view mercurial/store.py @ 31793:69d8fcf20014

help: document bundle specifications

I softly formalized the concept of a "bundle specification" a while
ago when I was working on clone bundles and stream clone bundles and
wanted a more robust way to define what exactly is in a bundle file.

The concept has existed for a while. Since it is part of the clone
bundles feature and exposed to the user via the "-t" argument to
`hg bundle`, it is something we need to support for the long haul.

After the 4.1 release, I heard a few people comment that they didn't
realize you could generate zstd bundles with `hg bundle`. I'm
partially to blame for not documenting it in bundle's docstring.

Additionally, I added a hacky, experimental feature for controlling
the compression level of bundles in 76104a4899ad. As the commit
message says, I went with a quick and dirty solution out of time
constraints. Furthermore, I wanted to eventually store this
configuration in the "bundlespec" so it could be made more flexible.

Given:

a) bundlespecs are here to stay
b) we don't have great documentation over what they are, despite being
   a user-facing feature
c) the list of available compression engines and their behavior isn't
   exposed
d) we need an extensible place to modify behavior of compression
   engines

I want to move forward with formalizing bundlespecs as a user-facing
feature. This commit does that by introducing a "bundlespec" help
page. Leaning on the just-added compression engine documentation
and API, the topic also conveniently lists available compression
engines and details about them. This makes features like zstd
bundle compression more discoverable. e.g. you can now
`hg help -k zstd` and it lists the "bundlespec" topic.

# store.py - repository store handling for Mercurial
#
# Copyright 2008 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 __future__ import absolute_import

import errno
import hashlib
import os
import stat

from .i18n import _
from . import (
    error,
    parsers,
    pycompat,
    util,
    vfs as vfsmod,
)

# This avoids a collision between a file named foo and a dir named
# foo.i or foo.d
def _encodedir(path):
    '''
    >>> _encodedir('data/foo.i')
    'data/foo.i'
    >>> _encodedir('data/foo.i/bla.i')
    'data/foo.i.hg/bla.i'
    >>> _encodedir('data/foo.i.hg/bla.i')
    'data/foo.i.hg.hg/bla.i'
    >>> _encodedir('data/foo.i\\ndata/foo.i/bla.i\\ndata/foo.i.hg/bla.i\\n')
    'data/foo.i\\ndata/foo.i.hg/bla.i\\ndata/foo.i.hg.hg/bla.i\\n'
    '''
    return (path
            .replace(".hg/", ".hg.hg/")
            .replace(".i/", ".i.hg/")
            .replace(".d/", ".d.hg/"))

encodedir = getattr(parsers, 'encodedir', _encodedir)

def decodedir(path):
    '''
    >>> decodedir('data/foo.i')
    'data/foo.i'
    >>> decodedir('data/foo.i.hg/bla.i')
    'data/foo.i/bla.i'
    >>> decodedir('data/foo.i.hg.hg/bla.i')
    'data/foo.i.hg/bla.i'
    '''
    if ".hg/" not in path:
        return path
    return (path
            .replace(".d.hg/", ".d/")
            .replace(".i.hg/", ".i/")
            .replace(".hg.hg/", ".hg/"))

def _reserved():
    ''' characters that are problematic for filesystems

    * ascii escapes (0..31)
    * ascii hi (126..255)
    * windows specials

    these characters will be escaped by encodefunctions
    '''
    winreserved = [ord(x) for x in u'\\:*?"<>|']
    for x in range(32):
        yield x
    for x in range(126, 256):
        yield x
    for x in winreserved:
        yield x

def _buildencodefun():
    '''
    >>> enc, dec = _buildencodefun()

    >>> enc('nothing/special.txt')
    'nothing/special.txt'
    >>> dec('nothing/special.txt')
    'nothing/special.txt'

    >>> enc('HELLO')
    '_h_e_l_l_o'
    >>> dec('_h_e_l_l_o')
    'HELLO'

    >>> enc('hello:world?')
    'hello~3aworld~3f'
    >>> dec('hello~3aworld~3f')
    'hello:world?'

