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------------------------------------------------------------------------------

--                                                                          --

--                         GNAT COMPILER COMPONENTS                         --

--                                                                          --

--                           S Y S T E M . R P C                            --

--                                                                          --

--                                 B o d y                                  --

--                                                                          --

--          Copyright (C) 1992-2009, Free Software Foundation, Inc.         --

--                                                                          --

-- GNAT is free software;  you can  redistribute it  and/or modify it under --

-- terms of the  GNU General Public License as published  by the Free Soft- --

-- ware  Foundation;  either version 3,  or (at your option) any later ver- --

-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --

-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --

-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --

--                                                                          --

-- As a special exception under Section 7 of GPL version 3, you are granted --

-- additional permissions described in the GCC Runtime Library Exception,   --

-- version 3.1, as published by the Free Software Foundation.               --

--                                                                          --

-- You should have received a copy of the GNU General Public License and    --

-- a copy of the GCC Runtime Library Exception along with this program;     --

-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --

-- <http://www.gnu.org/licenses/>.                                          --

--                                                                          --

-- GNAT was originally developed  by the GNAT team at  New York University. --

-- Extensive contributions were provided by Ada Core Technologies Inc.      --

--                                                                          --

------------------------------------------------------------------------------

--  Version for ???

with Unchecked_Deallocation;

with Ada.Streams;

with System.RPC.Net_Trace;

with System.RPC.Garlic;

with System.RPC.Streams;

pragma Elaborate (System.RPC.Garlic);

package body System.RPC is

   --  ??? general note: the debugging calls are very heavy, especially

   --  those that create exception handlers in every procedure. Do we

   --  really still need all this stuff?

   use type Ada.Streams.Stream_Element_Count;

   use type Ada.Streams.Stream_Element_Offset;

   use type Garlic.Protocol_Access;

   use type Garlic.Lock_Method;

   Max_Of_Message_Id : constant := 127;

   subtype Message_Id_Type is

     Integer range -Max_Of_Message_Id .. Max_Of_Message_Id;

   --  A message id is either a request id or reply id. A message id is

   --  provided with a message to a receiving stub which uses the opposite

   --  as a reply id. A message id helps to retrieve to which task is

   --  addressed a reply. When the environment task receives a message, the

   --  message id is extracted : a positive message id stands for a call, a

   --  negative message id stands for a reply. A null message id stands for

   --  an asynchronous request.

   subtype Request_Id_Type is Message_Id_Type range 1 .. Max_Of_Message_Id;

   --  When a message id is positive, it is a request

   type Message_Length_Per_Request is array (Request_Id_Type)

      of Ada.Streams.Stream_Element_Count;

   Header_Size : Ada.Streams.Stream_Element_Count :=

                   Streams.Get_Integer_Initial_Size +

                     Streams.Get_SEC_Initial_Size;

   --  Initial size needed for frequently used header streams

   Stream_Error : exception;

   --  Occurs when a read procedure is executed on an empty stream

   --  or when a write procedure is executed on a full stream

   Partition_RPC_Receiver : RPC_Receiver;

   --  Cache the RPC_Receiver passed by Establish_RPC_Receiver

   type Anonymous_Task_Node;

   type Anonymous_Task_Node_Access is access Anonymous_Task_Node;

   --  Types we need to construct a singly linked list of anonymous tasks

   --  This pool is maintained to avoid a task creation each time a RPC

   --  occurs - to be cont'd

   task type Anonymous_Task_Type (Self : Anonymous_Task_Node_Access) is

      entry Start

         (Message_Id   : Message_Id_Type;

          Partition    : Partition_ID;

          Params_Size  : Ada.Streams.Stream_Element_Count;

          Result_Size  : Ada.Streams.Stream_Element_Count;

          Protocol     : Garlic.Protocol_Access);

      --  This entry provides an anonymous task a remote call to perform.

      --  This task calls for a Request id is provided to construct the

      --  reply id by using -Request. Partition is used to send the reply

      --  message. Params_Size is the size of the calling stub Params stream.

      --  Then Protocol (used by the environment task previously) allows

      --  extraction of the message following the header (The header is

      --  extracted by the environment task)

      --  Note: grammar in above is obscure??? needs cleanup

   end Anonymous_Task_Type;

   type Anonymous_Task_Access is access Anonymous_Task_Type;

   type Anonymous_Task_List is record

      Head     : Anonymous_Task_Node_Access;

      Tail     : Anonymous_Task_Node_Access;

   end record;

   type Anonymous_Task_Node is record

      Element : Anonymous_Task_Access;

      Next    : Anonymous_Task_Node_Access;

   end record;

   --  Types we need to construct a singly linked list of anonymous tasks.

