| /* Sorting algorithms. |
| Copyright (C) 2000-2024 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 |