--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/env/lib/python3.7/site-packages/distlib/database.py	Sat May 02 07:14:21 2020 -0400
@@ -0,0 +1,1339 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright (C) 2012-2017 The Python Software Foundation.
+# See LICENSE.txt and CONTRIBUTORS.txt.
+#
+"""PEP 376 implementation."""
+
+from __future__ import unicode_literals
+
+import base64
+import codecs
+import contextlib
+import hashlib
+import logging
+import os
+import posixpath
+import sys
+import zipimport
+
+from . import DistlibException, resources
+from .compat import StringIO
+from .version import get_scheme, UnsupportedVersionError
+from .metadata import (Metadata, METADATA_FILENAME, WHEEL_METADATA_FILENAME,
+                       LEGACY_METADATA_FILENAME)
+from .util import (parse_requirement, cached_property, parse_name_and_version,
+                   read_exports, write_exports, CSVReader, CSVWriter)
+
+
+__all__ = ['Distribution', 'BaseInstalledDistribution',
+           'InstalledDistribution', 'EggInfoDistribution',
+           'DistributionPath']
+
+
+logger = logging.getLogger(__name__)
+
+EXPORTS_FILENAME = 'pydist-exports.json'
+COMMANDS_FILENAME = 'pydist-commands.json'
+
+DIST_FILES = ('INSTALLER', METADATA_FILENAME, 'RECORD', 'REQUESTED',
+              'RESOURCES', EXPORTS_FILENAME, 'SHARED')
+
+DISTINFO_EXT = '.dist-info'
+
+
+class _Cache(object):
+    """
+    A simple cache mapping names and .dist-info paths to distributions
+    """
+    def __init__(self):
+        """
+        Initialise an instance. There is normally one for each DistributionPath.
+        """
+        self.name = {}
+        self.path = {}
+        self.generated = False
+
+    def clear(self):
+        """
+        Clear the cache, setting it to its initial state.
+        """
+        self.name.clear()
+        self.path.clear()
+        self.generated = False
+
+    def add(self, dist):
+        """
+        Add a distribution to the cache.
+        :param dist: The distribution to add.
+        """
+        if dist.path not in self.path:
+            self.path[dist.path] = dist
+            self.name.setdefault(dist.key, []).append(dist)
+
+
+class DistributionPath(object):
+    """
+    Represents a set of distributions installed on a path (typically sys.path).
+    """
+    def __init__(self, path=None, include_egg=False):
+        """
+        Create an instance from a path, optionally including legacy (distutils/
+        setuptools/distribute) distributions.
+        :param path: The path to use, as a list of directories. If not specified,
+                     sys.path is used.
+        :param include_egg: If True, this instance will look for and return legacy
+                            distributions as well as those based on PEP 376.
+        """
+        if path is None:
+            path = sys.path
+        self.path = path
+        self._include_dist = True
+        self._include_egg = include_egg
+
+        self._cache = _Cache()
+        self._cache_egg = _Cache()
+        self._cache_enabled = True
+        self._scheme = get_scheme('default')
+
+    def _get_cache_enabled(self):
+        return self._cache_enabled
+
+    def _set_cache_enabled(self, value):
+        self._cache_enabled = value
+
+    cache_enabled = property(_get_cache_enabled, _set_cache_enabled)
+
+    def clear_cache(self):
+        """
+        Clears the internal cache.
+        """
+        self._cache.clear()
+        self._cache_egg.clear()
+
+
+    def _yield_distributions(self):
+        """
+        Yield .dist-info and/or .egg(-info) distributions.
+        """
+        # We need to check if we've seen some resources already, because on
+        # some Linux systems (e.g. some Debian/Ubuntu variants) there are
+        # symlinks which alias other files in the environment.
