ceph/src/boost/libs/regex/doc/locale.qbk

   1 [/
   2   Copyright 2006-2007 John Maddock.
   3   Distributed under the Boost Software License, Version 1.0.
   4   (See accompanying file LICENSE_1_0.txt or copy at
   5   http://www.boost.org/LICENSE_1_0.txt).
   6 ]
   7
   8 [section:locale Localization]
   9
  10 Boost.Regex provides extensive support for run-time localization, the
  11 localization model used can be split into two parts: front-end and back-end.
  12
  13 Front-end localization deals with everything which the user sees -
  14 error messages, and the regular expression syntax itself. For example a
  15 French application could change \[\[:word:\]\] to \[\[:mot:\]\] and \\w to \\m.
  16 Modifying the front end locale requires active support from the developer,
  17 by providing the library with a message catalogue to load, containing the
  18 localized strings. Front-end locale is affected by the LC_MESSAGES category only.
  19
  20 Back-end localization deals with everything that occurs after the expression
  21 has been parsed - in other words everything that the user does not see or
  22 interact with directly. It deals with case conversion, collation, and character
  23 class membership. The back-end locale does not require any intervention from
  24 the developer - the library will acquire all the information it requires for
  25 the current locale from the underlying operating system / run time library.
  26 This means that if the program user does not interact with regular
  27 expressions directly - for example if the expressions are embedded in your
  28 C++ code - then no explicit localization is required, as the library will
  29 take care of everything for you. For example embedding the expression
  30 \[\[:word:\]\]+ in your code will always match a whole word, if the
  31 program is run on a machine with, for example, a Greek locale, then it
  32 will still match a whole word, but in Greek characters rather than Latin ones.
  33 The back-end locale is affected by the LC_TYPE and LC_COLLATE categories.
  34
  35 There are three separate localization mechanisms supported by Boost.Regex:
  36
  37 [h4 Win32 localization model.]
  38
  39 This is the default model when the library is compiled under Win32, and is
  40 encapsulated by the traits class `w32_regex_traits`. When this model is in
  41 effect each [basic_regex] object gets it's own LCID, by default this is
  42 the users default setting as returned by GetUserDefaultLCID, but you can
  43 call imbue on the `basic_regex` object to set it's locale to some other
  44 LCID if you wish. All the settings used by Boost.Regex are acquired directly
  45 from the operating system bypassing the C run time library. Front-end
  46 localization requires a resource dll, containing a string table with the
  47 user-defined strings. The traits class exports the function:
  48
  49    static std::string set_message_catalogue(const std::string& s);
  50
  51 which needs to be called with a string identifying the name of the resource
  52 dll, before your code compiles any regular expressions (but not necessarily
  53 before you construct any `basic_regex` instances):
  54
  55    boost::w32_regex_traits<char>::set_message_catalogue("mydll.dll");
  56
  57 The library provides full Unicode support under NT, under Windows 9x
  58 the library degrades gracefully - characters 0 to 255 are supported, the
  59 remainder are treated as "unknown" graphic characters.
  60
  61 [h4 C localization model.]
  62
  63 This model has been deprecated in favor of the C++ locale for all non-Windows
  64 compilers that support it.  This locale is encapsulated by the traits class
  65 `c_regex_traits`, Win32 users can force this model to take effect by
  66 defining the pre-processor symbol BOOST_REGEX_USE_C_LOCALE. When this model is
  67 in effect there is a single global locale, as set by `setlocale`. All settings
  68 are acquired from your run time library, consequently Unicode support is
  69 dependent upon your run time library implementation.
  70
  71 Front end localization is not supported.
  72
  73 Note that calling setlocale invalidates all compiled regular expressions,
  74 calling `setlocale(LC_ALL, "C")` will make this library behave equivalent to
  75 most traditional regular expression libraries including version 1 of this library.
  76
  77 [h4 C++ localization model.]
  78
  79 This model is the default for non-Windows compilers.
  80
  81 When this model is in effect each instance of [basic_regex] has its own
  82 instance of `std::locale`, class [basic_regex] also has a member function
  83 `imbue` which allows the locale for the expression to be set on a
  84 per-instance basis. Front end localization requires a POSIX message catalogue,
  85 which will be loaded via the `std::messages` facet of the expression's locale,
  86 the traits class exports the symbol:
  87
  88    static std::string set_message_catalogue(const std::string& s);
  89
  90 which needs to be called with a string identifying the name of the
  91 message catalogue, before your code compiles any regular expressions
  92 (but not necessarily before you construct any basic_regex instances):
  93
  94    boost::cpp_regex_traits<char>::set_message_catalogue("mycatalogue");
  95
  96 Note that calling `basic_regex<>::imbue` will invalidate any expression
  97 currently compiled in that instance of [basic_regex].
