[#boost-urls-url-set_encoded_host]
= xref:boost.adoc[boost]::xref:boost/urls.adoc[urls]::xref:boost/urls/url.adoc[url]::set&lowbar;encoded&lowbar;host
:relfileprefix: ../../../
:mrdocs:

Set the host

== Synopsis

Declared in `&lt;https://www.github.com/boostorg/url/blob/develop/include/boost/url/url.hpp#L444[boost&sol;url&sol;url&period;hpp]&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
xref:boost/urls/url.adoc[url]&
set&lowbar;encoded&lowbar;host(xref:boost/urls/pct_string_view.adoc[pct&lowbar;string&lowbar;view] s);
----

== Description

Depending on the contents of the passed string, this function sets the host&colon;

* If the string is a valid IPv4 address, then the host is set to the address&period; The host type is xref:boost/urls/host_type.adoc[`host&lowbar;type&colon;&colon;ipv4`]&period;
* If the string is a valid IPv6 address enclosed in square brackets, then the host is set to that address&period; The host type is xref:boost/urls/host_type.adoc[`host&lowbar;type&colon;&colon;ipv6`]&period;
* If the string is a valid IPvFuture address enclosed in square brackets, then the host is set to that address&period; The host type is xref:boost/urls/host_type.adoc[`host&lowbar;type&colon;&colon;ipvfuture`]&period;
* Otherwise, the host name is set to the string&period; This string can contain percent escapes, or can be empty&period; Escapes in the string are preserved, and reserved characters in the string are percent&hyphen;escaped in the result&period; The host type is xref:boost/urls/host_type.adoc[`host&lowbar;type&colon;&colon;name`]&period;

In all cases, when this function returns, the URL contains an authority&period;

== Example

[,cpp]
----
assert( url( "http://www.example.com" ).set_host( "127.0.0.1" ).buffer() == "http://127.0.0.1" );
----
== Postconditions

[,cpp]
----
this->has_authority() == true
----
== Complexity

Linear in `this&hyphen;&gt;size() &plus; s&period;size()`&period;

== Exception Safety

Strong guarantee&period; Calls to allocate may throw&period; Exceptions thrown on invalid input&period;

== BNF

[,cpp]
----
host        = IP-literal / IPv4address / reg-name

IP-literal  = "[" ( IPv6address / IPvFuture  ) "]"

reg-name    = *( unreserved / pct-encoded / "-" / ".")
----
== Specification

* https://en.wikipedia.org/wiki/IPv4[IPv4 (Wikipedia)]
* https://datatracker.ietf.org/doc/html/rfc4291[IP Version 6 Addressing Architecture (rfc4291)]
* https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2[3&period;2&period;2&period; Host (rfc3986)]

== Return Value

`&ast;this`

== Parameters

[cols="1,4"]
|===
| Name| Description
| *s*
| The string to set&period;
|===

== See Also

xref:boost/urls/url_base/set_encoded_host_address.adoc[`set&lowbar;encoded&lowbar;host&lowbar;address`], xref:boost/urls/url_base/set_encoded_host_name.adoc[`set&lowbar;encoded&lowbar;host&lowbar;name`], xref:boost/urls/url_base/set_host.adoc[`set&lowbar;host`], xref:boost/urls/url_base/set_host_address.adoc[`set&lowbar;host&lowbar;address`], xref:boost/urls/url_base/set_host_ipv4.adoc[`set&lowbar;host&lowbar;ipv4`], xref:boost/urls/url_base/set_host_ipv6.adoc[`set&lowbar;host&lowbar;ipv6`], xref:boost/urls/url_base/set_host_ipvfuture.adoc[`set&lowbar;host&lowbar;ipvfuture`], xref:boost/urls/url_base/set_host_name.adoc[`set&lowbar;host&lowbar;name`]&period;


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