obsolete: helper class to access obsolete marker data

mercurial/obsolete.py

@@ -1,192 +1,220 b''
 # obsolete.py - obsolete markers handling
 #
 # Copyright 2012 Pierre-Yves David <[e-mail]>
 #                Logilab SA        <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 """Obsolete markers handling
 
 An obsolete marker maps an old changeset to a list of new
 changesets. If the list of new changesets is empty, the old changeset
 is said to be "killed". Otherwise, the old changeset is being
 "replaced" by the new changesets.
 
 Obsolete markers can be used to record and distribute changeset graph
 transformations performed by history rewriting operations, and help
 building new tools to reconciliate conflicting rewriting actions. To
 facilitate conflicts resolution, markers include various annotations
 besides old and news changeset identifiers, such as creation date or
 author name.
 
 
 Format
 ------
 
 Markers are stored in an append-only file stored in
 '.hg/store/obsstore'.
 
 The file starts with a version header:
 
 - 1 unsigned byte: version number, starting at zero.
 
 
 The header is followed by the markers. Each marker is made of:
 
 - 1 unsigned byte: number of new changesets "R", could be zero.
 
 - 1 unsigned 32-bits integer: metadata size "M" in bytes.
 
 - 1 byte: a bit field. It is reserved for flags used in obsolete
   markers common operations, to avoid repeated decoding of metadata
   entries.
 
 - 20 bytes: obsoleted changeset identifier.
 
 - N*20 bytes: new changesets identifiers.
 
 - M bytes: metadata as a sequence of nul-terminated strings. Each
   string contains a key and a value, separated by a color ':', without
   additional encoding. Keys cannot contain '\0' or ':' and values
   cannot contain '\0'.
 """
 import struct
 from mercurial import util
 from i18n import _
 
 _pack = struct.pack
 _unpack = struct.unpack
 
 
 
 # data used for parsing and writing
 _fmversion = 0
 _fmfixed   = '>BIB20s'
 _fmnode = '20s'
 _fmfsize = struct.calcsize(_fmfixed)
 _fnodesize = struct.calcsize(_fmnode)
 
 def _readmarkers(data):
     """Read and enumerate markers from raw data"""
     off = 0
     diskversion = _unpack('>B', data[off:off + 1])[0]
     off += 1
     if diskversion != _fmversion:
         raise util.Abort(_('parsing obsolete marker: unknown version %r')
                          % diskversion)
 
     # Loop on markers
     l = len(data)
     while off + _fmfsize <= l:
         # read fixed part
         cur = data[off:off + _fmfsize]
         off += _fmfsize
         nbsuc, mdsize, flags, pre = _unpack(_fmfixed, cur)
         # read replacement
         sucs = ()
         if nbsuc:
             s = (_fnodesize * nbsuc)
             cur = data[off:off + s]
             sucs = _unpack(_fmnode * nbsuc, cur)
             off += s
         # read metadata
         # (metadata will be decoded on demand)
         metadata = data[off:off + mdsize]
         if len(metadata) != mdsize:
             raise util.Abort(_('parsing obsolete marker: metadata is too '
                                'short, %d bytes expected, got %d')
                              % (len(metadata), mdsize))
         off += mdsize
         yield (pre, sucs, flags, metadata)
 
 def encodemeta(meta):
     """Return encoded metadata string to string mapping.
 
     Assume no ':' in key and no '\0' in both key and value."""
     for key, value in meta.iteritems():
         if ':' in key or '\0' in key:
             raise ValueError("':' and '\0' are forbidden in metadata key'")
         if '\0' in value:
             raise ValueError("':' are forbidden in metadata value'")
     return '\0'.join(['%s:%s' % (k, meta[k]) for k in sorted(meta)])
 
 def decodemeta(data):
     """Return string to string dictionary from encoded version."""
     d = {}
     for l in data.split('\0'):
         if l:
             key, value = l.split(':')
             d[key] = value
     return d
 
+class marker(object):
+    """Wrap obsolete marker raw data"""
+
+    def __init__(self, repo, data):
+        # the repo argument will be used to create changectx in later version
+        self._repo = repo
+        self._data = data
+        self._decodedmeta = None
+
+    def precnode(self):
+        """Precursor changeset node identifier"""
+        return self._data[0]
+
+    def succnodes(self):
+        """List of successor changesets node identifiers"""
+        return self._data[1]
+
+    def metadata(self):
+        """Decoded metadata dictionary"""
+        if self._decodedmeta is None:
+            self._decodedmeta = decodemeta(self._data[3])
+        return self._decodedmeta
+
+    def date(self):
+        """Creation date as (unixtime, offset)"""
+        parts = self.metadata()['date'].split(' ')
+        return (float(parts[0]), int(parts[1]))
+
 class obsstore(object):
     """Store obsolete markers
 
     Markers can be accessed with two mappings:
     - precursors: old -> set(new)
     - successors: new -> set(old)
     """
 
     def __init__(self):
         self._all = []
         # new markers to serialize
         self._new = []
         self.precursors = {}
         self.successors = {}
 
     def create(self, prec, succs=(), flag=0, metadata=None):
         """obsolete: add a new obsolete marker
 
         * ensuring it is hashable
         * check mandatory metadata
         * encode metadata
         """
         if metadata is None:
             metadata = {}
         if len(prec) != 20:
             raise ValueError(prec)
         for succ in succs:
             if len(succ) != 20:
                 raise ValueError(prec)
         marker = (str(prec), tuple(succs), int(flag), encodemeta(metadata))
         self.add(marker)
 
     def add(self, marker):
         """Add a new marker to the store
 
         This marker still needs to be written to disk"""
         self._new.append(marker)
         self._load(marker)
 
     def loadmarkers(self, data):
         """Load all markers in data, mark them as known."""
         for marker in _readmarkers(data):
             self._load(marker)
 
     def flushmarkers(self, stream):
         """Write all markers to a stream
 
         After this operation, "new" markers are considered "known"."""
         self._writemarkers(stream)
         self._new[:] = []
 
     def _load(self, marker):
         self._all.append(marker)
         pre, sucs = marker[:2]
         self.precursors.setdefault(pre, set()).add(marker)
         for suc in sucs:
             self.successors.setdefault(suc, set()).add(marker)
 
     def _writemarkers(self, stream):
         # Kept separate from flushmarkers(), it will be reused for
         # markers exchange.
         stream.write(_pack('>B', _fmversion))
         for marker in self._all:
             pre, sucs, flags, metadata = marker
             nbsuc = len(sucs)
             format = _fmfixed + (_fmnode * nbsuc)
             data = [nbsuc, len(metadata), flags, pre]
             data.extend(sucs)
             stream.write(_pack(format, *data))
             stream.write(metadata)