cborutil: implement sans I/O decoder
The vendored CBOR package decodes by calling read(n) on an object.
There are a number of disadvantages to this:
* Uses blocking I/O. If sufficient data is not available, the decoder
will hang until it is.
* No support for partial reads. If the read(n) returns less data than
requested, the decoder raises an error.
* Requires the use of a file like object. If the original data is in
say a buffer, we need to "cast" it to e.g. a BytesIO to appease the
decoder.
In addition, the vendored CBOR decoder doesn't provide flexibility
that we desire. Specifically:
* It buffers indefinite length bytestrings instead of streaming them.
* It doesn't allow limiting the set of types that can be decoded. This
property is useful when implementing a "hardened" decoder that is
less susceptible to abusive input.
* It doesn't provide sufficient "hook points" and introspection to
institute checks around behavior. These are useful for implementing
a "hardened" decoder.
This all adds up to a reasonable set of justifications for writing our
own decoder.
So, this commit implements our own CBOR decoder.
At the heart of the decoder is a function that decodes a single "item"
from a buffer. This item can be a complete simple value or a special
value, such as "start of array." Using this function, we can build a
decoder that effectively iterates over the stream of decoded items and
builds up higher-level values, such as arrays, maps, sets, and indefinite
length bytestrings. And we can do this without performing I/O in the
decoder itself.
The core of the sans I/O decoder will probably not be used directly.
Instead, it is expected that we'll build utility functions for invoking
the decoder given specific input types. This will allow extreme
flexibility in how data is delivered to the decoder.
I'm pretty happy with the state of the decoder modulo the TODO items
to track wanted features to help with a "hardened" decoder. The one
thing I could be convinced to change is the handling of semantic tags.
Since we only support a single semantic tag (sets), I thought it would
be easier to handle them inline in decodeitem(). This is simpler now.
But if we add support for other semantic tags, it will likely be easier
to move semantic tag handling outside of decodeitem(). But, properly
supporting semantic tags opens up a whole can of worms, as many
semantic tags imply new types. I'm optimistic we won't need these in
Mercurial. But who knows.
I'm also pretty happy with the test coverage. Writing comprehensive
tests for partial decoding did flush out a handful of bugs. One
general improvement to testing would be fuzz testing for partial
decoding. I may implement that later. I also anticipate switching the
wire protocol code to this new decoder will flush out any lingering
bugs.
Differential Revision: https://phab.mercurial-scm.org/D4414
# destutil.py - Mercurial utility function for command destination
#
# Copyright Matt Mackall <mpm@selenic.com> and other
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from __future__ import absolute_import
from .i18n import _
from . import (
bookmarks,
error,
obsutil,
scmutil,
stack
)
def orphanpossibledestination(repo, rev):
"""Return all changesets that may be a new parent for orphan `rev`.
This function works fine on non-orphan revisions, it's just silly
because there's no destination implied by obsolete markers, so
it'll return nothing.
"""
tonode = repo.changelog.node
parents = repo.changelog.parentrevs
torev = repo.changelog.rev
dest = set()
tovisit = list(parents(rev))
while tovisit:
r = tovisit.pop()
succsets = obsutil.successorssets(repo, tonode(r))
if not succsets:
# if there are no successors for r, r was probably pruned
# and we should walk up to r's parents to try and find
# some successors.
tovisit.extend(parents(r))
else:
