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# ancestor.py - generic DAG ancestor algorithm for mercurial
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#
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# Copyright 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 of the
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# GNU General Public License version 2 or any later version.
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from __future__ import absolute_import
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import collections
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import heapq
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from .node import nullrev
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def commonancestorsheads(pfunc, *nodes):
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"""Returns a set with the heads of all common ancestors of all nodes,
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heads(::nodes[0] and ::nodes[1] and ...) .
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pfunc must return a list of parent vertices for a given vertex.
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"""
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if not isinstance(nodes, set):
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nodes = set(nodes)
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if nullrev in nodes:
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return set()
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if len(nodes) <= 1:
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return nodes
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allseen = (1 << len(nodes)) - 1
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seen = [0] * (max(nodes) + 1)
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for i, n in enumerate(nodes):
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seen[n] = 1 << i
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poison = 1 << (i + 1)
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gca = set()
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interesting = len(nodes)
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nv = len(seen) - 1
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while nv >= 0 and interesting:
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v = nv
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nv -= 1
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if not seen[v]:
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continue
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sv = seen[v]
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if sv < poison:
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interesting -= 1
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if sv == allseen:
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gca.add(v)
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sv |= poison
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if v in nodes:
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# history is linear
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return {v}
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if sv < poison:
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for p in pfunc(v):
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sp = seen[p]
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if p == nullrev:
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continue
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if sp == 0:
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seen[p] = sv
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interesting += 1
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elif sp != sv:
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seen[p] |= sv
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else:
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for p in pfunc(v):
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if p == nullrev:
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continue
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sp = seen[p]
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if sp and sp < poison:
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interesting -= 1
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seen[p] = sv
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return gca
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def ancestors(pfunc, *orignodes):
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"""
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Returns the common ancestors of a and b that are furthest from a
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root (as measured by longest path).
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pfunc must return a list of parent vertices for a given vertex.
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"""
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def deepest(nodes):
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interesting = {}
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count = max(nodes) + 1
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depth = [0] * count
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seen = [0] * count
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mapping = []
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for (i, n) in enumerate(sorted(nodes)):
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depth[n] = 1
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b = 1 << i
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seen[n] = b
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interesting[b] = 1
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mapping.append((b, n))
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nv = count - 1
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while nv >= 0 and len(interesting) > 1:
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v = nv
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nv -= 1
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dv = depth[v]
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if dv == 0:
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continue
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sv = seen[v]
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for p in pfunc(v):
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if p == nullrev:
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continue
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dp = depth[p]
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nsp = sp = seen[p]
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if dp <= dv:
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depth[p] = dv + 1
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if sp != sv:
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interesting[sv] += 1
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nsp = seen[p] = sv
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if sp:
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interesting[sp] -= 1
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if interesting[sp] == 0:
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del interesting[sp]
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elif dv == dp - 1:
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nsp = sp | sv
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if nsp == sp:
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continue
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seen[p] = nsp
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interesting.setdefault(nsp, 0)
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interesting[nsp] += 1
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interesting[sp] -= 1
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if interesting[sp] == 0:
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del interesting[sp]
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interesting[sv] -= 1
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if interesting[sv] == 0:
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del interesting[sv]
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if len(interesting) != 1:
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return []
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k = 0
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for i in interesting:
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k |= i
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return set(n for (i, n) in mapping if k & i)
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gca = commonancestorsheads(pfunc, *orignodes)
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if len(gca) <= 1:
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return gca
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return deepest(gca)
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class incrementalmissingancestors(object):
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'''persistent state used to calculate missing ancestors incrementally
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Although similar in spirit to lazyancestors below, this is a separate class
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because trying to support contains and missingancestors operations with the
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same internal data structures adds needless complexity.'''
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def __init__(self, pfunc, bases):
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self.bases = set(bases)
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if not self.bases:
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self.bases.add(nullrev)
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self.pfunc = pfunc
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def hasbases(self):
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'''whether the common set has any non-trivial bases'''
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return self.bases and self.bases != {nullrev}
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def addbases(self, newbases):
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'''grow the ancestor set by adding new bases'''
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self.bases.update(newbases)
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def removeancestorsfrom(self, revs):
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'''remove all ancestors of bases from the set revs (in place)'''
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bases = self.bases
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pfunc = self.pfunc
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revs.difference_update(bases)
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# nullrev is always an ancestor
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revs.discard(nullrev)
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if not revs:
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return
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# anything in revs > start is definitely not an ancestor of bases
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# revs <= start needs to be investigated
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start = max(bases)
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keepcount = sum(1 for r in revs if r > start)
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if len(revs) == keepcount:
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# no revs to consider
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return
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for curr in xrange(start, min(revs) - 1, -1):
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if curr not in bases:
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continue
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revs.discard(curr)
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bases.update(pfunc(curr))
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if len(revs) == keepcount:
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# no more potential revs to discard
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break
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def missingancestors(self, revs):
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'''return all the ancestors of revs that are not ancestors of self.bases
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This may include elements from revs.
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Equivalent to the revset (::revs - ::self.bases). Revs are returned in
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revision number order, which is a topological order.'''
