357 lines
12 KiB
Plaintext
357 lines
12 KiB
Plaintext
/*
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* Copyright 2010, Haiku, Inc. All Rights Reserved.
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* Distributed under the terms of the MIT License.
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*
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* Author:
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* Alex Wilson, yourpalal2@gmail.com
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*
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* Corresponds to:
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* /trunk/headers/os/support/Archivable.h rev 37751
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* /trunk/src/kits/support/Archivable.cpp rev 37751
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*/
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/*! \class BUnarchiver
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\ingroup support
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\ingroup libbe
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\brief A class that simplifies the unarchiving of complicated BArchivable
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hierarchies.
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The BUnarchiver class is a small class used to recover BArchivable objects
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that have been archived with the BArchiver class. It also provides ownership
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semantics, so that memory leaks can be avoided during the unarchival
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process. When retrieving an object (either via GetObject() or FindObject()),
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you can specify a BUnarchiver::ownership_policy. If you specify
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BUnarchiver::B_ASSUME_OWNERSHIP, you will become responsible for deleting
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the retrieved item. If you specify BUnarchiver::B_DONT_ASSUME_OWNERSHIP,
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you will not become responsible. You cannot take ownership of the same
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object twice. After the unarchival process finishes, any unclaimed objects,
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excluding the root object (the object being instantiated via
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instantiate_object() or BUnarchiver::InstantiateObject()), will be deleted.
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If you are updating a class that previously did not use the BArchiver and
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BUnarchiver helper classes, and want to maintain backwards compatibility
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with old archive, this can be done using the IsArchiveManaged() method.
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\warning Calling methods on your BUnarchiver with a legacy archive (one that
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was not managed by a BArchiver during archival) will result in a
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call to debugger().
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*/
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/*! \fn BUnarchiver::BUnarchiver(const BMessage* archive)
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\brief Constructs a BUnarchiver object to manage \c archive.
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\note To guarantee that your AllUnarchived() method will be called during
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archival, you must create a BUnarchiver object in your archive
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constructor. It is necessary to do this even if you won't use the
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BUnarchiver object in your archive constructor.
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\warning Do not construct a BUnarchiver object without first calling
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BUnarchiver::PrepareArchive() on \c archive. It is only safe to build a
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BUnarchiver without this call in your AllUnarchived() implementation.
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\see BUnarchiver::PrepareArchive()
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*/
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/*! \fn BUnarchiver::~BUnarchiver()
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\brief Destroys a BUnarchiver object.
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Calls this objects Finish() method, if it has not yet been called.
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*/
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/*! \fn status_t BUnarchiver::EnsureUnarchived(int32 token)
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\brief Ensure the object represented by \a token is unarchived and
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instantiated.
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\param token the object \a token
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*/
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/*! \fn status_t BUnarchiver::EnsureUnarchived(const char* name,
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int32 index = 0)
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\brief Ensure the object archived under \a name at \a index is unarchived
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and instantiated.
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\param name The archive \a name.
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\param index The archive \a index.
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*/
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/*! \fn bool BUnarchiver::IsInstantiated(int32 token)
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\brief Checks whether the object represented by \c token has been
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instantiated in this session.
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\param token The object \a token
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*/
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/*! \fn bool BUnarchiver::IsInstantiated(const char* name, int32 index = 0)
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\brief Checks whether the object archived under \a name at \a index has been
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instantiated in this session.
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\param name The archive \a name.
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\param index The arcive \a token.
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*/
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/*! \fn template<class T> status_t BUnarchiver::GetObject(int32 token,
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ownership_policy owning, T*& object)
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\brief Recover an object by token that was archived by a BArchiver object.
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If the object has not yet been instantiated, and this request is not coming
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from an AllUnarchived() implementation, the object will be instantiated now.
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If the retrieved object is not of the type T, then this method will fail.
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If this method fails, you will not receive ownership of the object, no
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matter what you specified in \c owning.
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\tparam T The type of \a object you wish to find.