+        seen = set()
+        for path in self.path:
+            finder = resources.finder_for_path(path)
+            if finder is None:
+                continue
+            r = finder.find('')
+            if not r or not r.is_container:
+                continue
+            rset = sorted(r.resources)
+            for entry in rset:
+                r = finder.find(entry)
+                if not r or r.path in seen:
+                    continue
+                if self._include_dist and entry.endswith(DISTINFO_EXT):
+                    possible_filenames = [METADATA_FILENAME,
+                                          WHEEL_METADATA_FILENAME,
+                                          LEGACY_METADATA_FILENAME]
+                    for metadata_filename in possible_filenames:
+                        metadata_path = posixpath.join(entry, metadata_filename)
+                        pydist = finder.find(metadata_path)
+                        if pydist:
+                            break
+                    else:
+                        continue
+
+                    with contextlib.closing(pydist.as_stream()) as stream:
+                        metadata = Metadata(fileobj=stream, scheme='legacy')
+                    logger.debug('Found %s', r.path)
+                    seen.add(r.path)
+                    yield new_dist_class(r.path, metadata=metadata,
+                                         env=self)
+                elif self._include_egg and entry.endswith(('.egg-info',
+                                                          '.egg')):
+                    logger.debug('Found %s', r.path)
+                    seen.add(r.path)
+                    yield old_dist_class(r.path, self)
+
+    def _generate_cache(self):
+        """
+        Scan the path for distributions and populate the cache with
+        those that are found.
+        """
+        gen_dist = not self._cache.generated
+        gen_egg = self._include_egg and not self._cache_egg.generated
+        if gen_dist or gen_egg:
+            for dist in self._yield_distributions():
+                if isinstance(dist, InstalledDistribution):
+                    self._cache.add(dist)
+                else:
+                    self._cache_egg.add(dist)
+
+            if gen_dist:
+                self._cache.generated = True
+            if gen_egg:
+                self._cache_egg.generated = True
+
+    @classmethod
+    def distinfo_dirname(cls, name, version):
+        """
+        The *name* and *version* parameters are converted into their
+        filename-escaped form, i.e. any ``'-'`` characters are replaced
+        with ``'_'`` other than the one in ``'dist-info'`` and the one
+        separating the name from the version number.
+
+        :parameter name: is converted to a standard distribution name by replacing
+                         any runs of non- alphanumeric characters with a single
+                         ``'-'``.
+        :type name: string
+        :parameter version: is converted to a standard version string. Spaces
+                            become dots, and all other non-alphanumeric characters
+                            (except dots) become dashes, with runs of multiple
+                            dashes condensed to a single dash.
+        :type version: string
+        :returns: directory name
+        :rtype: string"""
+        name = name.replace('-', '_')
+        return '-'.join([name, version]) + DISTINFO_EXT
+
+    def get_distributions(self):
+        """
+        Provides an iterator that looks for distributions and returns
+        :class:`InstalledDistribution` or
+        :class:`EggInfoDistribution` instances for each one of them.
+
+        :rtype: iterator of :class:`InstalledDistribution` and
+                :class:`EggInfoDistribution` instances
+        """
+        if not self._cache_enabled:
+            for dist in self._yield_distributions():
+                yield dist
+        else:
+            self._generate_cache()
+
+            for dist in self._cache.path.values():
+                yield dist
+
+            if self._include_egg:
+                for dist in self._cache_egg.path.values():
+                    yield dist
+
+    def get_distribution(self, name):
+        """
+        Looks for a named distribution on the path.
+
+        This function only returns the first result found, as no more than one
+        value is expected. If nothing is found, ``None`` is returned.
+
+        :rtype: :class:`InstalledDistribution`, :class:`EggInfoDistribution`
+                or ``None``
+        """
+        result = None
+        name = name.lower()
+        if not self._cache_enabled:
+            for dist in self._yield_distributions():
+                if dist.key == name:
+                    result = dist
+                    break
+        else:
+            self._generate_cache()
+
+            if name in self._cache.name:
+                result = self._cache.name[name][0]
+            elif self._include_egg and name in self._cache_egg.name:
+                result = self._cache_egg.name[name][0]
+        return result
+
+    def provides_distribution(self, name, version=None):
+        """
+        Iterates over all distributions to find which distributions provide *name*.
+        If a *version* is provided, it will be used to filter the results.
+
+        This function only returns the first result found, since no more than
+        one values are expected. If the directory is not found, returns ``None``.
+
+        :parameter version: a version specifier that indicates the version
+                            required, conforming to the format in ``PEP-345``
+
+        :type name: string
+        :type version: string
+        """
+        matcher = None
+        if version is not None:
+            try:
+                matcher = self._scheme.matcher('%s (%s)' % (name, version))
+            except ValueError:
+                raise DistlibException('invalid name or version: %r, %r' %
+                                      (name, version))
+
+        for dist in self.get_distributions():
+            # We hit a problem on Travis where enum34 was installed and doesn't
+            # have a provides attribute ...
