mercurial/branchmap.py

branchmap: store branchcache in a dedicated object

Value and key of branchcache would benefit from being hold by the same object.
Moreover some logic (update, write, validation) could be move on such object.

The creation of this object is the first step toward this move. The result will
clarify branchcache related code and hide most of the detail in the class
itself. This encapsulation will greatly helps implementation of branchcache for
filtered view of the repo.

# branchmap.py - logic to computes, maintain and stores branchmap for local repo
#
# Copyright 2005-2007 Matt Mackall <[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.

from node import bin, hex, nullid, nullrev
import encoding

def read(repo):
    partial = branchcache()
    try:
        f = repo.opener("cache/branchheads")
        lines = f.read().split('\n')
        f.close()
    except (IOError, OSError):
        return branchcache(), nullid, nullrev

    try:
        last, lrev = lines.pop(0).split(" ", 1)
        last, lrev = bin(last), int(lrev)
        if lrev >= len(repo) or repo[lrev].node() != last:
            # invalidate the cache
            raise ValueError('invalidating branch cache (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('invalidating branch cache because node '+
                                 '%s does not exist' % node)
            partial.setdefault(label, []).append(bin(node))
    except KeyboardInterrupt:
        raise
    except Exception, inst:
        if repo.ui.debugflag:
            repo.ui.warn(str(inst), '\n')
        partial, last, lrev =  branchcache(), nullid, nullrev
    return partial, last, lrev

def write(repo, branches, tip, tiprev):
    try:
        f = repo.opener("cache/branchheads", "w", atomictemp=True)
        f.write("%s %s\n" % (hex(tip), tiprev))
        for label, nodes in branches.iteritems():
            for node in nodes:
                f.write("%s %s\n" % (hex(node), encoding.fromlocal(label)))
        f.close()
    except (IOError, OSError):
        pass

def update(repo, partial, ctxgen):
    """Given a branchhead cache, partial, 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 partial to be correct.
    """
    # collect new branch entries
    newbranches = {}
    for c in ctxgen:
        newbranches.setdefault(c.branch(), []).append(c.node())
    # 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 = partial.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 = [repo.changelog.rev(node) for node in bheads
                     if repo.changelog.hasnode(node)]
        newheadrevs = [repo.changelog.rev(node) for node in newnodes
                       if repo.changelog.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(repo.changelog.ancestors([latest],
                                                     bheadrevs[0]))
            if ancestors:
                bheadrevs = [b for b in bheadrevs if b not in ancestors]
        partial[branch] = [repo.changelog.node(rev) for rev in bheadrevs]

    # 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.
    for branch in partial.keys():
        nodes = [head for head in partial[branch]
                 if repo.changelog.hasnode(head)]
        if not nodes:
            del partial[branch]

def updatecache(repo):
    repo = repo.unfiltered()  # Until we get a smarter cache management
    cl = repo.changelog
    tip = cl.tip()
    if repo._branchcache is not None and repo._branchcachetip == tip:
        return

    oldtip = repo._branchcachetip
    if oldtip is None or oldtip not in cl.nodemap:
        partial, last, lrev = read(repo)
    else:
        lrev = cl.rev(oldtip)
        partial = repo._branchcache

    catip = repo._cacheabletip()
    # if lrev == catip: cache is already up to date
    # if lrev >  catip: we have uncachable element in `partial` can't write
    #                   on disk
    if lrev < catip:
        ctxgen = (repo[r] for r in cl.revs(lrev + 1, catip))
        update(repo, partial, ctxgen)
        write(repo, partial, cl.node(catip), catip)
        lrev = catip
    # If cacheable tip were lower than actual tip, we need to update the
    # cache up to tip. This update (from cacheable to actual tip) is not
    # written to disk since it's not cacheable.
    tiprev = len(repo) - 1
    if lrev < tiprev:
        ctxgen = (repo[r] for r in cl.revs(lrev + 1, tiprev))
        update(repo, partial, ctxgen)
    repo._branchcache = partial
    repo._branchcachetip = tip

class branchcache(dict):
    """A dict like object that hold branches heads cache"""