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, 51 Franklin Street - Fifth Floor,
20 Boston, MA 02110-1301, USA. */
25 #include "libiberty.h"
30 #ifdef HAVE_SYS_PARAM_H
31 #include <sys/param.h>
41 #define UCHAR_MAX ((unsigned char)(-1))
44 /* POINTERS and WORK are both arrays of N pointers. When this
45 function returns POINTERS will be sorted in ascending order. */
47 void sort_pointers (size_t n
, void **pointers
, void **work
)
49 /* The type of a single digit. This can be any unsigned integral
50 type. When changing this, DIGIT_MAX should be changed as
52 typedef unsigned char digit_t
;
54 /* The maximum value a single digit can have. */
55 #define DIGIT_MAX (UCHAR_MAX + 1)
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. */
65 /* The algorithm used here is radix sort which takes time linear in
66 the number of elements in the array. */
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)
73 /* Figure out the endianness of the machine. */
74 for (i
= 0, j
= 0; i
< sizeof (size_t); ++i
)
79 big_endian_p
= (((char *)&j
)[0] == 0);
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
)
91 /* The offset from the start of the pointer will depend on the
92 endianness of the machine. */
94 j
= sizeof (void *) / sizeof (digit_t
) - i
;
98 /* Now, perform a stable sort on this digit. We use counting
100 memset (count
, 0, DIGIT_MAX
* sizeof (unsigned int));
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
;
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
113 digit
+= sizeof (void *) / sizeof (digit_t
))
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];
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
;
125 /* Swap WORK and POINTERS so that POINTERS contains the sorted
133 /* Everything below here is a unit test for the routines in this
140 void *xmalloc (size_t n
)
145 int main (int argc
, char **argv
)
158 pointers
= XNEWVEC (void*, k
);
159 work
= XNEWVEC (void*, k
);
161 for (i
= 0; i
< k
; ++i
)
163 pointers
[i
] = (void *) random ();
164 printf ("%x\n", pointers
[i
]);
167 sort_pointers (k
, pointers
, work
);
169 printf ("\nSorted\n\n");
173 for (i
= 0; i
< k
; ++i
)
175 printf ("%x\n", pointers
[i
]);
176 if (i
> 0 && (char*) pointers
[i
] < (char*) pointers
[i
- 1])
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