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Annotation of ExtFile/TM.pyc, revision 1.1.1.1

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                      5: TMRegistry and ProxyTM
                      6: 
                      7: Use case
                      8: --------
                      9: 
                     10: Persistent objects (ExtFiles) need to participate in ZODB transactions.
                     11: ExtFiles perform all operations using temporary files which are saved on
                     12: commit or deleted on abort.
                     13: 
                     14: Constraints
                     15: -----------
                     16: 
                     17: - TransactionManagers (TM) must not be persistent themselves, i.e. must
                     18:   not have a _p_jar attribute.
                     19: 
                     20: - We have to make sure the ExtFile's _abort is called *before* the ZODB
                     21:   destroys the attributes of the persistent object.
                     22: 
                     23: Solution
                     24: --------
                     25: 
                     26: - ProxyTM is a subclass of TM.TM that keeps a (hard) reference to the
                     27:   (wrapped) persistent object it manages. Calls to _begin, _finish, and
                     28:   _abort are forwarded to the target object.
                     29: 
                     30: - TMRegistry is a module-level container for ProxyTMs. It creates and
                     31:   holds ProxyTMs keyed by (target_id, thread_id).
                     32: 
                     33: - ExtFiles implement _finish and _abort and register with the machinery
                     34:   by calling TM.register(self).
                     35: 
                     36: - On commit (or abort) the ProxyTM notifies its target object and removes
                     37:   itself from the registry.
                     38: 
                     39: Hacks
                     40: -----
                     41: 
                     42: - We manipulate the transaction's _resources attribute directly. This is
                     43:   to guarantee the ProxyTM is processed before other resources. There may
                     44:   be a way to achieve this using official APIs only, but I can't seem to
                     45:   find one.
                     46: 
                     47: (&sTM(&saq_base(&s    get_ident(&stransactiont
                     48: TMRegistryc&BsPtZ&d&„Zd„Zd„Zd„Zd„Zd„Zd„Zd„Z    RS(    Nc&&Cs
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                     49: &
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                     54: t|ƒ&S(&N(RR&(&R&((RtcountWs&(
                     55: t__name__t
                     56: __module__RR    RRR
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                     59: _resourcesi(tTMR
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