    >>> enc('the\x07quick\xADshot')
    'the~07quick~adshot'
    >>> dec('the~07quick~adshot')
    'the\\x07quick\\xadshot'
    '''
    e = '_'
    xchr = pycompat.bytechr
    asciistr = list(map(xchr, range(127)))
    capitals = list(range(ord("A"), ord("Z") + 1))

    cmap = dict((x, x) for x in asciistr)
    for x in _reserved():
        cmap[xchr(x)] = "~%02x" % x
    for x in capitals + [ord(e)]:
        cmap[xchr(x)] = e + xchr(x).lower()

    dmap = {}
    for k, v in cmap.iteritems():
        dmap[v] = k
    def decode(s):
        i = 0
        while i < len(s):
            for l in xrange(1, 4):
                try:
                    yield dmap[s[i:i + l]]
                    i += l
                    break
                except KeyError:
                    pass
            else:
                raise KeyError
    return (lambda s: ''.join([cmap[s[c:c + 1]] for c in xrange(len(s))]),
            lambda s: ''.join(list(decode(s))))

_encodefname, _decodefname = _buildencodefun()

def encodefilename(s):
    '''
    >>> encodefilename('foo.i/bar.d/bla.hg/hi:world?/HELLO')
    'foo.i.hg/bar.d.hg/bla.hg.hg/hi~3aworld~3f/_h_e_l_l_o'
    '''
    return _encodefname(encodedir(s))

def decodefilename(s):
    '''
    >>> decodefilename('foo.i.hg/bar.d.hg/bla.hg.hg/hi~3aworld~3f/_h_e_l_l_o')
    'foo.i/bar.d/bla.hg/hi:world?/HELLO'
    '''
    return decodedir(_decodefname(s))

def _buildlowerencodefun():
    '''
    >>> f = _buildlowerencodefun()
    >>> f('nothing/special.txt')
    'nothing/special.txt'
    >>> f('HELLO')
    'hello'
    >>> f('hello:world?')
    'hello~3aworld~3f'
    >>> f('the\x07quick\xADshot')
    'the~07quick~adshot'
    '''
    cmap = dict([(chr(x), chr(x)) for x in xrange(127)])
    for x in _reserved():
        cmap[chr(x)] = "~%02x" % x
    for x in range(ord("A"), ord("Z") + 1):
        cmap[chr(x)] = chr(x).lower()
    return lambda s: "".join([cmap[c] for c in s])

lowerencode = getattr(parsers, 'lowerencode', None) or _buildlowerencodefun()

# Windows reserved names: con, prn, aux, nul, com1..com9, lpt1..lpt9
_winres3 = ('aux', 'con', 'prn', 'nul') # length 3
_winres4 = ('com', 'lpt')               # length 4 (with trailing 1..9)
def _auxencode(path, dotencode):
    '''
    Encodes filenames containing names reserved by Windows or which end in
    period or space. Does not touch other single reserved characters c.
    Specifically, c in '\\:*?"<>|' or ord(c) <= 31 are *not* encoded here.
    Additionally encodes space or period at the beginning, if dotencode is
    True. Parameter path is assumed to be all lowercase.
    A segment only needs encoding if a reserved name appears as a
    basename (e.g. "aux", "aux.foo"). A directory or file named "foo.aux"
    doesn't need encoding.