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\param token The \a token you got for this object from
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BArchiver::GetTokenForArchivable() during archival.
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\param owning Whether or not you wish to take ownership of the
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retrieved object.
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\param object Return parameter for the retrieved object of type T.
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\retval B_OK The object retrieved was of type T.
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\retval B_BAD_TYPE The object retrieved was not of type T.
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*/
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/*! \fn template<class T> status_t BUnarchiver::GetObject(int32 token,
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T*& object)
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\brief Recover and take ownership of an object represented by \a token.
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Equivalent to calling GetObject(token, \c B_ASSUME_OWNERSHIP, object)
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\tparam T The type of \a object you wish to find.
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\param token The \a token you got for this object from
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BArchiver::GetTokenForArchivable() during archival.
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\param object The return parameter for the retrieved object of type T.
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\retval B_OK The object retrieved was of type T.
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\retval B_BAD_TYPE The object retrieved was not of type T.
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*/
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/*!
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\fn template<class T> status_t BUnarchiver::FindObject(const char* name,
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int32 index, ownership_policy owning, T*& object)
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\brief Recover an object that had previously been archived using
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the BArchiver::AddArchivable() method. If the object has not yet been
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instantiated, and this request is not coming from an AllUnarchived()
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implementation, the object will be instantiated now.
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If the retrieved object is not of the type T, then this method will fail.
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If this method fails, you will not receive ownership of the object, no
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matter what you specified in \c owning.
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\tparam T The type of object you wish to find.
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\param name The name that was passed to BArchiver::AddArchivable() when
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adding this object.
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\param index The index of the object you wish to recover (\c 0-based,
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like BMessage::FindData().
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\param owning Dictates whether or not you wish to take ownership of the
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retrieved object.
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\param object Return parameter for the retrieved object of type T.
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\retval B_OK The object retrieved was of type T.
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\retval B_BAD_TYPE The object retrieved was not of type T.
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*/
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/*! \fn template<class T> status_t BUnarchiver::FindObject(const char* name,
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int32 index, T*& object)
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\brief Recover and take ownership of an object that had previously been
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archived using the BArchiver::AddArchivable() method.
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\tparam T The type of object you wish to find.
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\param name The name that was passed to BArchiver::AddArchivable() when
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adding this object.
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\param index The index of the object you wish to recover (\c 0-based,
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like #BMessage::FindData().
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\param object Return parameter for the retrieved object of type T.
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\retval B_OK The object retrieved was of type T.
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\retval B_BAD_TYPE The object retrieved was not of type T.
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*/
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/*! \fn template<class T> status_t BUnarchiver::FindObject(const char* name,
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ownership_policy owning, T*& object)
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\brief Recover an object at index \c 0 that had previously been
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archived using the BArchiver::AddArchivable() method.
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Equivalent to calling FindObject(name, \c 0, owning, object).
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\tparam T The type of \a object you wish to find.
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\param name The name that was passed to BArchiver::AddArchivable() when
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adding this object.
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\param owning Dictates whether or not you wish to take ownership of the
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retrieved object.
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\param object Return parameter for the retrieved object of type T.
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\retval B_OK The object retrieved was of type T.
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\retval B_BAD_TYPE The object retrieved was not of type T.
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*/
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/*! \fn template<class T> status_t BUnarchiver::FindObject(const char* name,
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T*& object)
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\brief Recover and take ownership of an object at index \c 0 that had
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previously been archived using the BArchiver::AddArchivable() method.
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Equivalent to calling FindObject(name, \c 0,
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BUnarchiver::B_ASSUME_OWNERSHIP, object).
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\tparam T The type of \a object you wish to find.
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\param name The name that was passed to BArchiver::AddArchivable() when
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adding this object.
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\param object Return parameter for the retrieved \a object of type T.
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\retval B_OK The \a object retrieved was of type T.
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\retval B_BAD_TYPE The \a object retrieved was not of type T.