# We should probably pick only one destination from split
# (case where '1 < len(ss)'), This could be the currently
# tipmost, but the correct result is less clear when
# results of the split have been moved such that they
# reside on multiple branches.
for ss in succsets:
for n in ss:
dr = torev(n)
if dr != -1:
dest.add(dr)
return dest
def _destupdateobs(repo, clean):
"""decide of an update destination from obsolescence markers"""
node = None
wc = repo[None]
p1 = wc.p1()
movemark = None
if p1.obsolete() and not p1.children():
# allow updating to successors
successors = obsutil.successorssets(repo, p1.node())
# behavior of certain cases is as follows,
#
# divergent changesets: update to highest rev, similar to what
# is currently done when there are more than one head
# (i.e. 'tip')
#
# replaced changesets: same as divergent except we know there
# is no conflict
#
# pruned changeset: no update is done; though, we could
# consider updating to the first non-obsolete parent,
# similar to what is current done for 'hg prune'
if successors:
# flatten the list here handles both divergent (len > 1)
# and the usual case (len = 1)
successors = [n for sub in successors for n in sub]
# get the max revision for the given successors set,
# i.e. the 'tip' of a set
node = repo.revs('max(%ln)', successors).first()
if bookmarks.isactivewdirparent(repo):
movemark = repo['.'].node()
return node, movemark, None
def _destupdatebook(repo, clean):
"""decide on an update destination from active bookmark"""
# we also move the active bookmark, if any
node = None
activemark, movemark = bookmarks.calculateupdate(repo.ui, repo)
if activemark is not None:
node = repo._bookmarks[activemark]
return node, movemark, activemark
def _destupdatebranch(repo, clean):
"""decide on an update destination from current branch
This ignores closed branch heads.
"""
wc = repo[None]
movemark = node = None
currentbranch = wc.branch()
if clean:
currentbranch = repo['.'].branch()
if currentbranch in repo.branchmap():
heads = repo.branchheads(currentbranch)
if heads:
node = repo.revs('max(.::(%ln))', heads).first()
if bookmarks.isactivewdirparent(repo):
movemark = repo['.'].node()
elif currentbranch == 'default' and not wc.p1():
# "null" parent belongs to "default" branch, but it doesn't exist, so
# update to the tipmost non-closed branch head
node = repo.revs('max(head() and not closed())').first()
else:
node = repo['.'].node()
return node, movemark, None
def _destupdatebranchfallback(repo, clean):
"""decide on an update destination from closed heads in current branch"""
wc = repo[None]
currentbranch = wc.branch()
movemark = None
if currentbranch in repo.branchmap():
# here, all descendant branch heads are closed
heads = repo.branchheads(currentbranch, closed=True)
assert heads, "any branch has at least one head"
node = repo.revs('max(.::(%ln))', heads).first()
assert node is not None, ("any revision has at least "
"one descendant branch head")
if bookmarks.isactivewdirparent(repo):
movemark = repo['.'].node()
else:
# here, no "default" branch, and all branches are closed
node = repo.lookup('tip')
assert node is not None, "'tip' exists even in empty repository"
return node, movemark, None
# order in which each step should be evaluated
# steps are run until one finds a destination
destupdatesteps = ['evolution', 'bookmark', 'branch', 'branchfallback']
# mapping to ease extension overriding steps.
destupdatestepmap = {'evolution': _destupdateobs,
'bookmark': _destupdatebook,
'branch': _destupdatebranch,
'branchfallback': _destupdatebranchfallback,
}
def destupdate(repo, clean=False):
"""destination for bare update operation
return (rev, movemark, activemark)
- rev: the revision to update to,
- movemark: node to move the active bookmark from
(cf bookmark.calculate update),
- activemark: a bookmark to activate at the end of the update.
