EVOLUTION-NINJA
Edit File: cvslock.pyc
� ��^c @ s� d Z d d l Z d d l Z d d l Z d d l Z d Z d Z d Z d Z d Z d d d � � YZ d e f d � � YZ d d d � � YZ d � Z d e f d � � YZ d e f d � � YZ e d � Z d � Z e d k r� e � n d S( s� CVS locking algorithm. CVS locking strategy ==================== As reverse engineered from the CVS 1.3 sources (file lock.c): - Locking is done on a per repository basis (but a process can hold write locks for multiple directories); all lock files are placed in the repository and have names beginning with "#cvs.". - Before even attempting to lock, a file "#cvs.tfl.<pid>" is created (and removed again), to test that we can write the repository. [The algorithm can still be fooled (1) if the repository's mode is changed while attempting to lock; (2) if this file exists and is writable but the directory is not.] - While creating the actual read/write lock files (which may exist for a long time), a "meta-lock" is held. The meta-lock is a directory named "#cvs.lock" in the repository. The meta-lock is also held while a write lock is held. - To set a read lock: - acquire the meta-lock - create the file "#cvs.rfl.<pid>" - release the meta-lock - To set a write lock: - acquire the meta-lock - check that there are no files called "#cvs.rfl.*" - if there are, release the meta-lock, sleep, try again - create the file "#cvs.wfl.<pid>" - To release a write lock: - remove the file "#cvs.wfl.<pid>" - rmdir the meta-lock - To release a read lock: - remove the file "#cvs.rfl.<pid>" Additional notes ---------------- - A process should read-lock at most one repository at a time. - A process may write-lock as many repositories as it wishes (to avoid deadlocks, I presume it should always lock them top-down in the directory hierarchy). - A process should make sure it removes all its lock files and directories when it crashes. - Limitation: one user id should not be committing files into the same repository at the same time. Turn this into Python code -------------------------- rl = ReadLock(repository, waittime) wl = WriteLock(repository, waittime) list = MultipleWriteLock([repository1, repository2, ...], waittime) i����Ni i s #cvs.lcks #cvs.rfl.s #cvs.wfl.t Errorc B s# e Z d � Z d � Z d � Z RS( c C s | | _ d S( N( t msg( t selfR ( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyt __init__` s c C s t | j � S( N( t reprR ( R ( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyt __repr__c s c C s t | j � S( N( t strR ( R ( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyt __str__f s ( t __name__t __module__R R R ( ( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyR ^ s t Lockedc B s e Z RS( ( R R ( ( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyR j s t Lockc B sV e Z d e d � Z d � Z d � Z d � Z d � Z d � Z d � Z d � Z RS( t .c C sx | | _ | | _ d | _ d | _ t t j � � } | j t � | _ | j t | � | _ | j t | � | _ d S( N( t repositoryt delayt Nonet lockdirt lockfileR t ost getpidt joint CVSLCKt cvslckt CVSRFLt cvsrflt CVSWFLt cvswfl( R R R t pid( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyR p s c C s d GH| j � d S( Nt __del__( t unlock( R ( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyR z s c C s� x� y' | j | _ t j | j d � d SWq t j k r� } d | _ | d t k r� y t j | j � } Wn t j k r� q n X| j | � q n t d | j | f � � q Xq Wd S( Ni� i s failed to lock %s: %s( R R R t mkdirt errorR t EEXISTt statt sleepR R ( R R t st( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyt setlockdir~ s c C s | j � | j � d S( N( t unlockfilet unlockdir( R ( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyR � s c C sP | j rL d G| j GHy t j | j � Wn t j k r? n Xd | _ n d S( Nt unlink( R R R' R R ( R ( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyR% � s c C sP | j rL d G| j GHy t j | j � Wn t j k r? n Xd | _ n d S( Nt rmdir( R R R( R R ( R ( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyR& � s c C s t | | j | j � d S( N( R" R R ( R R# ( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyR" � s c C s t j j | j | � S( N( R t pathR R ( R t name( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyR � s ( R R t DELAYR R R$ R R% R& R" R ( ( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyR n s c C s� | d k r t | � � n | t j } y t j | � } | d } Wn t k rb d | } n Xd t j t j � � d d !Gd | G| GHt j | � d S( Ni s uid %ds [%s]i i s Waiting for %s's lock in( R R! t ST_UIDt pwdt getpwuidt KeyErrort timet ctimeR" ( R# R R t uidt pwentt user( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyR" � s t ReadLockc B s e Z e d � Z RS( c C sz t j | | | � d } z< | j � | j | _ t | j d � } | j � d } Wd | sk | j � n | j � Xd S( Ni t wi ( R R R$ R R t opent closeR% R& ( R R R t okt fp( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyR � s ( R R R+ R ( ( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyR5 � s t WriteLockc B s e Z e d � Z d � Z RS( c C s} t j | | | � | j � x1 | j � } | s6 Pn | j � | j | � q W| j | _ t | j d � } | j � d S( NR6 ( R R R$ t readers_existR& R" R R R7 R8 ( R R R R2 R: ( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyR � s c C sw t t � } xd t j | j � D]P } | | t k r y t j | j | � � } Wn t j k rj q n X| Sq Wd S( N( t lenR R t listdirR R! R R R ( R t nR* R# ( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyR< � s ( R R R+ R R< ( ( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyR; � s c C sj xc g } xC | D]: } y | j t | d � � Wq t k rI } ~ Pq Xq WPt | j | | � q Wt S( Ni ( t appendR; R R" R t list( t repositoriesR t lockst rt instance( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyt MultipleWriteLock� s c C s� d d l } | j d r) | j d } n d } d } d } zD d GHt | � } d GH| j � d GHt | � } d GH| j � Wd d g GHd | _ d g GH| r� | j � n d g GH| r� | j � n d g GHd } d g GHd } d g GHXd S( Ni����i R s attempting write lock ...s got it.s attempting read lock ...i i i i i ( t syst argvR R; R R5 t exc_traceback( RG R t rlt wl( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyt test� s8 t __main__( ( ( t __doc__R R0 R! R- R+ R R R R R R R R" R5 R; RF RL R ( ( ( s* /usr/lib64/python2.7/Demo/pdist/cvslock.pyt <module>G s& ? !