shallowutil: narrow scope of try/except block

This will make this code easier to understand in the future.

Differential Revision: https://phab.mercurial-scm.org/D11007

hgext/remotefilelog/shallowutil.py

@@ -1,544 +1,545 b''
 # shallowutil.py -- remotefilelog utilities
 #
 # Copyright 2014 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.
 from __future__ import absolute_import
 
 import collections
 import errno
 import os
 import stat
 import struct
 import tempfile
 
 from mercurial.i18n import _
 from mercurial.pycompat import open
 from mercurial.node import hex
 from mercurial import (
     error,
     pycompat,
     revlog,
     util,
 )
 from mercurial.utils import (
     hashutil,
     storageutil,
     stringutil,
 )
 from . import constants
 
 if not pycompat.iswindows:
     import grp
 
 
 def isenabled(repo):
     """returns whether the repository is remotefilelog enabled or not"""
     return constants.SHALLOWREPO_REQUIREMENT in repo.requirements
 
 
 def getcachekey(reponame, file, id):
     pathhash = hex(hashutil.sha1(file).digest())
     return os.path.join(reponame, pathhash[:2], pathhash[2:], id)
 
 
 def getlocalkey(file, id):
     pathhash = hex(hashutil.sha1(file).digest())
     return os.path.join(pathhash, id)
 
 
 def getcachepath(ui, allowempty=False):
     cachepath = ui.config(b"remotefilelog", b"cachepath")
     if not cachepath:
         if allowempty:
             return None
         else:
             raise error.Abort(
                 _(b"could not find config option remotefilelog.cachepath")
             )
     return util.expandpath(cachepath)
 
 
 def getcachepackpath(repo, category):
     cachepath = getcachepath(repo.ui)
     if category != constants.FILEPACK_CATEGORY:
         return os.path.join(cachepath, repo.name, b'packs', category)
     else:
         return os.path.join(cachepath, repo.name, b'packs')
 
 
 def getlocalpackpath(base, category):
     return os.path.join(base, b'packs', category)
 
 
 def createrevlogtext(text, copyfrom=None, copyrev=None):
     """returns a string that matches the revlog contents in a
     traditional revlog
     """
     meta = {}
     if copyfrom or text.startswith(b'\1\n'):
         if copyfrom:
             meta[b'copy'] = copyfrom
             meta[b'copyrev'] = copyrev
         text = storageutil.packmeta(meta, text)
 
     return text
 
 
 def parsemeta(text):
     """parse mercurial filelog metadata"""
     meta, size = storageutil.parsemeta(text)
     if text.startswith(b'\1\n'):
         s = text.index(b'\1\n', 2)
         text = text[s + 2 :]
     return meta or {}, text
 
 
 def sumdicts(*dicts):
     """Adds all the values of *dicts together into one dictionary. This assumes
     the values in *dicts are all summable.
 
     e.g. [{'a': 4', 'b': 2}, {'b': 3, 'c': 1}] -> {'a': 4, 'b': 5, 'c': 1}
     """
     result = collections.defaultdict(lambda: 0)
     for dict in dicts:
         for k, v in pycompat.iteritems(dict):
             result[k] += v
     return result
 
 
 def prefixkeys(dict, prefix):
     """Returns ``dict`` with ``prefix`` prepended to all its keys."""
     result = {}
     for k, v in pycompat.iteritems(dict):
         result[prefix + k] = v
     return result
 
 
 def reportpackmetrics(ui, prefix, *stores):
     dicts = [s.getmetrics() for s in stores]
     dict = prefixkeys(sumdicts(*dicts), prefix + b'_')
     ui.log(prefix + b"_packsizes", b"\n", **pycompat.strkwargs(dict))
 
 
 def _parsepackmeta(metabuf):
     """parse datapack meta, bytes (<metadata-list>) -> dict
 
     The dict contains raw content - both keys and values are strings.
     Upper-level business may want to convert some of them to other types like
     integers, on their own.
 
