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[4093] Updated eval section of Developer's Guide.

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This commit is contained in:
Marcin Siodelski
2015-11-19 16:26:49 +01:00
parent ae94eaf209
commit b070bb9cb3
1 changed files with 14 additions and 7 deletions
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19
src/lib/eval/eval.dox
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@@ -18,8 +18,9 @@
@section dhcpEvalIntroduction Introduction @section dhcpEvalIntroduction Introduction
The core of the libeval library is a parser that is able to parse an The core of the libeval library is a parser that is able to parse an
expression (e.g. option[123] == 'APC'). This is currently used for client expression (e.g. option[123].text == 'APC'). This is currently used for
classification, but in the future may be also used for other applications. client classification, but in the future may be also used for other
applications.
The external interface to the library is the @ref isc::eval::EvalContext The external interface to the library is the @ref isc::eval::EvalContext
class. Once instantiated, it offers a major method: class. Once instantiated, it offers a major method:
@@ -79,12 +80,17 @@
14. TokenPtr hex(new TokenHexString($1)); 14. TokenPtr hex(new TokenHexString($1));
15. ctx.expression.push_back(hex); 15. ctx.expression.push_back(hex);
16. } 16. }
17. | OPTION '[' INTEGER ']' 17. | OPTION '[' INTEGER ']' DOTTEXT
18. { 18. {
19. TokenPtr opt(new TokenOption($3)); 19. TokenPtr opt(new TokenOption($3, TokenOption::TEXTUAL));
20. ctx.expression.push_back(opt); 20. ctx.expression.push_back(opt);
21. } 21. }
22. ; 22. | OPTION '[' INTEGER ']' DOTHEX
23. {
24. TokenPtr opt(new TokenOption($3, TokenOption::HEXADECIMAL));
25. ctx.expression.push_back(opt);
26. }
27. ;
@endcode @endcode
This code determines that the grammar starts from expression (line 1). This code determines that the grammar starts from expression (line 1).
@@ -92,7 +98,8 @@ The actual definition of expression (lines 3-5) may either be a
single token or an expression "token == token" (EQUAL has been defined as single token or an expression "token == token" (EQUAL has been defined as
"==" elsewhere). Token is further "==" elsewhere). Token is further
defined in lines 7-22: it may either be a string (lines 7-11), defined in lines 7-22: it may either be a string (lines 7-11),
a hex string (lines 12-16) or option (lines 17-21). a hex string (lines 12-16), option in the textual format (lines 17-21)
or option in a hexadecimal format (lines 22-26).
When the actual case is determined, the respective C++ action When the actual case is determined, the respective C++ action
is executed. For example, if the token is a string, the TokenString class is is executed. For example, if the token is a string, the TokenString class is
instantiated with the appropriate value and put onto the expression vector. instantiated with the appropriate value and put onto the expression vector.