text: # branchmap.py - logic to computes, maintain and stores branchmap for local repo
  #
  # Copyright 2005-2007 Matt Mackall <mpm@selenic.com>
  #
  # This software may be used and distributed according to the terms of the
  # GNU General Public License version 2 or any later version.
  
  from node import bin, hex, nullid, nullrev
  import encoding
  import util, repoview
  
  def _filename(repo):
      """name of a branchcache file for a given repo or repoview"""
      filename = "cache/branchheads"
      if repo.filtername:
          filename = '%s-%s' % (filename, repo.filtername)
      return filename
  
  def read(repo):
      try:
          f = repo.opener(_filename(repo))
          lines = f.read().split('\n')
          f.close()
      except (IOError, OSError):
          return None
  
      try:
          cachekey = lines.pop(0).split(" ", 2)
          last, lrev = cachekey[:2]
          last, lrev = bin(last), int(lrev)
          filteredhash = None
          if len(cachekey) > 2:
              filteredhash = bin(cachekey[2])
          partial = branchcache(tipnode=last, tiprev=lrev,
                                filteredhash=filteredhash)
          if not partial.validfor(repo):
              # invalidate the cache
              raise ValueError('tip differs')
          for l in lines:
              if not l:
                  continue
              node, label = l.split(" ", 1)
              label = encoding.tolocal(label.strip())
              if not node in repo:
                  raise ValueError('node %s does not exist' % node)
              partial.setdefault(label, []).append(bin(node))
      except KeyboardInterrupt:
          raise
      except Exception, inst:
          if repo.ui.debugflag:
              msg = 'invalid branchheads cache'
              if repo.filtername is not None:
                  msg += ' (%s)' % repo.filtername
              msg += ': %s\n'
              repo.ui.warn(msg % inst)
          partial = None
      return partial
  
  
  
  def updatecache(repo):
      cl = repo.changelog
      filtername = repo.filtername
      partial = repo._branchcaches.get(filtername)
  
      revs = []
      if partial is None or not partial.validfor(repo):
          partial = read(repo)
          if partial is None:
              subsetname = repoview.subsettable.get(filtername)
              if subsetname is None:
                  partial = branchcache()
              else:
                  subset = repo.filtered(subsetname)
                  partial = subset.branchmap().copy()
                  extrarevs = subset.changelog.filteredrevs - cl.filteredrevs
                  revs.extend(r for  r in extrarevs if r <= partial.tiprev)
      revs.extend(cl.revs(start=partial.tiprev + 1))
      if revs:
          partial.update(repo, revs)
          partial.write(repo)
      assert partial.validfor(repo), filtername
      repo._branchcaches[repo.filtername] = partial
  
  class branchcache(dict):
      """A dict like object that hold branches heads cache"""
  
      def __init__(self, entries=(), tipnode=nullid, tiprev=nullrev,
                   filteredhash=None):
          super(branchcache, self).__init__(entries)
          self.tipnode = tipnode
          self.tiprev = tiprev
          self.filteredhash = filteredhash
  
      def _hashfiltered(self, repo):
          """build hash of revision filtered in the current cache
  
          Tracking tipnode and tiprev is not enough to ensure validity of the
          cache as they do not help to distinct cache that ignored various
          revision bellow tiprev.
  
          To detect such difference, we build a cache of all ignored revisions.
          """
          cl = repo.changelog
          if not cl.filteredrevs:
              return None
          key = None
          revs = sorted(r for r in cl.filteredrevs if r <= self.tiprev)
          if revs:
              s = util.sha1()
              for rev in revs:
                  s.update('%s;' % rev)
              key = s.digest()
          return key
  
      def validfor(self, repo):
          """Is the cache content valid regarding a repo
  
