// forResolve returns the most appropriate address in address for
// a call to ResolveTCPAddr, ResolveUDPAddr, or ResolveIPAddr.
// IPv4 is preferred, unless addr contains an IPv6 literal.
private static Addr forResolve(this addrList addrs, @string network, @string addr)
{
bool want6 = default;
switch (network)
{
case "ip":
// IPv6 literal (addr does NOT contain a port)
want6 = count(addr, ':') > 0L;
break;
case "tcp":
// IPv6 literal. (addr contains a port, so look for '[')
case "udp":
// IPv6 literal. (addr contains a port, so look for '[')
want6 = count(addr, '[') > 0L;
break;
}
if (want6)
{
return(addrs.first(isNotIPv4));
}
return(addrs.first(isIPv4));
}
// first returns the first address which satisfies strategy, or if
// none do, then the first address of any kind.
private static Addr first(this addrList addrs, Func <Addr, bool> strategy)
{
foreach (var(_, addr) in addrs)
{
if (strategy(addr))
{
return(addr);
}
}
return(addrs[0L]);
}
// partition divides an address list into two categories, using a
// strategy function to assign a boolean label to each address.
// The first address, and any with a matching label, are returned as
// primaries, while addresses with the opposite label are returned
// as fallbacks. For non-empty inputs, primaries is guaranteed to be
// non-empty.
private static (addrList, addrList) partition(this addrList addrs, Func <Addr, bool> strategy)
{
addrList primaries = default;
addrList fallbacks = default;
bool primaryLabel = default;
foreach (var(i, addr) in addrs)
{
var label = strategy(addr);
if (i == 0L || label == primaryLabel)
{
primaryLabel = label;
primaries = append(primaries, addr);
}
else
{
fallbacks = append(fallbacks, addr);
}
}
return;
}
// filterAddrList applies a filter to a list of IP addresses,
// yielding a list of Addr objects. Known filters are nil, ipv4only,
// and ipv6only. It returns every address when the filter is nil.
// The result contains at least one address when error is nil.
private static (addrList, error) filterAddrList(Func <IPAddr, bool> filter, slice <IPAddr> ips, Func <IPAddr, Addr> inetaddr, @string originalAddr)
{
addrList _p0 = default;
error _p0 = default !;