func recvmsg()

in Sources/NIOPosix/Socket.swift [227:276]
43 lines of code
3 McCabe index (conditional complexity)

    func recvmsg(pointer: UnsafeMutableRawBufferPointer,
                 storage: inout sockaddr_storage,
                 storageLen: inout socklen_t,
                 controlBytes: inout UnsafeReceivedControlBytes) throws -> IOResult<Int> {
        var vec = iovec(iov_base: pointer.baseAddress, iov_len: numericCast(pointer.count))

        return try withUnsafeMutablePointer(to: &vec) { vecPtr in
            return try storage.withMutableSockAddr { (sockaddrPtr, _) in
#if os(Windows)
                var messageHeader =
                    WSAMSG(name: sockaddrPtr, namelen: storageLen,
                           lpBuffers: vecPtr, dwBufferCount: 1,
                           Control: WSABUF(len: ULONG(controlBytes.controlBytesBuffer.count),
                                           buf: controlBytes.controlBytesBuffer.baseAddress?
                                                    .bindMemory(to: CHAR.self,
                                                                capacity: controlBytes.controlBytesBuffer.count)),
                           dwFlags: 0)
                defer {
                    // We need to write back the length of the message.
                    storageLen = messageHeader.namelen
                }
#else
                var messageHeader = msghdr(msg_name: sockaddrPtr,
                                           msg_namelen: storageLen,
                                           msg_iov: vecPtr,
                                           msg_iovlen: 1,
                                           msg_control: controlBytes.controlBytesBuffer.baseAddress,
                                           msg_controllen: .init(controlBytes.controlBytesBuffer.count),
                                           msg_flags: 0)
                defer {
                    // We need to write back the length of the message.
                    storageLen = messageHeader.msg_namelen
                }
#endif

                let result = try withUnsafeMutablePointer(to: &messageHeader) { messageHeader in
                    return try withUnsafeHandle { fd in
                        return try NIOBSDSocket.recvmsg(socket: fd, msgHdr: messageHeader, flags: 0)
                    }
                }
                
                // Only look at the control bytes if all is good.
                if case .processed = result {
                    controlBytes.receivedControlMessages = UnsafeControlMessageCollection(messageHeader: messageHeader)
                }
                
                return result
            }
        }
    }