+            if not hasattr(dist, 'provides'):
+                logger.debug('No "provides": %s', dist)
+            else:
+                provided = dist.provides
+
+                for p in provided:
+                    p_name, p_ver = parse_name_and_version(p)
+                    if matcher is None:
+                        if p_name == name:
+                            yield dist
+                            break
+                    else:
+                        if p_name == name and matcher.match(p_ver):
+                            yield dist
+                            break
+
+    def get_file_path(self, name, relative_path):
+        """
+        Return the path to a resource file.
+        """
+        dist = self.get_distribution(name)
+        if dist is None:
+            raise LookupError('no distribution named %r found' % name)
+        return dist.get_resource_path(relative_path)
+
+    def get_exported_entries(self, category, name=None):
+        """
+        Return all of the exported entries in a particular category.
+
+        :param category: The category to search for entries.
+        :param name: If specified, only entries with that name are returned.
+        """
+        for dist in self.get_distributions():
+            r = dist.exports
+            if category in r:
+                d = r[category]
+                if name is not None:
+                    if name in d:
+                        yield d[name]
+                else:
+                    for v in d.values():
+                        yield v
+
+
+class Distribution(object):
+    """
+    A base class for distributions, whether installed or from indexes.
+    Either way, it must have some metadata, so that's all that's needed
+    for construction.
+    """
+
+    build_time_dependency = False
+    """
+    Set to True if it's known to be only a build-time dependency (i.e.
+    not needed after installation).
+    """
+
+    requested = False
+    """A boolean that indicates whether the ``REQUESTED`` metadata file is
+    present (in other words, whether the package was installed by user
+    request or it was installed as a dependency)."""
+
+    def __init__(self, metadata):
+        """
+        Initialise an instance.
+        :param metadata: The instance of :class:`Metadata` describing this
+        distribution.
+        """
+        self.metadata = metadata
+        self.name = metadata.name
+        self.key = self.name.lower()    # for case-insensitive comparisons
+        self.version = metadata.version
+        self.locator = None
+        self.digest = None
+        self.extras = None      # additional features requested
+        self.context = None     # environment marker overrides
+        self.download_urls = set()
+        self.digests = {}
+
+    @property
+    def source_url(self):
+        """
+        The source archive download URL for this distribution.
+        """
+        return self.metadata.source_url
+
+    download_url = source_url   # Backward compatibility
+
+    @property
+    def name_and_version(self):
+        """
+        A utility property which displays the name and version in parentheses.
+        """
+        return '%s (%s)' % (self.name, self.version)
+
+    @property
+    def provides(self):
+        """
+        A set of distribution names and versions provided by this distribution.
+        :return: A set of "name (version)" strings.
+        """
+        plist = self.metadata.provides
+        s = '%s (%s)' % (self.name, self.version)
+        if s not in plist:
+            plist.append(s)
+        return plist
+
+    def _get_requirements(self, req_attr):
+        md = self.metadata
+        logger.debug('Getting requirements from metadata %r', md.todict())
+        reqts = getattr(md, req_attr)
+        return set(md.get_requirements(reqts, extras=self.extras,
+                                       env=self.context))
+
+    @property
+    def run_requires(self):
+        return self._get_requirements('run_requires')
+
+    @property
+    def meta_requires(self):
+        return self._get_requirements('meta_requires')
+
+    @property
+    def build_requires(self):
+        return self._get_requirements('build_requires')
+
+    @property
+    def test_requires(self):
+        return self._get_requirements('test_requires')
+
+    @property
+    def dev_requires(self):
+        return self._get_requirements('dev_requires')
+
+    def matches_requirement(self, req):
+        """
+        Say if this instance matches (fulfills) a requirement.
+        :param req: The requirement to match.
+        :rtype req: str
+        :return: True if it matches, else False.