  98
  99 Finally note that if you build the library with a non-default localization model,
 100 then the appropriate pre-processor symbol (BOOST_REGEX_USE_C_LOCALE or
 101 BOOST_REGEX_USE_CPP_LOCALE) must be defined both when you build the support
 102 library, and when you include `<boost/regex.hpp>` or `<boost/cregex.hpp>`
 103 in your code. The best way to ensure this is to add the #define to
 104 `<boost/regex/user.hpp>`.
 105
 106 [h4 Providing a message catalogue]
 107
 108 In order to localize the front end of the library, you need to provide the
 109 library with the appropriate message strings contained either in a resource
 110 dll's string table (Win32 model), or a POSIX message catalogue (C++ models).
 111 In the latter case the messages must appear in message set zero of the
 112 catalogue. The messages and their id's are as follows:
 113
 114 [table
 115         [[Message][id][Meaning][Default value]]
 116         [[101][The character used to start a sub-expression.]["("        ]]
 117         [[102][The character used to end a sub-expression declaration.][")"      ]]
 118         [[103][The character used to denote an end of line assertion.]["$"       ]]
 119         [[104][The character used to denote the start of line assertion.]["^"    ]]
 120         [[105][The character used to denote the "match any character expression".]["."   ]]
 121         [[106][The match zero or more times repetition operator.]["*"    ]]
 122         [[107][The match one or more repetition operator.]["+"   ]]
 123         [[108][The match zero or one repetition operator.]["?"   ]]
 124         [[109][The character set opening character.]["\["        ]]
 125         [[110][The character set closing character.]["\]"        ]]
 126         [[111][The alternation operator.]["|"    ]]
 127         [[112][The escape character.]["\\"       ]]
 128         [[113][The hash character (not currently used).]["#"     ]]
 129         [[114][The range operator.]["-"          ]]
 130         [[115][The repetition operator opening character.]["{"   ]]
 131         [[116][The repetition operator closing character.]["}"   ]]
 132         [[117][The digit characters.]["0123456789"       ]]
 133         [[118][The character which when preceded by an escape character represents the word boundary assertion.]["b"     ]]
 134         [[119][The character which when preceded by an escape character represents the non-word boundary assertion.]["B"         ]]
 135         [[120][The character which when preceded by an escape character represents the word-start boundary assertion.]["<"       ]]
 136         [[121][The character which when preceded by an escape character represents the word-end boundary assertion.][">"         ]]
 137         [[122][The character which when preceded by an escape character represents any word character.]["w"      ]]
 138         [[123][The character which when preceded by an escape character represents a non-word character.]["W"    ]]
 139         [[124][The character which when preceded by an escape character represents a start of buffer assertion.]["`A"    ]]
 140         [[125][The character which when preceded by an escape character represents an end of buffer assertion.]["'z"     ]]
 141         [[126][The newline character. ]["\\n"    ]]
 142         [[127][The comma separator.][","         ]]
 143         [[128][The character which when preceded by an escape character represents the bell character.]["a"      ]]
 144         [[129][The character which when preceded by an escape character represents the form feed character.]["f"         ]]
 145         [[130][The character which when preceded by an escape character represents the newline character.]["n"   ]]
 146         [[131][The character which when preceded by an escape character represents the carriage return character.]["r"   ]]
 147         [[132][The character which when preceded by an escape character represents the tab character.]["t"       ]]
 148         [[133][The character which when preceded by an escape character represents the vertical tab character.]["v"      ]]
 149         [[134][The character which when preceded by an escape character represents the start of a hexadecimal character constant.]["x"   ]]
 150         [[135][The character which when preceded by an escape character represents the start of an ASCII escape character.]["c"          ]]
 151         [[136][The colon character.][":"         ]]
 152         [[137][The equals character.]["="        ]]
 153         [[138][The character which when preceded by an escape character represents the ASCII escape character.]["e"      ]]
 154         [[139][The character which when preceded by an escape character represents any lower case character.]["l"        ]]
 155         [[140][The character which when preceded by an escape character represents any non-lower case character.]["L"    ]]
 156         [[141][The character which when preceded by an escape character represents any upper case character.]["u"        ]]
 157         [[142][The character which when preceded by an escape character represents any non-upper case character.]["U"    ]]
