitchell <mark@codesourcery.com>. |
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This file is part of GNU CC. |
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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. |
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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. |
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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. */ |
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#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 |
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#ifndef UCHAR_MAX |
#define UCHAR_MAX ((unsigned char)(-1)) |
#endif |
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/* POINTERS and WORK are both arrays of N pointers. When this |
function returns POINTERS will be sorted in ascending order. */ |
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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; |
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/* The maximum value a single digit can have. */ |
#define DIGIT_MAX (UCHAR_MAX + 1) |
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/* 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; |
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/* The algorithm used here is radix sort which takes time linear in |
the number of elements in the array. */ |
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/* 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 (); |
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/* 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); |
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/* 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; |
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/* 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; |
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/* Now, perform a stable sort on this digit. We use counting |
sort. */ |
memset (count, 0, DIGIT_MAX * sizeof (unsigned int)); |
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/* 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; |
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/* 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]; |
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/* 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]; |
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/* Now, drop the pointers into their correct locations. */ |
for (pointerp = pointers + n - 1; pointerp >= pointers; --pointerp) |
work[--count[((digit_t *) pointerp)[j]]] = *pointerp; |
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/* Swap WORK and POINTERS so that POINTERS contains the sorted |
array. */ |
pointerp = pointers; |
pointers = work; |
work = pointerp; |
} |
} |
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/* Everything below here is a unit test for the routines in this |
file. */ |
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#ifdef UNIT_TEST |
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#include <stdio.h> |
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void *xmalloc (size_t n) |
{ |
return malloc (n); |
} |
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int main (int argc, char **argv) |
{ |
int k; |
int result; |
size_t i; |
void **pointers; |
void **work; |
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if (argc > 1) |
k = atoi (argv[1]); |
else |
k = 10; |
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pointers = XNEWVEC (void*, k); |
work = XNEWVEC (void*, k); |
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for (i = 0; i < k; ++i) |
{ |
pointers[i] = (void *) random (); |
printf ("%x\n", pointers[i]); |
} |
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sort_pointers (k, pointers, work); |
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printf ("\nSorted\n\n"); |
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result = 0; |
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for (i = 0; i < k; ++i) |
{ |
printf ("%x\n", pointers[i]); |
if (i > 0 && (char*) pointers[i] < (char*) pointers[i - 1]) |
result = 1; |
} |
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free (pointers); |
free (work); |
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return result; |
} |
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#endif |