Method write_some

Source/Common/AsyncNet.h:73–118

* Blocks until at least one byte of data was sent */

   * Blocks until at least one byte of data was sent
   */
  size_t write_some(const mutable_buffer& Buffers, error& ec) {
    auto iov = (iovec*)alloca(sizeof(mutable_buffer) * Buffers.count_chunks());
    size_t NumIovs = 0;
    for (auto Buffer = &Buffers; Buffer; Buffer = Buffer->Next) {
      iov[NumIovs].iov_base = Buffer->Data.data();
      iov[NumIovs].iov_len = Buffer->Data.size_bytes();
      ++NumIovs;
    }
    msghdr msg {
      .msg_name = nullptr,
      .msg_namelen = 0,
      .msg_iov = iov,
      .msg_iovlen = NumIovs,
    };

    // Setup the ancillary buffer. This is where we will be getting pipe FDs
    // We only need 4 bytes for the FD
    constexpr size_t CMSG_SIZE = CMSG_SPACE(sizeof(int));
    alignas(cmsghdr) uint8_t AncBuf[CMSG_SIZE];

    if (Buffers.FD) {
      // Enable ancillary buffer
      msg.msg_control = AncBuf;
      msg.msg_controllen = CMSG_SIZE;

      // Now we need to setup the ancillary buffer data. We are only sending an FD
      cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
      cmsg->cmsg_len = CMSG_LEN(sizeof(int));
      cmsg->cmsg_level = SOL_SOCKET;
      cmsg->cmsg_type = SCM_RIGHTS;

      // We are giving the daemon the write side of the pipe
      memcpy(CMSG_DATA(cmsg), Buffers.FD.value(), sizeof(int));
    }

    ssize_t Ret;
    do {
      Ret = ::sendmsg(FD, &msg, 0);
    } while (Ret < 0 && (errno == EINTR || errno == EAGAIN));
    if (Ret < 0) {
      ec = error::generic_errno;
      return 0;
    }
    ec = error::success;
    return Ret;
  }

private:
  static size_t read_some_from_fd(const mutable_buffer& Buffers, error& ec, int FD) {