Expression Functions
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Clearsilver has some built-in functions for expressions. These functions allow access and manipulation of expression arguments. Currently, all functions return string or numeric values. Functions can be used in expressions anywhere a variable could be used.
| Function | Arguments | Description |
|---|---|---|
| subcount(var) | An HDF variable | Returns the number of child nodes for the HDF variable |
| name(local) | A local variable | Returns the HDF variable name for a local variable alias |
| first(local) | A local variable | Returns true iff the local variable is the first in a loop or each |
| last(local) | A local variable | Returns true iff the local variable is the last in a loop or each |
| abs(expr) | A numeric expression | Returns the absolute value of the numeric expressions |
| max(expr, expr) | Two numeric expressions | Returns the larger of two numeric expressions |
| min(expr, expr) | Two numeric expressions | Returns the smaller of two numeric expressions |
| string.slice(expr, start, end) | A string expression, and two numeric expressions | Returns the string slice starting at start and ending at end, similar to the Python slice operator |
| string.find(string, substr) | Two string expressions | Returns the numeric position of the substring in the string (if found), otherwise returns -1 similar to the Python string.find method |
| string.length(expr) | A string expression | Returns the length of the string expression |
| _(expr) | A string expression | Only available if compiled with gettext support, returns the translated version of the string expression as returned by gettext() |
Template Filters
Section titled “Template Filters”The Clearsilver API allows the user to add string manipulation functions to the built-in functions. These functions can take just one string argument and return a string. The Clearsilver CGI Kit has several Web specific filters that are added to Clearsilver. These filters can be added in C via the cgi_register_strfuncs() function, and are included by default in the CS layer of most of the language wrappers.
| url_escape | This URL encodes the string. This converts characters such as ?, &, and = into their URL safe equivilants using the %hh syntax. |
| html_escape | This HTML escapes the string. This converts characters such as >, <, and & into their HTML safe equivilants such as >, <, and &. |
| js_escape | This Javascript escapes the string so it will be valid data for placement into a Javascript string. This converts characters such as ", ', and \ into their Javascript string safe equivilants \", \', and \\. |
| text_html | This pretty-formats normal text into an HTML fragment, attempting to detect paragraph boundaries and allowing it to wrap reasonably. |
| html_strip | This removes all HTML tags and then converts any & based HTML escaped data into normal text. Combine this with html_escape() if you would like to strip the HTML tags from text and display the result in an HTML safe way. |
| url_validate | Function to validate a URL for protecting against XSS. Ensures that the URL is a relative URL or an absolute url with a safe scheme (currently http, https, ftp or mailto). This is to avoid dangerous schemes like javascript. It then HTML escapes the URL. An unsafe URL is replaced by ’#’. |
| css_url_validate | Similar to url_validate except it escapes the URL for use in CSS. |
| null_escape | This escape function just outputs the given string as is. The auto-escape system assumes that anything explicitly escaped is correctly escaped. |
These filters can be used anywhere in an expression. This makes them extremely useful for composing URLs or forcing data to be HTML safe. Here are some examples:
<?cs var:html_escape(Page.Title) ?><?cs set:url = "http://www.google.com/q=" + url_escape(Query.q) ?>
<IMG onclick="handleClick('<?cs var:js_escape(url)')" SRC="foo.gif">
<A HREF="/newurl?_done=<?cs var:url_escape(url) ?>">click here</A>