:relfileprefix: ../../../
[#boost-urls-authority_view-host_ipv6_address]

= xref:boost.adoc[pass:[boost]]::xref:boost/urls.adoc[pass:[urls]]::xref:boost/urls/authority_view.adoc[pass:[authority_view]]::host_ipv6_address


Return the host IPv6 address


== Synopsis

Declared in header `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/authority_view.hpp#L943[boost/url/authority_view.hpp,window=blank_]>`

[source,cpp,subs="verbatim,macros,-callouts"]
----
xref:boost/urls/ipv6_address.adoc[ipv6_address]
host_ipv6_address() const noexcept;
----

== Description


If the host type is
xref:boost/urls/host_type/ipv6.adoc[host_type::ipv6]
,        this function returns the address as
a value of type
xref:boost/urls/ipv6_address.adoc[ipv6_address]
.        Otherwise, if the host type is not an IPv6
address, it returns a default-constructed
value which is equal to the unspecified
address "0:0:0:0:0:0:0:0".

=== Example
[,cpp]
----
assert( url_view( "ftp://[::1]/" ).host_ipv6_address() == ipv6_address( "::1" ) );
----

=== Complexity

Constant.

=== Exception Safety

Throws nothing.

=== BNF
[,cpp]
----
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
----

=== Specification

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