    >>> s = '.foo/aux.txt/txt.aux/con/prn/nul/foo.'
    >>> _auxencode(s.split('/'), True)
    ['~2efoo', 'au~78.txt', 'txt.aux', 'co~6e', 'pr~6e', 'nu~6c', 'foo~2e']
    >>> s = '.com1com2/lpt9.lpt4.lpt1/conprn/com0/lpt0/foo.'
    >>> _auxencode(s.split('/'), False)
    ['.com1com2', 'lp~749.lpt4.lpt1', 'conprn', 'com0', 'lpt0', 'foo~2e']
    >>> _auxencode(['foo. '], True)
    ['foo.~20']
    >>> _auxencode([' .foo'], True)
    ['~20.foo']
    '''
    for i, n in enumerate(path):
        if not n:
            continue
        if dotencode and n[0] in '. ':
            n = "~%02x" % ord(n[0:1]) + n[1:]
            path[i] = n
        else:
            l = n.find('.')
            if l == -1:
                l = len(n)
            if ((l == 3 and n[:3] in _winres3) or
                (l == 4 and n[3:4] <= '9' and n[3:4] >= '1'
                        and n[:3] in _winres4)):
                # encode third letter ('aux' -> 'au~78')
                ec = "~%02x" % ord(n[2:3])
                n = n[0:2] + ec + n[3:]
                path[i] = n
        if n[-1] in '. ':
            # encode last period or space ('foo...' -> 'foo..~2e')
            path[i] = n[:-1] + "~%02x" % ord(n[-1:])
    return path

_maxstorepathlen = 120
_dirprefixlen = 8
_maxshortdirslen = 8 * (_dirprefixlen + 1) - 4

def _hashencode(path, dotencode):
    digest = hashlib.sha1(path).hexdigest()
    le = lowerencode(path[5:]).split('/') # skips prefix 'data/' or 'meta/'
    parts = _auxencode(le, dotencode)
    basename = parts[-1]
    _root, ext = os.path.splitext(basename)
    sdirs = []
    sdirslen = 0
    for p in parts[:-1]:
        d = p[:_dirprefixlen]
        if d[-1] in '. ':
            # Windows can't access dirs ending in period or space
            d = d[:-1] + '_'
        if sdirslen == 0:
            t = len(d)
        else:
            t = sdirslen + 1 + len(d)
            if t > _maxshortdirslen:
                break
        sdirs.append(d)
        sdirslen = t
    dirs = '/'.join(sdirs)
    if len(dirs) > 0:
        dirs += '/'
    res = 'dh/' + dirs + digest + ext
    spaceleft = _maxstorepathlen - len(res)
    if spaceleft > 0:
        filler = basename[:spaceleft]
        res = 'dh/' + dirs + filler + digest + ext
    return res

def _hybridencode(path, dotencode):
    '''encodes path with a length limit

    Encodes all paths that begin with 'data/', according to the following.

    Default encoding (reversible):

    Encodes all uppercase letters 'X' as '_x'. All reserved or illegal
    characters are encoded as '~xx', where xx is the two digit hex code
    of the character (see encodefilename).
    Relevant path components consisting of Windows reserved filenames are
    masked by encoding the third character ('aux' -> 'au~78', see _auxencode).

    Hashed encoding (not reversible):

    If the default-encoded path is longer than _maxstorepathlen, a
    non-reversible hybrid hashing of the path is done instead.
    This encoding uses up to _dirprefixlen characters of all directory
    levels of the lowerencoded path, but not more levels than can fit into
    _maxshortdirslen.
    Then follows the filler followed by the sha digest of the full path.
    The filler is the beginning of the basename of the lowerencoded path
    (the basename is everything after the last path separator). The filler
    is as long as possible, filling in characters from the basename until
    the encoded path has _maxstorepathlen characters (or all chars of the
    basename have been taken).
    The extension (e.g. '.i' or '.d') is preserved.

