
(********************************************************************)
(*                                                                  *)
(*  listener.s7i  Support for inet listener                         *)
(*  Copyright (C) 2007 - 2009, 2011  Thomas Mertes                  *)
(*                                                                  *)
(*  This file is part of the Seed7 Runtime Library.                 *)
(*                                                                  *)
(*  The Seed7 Runtime Library is free software; you can             *)
(*  redistribute it and/or modify it under the terms of the GNU     *)
(*  Lesser General Public License as published by the Free Software *)
(*  Foundation; either version 2.1 of the License, or (at your      *)
(*  option) any later version.                                      *)
(*                                                                  *)
(*  The Seed7 Runtime Library is distributed in the hope that it    *)
(*  will be useful, but WITHOUT ANY WARRANTY; without even the      *)
(*  implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR *)
(*  PURPOSE.  See the GNU Lesser General Public License for more    *)
(*  details.                                                        *)
(*                                                                  *)
(*  You should have received a copy of the GNU Lesser General       *)
(*  Public License along with this program; if not, write to the    *)
(*  Free Software Foundation, Inc., 51 Franklin Street,             *)
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(*                                                                  *)
(********************************************************************)


include "sockbase.s7i";
include "socket.s7i";
include "poll.s7i";


const type: inetListener is sub baseListener struct
    var PRIMITIVE_SOCKET: sock is PRIMITIVE_NULL_SOCKET;
    var socketAddress: addr is socketAddress.value;
    var string: service is "";
    var pollData: checkedSocks is pollData.value;
    var file: existingConnection is STD_NULL;
    var file: newConnection is STD_NULL;
  end struct;


type_implements_interface(inetListener, listener);


(**
 *  Create a bound internet listener for a port at localhost.
 *  The listerner is responsible for incoming connections of the
 *  specified port. The listener also manages its accepted sockets.
 *  Processing requests from port 1080 can be done with:
 *   aListener := openInetListener(1080);
 *   listen(aListener, 10);
 *   while TRUE do
 *     sock := accept(aListener);
 *     # Read and process the request from sock.
 *     close(sock);
 *   end while;
 *  The example above manages requests from
 *  different clients sequentially. The function
 *  [[#waitForRequest(inout_listener,inout_file,inout_file)|waitForRequest]]
 *  can be used to process interleaved requests from several clients.
 *  @return the bound internet listener.
 *  @exception FILE_ERROR A system function returns an error.
 *  @exception RANGE_ERROR The port is not in the range 0 to 65535.
 *  @exception MEMORY_ERROR An out of memory situation occurred.
 *)
const func listener: openInetListener (in integer: portNumber) is func
  result
    var listener: newListener is listener.value;
  local
    var socketAddress: address is socketAddress.value;
    var PRIMITIVE_SOCKET: open_socket is PRIMITIVE_NULL_SOCKET;
    var inetListener: new_listener is inetListener.value;
  begin
    address := inetListenerAddress(portNumber);
    open_socket := PRIMITIVE_SOCKET(addrFamily(address), SOCK_STREAM, 0);
    if open_socket <> PRIMITIVE_NULL_SOCKET then
      new_listener.addr := address;
      new_listener.service := service(address);
      setSockOpt(open_socket, SO_REUSEADDR, TRUE);
      bind(open_socket, new_listener.addr);
      new_listener.sock := open_socket;
      addCheck(new_listener.checkedSocks, open_socket, POLLIN, STD_NULL);
      newListener := toInterface(new_listener);
    end if;
  end func;


(**
 *  Close the listener ''aListener''.
 *  A listener manages accepted sockets (its existing connections).
 *  When the listener is closed all references to the listener
 *  is removed from the accepted sockets.
 *)
const proc: close (inout inetListener: aListener) is func
  local
    var file: aFile is STD_NULL;
  begin
    close(aListener.sock);
    iterChecks(aListener.checkedSocks, POLLINOUT);
    for aFile range aListener.checkedSocks do
      if aFile <> STD_NULL then
        release(aFile);
      end if;
    end for;
    clear(aListener.checkedSocks);
  end func;


const proc: signOn (inout inetListener: aListener, in socket: sock) is func
  begin
    addCheck(aListener.checkedSocks, sock, POLLIN);
  end func;


const proc: signOff (inout inetListener: aListener, in socket: sock) is func
  begin
    removeCheck(aListener.checkedSocks, sock, POLLIN);
  end func;


