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CALL action - remote procedure call

CALL action for remote procedure call allows to call procedures, which are implemented in:

  • the script of an object of Event type that must be Server event type,
  • the script of an active picture (or sub picture),
  • JAPI process.

Remote procedure call may be executed:

  • synchronously - CALL action will wait to terminate the remote procedure execution and modified input-output parameters will be updated. If CALL action is noted down as an expression (_i := CALL ...), it is able to detect an unhandled error (exception) that occurred within the frame of the called procedure. The synchronous calling can cause deadlock. A dialog window with error message contains complete sequence of callings (CALL actions), that caused the deadlock.
  • asynchronously - CALL action generates only request to execute a remote procedure (not waiting for its termination). The possibility to check the procedure execution for this type of calling.
    Following procedures can be called asynchronously:
    • RPC procedure in particular script of the particular process,
    • RPC procedure in scripts (objects of Event type (named as "Server event") or Picture) that are active in all running processes (BROADCAST) of D2000 HI or D2000 EventHandler,
    • JAPI process.

The declaration of an remote procedure must begin with the key word RPC.

Declaration - synchronous call
[_ret :=] CALL [objIdent] ProcName [(paramIdent1 [,paramIdent2]...)] [SYNC] [ON procIdent [INSTANCE instanceExpr]] [PRTY exprIntPrty]
 


 


Declaration - asynchronous call
 CALL [objIdent] ProcName [(paramIdent1 [,paramIdent2]...)]  ASYNC [ON procIdent [INSTANCE instanceExpr]] [PRTY exprIntPrty]
 


 


Declaration - asynchronous call BROADCAST


 CALL [objIdent] ProcName [(paramIdent1 [,paramIdent2]...)]  ASYNC ON ALL [PRTY prtyIdent]
 
 


 


Declaration - synchronous call Client and Server configuration
[_ret :=] CALL [] ProcName [(paramIdent1 [,paramIdent2]...)] [SYNC] [ON procIdent [INSTANCE instanceExpr]] [PRTY exprIntPrty]
Parameters
ProcnameinProcedure name (must meet the rules for object name).
paramIdent1, paramIdent2, ..., paramIdentNinValue identifier for the first (second, third, .., N) parameter. Number of parameters must be identical with the number of parameters of the procedure called.
objIdentinObject identifier (picture or system server event) that contains the script with the given procedure.
Local variable, whose value is identical with the value of a RefId type variable linked to a graphic object of Picture type (subpicture procedure call).
When calling the RPC from Local Script to Remote script (HIS Server), the identifier objIdent is not used.
When calling JAPI process, the reference to object must be empty (see the example).
 
procIdentinProcess identifier, where the object objIdent is located (e.g. SELF.EVH, SELF.HIP or WS_BC.HIP).
If the CALL action is used within an active picture, then predefined variable _FROM_HIP contains identifier of HI process in which this picture is opened.
instanceExprinOptional expression of Int type. It addresses a specific instance during the procedure call.
prtyIdentinIdentifier of Int type. It defines the priority of executing RPC procedure. It can be assigned a value from the range: <Integer'Range> (-2147483648 to 2147483647).
If it is not set, the default value is 0. The procedure with higher priority (higher number) is processed as first.
Description
CALL action will execute calling of the RPC (RPCX) procedure with the name ProcName. The procedure name is followed by a list of comma separated parameters.

The number (an types) of parameters must be equal to the number of parameters of the called procedure (if the number is not equal, there is generated the exception _ERR_INV_NUM_PARAMS*).

If some of the parameters is specified as an input-output one in the procedure declaration, the corresponding parameter, during the procedure call, must not be a constant (if an error occurs, there will be generated the exception _ERR_SET_CONST).

procIdent is the reference to an object of Process type, where is the object procIdent opened in. For object of Event type it is the process D2000 EventHandler, which is its parent or process on which the called Event is opened (OPENEVENT action). For an object of Picture type it is the process D2000 HI, where is this picture opened in.
If the required object is not opened in the given process, the script generates the error _ERR_OBJECT_NOT_FOUND*.

The parameter INSTANCE determines the instance number of the object (picture or event).

If a local variable of RefId type is used for the identifier objIdent, the parameters INSTANCE and ON are not admissible (their value are given by the calling context).

