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##### static_url_base::set_host_address

(Inherited from `url_base`)

Set the host to an address.

###### Synopsis

    url_base&
    set_host_address(
        core::string_view s);

###### Description

Depending on the contents of the passed string, this function sets the host:

- If the string is a valid IPv4 address, then the host is set to the address. The host type is `host_type::ipv4`.
- If the string is a valid IPv6 address, then the host is set to that address. The host type is `host_type::ipv6`.
- If the string is a valid IPvFuture, then the host is set to that address. The host type is `host_type::ipvfuture`.
- Otherwise, the host name is set to the string, which may be empty. Reserved characters in the string are percent-escaped in the result. The host type is `host_type::name`.

In all cases, when this function returns, the URL contains an authority.

###### Example

    assert( url( "http://www.example.com" ).set_host_address( "127.0.0.1" ).buffer() == "http://127.0.0.1" );

###### Postconditions

    this->has_authority() == true

###### Complexity

Linear in `s.size()`.

###### Exception Safety

Strong guarantee. Calls to allocate may throw.

###### Parameters

Name | Description
--- | ---
`s` | The string to set.

###### BNF

    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

- IPv4 (Wikipedia)
- IP Version 6 Addressing Architecture (rfc4291)
- 3.2.2. Host (rfc3986)

###### See Also

`set_encoded_host`, `set_encoded_host_address`, `set_encoded_host_name`, `set_host`, `set_host_address`, `set_host_ipv4`, `set_host_ipv6`, `set_host_ipvfuture`, `set_host_name`.