comparison mercurial/ancestor.py @ 23334:59e6e5dd3605

ancestor.missingancestors: turn into a state-keeping class

This allows multiple efficient missing ancestor queries against the same set of
bases. In upcoming patches we'll also define ways to grow the set of bases.

The fact that the test output hasn't changed establishes this patch's
correctness.

23333:9a2489015592

    if len(gca) <= 1:
        return gca
    return deepest(gca)

def missingancestors(revs, bases, pfunc):
    """Return all the ancestors of revs that are not ancestors of bases.

    This may include elements from revs.

    Equivalent to the revset (::revs - ::bases). Revs are returned in
    revision number order, which is a topological order.

    revs and bases should both be iterables. pfunc must return a list of
    parent revs for a given revs.
    """

    revsvisit = set(revs)
    basesvisit = set(bases)
    if not basesvisit:
        basesvisit.add(nullrev)
    bothvisit = revsvisit.intersection(basesvisit)
    revsvisit.difference_update(bothvisit)
    if not revsvisit:
        return []
    start = max(max(revsvisit), max(basesvisit))
    # At this point, we hold the invariants that:
    # - revsvisit is the set of nodes we know are an ancestor of at least one
    #   of the nodes in revs
    # - basesvisit is the same for bases
    # - bothvisit is the set of nodes we know are ancestors of at least one of
    #   the nodes in revs and one of the nodes in bases, and that are smaller
    #   than curr. bothvisit and revsvisit are mutually exclusive, but bothvisit
    #   is a subset of basesvisit.
    # Now we walk down in reverse topo order, adding parents of nodes already
    # visited to the sets while maintaining the invariants. When a node is found
    # in both revsvisit and basesvisit, it is removed from revsvisit and added
    # to bothvisit. When revsvisit becomes empty, there are no more ancestors of
    # revs that aren't also ancestors of bases, so exit.

    missing = []
    for curr in xrange(start, nullrev, -1):
        if not revsvisit:
            break

        if curr in bothvisit:
            bothvisit.remove(curr)
            # curr's parents might have made it into revsvisit through another
            # path
            for p in pfunc(curr):
                revsvisit.discard(p)
                basesvisit.add(p)
                bothvisit.add(p)
            continue

        if curr in revsvisit:
            missing.append(curr)
            revsvisit.remove(curr)
            thisvisit = revsvisit
            othervisit = basesvisit
        elif curr in basesvisit:
            thisvisit = basesvisit
            othervisit = revsvisit
        else:
            # not an ancestor of revs or bases: ignore
            continue

        for p in pfunc(curr):
            if p == nullrev:
                pass
            elif p in othervisit or p in bothvisit:
                # p is implicitly in thisvisit. This means p is or should be
                # in bothvisit
                revsvisit.discard(p)
                basesvisit.add(p)
                bothvisit.add(p)
            else:
                # visit later
                thisvisit.add(p)

    missing.reverse()
    return missing

class lazyancestors(object):
    def __init__(self, pfunc, revs, stoprev=0, inclusive=False):
        """Create a new object generating ancestors for the given revs. Does
        not generate revs lower than stoprev.

23334:59e6e5dd3605

    if len(gca) <= 1:
        return gca
    return deepest(gca)

class incrementalmissingancestors(object):
    '''persistent state used to calculate missing ancestors incrementally

    Although similar in spirit to lazyancestors below, this is a separate class
    because trying to support contains and missingancestors operations with the
    same internal data structures adds needless complexity.'''
    def __init__(self, pfunc, bases):
        self.bases = set(bases)
        if not self.bases:
            self.bases.add(nullrev)
        self.pfunc = pfunc

    def missingancestors(self, revs):
        '''return all the ancestors of revs that are not ancestors of self.bases

        This may include elements from revs.

        Equivalent to the revset (::revs - ::self.bases). Revs are returned in
        revision number order, which is a topological order.'''
        revsvisit = set(revs)
        basesvisit = self.bases
        pfunc = self.pfunc
        bothvisit = revsvisit.intersection(basesvisit)
        revsvisit.difference_update(bothvisit)
        if not revsvisit:
            return []

        start = max(max(revsvisit), max(basesvisit))
        # At this point, we hold the invariants that:
        # - revsvisit is the set of nodes we know are an ancestor of at least
        #   one of the nodes in revs
        # - basesvisit is the same for bases
        # - bothvisit is the set of nodes we know are ancestors of at least one
        #   of the nodes in revs and one of the nodes in bases. bothvisit and
        #   revsvisit are mutually exclusive, but bothvisit is a subset of
        #   basesvisit.
        # Now we walk down in reverse topo order, adding parents of nodes
        # already visited to the sets while maintaining the invariants. When a
        # node is found in both revsvisit and basesvisit, it is removed from
        # revsvisit and added to bothvisit. When revsvisit becomes empty, there
        # are no more ancestors of revs that aren't also ancestors of bases, so
        # exit.

        missing = []
        for curr in xrange(start, nullrev, -1):
            if not revsvisit:
                break

            if curr in bothvisit:
                bothvisit.remove(curr)
                # curr's parents might have made it into revsvisit through
                # another path
                for p in pfunc(curr):
                    revsvisit.discard(p)
                    basesvisit.add(p)
                    bothvisit.add(p)
                continue

            if curr in revsvisit:
                missing.append(curr)
                revsvisit.remove(curr)
                thisvisit = revsvisit
                othervisit = basesvisit
            elif curr in basesvisit:
                thisvisit = basesvisit
                othervisit = revsvisit
            else:
                # not an ancestor of revs or bases: ignore
                continue

            for p in pfunc(curr):
                if p == nullrev:
                    pass
                elif p in othervisit or p in bothvisit:
                    # p is implicitly in thisvisit. This means p is or should be
                    # in bothvisit
                    revsvisit.discard(p)
                    basesvisit.add(p)
                    bothvisit.add(p)
                else:
                    # visit later
                    thisvisit.add(p)

        missing.reverse()
        return missing

def missingancestors(revs, bases, pfunc):
    inc = incrementalmissingancestors(pfunc, bases)
    return inc.missingancestors(revs)

class lazyancestors(object):
    def __init__(self, pfunc, revs, stoprev=0, inclusive=False):
        """Create a new object generating ancestors for the given revs. Does
        not generate revs lower than stoprev.