 158         [[143][The character which when preceded by an escape character represents any space character.]["s"     ]]
 159         [[144][The character which when preceded by an escape character represents any non-space character.]["S"         ]]
 160         [[145][The character which when preceded by an escape character represents any digit character.]["d"     ]]
 161         [[146][The character which when preceded by an escape character represents any non-digit character.]["D"         ]]
 162         [[147][The character which when preceded by an escape character represents the end quote operator.]["E"          ]]
 163         [[148][The character which when preceded by an escape character represents the start quote operator.]["Q"        ]]
 164         [[149][The character which when preceded by an escape character represents a Unicode combining character sequence.]["X"          ]]
 165         [[150][The character which when preceded by an escape character represents any single character.]["C"    ]]
 166         [[151][The character which when preceded by an escape character represents end of buffer operator.]["Z"          ]]
 167         [[152][The character which when preceded by an escape character represents the continuation assertion.]["G"      ]]
 168         [[153][The character which when preceded by (? indicates a zero width negated forward lookahead assert.][!       ]]
 169 ]
 170
 171 Custom error messages are loaded as follows:
 172
 173 [table
 174         [[Message ID][Error message ID][Default string   ]]
 175         [[201][REG_NOMATCH]["No match"   ]]
 176         [[202][REG_BADPAT]["Invalid regular expression"          ]]
 177         [[203][REG_ECOLLATE]["Invalid collation character"       ]]
 178         [[204][REG_ECTYPE]["Invalid character class name"        ]]
 179         [[205][REG_EESCAPE]["Trailing backslash"         ]]
 180         [[206][REG_ESUBREG]["Invalid back reference"     ]]
 181         [[207][REG_EBRACK]["Unmatched \[ or \[^"         ]]
 182         [[208][REG_EPAREN]["Unmatched ( or \\("          ]]
 183         [[209][REG_EBRACE]["Unmatched \\{"       ]]
 184         [[210][REG_BADBR]["Invalid content of \\{\\}"    ]]
 185         [[211][REG_ERANGE]["Invalid range end"   ]]
 186         [[212][REG_ESPACE]["Memory exhausted"    ]]
 187         [[213][REG_BADRPT]["Invalid preceding regular expression"        ]]
 188         [[214][REG_EEND]["Premature end of regular expression"   ]]
 189         [[215][REG_ESIZE]["Regular expression too big"   ]]
 190         [[216][REG_ERPAREN]["Unmatched ) or \\)"         ]]
 191         [[217][REG_EMPTY]["Empty expression"     ]]
 192         [[218][REG_E_UNKNOWN]["Unknown error"    ]]
 193 ]
 194
 195 Custom character class names are loaded as followed:
 196
 197 [table
 198         [[Message ID][Description][Equivalent default class name         ]]
 199         [[300][The character class name for alphanumeric characters.]["alnum"    ]]
 200         [[301][The character class name for alphabetic characters.]["alpha"      ]]
 201         [[302][The character class name for control characters.]["cntrl"         ]]
 202         [[303][The character class name for digit characters.]["digit"   ]]
 203         [[304][The character class name for graphics characters.]["graph"        ]]
 204         [[305][The character class name for lower case characters.]["lower"      ]]
 205         [[306][The character class name for printable characters.]["print"       ]]
 206         [[307][The character class name for punctuation characters.]["punct"     ]]
 207         [[308][The character class name for space characters.]["space"   ]]
 208         [[309][The character class name for upper case characters.]["upper"      ]]
 209         [[310][The character class name for hexadecimal characters.]["xdigit"    ]]
 210         [[311][The character class name for blank characters.]["blank"   ]]
 211         [[312][The character class name for word characters.]["word"     ]]
 212         [[313][The character class name for Unicode characters.]["unicode"       ]]
 213 ]
 214
 215 Finally, custom collating element names are loaded starting from message
 216 id 400, and terminating when the first load thereafter fails. Each message
 217 looks something like: "tagname string" where tagname is the name used
 218 inside [[.tagname.]] and string is the actual text of the collating element.
 219 Note that the value of collating element [[.zero.]] is used for the
 220 conversion of strings to numbers - if you replace this with another value then
 221 that will be used for string parsing - for example use the Unicode
 222 character 0x0660 for [[.zero.]] if you want to use Unicode Arabic-Indic
 223 digits in your regular expressions in place of Latin digits.
 224
 225 Note that the POSIX defined names for character classes and collating elements
 226 are always available - even if custom names are defined, in contrast,
 227 custom error messages, and custom syntax messages replace the default ones.
 228
 229 [endsect]
 230
 231