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revsvisit = set(revs)
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basesvisit = self.bases
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pfunc = self.pfunc
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bothvisit = revsvisit.intersection(basesvisit)
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revsvisit.difference_update(bothvisit)
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if not revsvisit:
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return []
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start = max(max(revsvisit), max(basesvisit))
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# At this point, we hold the invariants that:
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# - revsvisit is the set of nodes we know are an ancestor of at least
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# one of the nodes in revs
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# - basesvisit is the same for bases
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# - bothvisit is the set of nodes we know are ancestors of at least one
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# of the nodes in revs and one of the nodes in bases. bothvisit and
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# revsvisit are mutually exclusive, but bothvisit is a subset of
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# basesvisit.
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# Now we walk down in reverse topo order, adding parents of nodes
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# already visited to the sets while maintaining the invariants. When a
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# node is found in both revsvisit and basesvisit, it is removed from
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# revsvisit and added to bothvisit. When revsvisit becomes empty, there
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# are no more ancestors of revs that aren't also ancestors of bases, so
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# exit.
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missing = []
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for curr in xrange(start, nullrev, -1):
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if not revsvisit:
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break
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if curr in bothvisit:
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bothvisit.remove(curr)
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# curr's parents might have made it into revsvisit through
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# another path
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for p in pfunc(curr):
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revsvisit.discard(p)
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basesvisit.add(p)
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bothvisit.add(p)
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continue
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if curr in revsvisit:
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missing.append(curr)
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revsvisit.remove(curr)
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thisvisit = revsvisit
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othervisit = basesvisit
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elif curr in basesvisit:
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thisvisit = basesvisit
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othervisit = revsvisit
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else:
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# not an ancestor of revs or bases: ignore
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continue
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for p in pfunc(curr):
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if p == nullrev:
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pass
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elif p in othervisit or p in bothvisit:
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# p is implicitly in thisvisit. This means p is or should be
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# in bothvisit
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revsvisit.discard(p)
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basesvisit.add(p)
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bothvisit.add(p)
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else:
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# visit later
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thisvisit.add(p)
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missing.reverse()
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return missing
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class lazyancestors(object):
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def __init__(self, pfunc, revs, stoprev=0, inclusive=False):
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"""Create a new object generating ancestors for the given revs. Does
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not generate revs lower than stoprev.
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This is computed lazily starting from revs. The object supports
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iteration and membership.
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cl should be a changelog and revs should be an iterable. inclusive is
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a boolean that indicates whether revs should be included. Revs lower
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than stoprev will not be generated.
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Result does not include the null revision."""
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self._parentrevs = pfunc
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self._initrevs = revs
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self._stoprev = stoprev
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self._inclusive = inclusive
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# Initialize data structures for __contains__.
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# For __contains__, we use a heap rather than a deque because
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# (a) it minimizes the number of parentrevs calls made
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# (b) it makes the loop termination condition obvious
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# Python's heap is a min-heap. Multiply all values by -1 to convert it
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# into a max-heap.
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self._containsvisit = [-rev for rev in revs]
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heapq.heapify(self._containsvisit)
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if inclusive:
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self._containsseen = set(revs)
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else:
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self._containsseen = set()
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def __nonzero__(self):
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"""False if the set is empty, True otherwise."""
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try:
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next(iter(self))
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return True
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except StopIteration:
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return False
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__bool__ = __nonzero__
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def __iter__(self):
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"""Generate the ancestors of _initrevs in reverse topological order.
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If inclusive is False, yield a sequence of revision numbers starting
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with the parents of each revision in revs, i.e., each revision is *not*
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considered an ancestor of itself. Results are in breadth-first order:
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parents of each rev in revs, then parents of those, etc.
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If inclusive is True, yield all the revs first (ignoring stoprev),
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then yield all the ancestors of revs as when inclusive is False.
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If an element in revs is an ancestor of a different rev it is not
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yielded again."""
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seen = set()
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revs = self._initrevs
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if self._inclusive:
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for rev in revs:
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yield rev
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seen.update(revs)
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parentrevs = self._parentrevs
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stoprev = self._stoprev
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visit = collections.deque(revs)
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see = seen.add
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schedule = visit.append
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while visit:
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for parent in parentrevs(visit.popleft()):
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if parent >= stoprev and parent not in seen:
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schedule(parent)
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see(parent)
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yield parent
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def __contains__(self, target):
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"""Test whether target is an ancestor of self._initrevs."""
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# Trying to do both __iter__ and __contains__ using the same visit
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# heap and seen set is complex enough that it slows down both. Keep
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# them separate.
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seen = self._containsseen
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if target in seen:
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return True
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parentrevs = self._parentrevs
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visit = self._containsvisit
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stoprev = self._stoprev
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heappop = heapq.heappop
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heappush = heapq.heappush
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see = seen.add
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targetseen = False
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while visit and -visit[0] > target and not targetseen:
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for parent in parentrevs(-heappop(visit)):
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if parent < stoprev or parent in seen:
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continue
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# We need to make sure we push all parents into the heap so
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# that we leave it in a consistent state for future calls.
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heappush(visit, -parent)
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see(parent)
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if parent == target:
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targetseen = True
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return targetseen
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