+        """
+        # Requirement may contain extras - parse to lose those
+        # from what's passed to the matcher
+        r = parse_requirement(req)
+        scheme = get_scheme(self.metadata.scheme)
+        try:
+            matcher = scheme.matcher(r.requirement)
+        except UnsupportedVersionError:
+            # XXX compat-mode if cannot read the version
+            logger.warning('could not read version %r - using name only',
+                           req)
+            name = req.split()[0]
+            matcher = scheme.matcher(name)
+
+        name = matcher.key   # case-insensitive
+
+        result = False
+        for p in self.provides:
+            p_name, p_ver = parse_name_and_version(p)
+            if p_name != name:
+                continue
+            try:
+                result = matcher.match(p_ver)
+                break
+            except UnsupportedVersionError:
+                pass
+        return result
+
+    def __repr__(self):
+        """
+        Return a textual representation of this instance,
+        """
+        if self.source_url:
+            suffix = ' [%s]' % self.source_url
+        else:
+            suffix = ''
+        return '<Distribution %s (%s)%s>' % (self.name, self.version, suffix)
+
+    def __eq__(self, other):
+        """
+        See if this distribution is the same as another.
+        :param other: The distribution to compare with. To be equal to one
+                      another. distributions must have the same type, name,
+                      version and source_url.
+        :return: True if it is the same, else False.
+        """
+        if type(other) is not type(self):
+            result = False
+        else:
+            result = (self.name == other.name and
+                      self.version == other.version and
+                      self.source_url == other.source_url)
+        return result
+
+    def __hash__(self):
+        """
+        Compute hash in a way which matches the equality test.
+        """
+        return hash(self.name) + hash(self.version) + hash(self.source_url)
+
+
+class BaseInstalledDistribution(Distribution):
+    """
+    This is the base class for installed distributions (whether PEP 376 or
+    legacy).
+    """
+
+    hasher = None
+
+    def __init__(self, metadata, path, env=None):
+        """
+        Initialise an instance.
+        :param metadata: An instance of :class:`Metadata` which describes the
+                         distribution. This will normally have been initialised
+                         from a metadata file in the ``path``.
+        :param path:     The path of the ``.dist-info`` or ``.egg-info``
+                         directory for the distribution.
+        :param env:      This is normally the :class:`DistributionPath`
+                         instance where this distribution was found.
+        """
+        super(BaseInstalledDistribution, self).__init__(metadata)
+        self.path = path
+        self.dist_path = env
+
+    def get_hash(self, data, hasher=None):
+        """
+        Get the hash of some data, using a particular hash algorithm, if
+        specified.
+
+        :param data: The data to be hashed.
+        :type data: bytes
+        :param hasher: The name of a hash implementation, supported by hashlib,
+                       or ``None``. Examples of valid values are ``'sha1'``,
+                       ``'sha224'``, ``'sha384'``, '``sha256'``, ``'md5'`` and
+                       ``'sha512'``. If no hasher is specified, the ``hasher``
+                       attribute of the :class:`InstalledDistribution` instance
+                       is used. If the hasher is determined to be ``None``, MD5
+                       is used as the hashing algorithm.
+        :returns: The hash of the data. If a hasher was explicitly specified,
+                  the returned hash will be prefixed with the specified hasher
+                  followed by '='.
+        :rtype: str
+        """
+        if hasher is None:
+            hasher = self.hasher
+        if hasher is None:
+            hasher = hashlib.md5
+            prefix = ''
+        else:
+            hasher = getattr(hashlib, hasher)
+            prefix = '%s=' % self.hasher
+        digest = hasher(data).digest()
+        digest = base64.urlsafe_b64encode(digest).rstrip(b'=').decode('ascii')
+        return '%s%s' % (prefix, digest)
+
+
+class InstalledDistribution(BaseInstalledDistribution):
+    """
+    Created with the *path* of the ``.dist-info`` directory provided to the
+    constructor. It reads the metadata contained in ``pydist.json`` when it is
+    instantiated., or uses a passed in Metadata instance (useful for when
+    dry-run mode is being used).
