:relfileprefix: ../../
[#boost-urls-pct_encoded_rule]

== xref:boost.adoc[pass:[boost]]::xref:boost/urls.adoc[pass:[urls]]::pct_encoded_rule


Rule for a string with percent-encoded escapes


=== Synopsis

Declared in header `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/rfc/pct_encoded_rule.hpp#L131[boost/url/rfc/pct_encoded_rule.hpp,window=blank_]>`

[source,cpp,subs="verbatim,macros,-callouts"]
----
template<class CharSet>
constexpr
pass:q[_implementation-defined_]
pct_encoded_rule(CharSet const& cs) noexcept;
----

=== Description


This function returns a rule which matches
a percent-encoded string, permitting characters
in the string which are also in the specified
character set to be used unescaped.
[,cpp]
----
using value_type = pct_string_view;
----

=== Rules are used with the function

xref:boost/urls/grammar/parse-02.adoc[grammar::parse]
.
[,cpp]
----
//  pchar         = unreserved / pct-encoded / sub-delims / ":" / "@"

system::result< pct_string_view > rv = grammar::parse( "Program%20Files", pct_encoded_rule( pchars ) );
----
[,cpp]
----
pct-encoded   = "%" HEXDIG HEXDIG
----

* link:https://datatracker.ietf.org/doc/html/rfc3986#section-2.1[        2.1. Percent-Encoding (rfc3986)]





=== Parameters

|===
| Name | Description 

| *cs*
| 
The character set indicating
which characters are allowed without escapes.
Any character which is not in this set must be
escaped, or else parsing returns an error.

|===




=== See Also


xref:boost/urls/grammar/parse-02.adoc[grammar::parse]
,
xref:boost/urls/pchars.adoc[pchars]
,
xref:boost/urls/pct_string_view.adoc[pct_string_view]
.