[#boost-urls-pct_encoded_rule]
= xref:boost.adoc[boost]::xref:boost/urls.adoc[urls]::pct&lowbar;encoded&lowbar;rule
:relfileprefix: ../../
:mrdocs:

Rule for a string with percent&hyphen;encoded escapes

== Synopsis

Declared in `&lt;https://www.github.com/boostorg/url/blob/develop/include/boost/url/rfc/pct_encoded_rule.hpp#L84[boost&sol;url&sol;rfc&sol;pct&lowbar;encoded&lowbar;rule&period;hpp]&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template&lt;xref:boost/urls/grammar/CharSet.adoc[grammar::CharSet] CS&gt;
constexpr
&sol;&ast; implementation-defined &ast;&sol;
pct&lowbar;encoded&lowbar;rule(CS const& cs) noexcept;
----

== Description

This function returns a rule which matches a percent&hyphen;encoded string, permitting characters in the string which are also in the specified character set to be used unescaped&period;

== Value Type
[,cpp]
----
using value_type = pct_string_view;
----
== Example
Rules are used with the function xref:boost/urls/grammar/parse-09.adoc[`grammar&colon;&colon;parse`]&period;

[,cpp]
----
//  pchar         = unreserved / pct-encoded / sub-delims / ":" / "@"

system::result< pct_string_view > rv = grammar::parse( "Program%20Files", pct_encoded_rule( pchars ) );
----
== BNF
[,cpp]
----
pct-encoded   = "%" HEXDIG HEXDIG
----
== Specification
* https://datatracker.ietf.org/doc/html/rfc3986#section-2.1[]

== Return Value

A rule object&period;

== Parameters

[cols=2]
|===
| Name
| Description
| *cs*
| The character set indicating which characters are allowed without escapes&period; Any character which is not in this set must be escaped, or else parsing returns an error&period;
|===

== See Also

xref:boost/urls/grammar/parse-09.adoc[`grammar&colon;&colon;parse`], xref:boost/urls/pchars.adoc[`pchars`], xref:boost/urls/pct_string_view.adoc[`pct&lowbar;string&lowbar;view`]&period;


[.small]#Created with https://www.mrdocs.com[MrDocs]#
