ceph/src/boost/libs/spirit/classic/doc/escape_char_parser.html

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  26 <p><a name="escape_char_parser"></a>The Escape Character Parser is a utility
  27   parser, which parses escaped character sequences used in C/C++,
  28   LEX or Perl regular expressions. Combined with the confix_p utility parser, it is useful for parsing C/C++ strings containing double quotes and other escaped
  29   characters:</p>
  30 <pre>    confix_p<span class="special">(</span><em class="literal">'"'</em><span class="special">,</span> <span class="special">*</span>c_escape_ch_p<span class="special">,</span> <em><span class="literal">'"</span></em><span class="literal"><em>'</em></span><span class="special">)</span></pre>
  31 <p>There are two different types of the Escape Character Parser:
  32   <tt>c_escape_ch_p</tt>, which parses C/C++ escaped character sequences and
  33   <tt>lex_escape_ch_p</tt>, which parses LEX style escaped character sequences.
  34   The following table shows the valid character sequences understood by these
  35   utility parsers.</p>
  36 <table width="90%" border="0" align="center">
  37   <tr>
  38     <td colspan="2" class="table_title"><b>Summary of valid escaped character
  39       sequences</b></td>
  40   </tr>
  41   <tr>
  42     <td width="29%" height="27" class="table_cells"><b>c_escape_ch_p</b></td>
  43     <td width="71%" class="table_cells"><p><code>\b, \t, \n, \f, \r, \\, \&quot;,
  44         \', \xHH, \OOO</code><br>
  45         where: H is some hexadecimal digit (0..9, a..f, A..F) and O is some octal
  46         digit (0..7)</p></td>
  47   </tr>
  48   <tr>
  49     <td height="27" class="table_cells"><strong>lex_escape_ch_p</strong></td>
  50     <td class="table_cells">
  51       <p>all C/C++ escaped character sequences as described above and additionally
  52         any other character, which follows a backslash</p>
  53     </td>
  54   </tr>
  55 </table>
  56 <p>If there is a semantic action attached directly to the Escape Character Parser,
  57   all valid escaped characters are converted to their character equivalent
  58   (i.e. a backslash followed by a 'r' is converted to '\r'), which is
  59   fed to the attached actor. The number of hexadecimal
  60   or octal digits parsed depends on the size of one input character. An
  61   overflow will be detected and will generate a non-match.  lex_escape_ch_p
  62   will strip the leading backslash for all character
  63   sequences which are not listed as valid C/C++ escape sequences when passing
  64   the unescaped character to an attached action.</p>
  65 <p>Please note though, that if there is a semantic action attached to an
  66   outermost parser (for instance as in <tt>(*c_escape_ch_p)[some_actor]</tt>,
  67   where the action is attached to the kleene star generated parser) no conversion
  68   takes place at the moment, but nevertheless the escaped characters are parsed
  69   correctly. This limitation will be removed in a future version of the library.</p>
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  81 <p class="copyright">Copyright &copy; 2001-2002 Daniel C. Nuffer<br>
  82 Copyright &copy; 2003 Hartmut Kaiser <br>
  83   <br>
  84 <font size="2">Use, modification and distribution is subject to the Boost Software
  85     License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
  86     http://www.boost.org/LICENSE_1_0.txt) </font> </p>
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