hgext/largefiles/basestore.py

largefiles: don't allow corruption to propagate after detection

basestore.get uses util.atomictempfile when checking and receiving a new
largefile ... but the close/discard logic was too clever for largefiles.
Largefiles relied on being able to discard the file and thus prevent it from
being written to the store. That was however too brittle. lfutil.copyandhash
closes the infile after writing to it ... with a 'blecch' comment. The discard
was thus a silent noop, and as a result of that corruption would be detected
... and then the corrupted files would be used anyway.

Instead we now use a tmp file and rename or unlink it after validating it.

A better solution should be implemented ... but not now.

# Copyright 2009-2010 Gregory P. Ward
# Copyright 2009-2010 Intelerad Medical Systems Incorporated
# Copyright 2010-2011 Fog Creek Software
# Copyright 2010-2011 Unity Technologies
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

'''base class for store implementations and store-related utility code'''

import binascii
import re

from mercurial import util, node, hg
from mercurial.i18n import _

import lfutil

class StoreError(Exception):
    '''Raised when there is a problem getting files from or putting
    files to a central store.'''
    def __init__(self, filename, hash, url, detail):
        self.filename = filename
        self.hash = hash
        self.url = url
        self.detail = detail

    def longmessage(self):
        return (_("error getting id %s from url %s for file %s: %s\n") %
                 (self.hash, self.url, self.filename, self.detail))

    def __str__(self):
        return "%s: %s" % (self.url, self.detail)

class basestore(object):
    def __init__(self, ui, repo, url):
        self.ui = ui
        self.repo = repo
        self.url = url

    def put(self, source, hash):
        '''Put source file into the store under <filename>/<hash>.'''
        raise NotImplementedError('abstract method')

    def exists(self, hashes):
        '''Check to see if the store contains the given hashes.'''
        raise NotImplementedError('abstract method')

    def get(self, files):
        '''Get the specified largefiles from the store and write to local
        files under repo.root.  files is a list of (filename, hash)
        tuples.  Return (success, missing), lists of files successfully
        downloaded and those not found in the store.  success is a list
        of (filename, hash) tuples; missing is a list of filenames that
        we could not get.  (The detailed error message will already have
        been presented to the user, so missing is just supplied as a
        summary.)'''
        success = []
        missing = []
        ui = self.ui

        at = 0
        for filename, hash in files:
            ui.progress(_('getting largefiles'), at, unit='lfile',
                total=len(files))
            at += 1
            ui.note(_('getting %s:%s\n') % (filename, hash))

            storefilename = lfutil.storepath(self.repo, hash)
            tmpfile = util.atomictempfile(storefilename + '.tmp',
                                          createmode=self.repo.store.createmode)

            try:
                hhash = binascii.hexlify(self._getfile(tmpfile, filename, hash))
            except StoreError, err:
                ui.warn(err.longmessage())
                hhash = ""
            tmpfile.close() # has probably already been closed!

            if hhash != hash:
                if hhash != "":
                    ui.warn(_('%s: data corruption (expected %s, got %s)\n')
                            % (filename, hash, hhash))
                util.unlink(storefilename + '.tmp')
                missing.append(filename)
                continue

            util.rename(storefilename + '.tmp', storefilename)
            lfutil.linktousercache(self.repo, hash)
            success.append((filename, hhash))

        ui.progress(_('getting largefiles'), None)
        return (success, missing)

    def verify(self, revs, contents=False):
        '''Verify the existence (and, optionally, contents) of every big
        file revision referenced by every changeset in revs.
        Return 0 if all is well, non-zero on any errors.'''
        write = self.ui.write
        failed = False

        write(_('searching %d changesets for largefiles\n') % len(revs))
        verified = set()                # set of (filename, filenode) tuples

        for rev in revs:
            cctx = self.repo[rev]
            cset = "%d:%s" % (cctx.rev(), node.short(cctx.node()))

            failed = util.any(self._verifyfile(
                cctx, cset, contents, standin, verified) for standin in cctx)

        numrevs = len(verified)
        numlfiles = len(set([fname for (fname, fnode) in verified]))
        if contents:
            write(_('verified contents of %d revisions of %d largefiles\n')
                  % (numrevs, numlfiles))
        else:
            write(_('verified existence of %d revisions of %d largefiles\n')
                  % (numrevs, numlfiles))

        return int(failed)

    def _getfile(self, tmpfile, filename, hash):
        '''Fetch one revision of one file from the store and write it
        to tmpfile.  Compute the hash of the file on-the-fly as it
        downloads and return the binary hash.  Close tmpfile.  Raise
        StoreError if unable to download the file (e.g. it does not
        exist in the store).'''
        raise NotImplementedError('abstract method')

    def _verifyfile(self, cctx, cset, contents, standin, verified):
        '''Perform the actual verification of a file in the store.
        '''
        raise NotImplementedError('abstract method')

import localstore, wirestore

_storeprovider = {
    'file':  [localstore.localstore],
    'http':  [wirestore.wirestore],
    'https': [wirestore.wirestore],
    'ssh': [wirestore.wirestore],
    }

_scheme_re = re.compile(r'^([a-zA-Z0-9+-.]+)://')

# During clone this function is passed the src's ui object
# but it needs the dest's ui object so it can read out of
# the config file. Use repo.ui instead.
def _openstore(repo, remote=None, put=False):
    ui = repo.ui

    if not remote:
        lfpullsource = getattr(repo, 'lfpullsource', None)
        if lfpullsource:
            path = ui.expandpath(lfpullsource)
        else:
            path = ui.expandpath('default-push', 'default')

        # ui.expandpath() leaves 'default-push' and 'default' alone if
        # they cannot be expanded: fallback to the empty string,
        # meaning the current directory.
        if path == 'default-push' or path == 'default':
            path = ''
            remote = repo
        else:
            remote = hg.peer(repo, {}, path)

    # The path could be a scheme so use Mercurial's normal functionality
    # to resolve the scheme to a repository and use its path
    path = util.safehasattr(remote, 'url') and remote.url() or remote.path

    match = _scheme_re.match(path)
    if not match:                       # regular filesystem path
        scheme = 'file'
    else:
        scheme = match.group(1)

    try:
        storeproviders = _storeprovider[scheme]
    except KeyError:
        raise util.Abort(_('unsupported URL scheme %r') % scheme)

    for classobj in storeproviders:
        try:
            return classobj(ui, repo, remote)
        except lfutil.storeprotonotcapable:
            pass

    raise util.Abort(_('%s does not appear to be a largefile store') % path)