   --  This pool is maintained to avoid a task creation each time a RPC occurs.

   protected Garbage_Collector is

      procedure Allocate

         (Item : out Anonymous_Task_Node_Access);

      --  Anonymous task pool management : if there is an anonymous task

      --  left, use it. Otherwise, allocate a new one

      procedure Deallocate

         (Item : in out Anonymous_Task_Node_Access);

      --  Anonymous task pool management : queue this task in the pool

      --  of inactive anonymous tasks.

   private

      Anonymous_List : Anonymous_Task_Node_Access;

      --  The list root of inactive anonymous tasks

   end Garbage_Collector;

   task Dispatcher is

      entry New_Request (Request : out Request_Id_Type);

      --  To get a new request

      entry Wait_On (Request_Id_Type)

        (Length : out Ada.Streams.Stream_Element_Count);

      --  To block the calling stub when it waits for a reply

      --  When it is resumed, we provide the size of the reply

      entry Wake_Up

        (Request : Request_Id_Type;

         Length  : Ada.Streams.Stream_Element_Count);

      --  To wake up the calling stub when the environment task has

      --  received a reply for this request

   end Dispatcher;

   task Environnement is

      entry Start;

      --  Receive no message until Partition_Receiver is set

      --  Establish_RPC_Receiver decides when the environment task

      --  is allowed to start

   end Environnement;

   protected Partition_Receiver is

      entry Is_Set;

      --  Blocks if the Partition_RPC_Receiver has not been set

      procedure Set;

      --  Done by Establish_RPC_Receiver when Partition_RPC_Receiver

      --  is known

   private

      Was_Set : Boolean := False;

      --  True when Partition_RPC_Receiver has been set

   end Partition_Receiver;

   --  Anonymous tasks have to wait for the Partition_RPC_Receiver

   --  to be established

   type Debug_Level is

      (D_Elaborate,        --  About the elaboration of this package

       D_Communication,    --  About calls to Send and Receive

       D_Debug,            --  Verbose

       D_Exception);       --  Exception handler

   --  Debugging levels

   package Debugging is new System.RPC.Net_Trace (Debug_Level, "RPC : ");

   --  Debugging package

   procedure D

     (Flag : Debug_Level; Info : String) renames Debugging.Debug;

   --  Shortcut

   ------------------------

   -- Partition_Receiver --

   ------------------------

   protected body Partition_Receiver is

      -------------------------------

      -- Partition_Receiver.Is_Set --

      -------------------------------

      entry Is_Set when Was_Set is

      begin

         null;

      end Is_Set;

      ----------------------------

      -- Partition_Receiver.Set --

      ----------------------------

      procedure Set is

      begin

         Was_Set := True;

      end Set;

   end Partition_Receiver;

   ---------------

   -- Head_Node --

   ---------------

   procedure Head_Node

     (Index  : out Packet_Node_Access;

      Stream : Params_Stream_Type)

   is

   begin

      Index := Stream.Extra.Head;

   exception

      when others =>

         D (D_Exception, "exception in Head_Node");

         raise;

   end Head_Node;

   ---------------

   -- Tail_Node --

   ---------------

   procedure Tail_Node

     (Index  : out Packet_Node_Access;

      Stream : Params_Stream_Type)

   is

   begin

      Index := Stream.Extra.Tail;

   exception

      when others =>

         D (D_Exception, "exception in Tail_Node");

         raise;

   end Tail_Node;

   ---------------

   -- Null_Node --

   ---------------

   function Null_Node (Index : Packet_Node_Access) return Boolean is

   begin

      return Index = null;

   exception

      when others =>

         D (D_Exception, "exception in Null_Node");

         raise;

   end Null_Node;

   ----------------------

   -- Delete_Head_Node --

   ----------------------

   procedure Delete_Head_Node (Stream : in out Params_Stream_Type) is

      procedure Free is

        new Unchecked_Deallocation

        (Packet_Node, Packet_Node_Access);

      Next_Node : Packet_Node_Access := Stream.Extra.Head.Next;

   begin

      --  Delete head node and free memory usage

      Free (Stream.Extra.Head);

      Stream.Extra.Head := Next_Node;

      --  If the extra storage is empty, update tail as well

      if Stream.Extra.Head = null then

         Stream.Extra.Tail := null;

      end if;

   exception

      when others =>

         D (D_Exception, "exception in Delete_Head_Node");

         raise;

   end Delete_Head_Node;