    The string 'data/' at the beginning is replaced with 'dh/', if the hashed
    encoding was used.
    '''
    path = encodedir(path)
    ef = _encodefname(path).split('/')
    res = '/'.join(_auxencode(ef, dotencode))
    if len(res) > _maxstorepathlen:
        res = _hashencode(path, dotencode)
    return res

def _pathencode(path):
    de = encodedir(path)
    if len(path) > _maxstorepathlen:
        return _hashencode(de, True)
    ef = _encodefname(de).split('/')
    res = '/'.join(_auxencode(ef, True))
    if len(res) > _maxstorepathlen:
        return _hashencode(de, True)
    return res

_pathencode = getattr(parsers, 'pathencode', _pathencode)

def _plainhybridencode(f):
    return _hybridencode(f, False)

def _calcmode(vfs):
    try:
        # files in .hg/ will be created using this mode
        mode = vfs.stat().st_mode
            # avoid some useless chmods
        if (0o777 & ~util.umask) == (0o777 & mode):
            mode = None
    except OSError:
        mode = None
    return mode

_data = ('data meta 00manifest.d 00manifest.i 00changelog.d 00changelog.i'
         ' phaseroots obsstore')

class basicstore(object):
    '''base class for local repository stores'''
    def __init__(self, path, vfstype):
        vfs = vfstype(path)
        self.path = vfs.base
        self.createmode = _calcmode(vfs)
        vfs.createmode = self.createmode
        self.rawvfs = vfs
        self.vfs = vfsmod.filtervfs(vfs, encodedir)
        self.opener = self.vfs

    def join(self, f):
        return self.path + '/' + encodedir(f)

    def _walk(self, relpath, recurse):
        '''yields (unencoded, encoded, size)'''
        path = self.path
        if relpath:
            path += '/' + relpath
        striplen = len(self.path) + 1
        l = []
        if self.rawvfs.isdir(path):
            visit = [path]
            readdir = self.rawvfs.readdir
            while visit:
                p = visit.pop()
                for f, kind, st in readdir(p, stat=True):
                    fp = p + '/' + f
                    if kind == stat.S_IFREG and f[-2:] in ('.d', '.i'):
                        n = util.pconvert(fp[striplen:])
                        l.append((decodedir(n), n, st.st_size))
                    elif kind == stat.S_IFDIR and recurse:
                        visit.append(fp)
        l.sort()
        return l

    def datafiles(self):
        return self._walk('data', True) + self._walk('meta', True)

    def topfiles(self):
        # yield manifest before changelog
        return reversed(self._walk('', False))

    def walk(self):
        '''yields (unencoded, encoded, size)'''
        # yield data files first
        for x in self.datafiles():
            yield x
        for x in self.topfiles():
            yield x

    def copylist(self):
        return ['requires'] + _data.split()

    def write(self, tr):
        pass

    def invalidatecaches(self):
        pass

    def markremoved(self, fn):
        pass

    def __contains__(self, path):
        '''Checks if the store contains path'''
        path = "/".join(("data", path))
        # file?
        if self.vfs.exists(path + ".i"):
            return True
        # dir?
        if not path.endswith("/"):
            path = path + "/"
        return self.vfs.exists(path)

class encodedstore(basicstore):
    def __init__(self, path, vfstype):
        vfs = vfstype(path + '/store')
        self.path = vfs.base
        self.createmode = _calcmode(vfs)
        vfs.createmode = self.createmode
        self.rawvfs = vfs
        self.vfs = vfsmod.filtervfs(vfs, encodefilename)
        self.opener = self.vfs

    def datafiles(self):
        for a, b, size in super(encodedstore, self).datafiles():
            try:
                a = decodefilename(a)
            except KeyError:
                a = None
            yield a, b, size

    def join(self, f):
        return self.path + '/' + encodefilename(f)

    def copylist(self):
        return (['requires', '00changelog.i'] +
                ['store/' + f for f in _data.split()])

class fncache(object):
    # the filename used to be partially encoded
    # hence the encodedir/decodedir dance
    def __init__(self, vfs):
        self.vfs = vfs
        self.entries = None
        self._dirty = False

    def _load(self):
        '''fill the entries from the fncache file'''
        self._dirty = False
        try:
            fp = self.vfs('fncache', mode='rb')
        except IOError:
            # skip nonexistent file
            self.entries = set()
            return
        self.entries = set(decodedir(fp.read()).splitlines())
        if '' in self.entries:
            fp.seek(0)
            for n, line in enumerate(util.iterfile(fp)):
                if not line.rstrip('\n'):
                    t = _('invalid entry in fncache, line %d') % (n + 1)
                    raise error.Abort(t)
        fp.close()