+    """
+
+    hasher = 'sha256'
+
+    def __init__(self, path, metadata=None, env=None):
+        self.modules = []
+        self.finder = finder = resources.finder_for_path(path)
+        if finder is None:
+            raise ValueError('finder unavailable for %s' % path)
+        if env and env._cache_enabled and path in env._cache.path:
+            metadata = env._cache.path[path].metadata
+        elif metadata is None:
+            r = finder.find(METADATA_FILENAME)
+            # Temporary - for Wheel 0.23 support
+            if r is None:
+                r = finder.find(WHEEL_METADATA_FILENAME)
+            # Temporary - for legacy support
+            if r is None:
+                r = finder.find('METADATA')
+            if r is None:
+                raise ValueError('no %s found in %s' % (METADATA_FILENAME,
+                                                        path))
+            with contextlib.closing(r.as_stream()) as stream:
+                metadata = Metadata(fileobj=stream, scheme='legacy')
+
+        super(InstalledDistribution, self).__init__(metadata, path, env)
+
+        if env and env._cache_enabled:
+            env._cache.add(self)
+
+        r = finder.find('REQUESTED')
+        self.requested = r is not None
+        p  = os.path.join(path, 'top_level.txt')
+        if os.path.exists(p):
+            with open(p, 'rb') as f:
+                data = f.read().decode('utf-8')
+            self.modules = data.splitlines()
+
+    def __repr__(self):
+        return '<InstalledDistribution %r %s at %r>' % (
+            self.name, self.version, self.path)
+
+    def __str__(self):
+        return "%s %s" % (self.name, self.version)
+
+    def _get_records(self):
+        """
+        Get the list of installed files for the distribution
+        :return: A list of tuples of path, hash and size. Note that hash and
+                 size might be ``None`` for some entries. The path is exactly
+                 as stored in the file (which is as in PEP 376).
+        """
+        results = []
+        r = self.get_distinfo_resource('RECORD')
+        with contextlib.closing(r.as_stream()) as stream:
+            with CSVReader(stream=stream) as record_reader:
+                # Base location is parent dir of .dist-info dir
+                #base_location = os.path.dirname(self.path)
+                #base_location = os.path.abspath(base_location)
+                for row in record_reader:
+                    missing = [None for i in range(len(row), 3)]
+                    path, checksum, size = row + missing
+                    #if not os.path.isabs(path):
+                    #    path = path.replace('/', os.sep)
+                    #    path = os.path.join(base_location, path)
+                    results.append((path, checksum, size))
+        return results
+
+    @cached_property
+    def exports(self):
+        """
+        Return the information exported by this distribution.
+        :return: A dictionary of exports, mapping an export category to a dict
+                 of :class:`ExportEntry` instances describing the individual
+                 export entries, and keyed by name.
+        """
+        result = {}
+        r = self.get_distinfo_resource(EXPORTS_FILENAME)
+        if r:
+            result = self.read_exports()
+        return result
+
+    def read_exports(self):
+        """
+        Read exports data from a file in .ini format.
+
+        :return: A dictionary of exports, mapping an export category to a list
+                 of :class:`ExportEntry` instances describing the individual
+                 export entries.
+        """
+        result = {}
+        r = self.get_distinfo_resource(EXPORTS_FILENAME)
+        if r:
+            with contextlib.closing(r.as_stream()) as stream:
+                result = read_exports(stream)
+        return result
+
+    def write_exports(self, exports):
+        """
+        Write a dictionary of exports to a file in .ini format.
+        :param exports: A dictionary of exports, mapping an export category to
+                        a list of :class:`ExportEntry` instances describing the
+                        individual export entries.
+        """
+        rf = self.get_distinfo_file(EXPORTS_FILENAME)
+        with open(rf, 'w') as f:
+            write_exports(exports, f)
+
+    def get_resource_path(self, relative_path):
+        """
+        NOTE: This API may change in the future.
+
+        Return the absolute path to a resource file with the given relative
+        path.
+
+        :param relative_path: The path, relative to .dist-info, of the resource
+                              of interest.
+        :return: The absolute path where the resource is to be found.
+        """
+        r = self.get_distinfo_resource('RESOURCES')
+        with contextlib.closing(r.as_stream()) as stream:
+            with CSVReader(stream=stream) as resources_reader:
+                for relative, destination in resources_reader:
+                    if relative == relative_path:
+                        return destination
+        raise KeyError('no resource file with relative path %r '
+                       'is installed' % relative_path)
+
+    def list_installed_files(self):
+        """
+        Iterates over the ``RECORD`` entries and returns a tuple
+        ``(path, hash, size)`` for each line.
