upstream/mercurial-mirror Files · mercurial/txnutil.py

revlog: rewrite censoring logic...

revlog: rewrite censoring logic I was able to corrupt a revlog relatively easily with the existing censoring code. The underlying problem is that the existing code doesn't fully take delta chains into account. When copying revisions that occur after the censored revision, the delta base can refer to a censored revision. Then at read time, things blow up due to the revision data not being a compressed delta. This commit rewrites the revlog censoring code to take a higher-level approach. We now create a new revlog instance pointing at temp files. We iterate through each revision in the source revlog and insert those revisions into the new revlog, replacing the censored revision's data along the way. The new implementation isn't as efficient as the old one. This is because it will fully engage delta computation on insertion. But I don't think it matters. The new implementation is a bit hacky because it attempts to reload the revlog instance with a new revlog index/data file. This is fragile. But this is needed because the index (which could be backed by C) would have a cached copy of the old, possibly changed data and that could lead to problems accessing index or revision data later. One benefit of the new approach is that we integrate with the transaction. The old revlog is backed up and if the transaction is rolled back, the original revlog is restored. As part of this, we had to teach the transaction about the store vfs. I'm not super keen about this. But this was the easiest way to hook things up to the transaction. We /could/ just ignore the transaction like we were doing before. But any file mutation should be governed by transaction semantics, including undo during rollback. Differential Revision: https://phab.mercurial-scm.org/D4869

FUJIWARA Katsunori - - Load All Authors

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      # txnutil.py - transaction related utilities

      #

      #  Copyright FUJIWARA Katsunori <foozy@lares.dti.ne.jp> and others

      #

      # This software may be used and distributed according to the terms of the

      # GNU General Public License version 2 or any later version.

      from __future__ import absolute_import

      import errno

      from . import (

          encoding,

      )

      def mayhavepending(root):

          '''return whether 'root' may have pending changes, which are

          visible to this process.

          '''

          return root == encoding.environ.get('HG_PENDING')

      def trypending(root, vfs, filename, **kwargs):

          '''Open  file to be read according to HG_PENDING environment variable

          This opens '.pending' of specified 'filename' only when HG_PENDING

          is equal to 'root'.

          This returns '(fp, is_pending_opened)' tuple.

          '''

          if mayhavepending(root):

              try:

                  return (vfs('%s.pending' % filename, **kwargs), True)

              except IOError as inst:

                  if inst.errno != errno.ENOENT:

                      raise

          return (vfs(filename, **kwargs), False)

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				# txnutil.py - transaction related utilities
				#
				# Copyright FUJIWARA Katsunori <foozy@lares.dti.ne.jp> and others
				#
				# This software may be used and distributed according to the terms of the
				# GNU General Public License version 2 or any later version.

				from __future__ import absolute_import

				import errno

				from . import (
				encoding,
				)

				def mayhavepending(root):
				'''return whether 'root' may have pending changes, which are
				visible to this process.
				'''
				return root == encoding.environ.get('HG_PENDING')

				def trypending(root, vfs, filename, **kwargs):
				'''Open file to be read according to HG_PENDING environment variable

				This opens '.pending' of specified 'filename' only when HG_PENDING
				is equal to 'root'.

				This returns '(fp, is_pending_opened)' tuple.
				'''
				if mayhavepending(root):
				try:
				return (vfs('%s.pending' % filename, **kwargs), True)
				except IOError as inst:
				if inst.errno != errno.ENOENT:
				raise
				return (vfs(filename, **kwargs), False)