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