1 /* Sorting algorithms.
2 Copyright (C) 2000-2023 Free Software Foundation, Inc.
3 Contributed by Mark Mitchell <mark@codesourcery.com>.
4
5 This file is part of GNU CC.
6
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)
10 any later version.
11
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.
16
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, 51 Franklin Street - Fifth Floor,
20 Boston, MA 02110-1301, USA. */
21
22 #ifdef HAVE_CONFIG_H
23 #include "config.h"
24 #endif
25 #include "libiberty.h"
26 #include "sort.h"
27 #ifdef HAVE_LIMITS_H
28 #include <limits.h>
29 #endif
30 #ifdef HAVE_SYS_PARAM_H
31 #include <sys/param.h>
32 #endif
33 #ifdef HAVE_STDLIB_H
34 #include <stdlib.h>
35 #endif
36 #ifdef HAVE_STRING_H
37 #include <string.h>
38 #endif
39
40 #ifndef UCHAR_MAX
41 #define UCHAR_MAX ((unsigned char)(-1))
42 #endif
43
44 /* POINTERS and WORK are both arrays of N pointers. When this
45 function returns POINTERS will be sorted in ascending order. */
46
47 void sort_pointers (size_t n, void **pointers, void **work)
48 {
49 /* The type of a single digit. This can be any unsigned integral
50 type. When changing this, DIGIT_MAX should be changed as
51 well. */
52 typedef unsigned char digit_t;
53
54 /* The maximum value a single digit can have. */
55 #define DIGIT_MAX (UCHAR_MAX + 1)
56
57 /* The Ith entry is the number of elements in *POINTERSP that have I
58 in the digit on which we are currently sorting. */
59 unsigned int count[DIGIT_MAX];
60 /* Nonzero if we are running on a big-endian machine. */
61 int big_endian_p;
62 size_t i;
63 size_t j;
64
65 /* The algorithm used here is radix sort which takes time linear in
66 the number of elements in the array. */
67
68 /* The algorithm here depends on being able to swap the two arrays
69 an even number of times. */
70 if ((sizeof (void *) / sizeof (digit_t)) % 2 != 0)
71 abort ();
72
73 /* Figure out the endianness of the machine. */
74 for (i = 0, j = 0; i < sizeof (size_t); ++i)
75 {
76 j *= (UCHAR_MAX + 1);
77 j += i;
78 }
79 big_endian_p = (((char *)&j)[0] == 0);
80
81 /* Move through the pointer values from least significant to most
82 significant digits. */
83 for (i = 0; i < sizeof (void *) / sizeof (digit_t); ++i)
84 {
85 digit_t *digit;
86 digit_t *bias;
87 digit_t *top;
88 unsigned int *countp;
89 void **pointerp;
90
91 /* The offset from the start of the pointer will depend on the
92 endianness of the machine. */
93 if (big_endian_p)
94 j = sizeof (void *) / sizeof (digit_t) - i;
95 else
96 j = i;
97
98 /* Now, perform a stable sort on this digit. We use counting
99 sort. */
100 memset (count, 0, DIGIT_MAX * sizeof (unsigned int));
101
102 /* Compute the address of the appropriate digit in the first and
103 one-past-the-end elements of the array. On a little-endian
104 machine, the least-significant digit is closest to the front. */
105 bias = ((digit_t *) pointers) + j;
106 top = ((digit_t *) (pointers + n)) + j;
107
108 /* Count how many there are of each value. At the end of this
109 loop, COUNT[K] will contain the number of pointers whose Ith
110 digit is K. */
111 for (digit = bias;
112 digit < top;
113 digit += sizeof (void *) / sizeof (digit_t))
114 ++count[*digit];
115
116 /* Now, make COUNT[K] contain the number of pointers whose Ith
117 digit is less than or equal to K. */
118 for (countp = count + 1; countp < count + DIGIT_MAX; ++countp)
119 *countp += countp[-1];
120
121 /* Now, drop the pointers into their correct locations. */
122 for (pointerp = pointers + n - 1; pointerp >= pointers; --pointerp)
123 work[--count[((digit_t *) pointerp)[j]]] = *pointerp;
124
125 /* Swap WORK and POINTERS so that POINTERS contains the sorted
126 array. */
127 pointerp = pointers;
128 pointers = work;
129 work = pointerp;
130 }
131 }
132
133 /* Everything below here is a unit test for the routines in this
134 file. */
135
136 #ifdef UNIT_TEST
137
138 #include <stdio.h>
139
140 void *xmalloc (size_t n)
141 {
142 return malloc (n);
143 }
144
145 int main (int argc, char **argv)
146 {
147 int k;
148 int result;
149 size_t i;
150 void **pointers;
151 void **work;
152
153 if (argc > 1)
154 k = atoi (argv[1]);
155 else
156 k = 10;
157
158 pointers = XNEWVEC (void*, k);
159 work = XNEWVEC (void*, k);
160
161 for (i = 0; i < k; ++i)
162 {
163 pointers[i] = (void *) random ();
164 printf ("%x\n", pointers[i]);
165 }
166
167 sort_pointers (k, pointers, work);
168
169 printf ("\nSorted\n\n");
170
171 result = 0;
172
173 for (i = 0; i < k; ++i)
174 {
175 printf ("%x\n", pointers[i]);
176 if (i > 0 && (char*) pointers[i] < (char*) pointers[i - 1])
177 result = 1;
178 }
179
180 free (pointers);
181 free (work);
182
183 return result;
184 }
185
186 #endif