87 lines
3.1 KiB
C
87 lines
3.1 KiB
C
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/**
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* PANDA 3D SOFTWARE
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* Copyright (c) Carnegie Mellon University. All rights reserved.
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*
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* All use of this software is subject to the terms of the revised BSD
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* license. You should have received a copy of this license along
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* with this source code in a file named "LICENSE."
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*
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* @file dcast.h
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* @author drose
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* @date 2001-08-06
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*/
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#ifndef DCAST_H
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#define DCAST_H
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#include "pandabase.h"
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#include "typeHandle.h"
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#include "typedObject.h"
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#include "config_express.h"
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// The DCAST (downcast) macro is defined as a convenience for downcasting from
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// some TypedObject pointer (or a PointerTo). It's just a normal C++-style
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// downcast, except it first checks get_type() to make sure the downcasting is
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// safe. If you compile with NDEBUG, or set verify-dcast to #f, this check is
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// removed.
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// DCAST will return NULL if the downcasting is unsafe. If you'd rather it
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// abort out of the function (a la nassertvnassertr), then see DCAST_INTO_V
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// and DCAST_INTO_R, below.
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template<class WantType>
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INLINE WantType *_dcast(WantType *, TypedObject *ptr);
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template<class WantType>
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INLINE const WantType *_dcast(WantType *, const TypedObject *ptr);
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// Note: it is important that DCAST not repeat the pointer parameter, since
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// many users of DCAST may want to use the result of a function as the pointer
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// parameter, and it could be terribly confusing and difficult to trace if the
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// function were inadvertently executed twice. This happened!
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#define DCAST(want_type, pointer) _dcast((want_type*)0, pointer)
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// DCAST_INTO_V and DCAST_INTO_R are similar in purpose to DCAST, except they:
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// (a) automatically assign a variable instead of returning the downcasted
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// pointer, and (b) they immediately return out of the function if the
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// downcasting fails. DCAST_INTO_V is for use in a void function and returns
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// nothing; DCAST_INTO_R is for use in a non-void function and returns the
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// indicated value.
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// Both DCAST_INTO_V and DCAST_INTO_R accept as the first parameter a variable
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// of type (want_type *) or (const want_type *), instead of the name of the
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// type. This variable will be filled with the new pointer.
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// _dcast_ref is used to implement DCAST_INTO_V and DCAST_INTO_R. Its
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// difference from _dcast is that it takes a reference to a pointer as a first
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// parameter. The main point of this is to shut up the compiler about
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// pointers used before their value is assigned.
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template<class WantType>
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INLINE WantType *_dcast_ref(WantType *&, TypedObject *ptr);
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template<class WantType>
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INLINE const WantType *_dcast_ref(WantType *&, const TypedObject *ptr);
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#ifdef DO_DCAST
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// _dcast_verify performs the actual verification.
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EXPCL_PANDA_EXPRESS bool
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_dcast_verify(TypeHandle want_handle, size_t want_size,
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const TypedObject *ptr);
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#endif // DO_DCAST
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#define DCAST_INTO_V(to_pointer, from_pointer) \
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{ \
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(to_pointer) = _dcast_ref(to_pointer, from_pointer); \
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nassertv((void *)(to_pointer) != nullptr); \
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}
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#define DCAST_INTO_R(to_pointer, from_pointer, return_value) \
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{ \
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(to_pointer) = _dcast_ref(to_pointer, from_pointer); \
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nassertr((void *)(to_pointer) != nullptr, return_value); \
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}
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#include "dcast.T"
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#endif
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