    def write(self, tr):
        if self._dirty:
            tr.addbackup('fncache')
            fp = self.vfs('fncache', mode='wb', atomictemp=True)
            if self.entries:
                fp.write(encodedir('\n'.join(self.entries) + '\n'))
            fp.close()
            self._dirty = False

    def add(self, fn):
        if self.entries is None:
            self._load()
        if fn not in self.entries:
            self._dirty = True
            self.entries.add(fn)

    def remove(self, fn):
        if self.entries is None:
            self._load()
        try:
            self.entries.remove(fn)
            self._dirty = True
        except KeyError:
            pass

    def __contains__(self, fn):
        if self.entries is None:
            self._load()
        return fn in self.entries

    def __iter__(self):
        if self.entries is None:
            self._load()
        return iter(self.entries)

class _fncachevfs(vfsmod.abstractvfs, vfsmod.auditvfs):
    def __init__(self, vfs, fnc, encode):
        vfsmod.auditvfs.__init__(self, vfs)
        self.fncache = fnc
        self.encode = encode

    def __call__(self, path, mode='r', *args, **kw):
        if mode not in ('r', 'rb') and (path.startswith('data/') or
                                        path.startswith('meta/')):
            self.fncache.add(path)
        return self.vfs(self.encode(path), mode, *args, **kw)

    def join(self, path):
        if path:
            return self.vfs.join(self.encode(path))
        else:
            return self.vfs.join(path)

class fncachestore(basicstore):
    def __init__(self, path, vfstype, dotencode):
        if dotencode:
            encode = _pathencode
        else:
            encode = _plainhybridencode
        self.encode = encode
        vfs = vfstype(path + '/store')
        self.path = vfs.base
        self.pathsep = self.path + '/'
        self.createmode = _calcmode(vfs)
        vfs.createmode = self.createmode
        self.rawvfs = vfs
        fnc = fncache(vfs)
        self.fncache = fnc
        self.vfs = _fncachevfs(vfs, fnc, encode)
        self.opener = self.vfs

    def join(self, f):
        return self.pathsep + self.encode(f)

    def getsize(self, path):
        return self.rawvfs.stat(path).st_size

    def datafiles(self):
        for f in sorted(self.fncache):
            ef = self.encode(f)
            try:
                yield f, ef, self.getsize(ef)
            except OSError as err:
                if err.errno != errno.ENOENT:
                    raise

    def copylist(self):
        d = ('data meta dh fncache phaseroots obsstore'
             ' 00manifest.d 00manifest.i 00changelog.d 00changelog.i')
        return (['requires', '00changelog.i'] +
                ['store/' + f for f in d.split()])

    def write(self, tr):
        self.fncache.write(tr)

    def invalidatecaches(self):
        self.fncache.entries = None

    def markremoved(self, fn):
        self.fncache.remove(fn)

    def _exists(self, f):
        ef = self.encode(f)
        try:
            self.getsize(ef)
            return True
        except OSError as err:
            if err.errno != errno.ENOENT:
                raise
            # nonexistent entry
            return False

    def __contains__(self, path):
        '''Checks if the store contains path'''
        path = "/".join(("data", path))
        # check for files (exact match)
        e = path + '.i'
        if e in self.fncache and self._exists(e):
            return True
        # now check for directories (prefix match)
        if not path.endswith('/'):
            path += '/'
        for e in self.fncache:
            if e.startswith(path) and self._exists(e):
                return True
        return False

def store(requirements, path, vfstype):
    if 'store' in requirements:
        if 'fncache' in requirements:
            return fncachestore(path, vfstype, 'dotencode' in requirements)
        return encodedstore(path, vfstype)
    return basicstore(path, vfstype)