2 Copyright (C) 2000 Free Software Foundation, Inc.
3 Contributed by Mark Mitchell <mark@codesourcery.com>.
5 This file is part of GNU CC.
7 GNU CC is free software; you can redistribute it and/or modify it
8 under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 GNU CC is distributed in the hope that it will be useful, but
13 WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GNU CC; see the file COPYING. If not, write to
19 the Free Software Foundation, 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
25 #include "libiberty.h"
33 #define UCHAR_MAX ((unsigned char)(-1))
36 /* POINTERS and WORK are both arrays of N pointers. When this
37 function returns POINTERS will be sorted in ascending order. */
39 void sort_pointers (n, pointers, work)
44 /* The type of a single digit. This can be any unsigned integral
45 type. When changing this, DIGIT_MAX should be changed as
47 typedef unsigned char digit_t;
49 /* The maximum value a single digit can have. */
50 #define DIGIT_MAX (UCHAR_MAX + 1)
52 /* The Ith entry is the number of elements in *POINTERSP that have I
53 in the digit on which we are currently sorting. */
54 unsigned int count[DIGIT_MAX];
55 /* Nonzero if we are running on a big-endian machine. */
60 /* The algorithm used here is radix sort which takes time linear in
61 the number of elements in the array. */
63 /* The algorithm here depends on being able to swap the two arrays
64 an even number of times. */
65 if ((sizeof (void *) / sizeof (digit_t)) % 2 != 0)
68 /* Figure out the endianness of the machine. */
69 for (i = 0, j = 0; i < sizeof (size_t); ++i)
74 big_endian_p = (((char *)&j)[0] == 0);
76 /* Move through the pointer values from least significant to most
77 significant digits. */
78 for (i = 0; i < sizeof (void *) / sizeof (digit_t); ++i)
86 /* The offset from the start of the pointer will depend on the
87 endianness of the machine. */
89 j = sizeof (void *) / sizeof (digit_t) - i;
93 /* Now, perform a stable sort on this digit. We use counting
95 memset (count, 0, DIGIT_MAX * sizeof (unsigned int));
97 /* Compute the address of the appropriate digit in the first and
98 one-past-the-end elements of the array. On a little-endian
99 machine, the least-significant digit is closest to the front. */
100 bias = ((digit_t *) pointers) + j;
101 top = ((digit_t *) (pointers + n)) + j;
103 /* Count how many there are of each value. At the end of this
104 loop, COUNT[K] will contain the number of pointers whose Ith
108 digit += sizeof (void *) / sizeof (digit_t))
111 /* Now, make COUNT[K] contain the number of pointers whose Ith
112 digit is less than or equal to K. */
113 for (countp = count + 1; countp < count + DIGIT_MAX; ++countp)
114 *countp += countp[-1];
116 /* Now, drop the pointers into their correct locations. */
117 for (pointerp = pointers + n - 1; pointerp >= pointers; --pointerp)
118 work[--count[((digit_t *) pointerp)[j]]] = *pointerp;
120 /* Swap WORK and POINTERS so that POINTERS contains the sorted
128 /* Everything below here is a unit test for the routines in this
141 int main (int argc, char **argv)
154 pointers = xmalloc (k * sizeof (void *));
155 work = xmalloc (k * sizeof (void *));
157 for (i = 0; i < k; ++i)
159 pointers[i] = (void *) random ();
160 printf ("%x\n", pointers[i]);
163 sort_pointers (k, pointers, work);
165 printf ("\nSorted\n\n");
169 for (i = 0; i < k; ++i)
171 printf ("%x\n", pointers[i]);
172 if (i > 0 && (char*) pointers[i] < (char*) pointers[i - 1])