/* Sorting algorithms. Copyright (C) 2000 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, 59 Temple Place - Suite 330, Boston, MA 02111-1307, 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 (n, pointers, work) 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 (n) 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 = xmalloc (k * sizeof (void *)); work = xmalloc (k * sizeof (void *)); 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