/* Sorting algorithms. | |

Copyright (C) 2000-2021 Free Software Foundation, Inc. | |

Contributed by Mark Mitchell <mark@codesourcery.com>. | |

This file is part of GNU CC. | |

GNU CC is free software; you can redistribute it and/or modify it | |

under the terms of the GNU General Public License as published by | |

the Free Software Foundation; either version 2, or (at your option) | |

any later version. | |

GNU CC is distributed in the hope that it will be useful, but | |

WITHOUT ANY WARRANTY; without even the implied warranty of | |

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |

General Public License for more details. | |

You should have received a copy of the GNU General Public License | |

along with GNU CC; see the file COPYING. If not, write to | |

the Free Software Foundation, 51 Franklin Street - Fifth Floor, | |

Boston, MA 02110-1301, USA. */ | |

#ifdef HAVE_CONFIG_H | |

#include "config.h" | |

#endif | |

#include "libiberty.h" | |

#include "sort.h" | |

#ifdef HAVE_LIMITS_H | |

#include <limits.h> | |

#endif | |

#ifdef HAVE_SYS_PARAM_H | |

#include <sys/param.h> | |

#endif | |

#ifdef HAVE_STDLIB_H | |

#include <stdlib.h> | |

#endif | |

#ifdef HAVE_STRING_H | |

#include <string.h> | |

#endif | |

#ifndef UCHAR_MAX | |

#define UCHAR_MAX ((unsigned char)(-1)) | |

#endif | |

/* POINTERS and WORK are both arrays of N pointers. When this | |

function returns POINTERS will be sorted in ascending order. */ | |

void sort_pointers (size_t n, void **pointers, void **work) | |

{ | |

/* The type of a single digit. This can be any unsigned integral | |

type. When changing this, DIGIT_MAX should be changed as | |

well. */ | |

typedef unsigned char digit_t; | |

/* The maximum value a single digit can have. */ | |

#define DIGIT_MAX (UCHAR_MAX + 1) | |

/* The Ith entry is the number of elements in *POINTERSP that have I | |

in the digit on which we are currently sorting. */ | |

unsigned int count[DIGIT_MAX]; | |

/* Nonzero if we are running on a big-endian machine. */ | |

int big_endian_p; | |

size_t i; | |

size_t j; | |

/* The algorithm used here is radix sort which takes time linear in | |

the number of elements in the array. */ | |

/* The algorithm here depends on being able to swap the two arrays | |

an even number of times. */ | |

if ((sizeof (void *) / sizeof (digit_t)) % 2 != 0) | |

abort (); | |

/* Figure out the endianness of the machine. */ | |

for (i = 0, j = 0; i < sizeof (size_t); ++i) | |

{ | |

j *= (UCHAR_MAX + 1); | |

j += i; | |

} | |

big_endian_p = (((char *)&j)[0] == 0); | |

/* Move through the pointer values from least significant to most | |

significant digits. */ | |

for (i = 0; i < sizeof (void *) / sizeof (digit_t); ++i) | |

{ | |

digit_t *digit; | |

digit_t *bias; | |

digit_t *top; | |

unsigned int *countp; | |

void **pointerp; | |

/* The offset from the start of the pointer will depend on the | |

endianness of the machine. */ | |

if (big_endian_p) | |

j = sizeof (void *) / sizeof (digit_t) - i; | |

else | |

j = i; | |

/* Now, perform a stable sort on this digit. We use counting | |

sort. */ | |

memset (count, 0, DIGIT_MAX * sizeof (unsigned int)); | |

/* Compute the address of the appropriate digit in the first and | |

one-past-the-end elements of the array. On a little-endian | |

machine, the least-significant digit is closest to the front. */ | |

bias = ((digit_t *) pointers) + j; | |

top = ((digit_t *) (pointers + n)) + j; | |

/* Count how many there are of each value. At the end of this | |

loop, COUNT[K] will contain the number of pointers whose Ith | |

digit is K. */ | |

for (digit = bias; | |

digit < top; | |

digit += sizeof (void *) / sizeof (digit_t)) | |

++count[*digit]; | |

/* Now, make COUNT[K] contain the number of pointers whose Ith | |

digit is less than or equal to K. */ | |

for (countp = count + 1; countp < count + DIGIT_MAX; ++countp) | |

*countp += countp[-1]; | |

/* Now, drop the pointers into their correct locations. */ | |

for (pointerp = pointers + n - 1; pointerp >= pointers; --pointerp) | |

work[--count[((digit_t *) pointerp)[j]]] = *pointerp; | |

/* Swap WORK and POINTERS so that POINTERS contains the sorted | |

array. */ | |

pointerp = pointers; | |

pointers = work; | |

work = pointerp; | |

} | |

} | |

/* Everything below here is a unit test for the routines in this | |

file. */ | |

#ifdef UNIT_TEST | |

#include <stdio.h> | |

void *xmalloc (size_t n) | |

{ | |

return malloc (n); | |

} | |

int main (int argc, char **argv) | |

{ | |

int k; | |

int result; | |

size_t i; | |

void **pointers; | |

void **work; | |

if (argc > 1) | |

k = atoi (argv[1]); | |

else | |

k = 10; | |

pointers = XNEWVEC (void*, k); | |

work = XNEWVEC (void*, k); | |

for (i = 0; i < k; ++i) | |

{ | |

pointers[i] = (void *) random (); | |

printf ("%x\n", pointers[i]); | |

} | |

sort_pointers (k, pointers, work); | |

printf ("\nSorted\n\n"); | |

result = 0; | |

for (i = 0; i < k; ++i) | |

{ | |

printf ("%x\n", pointers[i]); | |

if (i > 0 && (char*) pointers[i] < (char*) pointers[i - 1]) | |

result = 1; | |

} | |

free (pointers); | |

free (work); | |

return result; | |

} | |

#endif |