(**
 *  Listen for [[socket]] connections and limit the incoming queue.
 *  The ''backlog'' argument defines the maximum length to which
 *  the queue of pending connections for ''aListener'' may grow.
 *  @exception FILE_ERROR A system function returns an error.
 *)
const proc: listen (in inetListener: aListener, in integer: backlog) is func
  begin
    listen(aListener.sock, backlog);
  end func;


(**
 *  Create a new accepted connection [[socket]] for ''aListener''.
 *  The function waits until at least one connection request is
 *  in the listeners queue of pending connections. Then it extracts
 *  the first connection request from the listeners queue. This
 *  request is accepted and a connection [[socket]] is created for it.
 *  A listener manages accepted sockets (its existing connections).
 *  When an accepted [[socket]] is closed it is signed off from the
 *  listener.
 *  @return the accepted connection [[socket]].
 *  @exception FILE_ERROR A system function returns an error.
 *  @exception MEMORY_ERROR An out of memory situation occurred.
 *)
const func file: accept (inout inetListener: aListener) is func
  result
    var file: newFile is STD_NULL;
  local
    var PRIMITIVE_SOCKET: accepted_socket is PRIMITIVE_NULL_SOCKET;
    var socket: new_socket is socket.value;
  begin
    accepted_socket := accept(aListener.sock, new_socket.addr);
    if accepted_socket <> PRIMITIVE_NULL_SOCKET then
      new_socket.sock := accepted_socket;
      new_socket.service := aListener.service;
      new_socket.acceptedFrom := aListener;
      newFile := toInterface(new_socket);
      addCheck(aListener.checkedSocks, newFile, POLLIN);
    end if;
  end func;


const proc: waitForRequest (inout inetListener: aListener) is func
  begin
    if hasNext(aListener.checkedSocks) then
      aListener.newConnection := STD_NULL;
      aListener.existingConnection := nextFile(aListener.checkedSocks);
      if aListener.existingConnection = STD_NULL then
        # Skip the listener, which returns STD_NULL, when it is ready.
        aListener.existingConnection := nextFile(aListener.checkedSocks);
      end if;
    else
      poll(aListener.checkedSocks);
      if getFinding(aListener.checkedSocks, aListener.sock) = POLLIN then
        aListener.newConnection := accept(aListener);
        # writeln("accepted");
      else
        aListener.newConnection := STD_NULL;
      end if;
      iterFindings(aListener.checkedSocks, POLLIN);
      aListener.existingConnection := nextFile(aListener.checkedSocks);
      if aListener.existingConnection = STD_NULL then
        # Skip the listener, which returns STD_NULL, when it is ready.
        aListener.existingConnection := nextFile(aListener.checkedSocks);
      end if;
    end if;
  end func;


const func file: getExistingConnection (in inetListener: aListener) is
  return aListener.existingConnection;


const func file: getNewConnection (in inetListener: aListener) is
  return aListener.newConnection;


(**
 *  Wait until a request can be read or an incoming connection is accepted.
 *  The function ''waitForRequest'' can be used to process interleaved
 *  requests from several clients. A listener manages accepted sockets
 *  (its existing connections). This function checks the accepted
 *  sockets for available input (it is possible to read without
 *  blocking). The port of the listener is also checked for incoming
 *  connections. The function returns when input is available for an
 *  existing connection or when a new incoming connection was accepted.
 *  Processing requests from port 2021 can be done with:
 *   aListener := openInetListener(2021);
 *   listen(aListener, 10);
 *   while TRUE do
 *     waitForRequest(aListener, existingConnection, newConnection);
 *     if existingConnection <> STD_NULL then
 *       # Read and process the request from existingConnection.
 *     end if;
 *     if newConnection <> STD_NULL then
 *       # Send welcome message to newConnection.
 *     end if;
 *   end while;
 *  @param existingConnection A random existing connection, were
 *         a read will not block, is assigned. When no existing
 *         connection has available input, [[null_file#STD_NULL|STD_NULL]]
 *         is assigned.
 *  @param newConnection A new accepted connection is assigned.
 *         When no incoming connection is present,
 *         [[null_file#STD_NULL|STD_NULL]] is assigned.
 *)
const proc: waitForRequest (inout listener: aListener,
    inout file: existingConnection, inout file: newConnection) is func
  begin
    waitForRequest(aListener);
    existingConnection := getExistingConnection(aListener);
    newConnection := getNewConnection(aListener);
  end func;