   ---------------

   -- Next_Node --

   ---------------

   procedure Next_Node (Node : in out Packet_Node_Access) is

   begin

      --  Node is set to the next node

      --  If not possible, Stream_Error is raised

      if Node = null then

         raise Stream_Error;

      else

         Node := Node.Next;

      end if;

   exception

      when others =>

         D (D_Exception, "exception in Next_Node");

         raise;

   end Next_Node;

   ---------------------

   -- Append_New_Node --

   ---------------------

   procedure Append_New_Node (Stream : in out Params_Stream_Type) is

      Index : Packet_Node_Access;

   begin

      --  Set Index to the end of the linked list

      Tail_Node (Index, Stream);

      if Null_Node (Index) then

         --  The list is empty : set head as well

         Stream.Extra.Head := new Packet_Node;

         Stream.Extra.Tail := Stream.Extra.Head;

      else

         --  The list is not empty : link new node with tail

         Stream.Extra.Tail.Next := new Packet_Node;

         Stream.Extra.Tail := Stream.Extra.Tail.Next;

      end if;

   exception

      when others =>

         D (D_Exception, "exception in Append_New_Node");

         raise;

   end Append_New_Node;

   ----------

   -- Read --

   ----------

   procedure Read

     (Stream : in out Params_Stream_Type;

      Item   : out Ada.Streams.Stream_Element_Array;

      Last   : out Ada.Streams.Stream_Element_Offset)

     renames System.RPC.Streams.Read;

   -----------

   -- Write --

   -----------

   procedure Write

     (Stream : in out Params_Stream_Type;

      Item   : Ada.Streams.Stream_Element_Array)

     renames System.RPC.Streams.Write;

   -----------------------

   -- Garbage_Collector --

   -----------------------

   protected body Garbage_Collector is

      --------------------------------

      -- Garbage_Collector.Allocate --

      --------------------------------

      procedure Allocate (Item : out Anonymous_Task_Node_Access) is

         New_Anonymous_Task_Node : Anonymous_Task_Node_Access;

         Anonymous_Task          : Anonymous_Task_Access;

      begin

         --  If the list is empty, allocate a new anonymous task

         --  Otherwise, reuse the first queued anonymous task

         if Anonymous_List = null then

            --  Create a new anonymous task

            --  Provide this new task with its id to allow it

            --  to enqueue itself into the free anonymous task list

            --  with the function Deallocate

            New_Anonymous_Task_Node := new Anonymous_Task_Node;

            Anonymous_Task :=

             new Anonymous_Task_Type (New_Anonymous_Task_Node);

            New_Anonymous_Task_Node.all := (Anonymous_Task, null);

         else

            --  Extract one task from the list

            --  Set the Next field to null to avoid possible bugs

            New_Anonymous_Task_Node  := Anonymous_List;

            Anonymous_List := Anonymous_List.Next;

            New_Anonymous_Task_Node.Next := null;

         end if;

         --  Item is an out parameter

         Item := New_Anonymous_Task_Node;

      exception

         when others =>

            D (D_Exception, "exception in Allocate (Anonymous Task)");

            raise;

      end Allocate;

      ----------------------------------

      -- Garbage_Collector.Deallocate --

      ----------------------------------

      procedure Deallocate (Item : in out Anonymous_Task_Node_Access) is

      begin

         --  Enqueue the task in the free list

         Item.Next := Anonymous_List;

         Anonymous_List := Item;

      exception

         when others =>

            D (D_Exception, "exception in Deallocate (Anonymous Task)");

            raise;

      end Deallocate;

   end Garbage_Collector;

   ------------

   -- Do_RPC --

   ------------

   procedure Do_RPC

     (Partition  : Partition_ID;

      Params     : access Params_Stream_Type;

      Result     : access Params_Stream_Type)

   is

      Protocol   : Protocol_Access;

      Request    : Request_Id_Type;

      Header     : aliased Params_Stream_Type (Header_Size);

      R_Length   : Ada.Streams.Stream_Element_Count;

   begin

      --  Parameters order :

      --       Opcode   (provided and used by garlic)

      --   (1) Size     (provided by s-rpc and used by garlic)

      --                (size of (2)+(3)+(4)+(5))

      --   (2) Request  (provided by calling stub (resp receiving stub) and

      --                 used by anonymous task (resp Do_RPC))

      --                *** ZERO IF APC ***

      --   (3) Res.len. (provided by calling stubs and used by anonymous task)

