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| 4 | <title>Escape Character Parser</title> |
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| 10 | <table width="100%" border="0" background="theme/bkd2.gif" cellspacing="2"> |
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| 11 | <tr> |
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| 12 | <td width="10" height="49"> <font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b> </b></font></td> |
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| 13 | <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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| 25 | </table> |
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| 26 | <p><a name="escape_char_parser"></a>The Escape Character Parser is a utility |
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| 27 | parser, which parses escaped character sequences used in C/C++, |
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| 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 |
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| 29 | characters:</p> |
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| 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> |
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| 31 | <p>There are two different types of the Escape Character Parser: |
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| 32 | <tt>c_escape_ch_p</tt>, which parses C/C++ escaped character sequences and |
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| 33 | <tt>lex_escape_ch_p</tt>, which parses LEX style escaped character sequences. |
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| 34 | The following table shows the valid character sequences understood by these |
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| 35 | utility parsers.</p> |
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| 36 | <table width="90%" border="0" align="center"> |
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| 37 | <tr> |
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| 38 | <td colspan="2" class="table_title"><b>Summary of valid escaped character |
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| 39 | sequences</b></td> |
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| 40 | </tr> |
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| 41 | <tr> |
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| 42 | <td width="29%" height="27" class="table_cells"><b>c_escape_ch_p</b></td> |
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| 43 | <td width="71%" class="table_cells"><p><code>\b, \t, \n, \f, \r, \\, \", |
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| 44 | \', \xHH, \OOO</code><br> |
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| 45 | where: H is some hexadecimal digit (0..9, a..f, A..F) and O is some octal |
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| 46 | digit (0..7)</p></td> |
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| 47 | </tr> |
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| 48 | <tr> |
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| 49 | <td height="27" class="table_cells"><strong>lex_escape_ch_p</strong></td> |
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| 50 | <td class="table_cells"> |
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| 51 | <p>all C/C++ escaped character sequences as described above and additionally |
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| 52 | any other character, which follows a backslash</p> |
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| 53 | </td> |
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| 54 | </tr> |
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| 55 | </table> |
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| 56 | <p>If there is a semantic action attached directly to the Escape Character Parser, |
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| 57 | all valid escaped characters are converted to their character equivalent |
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| 58 | (i.e. a backslash followed by a 'r' is converted to '\r'), which is |
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| 59 | fed to the attached actor. The number of hexadecimal |
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| 60 | or octal digits parsed depends on the size of one input character. An |
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| 61 | overflow will be detected and will generate a non-match. lex_escape_ch_p |
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| 62 | will strip the leading backslash for all character |
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| 63 | sequences which are not listed as valid C/C++ escape sequences when passing |
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| 64 | the unescaped character to an attached action.</p> |
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| 65 | <p>Please note though, that if there is a semantic action attached to an |
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| 66 | outermost parser (for instance as in <tt>(*c_escape_ch_p)[some_actor]</tt>, |
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| 67 | where the action is attached to the kleene star generated parser) no conversion |
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| 68 | takes place at the moment, but nevertheless the escaped characters are parsed |
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| 69 | correctly. This limitation will be removed in a future version of the library.</p> |
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| 70 | <table border="0"> |
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| 71 | <tr> |
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| 72 | <td width="10"></td> |
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| 73 | <td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td> |
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| 76 | </tr> |
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| 77 | </table> |
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| 78 | |
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| 79 | <br> |
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| 80 | <hr size="1"> |
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| 81 | <p class="copyright">Copyright © 2001-2002 Daniel C. Nuffer<br> |
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| 82 | Copyright © 2003 Hartmut Kaiser <br> |
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| 83 | <br> |
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| 84 | <font size="2">Use, modification and distribution is subject to the Boost Software |
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| 85 | License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at |
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| 86 | http://www.boost.org/LICENSE_1_0.txt) </font> </p> |
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| 87 | </body> |
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| 88 | </html> |
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