:relfileprefix: ../../../
[#45C6C2580A4449ACB38567265B3298EEC2D15B72]

= Function url::set_host_address

pass:v,q[Set the host to an address]


== Synopsis

Declared in header `</boost/url/url.hpp#L442[boost/url/url.hpp,window=blank_]>`

[source,cpp,subs="verbatim,macros,-callouts"]
----
xref:boost/urls/url.adoc[url]&
set_host_address(string_view s);
----

== Description

pass:v,q[Depending on the contents of the passed] pass:v,q[string, this function sets the host:]

* pass:v,q[If the string is a valid IPv4 address,]
pass:v,q[then the host is set to the address.]
pass:v,q[The host type is]
xref:boost/urls/host_type/ipv4.adoc[host_type::ipv4.]

* pass:v,q[If the string is a valid IPv6 address,]
pass:v,q[then the host is set to that address.]
pass:v,q[The host type is]
xref:boost/urls/host_type/ipv6.adoc[host_type::ipv6.]

* pass:v,q[If the string is a valid IPvFuture,]
pass:v,q[then the host is set to that address.]
pass:v,q[The host type is]
xref:boost/urls/host_type/ipvfuture.adoc[host_type::ipvfuture.]

* pass:v,q[Otherwise, the host name is set to]
pass:v,q[the string, which may be empty.]
pass:v,q[Reserved characters in the string are]
pass:v,q[percent-escaped in the result.]
pass:v,q[The host type is]
xref:boost/urls/host_type/name.adoc[host_type::name.]
pass:v,q[In all cases, when this function returns,]
pass:v,q[the URL contains an authority.]

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

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

=== Complexity
pass:v,q[Linear in `s.size()`.]

=== Exception Safety
pass:v,q[Strong guarantee.]
pass:v,q[Calls to allocate may throw.]

=== BNF
[,cpp]
----
IPv4address = dec-octet "." dec-octet "." dec-octet "." dec-octet

dec-octet   = DIGIT                 ; 0-9
            / %x31-39 DIGIT         ; 10-99
            / "1" 2DIGIT            ; 100-199
            / "2" %x30-34 DIGIT     ; 200-249
            / "25" %x30-35          ; 250-255

IPv6address =                            6( h16 ":" ) ls32
            /                       "::" 5( h16 ":" ) ls32
            / [               h16 ] "::" 4( h16 ":" ) ls32
            / [ *1( h16 ":" ) h16 ] "::" 3( h16 ":" ) ls32
            / [ *2( h16 ":" ) h16 ] "::" 2( h16 ":" ) ls32
            / [ *3( h16 ":" ) h16 ] "::"    h16 ":"   ls32
            / [ *4( h16 ":" ) h16 ] "::"              ls32
            / [ *5( h16 ":" ) h16 ] "::"              h16
            / [ *6( h16 ":" ) h16 ] "::"

ls32        = ( h16 ":" h16 ) / IPv4address
            ; least-significant 32 bits of address

h16         = 1*4HEXDIG
            ; 16 bits of address represented in hexadecimal

IPvFuture     = "v" 1*HEXDIG "." 1*( unreserved / sub-delims / ":" )

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

=== Specification

* link:https://en.wikipedia.org/wiki/IPv4[IPv4 (Wikipedia)]

* link:https://datatracker.ietf.org/doc/html/rfc4291[IP Version 6 Addressing Architecture (rfc4291)]

* link:https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2[            3.2.2. Host (rfc3986)]



== Return Value

* `` 


== Parameters

|===
| Name | Type 

| *s*
| `string_view`

|===