          - False when cached tipnode is unknown or if we detect a strip.
          - True when cache is up to date or a subset of current repo."""
          try:
              return ((self.tipnode == repo.changelog.node(self.tiprev))
                      and (self.filteredhash == self._hashfiltered(repo)))
          except IndexError:
              return False
  
      def copy(self):
          """return an deep copy of the branchcache object"""
          return branchcache(self, self.tipnode, self.tiprev, self.filteredhash)
  
      def write(self, repo):
          try:
              f = repo.opener(_filename(repo), "w", atomictemp=True)
              cachekey = [hex(self.tipnode), str(self.tiprev)]
              if self.filteredhash is not None:
                  cachekey.append(hex(self.filteredhash))
              f.write(" ".join(cachekey) + '\n')
              for label, nodes in sorted(self.iteritems()):
                  for node in nodes:
                      f.write("%s %s\n" % (hex(node), encoding.fromlocal(label)))
              f.close()
          except (IOError, OSError, util.Abort):
              # Abort may be raise by read only opener
              pass
  
      def update(self, repo, revgen):
          """Given a branchhead cache, self, that may have extra nodes or be
          missing heads, and a generator of nodes that are at least a superset of
          heads missing, this function updates self to be correct.
          """
          cl = repo.changelog
          # collect new branch entries
          newbranches = {}
          getbranch = cl.branch
          for r in revgen:
              newbranches.setdefault(getbranch(r), []).append(cl.node(r))
          # if older branchheads are reachable from new ones, they aren't
          # really branchheads. Note checking parents is insufficient:
          # 1 (branch a) -> 2 (branch b) -> 3 (branch a)
          for branch, newnodes in newbranches.iteritems():
              bheads = self.setdefault(branch, [])
              # Remove candidate heads that no longer are in the repo (e.g., as
              # the result of a strip that just happened).  Avoid using 'node in
              # self' here because that dives down into branchcache code somewhat
              # recursively.
              bheadrevs = [cl.rev(node) for node in bheads
                           if cl.hasnode(node)]
              newheadrevs = [cl.rev(node) for node in newnodes
                             if cl.hasnode(node)]
              ctxisnew = bheadrevs and min(newheadrevs) > max(bheadrevs)
              # Remove duplicates - nodes that are in newheadrevs and are already
              # in bheadrevs.  This can happen if you strip a node whose parent
              # was already a head (because they're on different branches).
              bheadrevs = sorted(set(bheadrevs).union(newheadrevs))
  
              # Starting from tip means fewer passes over reachable.  If we know
              # the new candidates are not ancestors of existing heads, we don't
              # have to examine ancestors of existing heads
              if ctxisnew:
                  iterrevs = sorted(newheadrevs)
              else:
                  iterrevs = list(bheadrevs)
  
              # This loop prunes out two kinds of heads - heads that are
              # superseded by a head in newheadrevs, and newheadrevs that are not
              # heads because an existing head is their descendant.
              while iterrevs:
                  latest = iterrevs.pop()
                  if latest not in bheadrevs:
                      continue
                  ancestors = set(cl.ancestors([latest],
                                                           bheadrevs[0]))
                  if ancestors:
                      bheadrevs = [b for b in bheadrevs if b not in ancestors]
              self[branch] = [cl.node(rev) for rev in bheadrevs]
              tiprev = max(bheadrevs)
              if tiprev > self.tiprev:
                  self.tipnode = cl.node(tiprev)
                  self.tiprev = tiprev
  
          # There may be branches that cease to exist when the last commit in the
          # branch was stripped.  This code filters them out.  Note that the
          # branch that ceased to exist may not be in newbranches because
          # newbranches is the set of candidate heads, which when you strip the
          # last commit in a branch will be the parent branch.
          droppednodes = []
          for branch in self.keys():
              nodes = [head for head in self[branch]
                       if cl.hasnode(head)]
              if not nodes:
                  droppednodes.extend(nodes)
                  del self[branch]
          if ((not self.validfor(repo)) or (self.tipnode in droppednodes)):
  
              # cache key are not valid anymore
              self.tipnode = nullid
              self.tiprev = nullrev
              for heads in self.values():
                  tiprev = max(cl.rev(node) for node in heads)
                  if tiprev > self.tiprev:
                      self.tipnode = cl.node(tiprev)
                      self.tiprev = tiprev
          self.filteredhash = self._hashfiltered(repo)
  