1 /* Sorting algorithms. 2 Copyright (C) 2000 Free Software Foundation, Inc. 3 Contributed by Mark Mitchell <mark (at) 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 187