     raise ValueError if the data is corrupted
     """
     metadict = {}
     offset = 0
     buflen = len(metabuf)
     while buflen - offset >= 3:
         key = metabuf[offset : offset + 1]
         offset += 1
         metalen = struct.unpack_from(b'!H', metabuf, offset)[0]
         offset += 2
         if offset + metalen > buflen:
             raise ValueError(b'corrupted metadata: incomplete buffer')
         value = metabuf[offset : offset + metalen]
         metadict[key] = value
         offset += metalen
     if offset != buflen:
         raise ValueError(b'corrupted metadata: redundant data')
     return metadict
 
 
 def _buildpackmeta(metadict):
     """reverse of _parsepackmeta, dict -> bytes (<metadata-list>)
 
     The dict contains raw content - both keys and values are strings.
     Upper-level business may want to serialize some of other types (like
     integers) to strings before calling this function.
 
     raise ProgrammingError when metadata key is illegal, or ValueError if
     length limit is exceeded
     """
     metabuf = b''
     for k, v in sorted(pycompat.iteritems((metadict or {}))):
         if len(k) != 1:
             raise error.ProgrammingError(b'packmeta: illegal key: %s' % k)
         if len(v) > 0xFFFE:
             raise ValueError(
                 b'metadata value is too long: 0x%x > 0xfffe' % len(v)
             )
         metabuf += k
         metabuf += struct.pack(b'!H', len(v))
         metabuf += v
     # len(metabuf) is guaranteed representable in 4 bytes, because there are
     # only 256 keys, and for each value, len(value) <= 0xfffe.
     return metabuf
 
 
 _metaitemtypes = {
     constants.METAKEYFLAG: (int, pycompat.long),
     constants.METAKEYSIZE: (int, pycompat.long),
 }
 
 
 def buildpackmeta(metadict):
     """like _buildpackmeta, but typechecks metadict and normalize it.
 
     This means, METAKEYSIZE and METAKEYSIZE should have integers as values,
     and METAKEYFLAG will be dropped if its value is 0.
     """
     newmeta = {}
     for k, v in pycompat.iteritems(metadict or {}):
         expectedtype = _metaitemtypes.get(k, (bytes,))
         if not isinstance(v, expectedtype):
             raise error.ProgrammingError(b'packmeta: wrong type of key %s' % k)
         # normalize int to binary buffer
         if int in expectedtype:
             # optimization: remove flag if it's 0 to save space
             if k == constants.METAKEYFLAG and v == 0:
                 continue
             v = int2bin(v)
         newmeta[k] = v
     return _buildpackmeta(newmeta)
 
 
 def parsepackmeta(metabuf):
     """like _parsepackmeta, but convert fields to desired types automatically.
 
     This means, METAKEYFLAG and METAKEYSIZE fields will be converted to
     integers.
     """
     metadict = _parsepackmeta(metabuf)
     for k, v in pycompat.iteritems(metadict):
         if k in _metaitemtypes and int in _metaitemtypes[k]:
             metadict[k] = bin2int(v)
     return metadict
 
 
 def int2bin(n):
     """convert a non-negative integer to raw binary buffer"""
     buf = bytearray()
     while n > 0:
         buf.insert(0, n & 0xFF)
         n >>= 8
     return bytes(buf)
 
 
 def bin2int(buf):
     """the reverse of int2bin, convert a binary buffer to an integer"""
     x = 0
     for b in bytearray(buf):
         x <<= 8
         x |= b
     return x
 
 
 class BadRemotefilelogHeader(error.StorageError):
     """Exception raised when parsing a remotefilelog blob header fails."""
 
 
 def parsesizeflags(raw):
     """given a remotefilelog blob, return (headersize, rawtextsize, flags)
 