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*/
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/*! \fn status_t BUnarchiver::Finish(status_t err = B_OK);
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\brief Report any unarchiving errors and possibly complete the archiving
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session.
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This method may finish an unarchiving session (triggering the call of all
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instantiated objects' AllUnarchived() methods) if the following conditions
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are true:
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\li No errors have been reported to this or any other BUnarchiver
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object within this session.
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\li This is the last remaining BUnarchiver that has not had its
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Finish() method invoked.
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If you call this method with an error code not equal to B_OK, then this
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unarchiving session has failed, instantiated objects will not have their
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AllUnarchived() methods called, and any subsequent calls to this method
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on any BUnarchiver objects in this session will return your error code.
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Furthermore, any objects that have been instantiated, but have not had
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their ownership assumed by another object will now be deleted (excluding
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the root object).
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\return The first error reported in this unarchiving session, or \c B_OK.
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*/
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/*!
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\fn const BMessage* BUnarchiver::ArchiveMessage() const
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\brief Returns the BMessage* used to construct this BUnarchiver.
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This is the archive that FindObject() uses.
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*/
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/*! \fn static bool BUnarchiver::IsArchiveManaged(const BMessage* archive)
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\brief Checks whether \a archive was managed by a BArchiver object.
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This method can be used to maintain archive backwards-compatibility for a
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class that has been updated to use the BArchiver class. If there is a
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possibility that you are may dealing with a legacy archive, you can use
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this method to find out before calling any methods on your BUnarchiver
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object.
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Here is an example of how you might use this method. Note that you
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must still call PrepareArchive(archive) either way.
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\code
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MyArchivableClas::MyArchivableClass(BMessage* archive)
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:
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BArchivable(BUnarchiver::PrepareArchive(archive))
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{
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BUnarchiver unarchiver(archive);
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if (BUnarchiver::IsArchiveManaged(archive)) {
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// ... calls to FindObject() or GetObject() here ...
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} else {
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// ... calls to BMessage::FindMessage() here ...
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}
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}
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\endcode
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\retval true if \a archive was managed by a BArchiver object.
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\retval false otherwise.
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*/
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/*! \fn static BMessage* BUnarchiver::PrepareArchive(BMessage* &archive)
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\brief Prepares \c archive for use by a BUnarchiver.
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This method must be called if you plan to use a BUnarchiver on an archive.
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It must be called once for each class an object inherits from that
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will use a BUnarchiver.
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\warning This method \b must be called \b before a call to the
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archive constructor of your parent class.
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Notice the use of this method in the example provided below.
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\code
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MyArchivableClas::MyArchivableClas(BMessage* archive)
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:
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BArchivable(BUnarchiver::PrepareArchive(archive))
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{
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// ...
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}
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\endcode
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\param archive The archive you wish to have prepared.
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\return The same #BMessage as is passed in.
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*/
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/*! \fn void BUnarchiver::AssumeOwnership(BArchivable* archivable)
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\brief Become the owner of \a archivable.
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After calling this method you are responsible for deleting the
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\a archivable.
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\param archivable The \a archivable object.
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*/
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/*! \fn void BUnarchiver::RelinquishOwnership(BArchivable* archivable)
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\brief Relinquish ownership of \a archivable. If \a archivable remains
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unclaimed at the end of the unarchiving session, it will be deleted
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(unless it is the root object).
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\param archivable The \a archivable object.
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*/
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/*! \fn template<class T> status_t BUnarchiver::InstantiateObject(
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BMessage* from, T*& object)
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\brief Attempt to instantiate an object of type T from BMessage*
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\a from.
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If the instantiated object is not of type T, then it will be deleted,
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and this method will return \c B_BAD_TYPE. This method is similar to
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the instantiate_object() function, but provides error reporting and
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protection from memory leaks.
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\param from The #BMessage to instantiate from.
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\param object Return parameter for the retrieved object of type T.
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\retval B_OK The object retrieved was of type T.
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\retval B_BAD_TYPE The object retrieved was not of type T.
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*/
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