89 lines
4.5 KiB
HTML
89 lines
4.5 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<title>Escape Character Parser</title>
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<body>
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<table width="100%" border="0" background="theme/bkd2.gif" cellspacing="2">
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<tr>
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<td width="10" height="49"> <font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b> </b></font></td>
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<td width="85%" height="49"> <font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Escape Character Parser</b></font></td>
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<tr>
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<td width="10"></td>
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<p><a name="escape_char_parser"></a>The Escape Character Parser is a utility
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parser, which parses escaped character sequences used in C/C++,
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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
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characters:</p>
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<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>
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<p>There are two different types of the Escape Character Parser:
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<tt>c_escape_ch_p</tt>, which parses C/C++ escaped character sequences and
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<tt>lex_escape_ch_p</tt>, which parses LEX style escaped character sequences.
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The following table shows the valid character sequences understood by these
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utility parsers.</p>
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<table width="90%" border="0" align="center">
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<tr>
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<td colspan="2" class="table_title"><b>Summary of valid escaped character
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sequences</b></td>
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</tr>
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<tr>
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<td width="29%" height="27" class="table_cells"><b>c_escape_ch_p</b></td>
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<td width="71%" class="table_cells"><p><code>\b, \t, \n, \f, \r, \\, \",
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\', \xHH, \OOO</code><br>
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where: H is some hexadecimal digit (0..9, a..f, A..F) and O is some octal
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digit (0..7)</p></td>
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</tr>
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<tr>
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<td height="27" class="table_cells"><strong>lex_escape_ch_p</strong></td>
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<td class="table_cells">
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<p>all C/C++ escaped character sequences as described above and additionally
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any other character, which follows a backslash</p>
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</td>
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</tr>
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</table>
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<p>If there is a semantic action attached directly to the Escape Character Parser,
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all valid escaped characters are converted to their character equivalent
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(i.e. a backslash followed by a 'r' is converted to '\r'), which is
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fed to the attached actor. The number of hexadecimal
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or octal digits parsed depends on the size of one input character. An
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overflow will be detected and will generate a non-match. lex_escape_ch_p
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will strip the leading backslash for all character
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sequences which are not listed as valid C/C++ escape sequences when passing
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the unescaped character to an attached action.</p>
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<p>Please note though, that if there is a semantic action attached to an
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outermost parser (for instance as in <tt>(*c_escape_ch_p)[some_actor]</tt>,
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where the action is attached to the kleene star generated parser) no conversion
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takes place at the moment, but nevertheless the escaped characters are parsed
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correctly. This limitation will be removed in a future version of the library.</p>
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<table border="0">
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<tr>
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<td width="10"></td>
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<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
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<td width="30"><a href="switch_parser.html"><img src="theme/l_arr.gif" width="20" height="19" border="0"></a></td>
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<td width="30"><a href="loops.html"><img src="theme/r_arr.gif" border="0"></a></td>
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</tr>
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</table>
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<br>
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<hr size="1">
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<p class="copyright">Copyright © 2001-2002 Daniel C. Nuffer<br>
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Copyright © 2003 Hartmut Kaiser <br>
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<br>
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<font size="2">Use, modification and distribution is subject to the Boost Software
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License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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http://www.boost.org/LICENSE_1_0.txt) </font> </p>
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</body>
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</html>
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