"""
node = movemark = activemark = None
for step in destupdatesteps:
node, movemark, activemark = destupdatestepmap[step](repo, clean)
if node is not None:
break
rev = repo[node].rev()
return rev, movemark, activemark
msgdestmerge = {
# too many matching divergent bookmark
'toomanybookmarks':
{'merge':
(_("multiple matching bookmarks to merge -"
" please merge with an explicit rev or bookmark"),
_("run 'hg heads' to see all heads")),
'rebase':
(_("multiple matching bookmarks to rebase -"
" please rebase to an explicit rev or bookmark"),
_("run 'hg heads' to see all heads")),
},
# no other matching divergent bookmark
'nootherbookmarks':
{'merge':
(_("no matching bookmark to merge - "
"please merge with an explicit rev or bookmark"),
_("run 'hg heads' to see all heads")),
'rebase':
(_("no matching bookmark to rebase - "
"please rebase to an explicit rev or bookmark"),
_("run 'hg heads' to see all heads")),
},
# branch have too many unbookmarked heads, no obvious destination
'toomanyheads':
{'merge':
(_("branch '%s' has %d heads - please merge with an explicit rev"),
_("run 'hg heads .' to see heads")),
'rebase':
(_("branch '%s' has %d heads - please rebase to an explicit rev"),
_("run 'hg heads .' to see heads")),
},
# branch have no other unbookmarked heads
'bookmarkedheads':
{'merge':
(_("heads are bookmarked - please merge with an explicit rev"),
_("run 'hg heads' to see all heads")),
'rebase':
(_("heads are bookmarked - please rebase to an explicit rev"),
_("run 'hg heads' to see all heads")),
},
# branch have just a single heads, but there is other branches
'nootherbranchheads':
{'merge':
(_("branch '%s' has one head - please merge with an explicit rev"),
_("run 'hg heads' to see all heads")),
'rebase':
(_("branch '%s' has one head - please rebase to an explicit rev"),
_("run 'hg heads' to see all heads")),
},
# repository have a single head
'nootherheads':
{'merge':
(_('nothing to merge'),
None),
'rebase':
(_('nothing to rebase'),
None),
},
# repository have a single head and we are not on it
'nootherheadsbehind':
{'merge':
(_('nothing to merge'),
_("use 'hg update' instead")),
'rebase':
(_('nothing to rebase'),
_("use 'hg update' instead")),
},
# We are not on a head
'notatheads':
{'merge':
(_('working directory not at a head revision'),
_("use 'hg update' or merge with an explicit revision")),
'rebase':
(_('working directory not at a head revision'),
_("use 'hg update' or rebase to an explicit revision"))
},
'emptysourceset':
{'merge':
(_('source set is empty'),
None),
'rebase':
(_('source set is empty'),
None),
},
'multiplebranchessourceset':
{'merge':
(_('source set is rooted in multiple branches'),
None),
'rebase':
(_('rebaseset is rooted in multiple named branches'),
_('specify an explicit destination with --dest')),
},
}
def _destmergebook(repo, action='merge', sourceset=None, destspace=None):
"""find merge destination in the active bookmark case"""
node = None
bmheads = bookmarks.headsforactive(repo)
curhead = repo._bookmarks[repo._activebookmark]
if len(bmheads) == 2:
if curhead == bmheads[0]:
node = bmheads[1]
else:
node = bmheads[0]
elif len(bmheads) > 2:
msg, hint = msgdestmerge['toomanybookmarks'][action]
raise error.ManyMergeDestAbort(msg, hint=hint)
elif len(bmheads) <= 1:
msg, hint = msgdestmerge['nootherbookmarks'][action]
raise error.NoMergeDestAbort(msg, hint=hint)
assert node is not None
return node
def _destmergebranch(repo, action='merge', sourceset=None, onheadcheck=True,
destspace=None):
"""find merge destination based on branch heads"""
node = None
if sourceset is None:
sourceset = [repo[repo.dirstate.p1()].rev()]
branch = repo.dirstate.branch()
elif not sourceset:
msg, hint = msgdestmerge['emptysourceset'][action]
raise error.NoMergeDestAbort(msg, hint=hint)
else:
branch = None
for ctx in repo.set('roots(%ld::%ld)', sourceset, sourceset):
if branch is not None and ctx.branch() != branch:
msg, hint = msgdestmerge['multiplebranchessourceset'][action]
raise error.ManyMergeDestAbort(msg, hint=hint)
branch = ctx.branch()
bheads = repo.branchheads(branch)
onhead = repo.revs('%ld and %ln', sourceset, bheads)
if onheadcheck and not onhead:
# Case A: working copy if not on a head. (merge only)
#
# This is probably a user mistake We bailout pointing at 'hg update'
if len(repo.heads()) <= 1:
msg, hint = msgdestmerge['nootherheadsbehind'][action]
else:
msg, hint = msgdestmerge['notatheads'][action]
raise error.Abort(msg, hint=hint)
# remove heads descendants of source from the set
bheads = list(repo.revs('%ln - (%ld::)', bheads, sourceset))
# filters out bookmarked heads
nbhs = list(repo.revs('%ld - bookmark()', bheads))
if destspace is not None:
# restrict search space
# used in the 'hg pull --rebase' case, see issue 5214.
nbhs = list(repo.revs('%ld and %ld', destspace, nbhs))
if len(nbhs) > 1:
# Case B: There is more than 1 other anonymous heads
#
# This means that there will be more than 1 candidate. This is
# ambiguous. We abort asking the user to pick as explicit destination
# instead.
msg, hint = msgdestmerge['toomanyheads'][action]
msg %= (branch, len(bheads) + 1)
raise error.ManyMergeDestAbort(msg, hint=hint)
elif not nbhs:
# Case B: There is no other anonymous heads
#
# This means that there is no natural candidate to merge with.
# We abort, with various messages for various cases.
if bheads:
msg, hint = msgdestmerge['bookmarkedheads'][action]
elif len(repo.heads()) > 1:
msg, hint = msgdestmerge['nootherbranchheads'][action]
msg %= branch
elif not onhead:
# if 'onheadcheck == False' (rebase case),
# this was not caught in Case A.
msg, hint = msgdestmerge['nootherheadsbehind'][action]
else:
msg, hint = msgdestmerge['nootherheads'][action]
raise error.NoMergeDestAbort(msg, hint=hint)
else:
node = nbhs[0]
assert node is not None
return node
def destmerge(repo, action='merge', sourceset=None, onheadcheck=True,
destspace=None):
"""return the default destination for a merge
(or raise exception about why it can't pick one)
:action: the action being performed, controls emitted error message
"""
# destspace is here to work around issues with `hg pull --rebase` see
# issue5214 for details
if repo._activebookmark:
node = _destmergebook(repo, action=action, sourceset=sourceset,
destspace=destspace)
else:
node = _destmergebranch(repo, action=action, sourceset=sourceset,
onheadcheck=onheadcheck, destspace=destspace)
return repo[node].rev()
def desthistedit(ui, repo):
"""Default base revision to edit for `hg histedit`."""
default = ui.config('histedit', 'defaultrev')
if default is None:
revs = stack.getstack(repo)
elif default:
revs = scmutil.revrange(repo, [default])
if revs:
# Take the first revision of the revset as the root
return revs.min()
return None
def stackbase(ui, repo):
revs = stack.getstack(repo)
return revs.first() if revs else None
def _statusotherbook(ui, repo):
bmheads = bookmarks.headsforactive(repo)
curhead = repo._bookmarks[repo._activebookmark]
if repo.revs('%n and parents()', curhead):
# we are on the active bookmark
bmheads = [b for b in bmheads if curhead != b]
if bmheads:
msg = _('%i other divergent bookmarks for "%s"\n')
ui.status(msg % (len(bmheads), repo._activebookmark))
def _statusotherbranchheads(ui, repo):
currentbranch = repo.dirstate.branch()
allheads = repo.branchheads(currentbranch, closed=True)
heads = repo.branchheads(currentbranch)
if repo.revs('%ln and parents()', allheads):
# we are on a head, even though it might be closed
#
# on closed otherheads
# ========= ==========
# o 0 all heads for current branch are closed
# N only descendant branch heads are closed
# x 0 there is only one non-closed branch head
# N there are some non-closed branch heads
# ========= ==========
otherheads = repo.revs('%ln - parents()', heads)
if repo['.'].closesbranch():
ui.warn(_('no open descendant heads on branch "%s", '
'updating to a closed head\n') %
(currentbranch))
if otherheads:
ui.warn(_("(committing will reopen the head, "
"use 'hg heads .' to see %i other heads)\n") %
(len(otherheads)))
else:
ui.warn(_('(committing will reopen branch "%s")\n') %
(currentbranch))
elif otherheads:
curhead = repo['.']
ui.status(_('updated to "%s: %s"\n') % (curhead,
curhead.description().split('\n')[0]))
ui.status(_('%i other heads for branch "%s"\n') %
(len(otherheads), currentbranch))
def statusotherdests(ui, repo):
"""Print message about other head"""
# XXX we should probably include a hint:
# - about what to do
# - how to see such heads
if repo._activebookmark:
_statusotherbook(ui, repo)
else:
_statusotherbranchheads(ui, repo)