stdlib/FreeBSD/radixsort.3

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  28 .\"     @(#)radixsort.3 8.2 (Berkeley) 1/27/94
  29 .\" $FreeBSD: src/lib/libc/stdlib/radixsort.3,v 1.12 2007/01/09 00:28:10 imp Exp $
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  31 .Dd January 27, 1994
  32 .Dt RADIXSORT 3
  33 .Os
  34 .Sh NAME
  35 .Nm radixsort , sradixsort
  36 .Nd radix sort
  37 .Sh LIBRARY
  38 .Lb libc
  39 .Sh SYNOPSIS
  40 .In limits.h
  41 .In stdlib.h
  42 .Ft int
  43 .Fn radixsort "const unsigned char **base" "int nmemb" "const unsigned char *table" "unsigned endbyte"
  44 .Ft int
  45 .Fn sradixsort "const unsigned char **base" "int nmemb" "const unsigned char *table" "unsigned endbyte"
  46 .Sh DESCRIPTION
  47 The
  48 .Fn radixsort
  49 and
  50 .Fn sradixsort
  51 functions
  52 are implementations of radix sort.
  53 .Pp
  54 These functions sort an array of pointers to byte strings, the initial
  55 member of which is referenced by
  56 .Fa base .
  57 The byte strings may contain any values; the end of each string
  58 is denoted by the user-specified value
  59 .Fa endbyte .
  60 .Pp
  61 Applications may specify a sort order by providing the
  62 .Fa table
  63 argument.
  64 If
  65 .Pf non- Dv NULL ,
  66 .Fa table
  67 must reference an array of
  68 .Dv UCHAR_MAX
  69 + 1 bytes which contains the sort
  70 weight of each possible byte value.
  71 The end-of-string byte must have a sort weight of 0 or 255
  72 (for sorting in reverse order).
  73 More than one byte may have the same sort weight.
  74 The
  75 .Fa table
  76 argument
  77 is useful for applications which wish to sort different characters
  78 equally, for example, providing a table with the same weights
  79 for A-Z as for a-z will result in a case-insensitive sort.
  80 If
  81 .Fa table
  82 is NULL, the contents of the array are sorted in ascending order
  83 according to the
  84 .Tn ASCII
  85 order of the byte strings they reference and
  86 .Fa endbyte
  87 has a sorting weight of 0.
  88 .Pp
  89 The
  90 .Fn sradixsort
  91 function is stable, that is, if two elements compare as equal, their
  92 order in the sorted array is unchanged.
  93 The
  94 .Fn sradixsort
  95 function uses additional memory sufficient to hold
  96 .Fa nmemb
  97 pointers.
  98 .Pp
  99 The
 100 .Fn radixsort
 101 function is not stable, but uses no additional memory.
 102 .Pp
 103 These functions are variants of most-significant-byte radix sorting; in
 104 particular, see
 105 .An "D.E. Knuth" Ns 's
 106 .%T "Algorithm R"
 107 and section 5.2.5, exercise 10.
 108 They take linear time relative to the number of bytes in the strings.
 109 .Sh RETURN VALUES
 110 .Rv -std radixsort
 111 .Sh ERRORS
 112 .Bl -tag -width Er
 113 .It Bq Er EINVAL
 114 The value of the
 115 .Fa endbyte
 116 element of
 117 .Fa table
 118 is not 0 or 255.
 119 .El
 120 .Pp
 121 Additionally, the
 122 .Fn sradixsort
 123 function
 124 may fail and set
 125 .Va errno
 126 for any of the errors specified for the library routine
 127 .Xr malloc 3 .
 128 .Sh SEE ALSO
 129 .Xr sort 1 ,
 130 .Xr qsort 3
 131 .Pp
 132 .Rs
 133 .%A Knuth, D.E.
 134 .%D 1968
 135 .%B "The Art of Computer Programming"
 136 .%T "Sorting and Searching"
 137 .%V Vol. 3
 138 .%P pp. 170-178
 139 .Re
 140 .Rs
 141 .%A Paige, R.
 142 .%D 1987
 143 .%T "Three Partition Refinement Algorithms"
 144 .%J "SIAM J. Comput."
 145 .%V Vol. 16
 146 .%N No. 6
 147 .Re
 148 .Rs
 149 .%A McIlroy, P.
 150 .%D 1993
 151 .%B "Engineering Radix Sort"
 152 .%T "Computing Systems"
 153 .%V Vol. 6:1
 154 .%P pp. 5-27
 155 .Re
 156 .Sh HISTORY
 157 The
 158 .Fn radixsort
 159 function first appeared in
 160 .Bx 4.4 .