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 // Copyright (c) 1999-2014 OPEN CASCADE SAS
 //
 // This file is part of Open CASCADE Technology software library.
 //
 // This library is free software; you can redistribute it and/or modify it under
 // the terms of the GNU Lesser General Public License version 2.1 as published
 // by the Free Software Foundation, with special exception defined in the file
 // OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
 // distribution for complete text of the license and disclaimer of any warranty.
 //
 // Alternatively, this file may be used under the terms of Open CASCADE
 // commercial license or contractual agreement.
 
 #ifndef Interface_Statics_HeaderFile
 #define Interface_Statics_HeaderFile
 
 //  Macros to help static Handles not to be "constructed" before main run
 //  In order to avoid it, the Handle to be statically reserved is encapsulated
 //  in a structure itself designated through a Null Pointer :
 //  Only the pointer is declared static, and initialized to NULL : then,
 //  there is no routine to call for static construction
 
 //  Remember that the object designated by a static Handle should not be created
 //  in the static declaration, but must anyway be created, during main run,
 //  once before its first use : this is the initialization step.
 
 
 //  This set of macros allows user to simply declare and use "static" Handles.
 //  It is available once having included this file :
 //  ***************************************************
 //         #include <Interface_Statics.hxx>
 
 //  Static construction is replaced by using the macro StaticHandle :
 //  ***************************************************
 //    Old statement  :  static Handle(pk_class) object;
 //    Is replaced by :  StaticHandle(pk_class,object);
 //    which creates a null pointer called 'object_s' and typed 'pk_class_struc'
 
 //  For first initialisation and use, several ways are available, all of them
 //  give an access to the Handle through a reference.
 //  It is required to initialize the static structure once, the macros Init*
 //  assume that it is created once and only once, even if they are called
 //  more than once.
 //  It is possible : to create the object at initialization time by a macro,
 //  or to create it after the macro call through its reference :
 
 //  ***************************************************
 //  Old statement (in a routine, not static) :
 //          if (object.IsNull()) object = new pk_class (..args if any..);
 //  can be maintained, but preceded by an initialization :
 //          InitHandle(pk_class,object);         // -> Null Handle
 
 //  ***************************************************
 //  or it can be replaced by a direct formula (creation called only once) :
 //          InitHandleVoid(pk_class,object);     // for a void constructor
 //   or     InitHandleArgs(pk_class,object,(..args..));
 //               (the arglist between embedded parentheses)
 //   or     InitHandleVal(pk_class,object,val);  // i.e. object = val;
 
 //  To simply use this pseudo-static object, consider
 //  either the static variable  object_s->H
 //  ***************************************************
 //  or take it by the macro (which does not initialize it)
 //          UseHandle(pk_class,object);
 
 
 //  Declaration of a static Handle : first use for a given type
 #define StaticHandle(type,var) static struct type##_struc { Handle(type) H; } *var##_s = NULL
 
 //  Another declaration for an already declared type (with StaticHandle)
 #define StaticHandleA(type,var) static struct type##_struc *var##_s = NULL
 
 //  Using it (IT MUST HAVE BEEN FORMERLY INITIALIZED)
 #define UseHandle(type,var) Handle(type)& var = var##_s->H
 
 //  Initializing it (as Null Handle)
 #define InitHandle(type,var) \
 if(!var##_s) { var##_s=new type##_struc;  }\
 Handle(type)& var = var##_s->H;
 
 //  Initializing it and Creating it by a Void Constructor
 #define InitHandleVoid(type,var) \
 if(!var##_s) { var##_s=new type##_struc; var##_s->H=new type; }\
 Handle(type)& var = var##_s->H;
 
 //  Initializing it and Creating it by a Constructor with Arguments
 //    (give them grouped in their parentheses)
 #define InitHandleArgs(type,var,args) \
 if(!var##_s) { var##_s=new type##_struc; var##_s->H=new type args; }\
 Handle(type)& var = var##_s->H;
 
 //  Initializing it from an already determined Value
 #define InitHandleVal(type,var,value) \
 if(!var##_s) { var##_s=new type##_struc; var##_s->H=value; }\
 Handle(type)& var = var##_s->H;
 
 #endif

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