     see remotefilelogserver.createfileblob for the format.
     raise RuntimeError if the content is illformed.
     """
     flags = revlog.REVIDX_DEFAULT_FLAGS
     size = None
     try:
         index = raw.index(b'\0')
+    except ValueError:
+        raise BadRemotefilelogHeader(
+            "unexpected remotefilelog header: illegal format"
+        )
+    if True:
         header = raw[:index]
         if header.startswith(b'v'):
             # v1 and above, header starts with 'v'
             if header.startswith(b'v1\n'):
                 for s in header.split(b'\n'):
                     if s.startswith(constants.METAKEYSIZE):
                         size = int(s[len(constants.METAKEYSIZE) :])
                     elif s.startswith(constants.METAKEYFLAG):
                         flags = int(s[len(constants.METAKEYFLAG) :])
             else:
                 raise BadRemotefilelogHeader(
                     b'unsupported remotefilelog header: %s' % header
                 )
         else:
             # v0, str(int(size)) is the header
             size = int(header)
-    except ValueError:
-        raise BadRemotefilelogHeader(
-            "unexpected remotefilelog header: illegal format"
-        )
     if size is None:
         raise BadRemotefilelogHeader(
             "unexpected remotefilelog header: no size found"
         )
     return index + 1, size, flags
 
 
 def buildfileblobheader(size, flags, version=None):
     """return the header of a remotefilelog blob.
 
     see remotefilelogserver.createfileblob for the format.
     approximately the reverse of parsesizeflags.
 
     version could be 0 or 1, or None (auto decide).
     """
     # choose v0 if flags is empty, otherwise v1
     if version is None:
         version = int(bool(flags))
     if version == 1:
         header = b'v1\n%s%d\n%s%d' % (
             constants.METAKEYSIZE,
             size,
             constants.METAKEYFLAG,
             flags,
         )
     elif version == 0:
         if flags:
             raise error.ProgrammingError(b'fileblob v0 does not support flag')
         header = b'%d' % size
     else:
         raise error.ProgrammingError(b'unknown fileblob version %d' % version)
     return header
 
 
 def ancestormap(raw):
     offset, size, flags = parsesizeflags(raw)
     start = offset + size
 
     mapping = {}
     while start < len(raw):
         divider = raw.index(b'\0', start + 80)
 
         currentnode = raw[start : (start + 20)]
         p1 = raw[(start + 20) : (start + 40)]
         p2 = raw[(start + 40) : (start + 60)]
         linknode = raw[(start + 60) : (start + 80)]
         copyfrom = raw[(start + 80) : divider]
 
         mapping[currentnode] = (p1, p2, linknode, copyfrom)
         start = divider + 1
 
     return mapping
 
 
 def readfile(path):
     f = open(path, b'rb')
     try:
         result = f.read()
 
         # we should never have empty files
         if not result:
             os.remove(path)
             raise IOError(b"empty file: %s" % path)
 
         return result
     finally:
         f.close()
 
 
 def unlinkfile(filepath):
     if pycompat.iswindows:
         # On Windows, os.unlink cannnot delete readonly files
         os.chmod(filepath, stat.S_IWUSR)
     os.unlink(filepath)
 
 
 def renamefile(source, destination):
     if pycompat.iswindows:
         # On Windows, os.rename cannot rename readonly files
         # and cannot overwrite destination if it exists
         os.chmod(source, stat.S_IWUSR)
         if os.path.isfile(destination):
             os.chmod(destination, stat.S_IWUSR)
             os.unlink(destination)
 
     os.rename(source, destination)
 
 
 def writefile(path, content, readonly=False):
     dirname, filename = os.path.split(path)
     if not os.path.exists(dirname):
         try:
             os.makedirs(dirname)
         except OSError as ex:
             if ex.errno != errno.EEXIST:
                 raise
 
     fd, temp = tempfile.mkstemp(prefix=b'.%s-' % filename, dir=dirname)
     os.close(fd)
 
     try:
         f = util.posixfile(temp, b'wb')
         f.write(content)
         f.close()
 
         if readonly:
             mode = 0o444
         else:
             # tempfiles are created with 0o600, so we need to manually set the
             # mode.
             oldumask = os.umask(0)
             # there's no way to get the umask without modifying it, so set it
             # back
             os.umask(oldumask)
             mode = ~oldumask
 
         renamefile(temp, path)
         os.chmod(path, mode)
     except Exception:
         try:
             unlinkfile(temp)
         except OSError:
             pass
         raise
 
 
 def sortnodes(nodes, parentfunc):
     """Topologically sorts the nodes, using the parentfunc to find
     the parents of nodes."""
     nodes = set(nodes)
     childmap = {}
     parentmap = {}
     roots = []
 
