// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

module mojo;

import "mojo/services/public/interfaces/network/net_address.mojom";
import "mojo/services/public/interfaces/network/network_error.mojom";

// UDPSocket and UDPSocketClient represent a UDP socket and its client. The
// typical flow of using the interfaces is:
// - Acquire a UDPSocket interface pointer and set a UDPSocketClient instance.
// - (optional) Set options which are allowed prior to Bind().
// - Bind the socket.
// - (optional) Set options which are allowed after Bind().
// - Send / request to receive datagrams. Received datagrams will be delivered
//   to UDPSocketClient.OnReceived().

[Client=UDPSocketClient]
interface UDPSocket {
  // Allows the socket to share the local address to which it will be bound with
  // other processes. Should be called before Bind().
  // (This is equivalent to SO_REUSEADDR of the POSIX socket API.)
  AllowAddressReuse() => (NetworkError result);

  // Binds the socket to the given address.
  // |bound_addr| is non-NULL on success. It might not be the same as |addr|.
  // For example, if port 0 is used in |addr|, an available port is picked and
  // returned in |bound_addr|.
  Bind(NetAddress addr) => (NetworkError result, NetAddress? bound_addr);

  // Sets the OS send buffer size (in bytes) for the socket. The socket must be
  // bound.
  SetSendBufferSize(uint32 size) => (NetworkError result);

  // Sets the OS receive buffer size (in bytes) for the socket. The socket must
  // be bound.
  SetReceiveBufferSize(uint32 size) => (NetworkError result);

  // Negotiates the maximum number of pending SendTo() requests. If
  // |requested_size| is set to 0, this method queries the current settings.
  //
  // The service stores SendTo() requests in a queue while they are waiting to
  // be executed (i.e., while they are waiting to be placed in the OS send
  // buffer and sent out). This method negotiates how many requests (not bytes)
  // this queue is able to store. If the queue is full, the service fails new
  // requests directly with error code ERR_INSUFFICIENT_RESOURCES and discards
  // those datagrams. If the client wants to avoid such failures, it needs to
  // keep track of how many SendTo() calls are pending and make sure the number
  // doesn't exceed the result of this method.
  NegotiateMaxPendingSendRequests(uint32 requested_size)
      => (uint32 actual_size);

  // Notifies that the client is ready to accept |number| of datagrams.
  // Correspondingly, OnReceived() of the UDPSocketClient interface will be
  // called |number| times (errors also count), unless the connection is closed
  // before that.
  //
  // It is allowed to call this method again before the previous request is
  // completely satisfied. For example:
  //   service->ReceiveMore(3);
  //   ...
  //   // OnReceived() is called.
  //   // OnReceived() is called.
  //   ...
  //   service->ReceiveMore(3);
  //   // The client expects 4 more calls to OnReceived().
  //
  // Please note that how ReceiveMore() is used will affect performance
  // significantly. For example:
  //   // Approach 1:
  //   service->ReceiveMore(3);
  //   // OnReceived() is called.
  //   // OnReceived() is called.
  //   // OnReceived() is called.
  //
  //   // Approach 2:
  //   service->ReceiveMore(1);
  //   // OnReceived() is called.
  //   service->ReceiveMore(1);
  //   // OnReceived() is called.
  //   service->ReceiveMore(1);
  //   // OnReceived() is called.
  //
  // It is very likely that approach 1 will perform better than approach 2,
  // because in approach 2 getting every datagram takes at least the time of a
  // round trip to the service side.
  ReceiveMore(uint32 datagram_number);

  // Sends data to the specified destination. The socket must be bound.
  // On success, |result.code| is a non-negative number indicating how many
  // bytes have been written. Otherwise, it is a network error code, including
  // (but not limited to):
  // - ERR_INSUFFICIENT_RESOURCES (-12): The service doesn't have sufficient
  //   resource to complete the operation. One possible cause is that the client
  //   tries to send too many datagrams in a short period of time.
  // TODO(yzshen): Formalize Mojo networking error codes.
  SendTo(NetAddress dest_addr, array<uint8> data) => (NetworkError result);
};

interface UDPSocketClient {
  // On success, |src_addr| and |data| are non-NULL, and |result.code| is a
  // non-negative number indicating how many bytes have been received. On
  // failure, |result.code| is a network error code.
  OnReceived(NetworkError result, NetAddress? src_addr, array<uint8>? data);
};