Citrix Systems 9.2 Benutzerhandbuch

TCP payload expressions are discussed in another chapter. For more 
information, see 

.

•

Text in an Secure Sockets Layer (SSL) certificate.

SSL and certificate expressions are discussed in another chapter. For 
information on SSL and certificate data, see 

 and 

Parsing a document body, such as the body of a POST request, can affect 

performance. You may want to test the performance impact of policies that 
evaluate a document body.

From a performance standpoint, it typically is best to use protocol-aware 
functions in an expression. For example, the following expression makes use of a 
protocol-aware function:

HTTP.REQ.URL.QUERY 

The performance of the previous expression is typically better than the following 
equivalent expression that is based on string parsing:

HTTP.REQ.URL.AFTER_STR("?") 

In the first case, the expression looks specifically at the URL query. In the second 
case, the expression scans the data for the first occurrence of a question mark. 

There is also a performance benefit from structured parsing of text, as in the 
following expression:

HTTP.REQ.HEADER("Example").TYPECAST_LIST_T(',').GET(1) 

(For more information on typecasting, see 

.) The typecasting expression, which collects 

comma-delimited data and structures it into a list, typically would perform better 
than the following unstructured equivalent:

HTTP.REQ.HEADER("Example").AFTER_STR(",").BEFORE_STR(",")

Finally, unstructured text expressions typically have better performance than 
regular expressions. For example, the following is an unstructured text 
expression:

HTTP.REQ.HEADER("Example").AFTER_STR("more")

The previous expression would generally provide better performance than the 
following equivalent, which uses a regular expression: