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
# blackbox.py - log repository events to a file for post-mortem debugging
#
# Copyright 2010 Nicolas Dumazet
# Copyright 2013 Facebook, Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
"""log repository events to a blackbox for debugging
Logs event information to .hg/blackbox.log to help debug and diagnose problems.
The events that get logged can be configured via the blackbox.track config key.
Examples::
[blackbox]
track = *
# dirty is *EXPENSIVE* (slow);
# each log entry indicates `+` if the repository is dirty, like :hg:`id`.
dirty = True
# record the source of log messages
logsource = True
[blackbox]
track = command, commandfinish, commandexception, exthook, pythonhook
[blackbox]
track = incoming
[blackbox]
# limit the size of a log file
maxsize = 1.5 MB
# rotate up to N log files when the current one gets too big
maxfiles = 3
"""
from __future__ import absolute_import
import errno
import re
from mercurial.i18n import _
from mercurial.node import hex
from mercurial import (
encoding,
pycompat,
registrar,
ui as uimod,
util,
)
from mercurial.utils import (
dateutil,
procutil,
)
# Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
# extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
# be specifying the version(s) of Mercurial they are tested with, or
# leave the attribute unspecified.
testedwith = 'ships-with-hg-core'
cmdtable = {}
command = registrar.command(cmdtable)
configtable = {}
configitem = registrar.configitem(configtable)
configitem('blackbox', 'dirty',
default=False,
)
configitem('blackbox', 'maxsize',
default='1 MB',
)
configitem('blackbox', 'logsource',
default=False,
)
configitem('blackbox', 'maxfiles',
default=7,
)
configitem('blackbox', 'track',
default=lambda: ['*'],
)
lastui = None
def _openlogfile(ui, vfs):
def rotate(oldpath, newpath):
try:
vfs.unlink(newpath)
except OSError as err:
if err.errno != errno.ENOENT:
ui.debug("warning: cannot remove '%s': %s\n" %
(newpath, err.strerror))
try:
if newpath:
vfs.rename(oldpath, newpath)
except OSError as err:
if err.errno != errno.ENOENT:
ui.debug("warning: cannot rename '%s' to '%s': %s\n" %
(newpath, oldpath, err.strerror))
maxsize = ui.configbytes('blackbox', 'maxsize')
name = 'blackbox.log'
if maxsize > 0:
try:
st = vfs.stat(name)
except OSError:
pass
else:
if st.st_size >= maxsize:
path = vfs.join(name)
maxfiles = ui.configint('blackbox', 'maxfiles')
for i in pycompat.xrange(maxfiles - 1, 1, -1):
rotate(oldpath='%s.%d' % (path, i - 1),
newpath='%s.%d' % (path, i))
rotate(oldpath=path,
newpath=maxfiles > 0 and path + '.1')
return vfs(name, 'a')
def wrapui(ui):
class blackboxui(ui.__class__):
@property
def _bbvfs(self):
vfs = None
repo = getattr(self, '_bbrepo', None)
if repo:
vfs = repo.vfs
if not vfs.isdir('.'):
vfs = None
return vfs
@util.propertycache
def track(self):
return self.configlist('blackbox', 'track')
def debug(self, *msg, **opts):
super(blackboxui, self).debug(*msg, **opts)
if self.debugflag:
self.log('debug', '%s', ''.join(msg))
def log(self, event, *msg, **opts):
global lastui
super(blackboxui, self).log(event, *msg, **opts)
if not '*' in self.track and not event in self.track:
return
if self._bbvfs:
ui = self
else:
# certain ui instances exist outside the context of
# a repo, so just default to the last blackbox that
# was seen.
ui = lastui
if not ui:
return
vfs = ui._bbvfs
if not vfs:
return
repo = getattr(ui, '_bbrepo', None)
if not lastui or repo:
lastui = ui
if getattr(ui, '_bbinlog', False):
# recursion and failure guard
return
ui._bbinlog = True
default = self.configdate('devel', 'default-date')
date = dateutil.datestr(default, '%Y/%m/%d %H:%M:%S')
user = procutil.getuser()
pid = '%d' % procutil.getpid()
formattedmsg = msg[0] % msg[1:]
rev = '(unknown)'
changed = ''
if repo:
ctx = repo[None]
parents = ctx.parents()
rev = ('+'.join([hex(p.node()) for p in parents]))
if (ui.configbool('blackbox', 'dirty') and
ctx.dirty(missing=True, merge=False, branch=False)):
changed = '+'
if ui.configbool('blackbox', 'logsource'):
src = ' [%s]' % event
else:
src = ''
try:
fmt = '%s %s @%s%s (%s)%s> %s'
args = (date, user, rev, changed, pid, src, formattedmsg)
with _openlogfile(ui, vfs) as fp:
fp.write(fmt % args)
except (IOError, OSError) as err:
self.debug('warning: cannot write to blackbox.log: %s\n' %
encoding.strtolocal(err.strerror))
# do not restore _bbinlog intentionally to avoid failed
# logging again
else:
ui._bbinlog = False
def setrepo(self, repo):
self._bbrepo = repo
ui.__class__ = blackboxui
uimod.ui = blackboxui
def uisetup(ui):
wrapui(ui)
def reposetup(ui, repo):
# During 'hg pull' a httppeer repo is created to represent the remote repo.
# It doesn't have a .hg directory to put a blackbox in, so we don't do
# the blackbox setup for it.
if not repo.local():
return
if util.safehasattr(ui, 'setrepo'):
ui.setrepo(repo)
# Set lastui even if ui.log is not called. This gives blackbox a
# fallback place to log.
global lastui
if lastui is None:
lastui = ui
repo._wlockfreeprefix.add('blackbox.log')
@command('^blackbox',
[('l', 'limit', 10, _('the number of events to show')),
],
_('hg blackbox [OPTION]...'))
def blackbox(ui, repo, *revs, **opts):
'''view the recent repository events
'''
if not repo.vfs.exists('blackbox.log'):
return
limit = opts.get(r'limit')
fp = repo.vfs('blackbox.log', 'r')
lines = fp.read().split('\n')
count = 0
output = []
for line in reversed(lines):
if count >= limit:
break
# count the commands by matching lines like: 2013/01/23 19:13:36 root>
if re.match('^\d{4}/\d{2}/\d{2} \d{2}:\d{2}:\d{2} .*> .*', line):
count += 1
output.append(line)
ui.status('\n'.join(reversed(output)))