     # Build a child and parent map
     for n in nodes:
         parents = [p for p in parentfunc(n) if p in nodes]
         parentmap[n] = set(parents)
         for p in parents:
             childmap.setdefault(p, set()).add(n)
         if not parents:
             roots.append(n)
 
     roots.sort()
     # Process roots, adding children to the queue as they become roots
     results = []
     while roots:
         n = roots.pop(0)
         results.append(n)
         if n in childmap:
             children = childmap[n]
             for c in children:
                 childparents = parentmap[c]
                 childparents.remove(n)
                 if len(childparents) == 0:
                     # insert at the beginning, that way child nodes
                     # are likely to be output immediately after their
                     # parents.  This gives better compression results.
                     roots.insert(0, c)
 
     return results
 
 
 def readexactly(stream, n):
     '''read n bytes from stream.read and abort if less was available'''
     s = stream.read(n)
     if len(s) < n:
         raise error.Abort(
             _(b"stream ended unexpectedly (got %d bytes, expected %d)")
             % (len(s), n)
         )
     return s
 
 
 def readunpack(stream, fmt):
     data = readexactly(stream, struct.calcsize(fmt))
     return struct.unpack(fmt, data)
 
 
 def readpath(stream):
     rawlen = readexactly(stream, constants.FILENAMESIZE)
     pathlen = struct.unpack(constants.FILENAMESTRUCT, rawlen)[0]
     return readexactly(stream, pathlen)
 
 
 def readnodelist(stream):
     rawlen = readexactly(stream, constants.NODECOUNTSIZE)
     nodecount = struct.unpack(constants.NODECOUNTSTRUCT, rawlen)[0]
     for i in pycompat.xrange(nodecount):
         yield readexactly(stream, constants.NODESIZE)
 
 
 def readpathlist(stream):
     rawlen = readexactly(stream, constants.PATHCOUNTSIZE)
     pathcount = struct.unpack(constants.PATHCOUNTSTRUCT, rawlen)[0]
     for i in pycompat.xrange(pathcount):
         yield readpath(stream)
 
 
 def getgid(groupname):
     try:
         gid = grp.getgrnam(pycompat.fsdecode(groupname)).gr_gid
         return gid
     except KeyError:
         return None
 
 
 def setstickygroupdir(path, gid, warn=None):
     if gid is None:
         return
     try:
         os.chown(path, -1, gid)
         os.chmod(path, 0o2775)
     except (IOError, OSError) as ex:
         if warn:
             warn(_(b'unable to chown/chmod on %s: %s\n') % (path, ex))
 
 
 def mkstickygroupdir(ui, path):
     """Creates the given directory (if it doesn't exist) and give it a
     particular group with setgid enabled."""
     gid = None
     groupname = ui.config(b"remotefilelog", b"cachegroup")
     if groupname:
         gid = getgid(groupname)
         if gid is None:
             ui.warn(_(b'unable to resolve group name: %s\n') % groupname)
 
     # we use a single stat syscall to test the existence and mode / group bit
     st = None
     try:
         st = os.stat(path)
     except OSError:
         pass
 
     if st:
         # exists
         if (st.st_mode & 0o2775) != 0o2775 or st.st_gid != gid:
             # permission needs to be fixed
             setstickygroupdir(path, gid, ui.warn)
         return
 
     oldumask = os.umask(0o002)
     try:
         missingdirs = [path]
         path = os.path.dirname(path)
         while path and not os.path.exists(path):
             missingdirs.append(path)
             path = os.path.dirname(path)
 
         for path in reversed(missingdirs):
             try:
                 os.mkdir(path)
             except OSError as ex:
                 if ex.errno != errno.EEXIST:
                     raise
 
         for path in missingdirs:
             setstickygroupdir(path, gid, ui.warn)
     finally:
         os.umask(oldumask)
 
 
 def getusername(ui):
     try:
         return stringutil.shortuser(ui.username())
     except Exception:
         return b'unknown'
 
 
 def getreponame(ui):
     reponame = ui.config(b'paths', b'default')
     if reponame:
         return os.path.basename(reponame)
     return b"unknown"