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# transaction.py - simple journalling scheme for mercurial
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#
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# This transaction scheme is intended to gracefully handle program
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# errors and interruptions. More serious failures like system crashes
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# can be recovered with an fsck-like tool. As the whole repository is
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# effectively log-structured, this should amount to simply truncating
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# anything that isn't referenced in the changelog.
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#
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# Copyright 2005, 2006 Matt Mackall <mpm@selenic.com>
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#
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# This software may be used and distributed according to the terms
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# of the GNU General Public License, incorporated herein by reference.
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from i18n import _
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import os
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class transaction(object):
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def __init__(self, report, opener, journal, after=None):
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self.journal = None
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# abort here if the journal already exists
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if os.path.exists(journal):
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raise AssertionError(_("journal already exists - run hg recover"))
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self.count = 1
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self.report = report
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self.opener = opener
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self.after = after
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self.entries = []
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self.map = {}
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self.journal = journal
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self.file = open(self.journal, "w")
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def __del__(self):
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if self.journal:
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if self.entries: self.abort()
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self.file.close()
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try: os.unlink(self.journal)
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except: pass
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def add(self, file, offset, data=None):
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if file in self.map: return
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self.entries.append((file, offset, data))
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self.map[file] = len(self.entries) - 1
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# add enough data to the journal to do the truncate
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self.file.write("%s\0%d\n" % (file, offset))
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self.file.flush()
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def find(self, file):
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if file in self.map:
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return self.entries[self.map[file]]
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return None
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def replace(self, file, offset, data=None):
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if file not in self.map:
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raise KeyError(file)
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index = self.map[file]
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self.entries[index] = (file, offset, data)
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self.file.write("%s\0%d\n" % (file, offset))
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self.file.flush()
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def nest(self):
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self.count += 1
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return self
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def running(self):
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return self.count > 0
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def close(self):
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self.count -= 1
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if self.count != 0:
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return
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self.file.close()
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self.entries = []
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if self.after:
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self.after()
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else:
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os.unlink(self.journal)
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self.journal = None
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def abort(self):
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if not self.entries: return
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self.report(_("transaction abort!\n"))
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for f, o, ignore in self.entries:
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try:
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self.opener(f, "a").truncate(o)
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except:
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self.report(_("failed to truncate %s\n") % f)
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self.entries = []
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self.report(_("rollback completed\n"))
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def rollback(opener, file):
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files = {}
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for l in open(file).readlines():
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f, o = l.split('\0')
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files[f] = o
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for f in files:
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o = files[f]
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opener(f, "a").truncate(int(o))
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os.unlink(file)
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