161 lines
4.4 KiB
Groff
161 lines
4.4 KiB
Groff
.\" Copyright (c) 1990, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)radixsort.3 8.2 (Berkeley) 1/27/94
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.\" $FreeBSD$
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.\"
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.Dd January 27, 1994
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.Dt RADIXSORT 3
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.Os
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.Sh NAME
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.Nm radixsort , sradixsort
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.Nd radix sort
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In limits.h
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.In stdlib.h
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.Ft int
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.Fn radixsort "const unsigned char **base" "int nmemb" "const unsigned char *table" "unsigned endbyte"
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.Ft int
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.Fn sradixsort "const unsigned char **base" "int nmemb" "const unsigned char *table" "unsigned endbyte"
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.Sh DESCRIPTION
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The
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.Fn radixsort
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and
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.Fn sradixsort
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functions
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are implementations of radix sort.
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.Pp
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These functions sort an array of pointers to byte strings, the initial
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member of which is referenced by
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.Fa base .
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The byte strings may contain any values; the end of each string
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is denoted by the user-specified value
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.Fa endbyte .
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.Pp
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Applications may specify a sort order by providing the
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.Fa table
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argument.
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If
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.Pf non- Dv NULL ,
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.Fa table
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must reference an array of
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.Dv UCHAR_MAX
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+ 1 bytes which contains the sort
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weight of each possible byte value.
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The end-of-string byte must have a sort weight of 0 or 255
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(for sorting in reverse order).
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More than one byte may have the same sort weight.
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The
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.Fa table
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argument
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is useful for applications which wish to sort different characters
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equally, for example, providing a table with the same weights
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for A-Z as for a-z will result in a case-insensitive sort.
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If
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.Fa table
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is NULL, the contents of the array are sorted in ascending order
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according to the
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.Tn ASCII
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order of the byte strings they reference and
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.Fa endbyte
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has a sorting weight of 0.
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.Pp
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The
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.Fn sradixsort
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function is stable, that is, if two elements compare as equal, their
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order in the sorted array is unchanged.
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The
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.Fn sradixsort
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function uses additional memory sufficient to hold
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.Fa nmemb
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pointers.
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.Pp
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The
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.Fn radixsort
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function is not stable, but uses no additional memory.
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.Pp
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These functions are variants of most-significant-byte radix sorting; in
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particular, see
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.An "D.E. Knuth" Ns 's
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.%T "Algorithm R"
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and section 5.2.5, exercise 10.
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They take linear time relative to the number of bytes in the strings.
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.Sh RETURN VALUES
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.Rv -std radixsort
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.Sh ERRORS
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The value of the
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.Fa endbyte
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element of
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.Fa table
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is not 0 or 255.
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.El
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.Pp
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Additionally, the
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.Fn sradixsort
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function
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may fail and set
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.Va errno
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for any of the errors specified for the library routine
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.Xr malloc 3 .
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.Sh SEE ALSO
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.Xr sort 1 ,
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.Xr qsort 3
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.Pp
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.Rs
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.%A Knuth, D.E.
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.%D 1968
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.%B "The Art of Computer Programming"
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.%T "Sorting and Searching"
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.%V Vol. 3
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.%P pp. 170-178
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.Re
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.Rs
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.%A Paige, R.
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.%D 1987
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.%T "Three Partition Refinement Algorithms"
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.%J "SIAM J. Comput."
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.%V Vol. 16
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.%N No. 6
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.Re
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.Rs
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.%A McIlroy, P.
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.%D 1993
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.%B "Engineering Radix Sort"
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.%T "Computing Systems"
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.%V Vol. 6:1
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.%P pp. 5-27
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.Re
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.Sh HISTORY
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The
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.Fn radixsort
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function first appeared in
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.Bx 4.4 .
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