1 /* Sorting algorithms.
2    Copyright (C) 2000 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 
sort_pointers(size_t n,void ** pointers,void ** work)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 
xmalloc(size_t n)140 void *xmalloc (size_t n)
141 {
142   return malloc (n);
143 }
144 
main(int argc,char ** argv)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
187