Doc/lib/libstringprep.tex

   1 \section{\module{stringprep} ---
   2          Internet String Preparation}
   3
   4 \declaremodule{standard}{stringprep}
   5 \modulesynopsis{String preparation, as per RFC 3453}
   6 \moduleauthor{Martin v. L\"owis}{martin@v.loewis.de}
   7 \sectionauthor{Martin v. L\"owis}{martin@v.loewis.de}
   8
   9 When identifying things (such as host names) in the internet, it is
  10 often necessary to compare such identifications for
  11 ``equality''. Exactly how this comparison is executed may depend on
  12 the application domain, e.g. whether it should be case-insensitive or
  13 not. It may be also necessary to restrict the possible
  14 identifications, to allow only identifications consisting of
  15 ``printable'' characters.
  16
  17 \rfc{3454} defines a procedure for ``preparing'' Unicode strings in
  18 internet protocols. Before passing strings onto the wire, they are
  19 processed with the preparation procedure, after which they have a
  20 certain normalized form. The RFC defines a set of tables, which can be
  21 combined into profiles. Each profile must define which tables it uses,
  22 and what other optional parts of the \code{stringprep} procedure are
  23 part of the profile. One example of a \code{stringprep} profile is
  24 \code{nameprep}, which is used for internationalized domain names.
  25
  26 The module \module{stringprep} only exposes the tables from RFC
  27 3454. As these tables would be very large to represent them as
  28 dictionaries or lists, the module uses the Unicode character database
  29 internally. The module source code itself was generated using the
  30 \code{mkstringprep.py} utility.
  31
  32 As a result, these tables are exposed as functions, not as data
  33 structures. There are two kinds of tables in the RFC: sets and
  34 mappings. For a set, \module{stringprep} provides the ``characteristic
  35 function'', i.e. a function that returns true if the parameter is part
  36 of the set. For mappings, it provides the mapping function: given the
  37 key, it returns the associated value. Below is a list of all functions
  38 available in the module.
  39
  40 \begin{funcdesc}{in_table_a1}{code}
  41 Determine whether \var{code} is in table{A.1} (Unassigned code points
  42 in Unicode 3.2).
  43 \end{funcdesc}
  44
  45 \begin{funcdesc}{in_table_b1}{code}
  46 Determine whether \var{code} is in table{B.1} (Commonly mapped to
  47 nothing).
  48 \end{funcdesc}
  49
  50 \begin{funcdesc}{map_table_b2}{code}
  51 Return the mapped value for \var{code} according to table{B.2}
  52 (Mapping for case-folding used with NFKC).
  53 \end{funcdesc}
  54
  55 \begin{funcdesc}{map_table_b3}{code}
  56 Return the mapped value for \var{code} according to table{B.3}
  57 (Mapping for case-folding used with no normalization).
  58 \end{funcdesc}
  59
  60 \begin{funcdesc}{in_table_c11}{code}
  61 Determine whether \var{code} is in table{C.1.1}
  62 (ASCII space characters).
  63 \end{funcdesc}
  64
  65 \begin{funcdesc}{in_table_c12}{code}
  66 Determine whether \var{code} is in table{C.1.2}
  67 (Non-ASCII space characters).
  68 \end{funcdesc}
  69
  70 \begin{funcdesc}{in_table_c11_c12}{code}
  71 Determine whether \var{code} is in table{C.1}
  72 (Space characters, union of C.1.1 and C.1.2).
  73 \end{funcdesc}
  74
  75 \begin{funcdesc}{in_table_c21}{code}
  76 Determine whether \var{code} is in table{C.2.1}
  77 (ASCII control characters).
  78 \end{funcdesc}
  79
  80 \begin{funcdesc}{in_table_c22}{code}
  81 Determine whether \var{code} is in table{C.2.2}
  82 (Non-ASCII control characters).
  83 \end{funcdesc}
  84
  85 \begin{funcdesc}{in_table_c21_c22}{code}
  86 Determine whether \var{code} is in table{C.2}
  87 (Control characters, union of C.2.1 and C.2.2).
  88 \end{funcdesc}
  89
  90 \begin{funcdesc}{in_table_c3}{code}
  91 Determine whether \var{code} is in table{C.3}
  92 (Private use).
  93 \end{funcdesc}
  94
  95 \begin{funcdesc}{in_table_c4}{code}
  96 Determine whether \var{code} is in table{C.4}
  97 (Non-character code points).
  98 \end{funcdesc}
  99
 100 \begin{funcdesc}{in_table_c5}{code}
 101 Determine whether \var{code} is in table{C.5}
 102 (Surrogate codes).
 103 \end{funcdesc}
 104
 105 \begin{funcdesc}{in_table_c6}{code}
 106 Determine whether \var{code} is in table{C.6}
 107 (Inappropriate for plain text).
 108 \end{funcdesc}
 109
 110 \begin{funcdesc}{in_table_c7}{code}
 111 Determine whether \var{code} is in table{C.7}
 112 (Inappropriate for canonical representation).
 113 \end{funcdesc}
 114
 115 \begin{funcdesc}{in_table_c8}{code}
 116 Determine whether \var{code} is in table{C.8}
 117 (Change display properties or are deprecated).
 118 \end{funcdesc}
 119
 120 \begin{funcdesc}{in_table_c9}{code}
 121 Determine whether \var{code} is in table{C.9}
 122 (Tagging characters).
 123 \end{funcdesc}
 124
 125 \begin{funcdesc}{in_table_d1}{code}
 126 Determine whether \var{code} is in table{D.1}
 127 (Characters with bidirectional property ``R'' or ``AL'').
 128 \end{funcdesc}
 129
 130 \begin{funcdesc}{in_table_d2}{code}
 131 Determine whether \var{code} is in table{D.2}
 132 (Characters with bidirectional property ``L'').
 133 \end{funcdesc}
 134