      --                *** ZERO IF APC ***

      --   (4) Receiver (provided by calling stubs and used by anonymous task)

      --   (5) Params   (provided by calling stubs and used by anonymous task)

      --  The call is a remote call or a local call. A local call occurs

      --  when the pragma All_Calls_Remote has been specified. Do_RPC is

      --  called and the execution has to be performed in the PCS

      if Partition /= Garlic.Get_My_Partition_ID then

         --  Get a request id to be resumed when the reply arrives

         Dispatcher.New_Request (Request);

         --  Build header = request (2) + result.initial_size (3)

         D (D_Debug, "Do_RPC - Build header");

         Streams.Allocate (Header);

         Streams.Integer_Write_Attribute            --  (2)

           (Header'Access, Request);

         System.RPC.Streams.SEC_Write_Attribute     --  (3)

           (Header'Access, Result.Initial_Size);

         --  Get a protocol method to communicate with the remote partition

         --  and give the message size

         D (D_Communication,

            "Do_RPC - Lookup for protocol to talk to partition" &

            Partition_ID'Image (Partition));

         Garlic.Initiate_Send

           (Partition,

            Streams.Get_Stream_Size (Header'Access) +

            Streams.Get_Stream_Size (Params), --  (1)

            Protocol,

            Garlic.Remote_Call);

         --  Send the header by using the protocol method

         D (D_Communication, "Do_RPC - Send Header to partition" &

            Partition_ID'Image (Partition));

         Garlic.Send

           (Protocol.all,

            Partition,

            Header'Access);                         --  (2) + (3)

         --  The header is deallocated

         Streams.Deallocate (Header);

         --  Send Params from Do_RPC

         D (D_Communication, "Do_RPC - Send Params to partition" &

            Partition_ID'Image (Partition));

         Garlic.Send

           (Protocol.all,

            Partition,

            Params);                                --  (4) + (5)

         --  Let Garlic know we have nothing else to send

         Garlic.Complete_Send

           (Protocol.all,

            Partition);

         D (D_Debug, "Do_RPC - Suspend");

         --  Wait for a reply and get the reply message length

         Dispatcher.Wait_On (Request) (R_Length);

         D (D_Debug, "Do_RPC - Resume");

         declare

            New_Result : aliased Params_Stream_Type (R_Length);

         begin

            --  Adjust the Result stream size right now to be able to load

            --  the stream in one receive call. Create a temporary result

            --  that will be substituted to Do_RPC one

            Streams.Allocate (New_Result);

            --  Receive the reply message from receiving stub

            D (D_Communication, "Do_RPC - Receive Result from partition" &

            Partition_ID'Image (Partition));

            Garlic.Receive

              (Protocol.all,

               Partition,

               New_Result'Access);

            --  Let Garlic know we have nothing else to receive

            Garlic.Complete_Receive

              (Protocol.all,

               Partition);

            --  Update calling stub Result stream

            D (D_Debug, "Do_RPC - Reconstruct Result");

            Streams.Deallocate (Result.all);

            Result.Initial := New_Result.Initial;

            Streams.Dump ("|||", Result.all);

         end;

      else

         --  Do RPC locally and first wait for Partition_RPC_Receiver to be

         --  set

         Partition_Receiver.Is_Set;

         D (D_Debug, "Do_RPC - Locally");

         Partition_RPC_Receiver.all (Params, Result);

      end if;

   exception

      when others =>

         D (D_Exception, "exception in Do_RPC");

         raise;

   end Do_RPC;

   ------------

   -- Do_APC --

   ------------

   procedure Do_APC

     (Partition  : Partition_ID;

      Params     : access Params_Stream_Type)

   is

      Message_Id : Message_Id_Type := 0;

      Protocol   : Protocol_Access;

      Header     : aliased Params_Stream_Type (Header_Size);

   begin

      --  For more informations, see above

      --  Request = 0 as we are not waiting for a reply message

      --  Result length = 0 as we don't expect a result at all

      if Partition /= Garlic.Get_My_Partition_ID then

         --  Build header = request (2) + result.initial_size (3)

         --  As we have an APC, the request id is null to indicate

         --  to the receiving stub that we do not expect a reply

         --  This comes from 0 = -0

         D (D_Debug, "Do_APC - Build Header");

         Streams.Allocate (Header);

         Streams.Integer_Write_Attribute

           (Header'Access, Integer (Message_Id));

         Streams.SEC_Write_Attribute

           (Header'Access, 0);

