[Issue 13159] New: std.socket.getAddress allocates once per DNS lookup hit

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13159

          Issue ID: 13159
           Summary: std.socket.getAddress allocates once per DNS lookup
                    hit
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: Phobos
          Assignee: nobody at puremagic.com
          Reporter: zorael at gmail.com

[Arch x86_64, dmd/phobos/druntime from git 140719]

std.socket.getAddress is very allocation-happy. A DNS lookup often/(always?)
gives more than one resulting IP, and getAddress naïvely concatenates each into
an Address[] array in a foreach loop. As a concrete example,
getAddress("irc.freenode.net", cast(ushort)6667) returned 51 hits.

In Address[] getAddress(in char[], in char[]) near line 1116:
>  // use getAddressInfo
>  Address[] results;
>  auto infos = getAddressInfo(hostname, service);
>   foreach (ref info; infos)
>       results ~= info.address;
>   return results;

Unless this is a valid use-case for ScopeBuffer, could we at least tack a
results.reserve(64) in there?

(I think AddressInfo.sizeof is 40 bytes.)

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