�
��^c@s�dZd
dl
Z
d
dlZd
dlZd
dlZdZdZdZdZdZ	ddd	��YZ
d
e
f
d��YZddd
��YZd�Z
def
d��YZdef
d��YZed�
Zd�Zedkr�e�
ndS(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
is#cvs.lcks	#cvs.rfl.s	#cvs.wfl.tErrorc
Bs#eZ
d�Zd
�Zd�ZRS(cCs
|
|_dS(
N(
tmsg(tselfR
((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyt__init__`s
c

Cs
t|j
�
S(
N(treprR
(
R((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyt__repr__cs
c

Cs
t|j
�
S(
N(tstrR
(
R((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyt__str__fs
(t__name__t
__module__RRR(((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyR^s		tLockedc
BseZ
RS((RR	(((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyR
js
tLockcBsVeZ
ded
�Zd�Zd�Zd�Zd�Zd�Zd�Z	d�Z
RS(	t
.cCsx|
|_||_
d|_d|_ttj��
}|jt	�
|_
|jt|�
|_|jt
|�
|_dS(
N(t
repositorytdelaytNonetlockdirtlockfileRtostgetpidtjointCVSLCKtcvslcktCVSRFLtcvsrfltCVSWFLtcvswfl(RR
Rtpid((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyRps
	
	
	
	



c


Csd
GH|j�
dS(Nt__del__(
tunlock(
R((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyRzs

c
Cs�x�y'|j|_
tj|jd
�
dSWqtjk
r�
}

d|_
|
dtkr�ytj|j�
}Wntjk
r�


qn
X|j|�

qnt	d|j
|
f�
�
qXqWdS(Ni�
isfailed to lock %s: %s(RRRtmkdirterrorRtEEXISTtstattsleepRR
(RR
tst((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyt
setlockdir~s 






	









c


Cs|j�
|j
�
dS(
N(t
unlockfilet	unlockdir(
R((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyR�s


c

CsP|jrLd
G|jGHyt
j|j�

Wnt
jk
r?


n
Xd|_ndS(Ntunlink(RRR'RR(
R((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyR%�s
	





c

CsP|jrLd
G|jGHyt
j|j�

Wnt
jk
r?


n
Xd|_ndS(Ntrmdir(RRR(RR(
R((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyR&�s
	





cCst|
|j
|j�
dS(
N(R"R
R(RR#((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyR"�s
cCstj
j|j|
�S(
N(RtpathRR
(Rtname((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyR�s
(RR	tDELAYRRR$RR%R&R"R(((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyRns
								cCs�|d
k
rt|�
�
n|t
j}ytj|�
}|d
}Wntk
rb


d|}n
Xdtjtj��
dd!Gd|G|
GHtj|�

dS(Nisuid %ds[%s]iisWaiting for %s's lock in(	R
R!tST_UIDtpwdtgetpwuidtKeyErrorttimetctimeR"(R#R
Rtuidtpwenttuser((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyR"�s













tReadLockcBseZ
ed�
ZRS(
cCsztj
||
|�
d
}z<|j�
|j|_t|jd�}|j�
d}Wd|sk|j�
n|j�
XdS(Nit
wi
(	RRR$RRtopentcloseR%R&(RR
Rtoktfp((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyR�s













(RR	R+R(((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyR5�st	WriteLockcBseZ
ed�
Zd
�ZRS(cCs}tj
||
|�
|j�
x1|j�}|s6Pn|j�
|j|�

q W|j|_t|jd
�}|j	�
dS(NR6(
RRR$t
readers_existR&R"RRR7R8(RR
RR2R:((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyR�s












c
Cswtt
�
}
xdtj|j�
D]P}||
 t
krytj|j|�
�
}Wntjk
rj


qn
X|SqWdS(
N(	tlenRRtlistdirR
R!RRR(Rt
nR*R#((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyR<�s








(RR	R+RR<(((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyR;�s
cCsjxcg}xC|D]:}y|jt
|d
��

Wqtk
rI
}
~PqXqWPt|j||
�
qWtS(Ni(tappendR;R
R"R
tlist(trepositoriesRtlockst
rtinstance((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pytMultipleWriteLock�s








	


cCs�d
dl}|j
dr)|j
d}
nd}
d}d}zDdGHt|
�
}dGH|j�
dGHt|
�
}dGH|j�
Wddg
GHd|_dg
GH|r�|j�
ndg
GH|r�|j�
nd	g
GHd}d
g
GHd}dg
GHXdS(Ni����i
Rsattempting write lock ...sgot it.sattempting read lock ...iiiii(tsystargvRR;RR5t
exc_traceback(RGR
trltwl((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyttest�s8
















	












t__main__(((t__doc__RR0R!R-R+R RRRRR
RR"R5R;RFRLR(((s*/usr/lib64/python2.7/Demo/pdist/cvslock.pyt<module>Gs&




?		!