         --  Get a protocol method to communicate with the remote partition

         --  and give the message size

         D (D_Communication,

            "Do_APC - Lookup for protocol to talk to partition" &

            Partition_ID'Image (Partition));

         Garlic.Initiate_Send

           (Partition,

            Streams.Get_Stream_Size (Header'Access) +

            Streams.Get_Stream_Size (Params),

            Protocol,

            Garlic.Remote_Call);

         --  Send the header by using the protocol method

         D (D_Communication, "Do_APC - Send Header to partition" &

            Partition_ID'Image (Partition));

         Garlic.Send

           (Protocol.all,

            Partition,

            Header'Access);

         --  The header is deallocated

         Streams.Deallocate (Header);

         --  Send Params from Do_APC

         D (D_Communication, "Do_APC - Send Params to partition" &

            Partition_ID'Image (Partition));

         Garlic.Send

           (Protocol.all,

            Partition,

            Params);

         --  Let Garlic know we have nothing else to send

         Garlic.Complete_Send

           (Protocol.all,

            Partition);

      else

         declare

            Result   : aliased Params_Stream_Type (0);

         begin

            --  Result is here a dummy parameter

            --  No reason to deallocate as it is not allocated at all

            Partition_Receiver.Is_Set;

            D (D_Debug, "Do_APC - Locally");

            Partition_RPC_Receiver.all (Params, Result'Access);

         end;

      end if;

   exception

      when others =>

         D (D_Exception, "exception in Do_APC");

         raise;

   end Do_APC;

   ----------------------------

   -- Establish_RPC_Receiver --

   ----------------------------

   procedure Establish_RPC_Receiver

     (Partition : Partition_ID;

      Receiver  : RPC_Receiver)

   is

   begin

      --  Set Partition_RPC_Receiver and allow RPC mechanism

      Partition_RPC_Receiver := Receiver;

      Partition_Receiver.Set;

      D (D_Elaborate, "Partition_Receiver is set");

   exception

      when others =>

         D (D_Exception, "exception in Establish_RPC_Receiver");

         raise;

   end Establish_RPC_Receiver;

   ----------------

   -- Dispatcher --

   ----------------

   task body Dispatcher is

      Last_Request : Request_Id_Type := Request_Id_Type'First;

      Current_Rqst : Request_Id_Type := Request_Id_Type'First;

      Current_Size : Ada.Streams.Stream_Element_Count;

   begin

      loop

         --  Three services:

         --    New_Request to get an entry in Dispatcher table

         --    Wait_On for Do_RPC calls

         --    Wake_Up called by environment task when a Do_RPC receives

         --    the result of its remote call

         select

            accept New_Request (Request : out Request_Id_Type) do

               Request := Last_Request;

               --  << TODO >>

               --  ??? Availability check

               if Last_Request = Request_Id_Type'Last then

                  Last_Request := Request_Id_Type'First;

               else

                  Last_Request := Last_Request + 1;

               end if;

            end New_Request;

         or

            accept Wake_Up

              (Request : Request_Id_Type;

               Length  : Ada.Streams.Stream_Element_Count)

            do

               --  The environment reads the header and has been notified

               --  of the reply id and the size of the result message

               Current_Rqst := Request;

               Current_Size := Length;

            end Wake_Up;

            --  << TODO >>

            --  ??? Must be select with delay for aborted tasks

            select

               accept Wait_On (Current_Rqst)

                 (Length  : out Ada.Streams.Stream_Element_Count)

               do

                  Length := Current_Size;

               end Wait_On;

            or

               --  To free the Dispatcher when a task is aborted

               delay 1.0;

            end select;

         or

            terminate;

         end select;

      end loop;

   exception

      when others =>

         D (D_Exception, "exception in Dispatcher body");

         raise;

   end Dispatcher;

   -------------------------

   -- Anonymous_Task_Type --

   -------------------------

   task body Anonymous_Task_Type is

      Whoami       : Anonymous_Task_Node_Access := Self;

      C_Message_Id : Message_Id_Type;                  --  Current Message Id

      C_Partition  : Partition_ID;                     --  Current Partition

      Params_S     : Ada.Streams.Stream_Element_Count; --  Params message size

      Result_S     : Ada.Streams.Stream_Element_Count; --  Result message size

      C_Protocol   : Protocol_Access;                  --  Current Protocol

   begin

      loop

         --  Get a new RPC to execute

         select

            accept Start

              (Message_Id   : Message_Id_Type;

               Partition    : Partition_ID;

               Params_Size  : Ada.Streams.Stream_Element_Count;

               Result_Size  : Ada.Streams.Stream_Element_Count;