If RPC procedure is called between Local and Remote part of "Client and Server Event" configuration (HIS Server), objIdent is not used.

 CALL [] ProcName [(paramIdent1 [,paramIdent2]...)] ...


The errors signed by the symbol * are generated in the called script. Called script (CALL action) ma detect this error merely during synchronous call and during the notation of an action with assignment. If an error occurs, its code will be assigned to the variable _ret that must be INT type.

Possible types of parameters, see the action PROCEDURE.

The calling of BROADCAST type is obligatory asynchronous. The process name (parameter procIdent) is key word ALL. By performing of this calling, the system distribute automatically a demand on procedure performing to all running processes of D2000 HI or D2000 Event Handler. These processes search all instances (or basic objects) of the scripts that are identified by parameter objIdent and generate the demands on procedure ProcName performing with relevant parameters.
The key word INSTANCE is disabled in this type of calling.

Since the D2000 V8.00.008 R9 the CALL action contains the new feature - optimization of the formal parameter transmission. This feature ensures the formal parameter of RPC procedure is a "link" to the real parameter. This causes the increasing of the speed of RPC procedure calling.
The conditions:
  • the calling is realized in the same process *.EVH,
  • the calling of procedure is synchronous,
  • the parameter must be of Record type,
  • the parameter must be IN/OUT.
The key word PRTY enables to set the priority of executing RPC procedure. The priority is defined by the parameter prtyIdent after PRTY.

RPC procedures are also intended for transfer data containers and a handle to database connections.

When calling JAPI process, these rules apply:
  • objIdent is an empty object (see the example),
  • the key word INSTANCE cannot be used,
  • RPC procedure, which is an implementation of ESL interface, cannot be called,
  • the process identifier (procIdent) must be of IC_HOBJ_EXPR (expression of HOBJ type) type,
  • the receiving of calls on JAPI process must be implemented as listener, which is registered by a method D2Session::setRPCListener.
Example
Synchronous call of the remote procedure of the system script:


 


INT _i
 TEXT _personName
 _personName := "Peter"
 _i := CALL [E.Work] AddPerson(_personName) SYNC ON _FROM_HIP
 
IF _i # _ERR_NO_ERROR THEN
 
  ; error when calling the remote procedure
 
ENDIF
 


Asynchronous call of the remote procedure of the active picture:


 


TEXT _msg
 
_msg := " ... "
 
CALL [P.Picture] SendMessage(_msg) ASYNC  ON WS_BC.HIP
 


Asynchronous call of the remote procedure of the active picture:


 


TEXT _msg
 
_msg := " ... "
 
CALL [_subPicture] SendMessage(_msg) ASYNC
 


Synchronous call of the remote procedure, which is implemented by the process:
 


 TEXT _msg
 INT _hbj 
 _msg := " ... "
 _hbj := ...... the value, which is obtained, for example when calling RPC procedure from JAPI client, where one of the parameters is HOBJ of the appropriate JAPI process.
 CALL [(0)] SendMessage(_msg) SYNC ON (_hbj)
 


Asynchronous call BROADCAST:


 


CALL [E.BROADCAST_RECEIVER] Broadcast(1) ASYNC ON ALL
 


Synchronous calling the remote procedure with priority:


 


INT _i
 INT _prty 
 TEXT _personName
 
  _personName := "Peter"
  _prty := 100
 _i := CALL [E.Work] AddPerson(_personName) SYNC ON SELF.HIP PRTY _prty
 IF _i # _ERR_NO_ERROR THEN
 ; error when calling the RPC procedure
 ENDIF
 


Synchronous calling the remote procedure from Local script to Remote one:
 


 INT _i
 TEXT _personName
 _personName := "Peter"
 _i := CALL [] AddPerson(_personName) SYNC ON SELF.HIP
 IF _i # _ERR_NO_ERROR THEN
 ; error when calling the RPC procedure
 ENDIF
Note
Called remote procedure must be finished by the action RETURN, or END ProcedureName. In opposite case, it is not able to update possible input-output parameters. For a synchronous call, the return value is adjusted to the error _ERR_MISSING_RETURN.

Related pages:

Script actions
CALL action - local procedure call
Transfer of handle to database connection between the running ESL scripts
Data container transfer between running ESL scripts

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