+
+        :returns: iterator of (path, hash, size)
+        """
+        for result in self._get_records():
+            yield result
+
+    def write_installed_files(self, paths, prefix, dry_run=False):
+        """
+        Writes the ``RECORD`` file, using the ``paths`` iterable passed in. Any
+        existing ``RECORD`` file is silently overwritten.
+
+        prefix is used to determine when to write absolute paths.
+        """
+        prefix = os.path.join(prefix, '')
+        base = os.path.dirname(self.path)
+        base_under_prefix = base.startswith(prefix)
+        base = os.path.join(base, '')
+        record_path = self.get_distinfo_file('RECORD')
+        logger.info('creating %s', record_path)
+        if dry_run:
+            return None
+        with CSVWriter(record_path) as writer:
+            for path in paths:
+                if os.path.isdir(path) or path.endswith(('.pyc', '.pyo')):
+                    # do not put size and hash, as in PEP-376
+                    hash_value = size = ''
+                else:
+                    size = '%d' % os.path.getsize(path)
+                    with open(path, 'rb') as fp:
+                        hash_value = self.get_hash(fp.read())
+                if path.startswith(base) or (base_under_prefix and
+                                             path.startswith(prefix)):
+                    path = os.path.relpath(path, base)
+                writer.writerow((path, hash_value, size))
+
+            # add the RECORD file itself
+            if record_path.startswith(base):
+                record_path = os.path.relpath(record_path, base)
+            writer.writerow((record_path, '', ''))
+        return record_path
+
+    def check_installed_files(self):
+        """
+        Checks that the hashes and sizes of the files in ``RECORD`` are
+        matched by the files themselves. Returns a (possibly empty) list of
+        mismatches. Each entry in the mismatch list will be a tuple consisting
+        of the path, 'exists', 'size' or 'hash' according to what didn't match
+        (existence is checked first, then size, then hash), the expected
+        value and the actual value.
+        """
+        mismatches = []
+        base = os.path.dirname(self.path)
+        record_path = self.get_distinfo_file('RECORD')
+        for path, hash_value, size in self.list_installed_files():
+            if not os.path.isabs(path):
+                path = os.path.join(base, path)
+            if path == record_path:
+                continue
+            if not os.path.exists(path):
+                mismatches.append((path, 'exists', True, False))
+            elif os.path.isfile(path):
+                actual_size = str(os.path.getsize(path))
+                if size and actual_size != size:
+                    mismatches.append((path, 'size', size, actual_size))
+                elif hash_value:
+                    if '=' in hash_value:
+                        hasher = hash_value.split('=', 1)[0]
+                    else:
+                        hasher = None
+
+                    with open(path, 'rb') as f:
+                        actual_hash = self.get_hash(f.read(), hasher)
+                        if actual_hash != hash_value:
+                            mismatches.append((path, 'hash', hash_value, actual_hash))
+        return mismatches
+
+    @cached_property
+    def shared_locations(self):
+        """
+        A dictionary of shared locations whose keys are in the set 'prefix',
+        'purelib', 'platlib', 'scripts', 'headers', 'data' and 'namespace'.
+        The corresponding value is the absolute path of that category for
+        this distribution, and takes into account any paths selected by the
+        user at installation time (e.g. via command-line arguments). In the
+        case of the 'namespace' key, this would be a list of absolute paths
+        for the roots of namespace packages in this distribution.
+
+        The first time this property is accessed, the relevant information is
+        read from the SHARED file in the .dist-info directory.
+        """
+        result = {}
+        shared_path = os.path.join(self.path, 'SHARED')
+        if os.path.isfile(shared_path):
+            with codecs.open(shared_path, 'r', encoding='utf-8') as f:
+                lines = f.read().splitlines()
+            for line in lines:
+                key, value = line.split('=', 1)
+                if key == 'namespace':
+                    result.setdefault(key, []).append(value)
+                else:
+                    result[key] = value
+        return result
+
+    def write_shared_locations(self, paths, dry_run=False):
+        """
+        Write shared location information to the SHARED file in .dist-info.
+        :param paths: A dictionary as described in the documentation for
+        :meth:`shared_locations`.
+        :param dry_run: If True, the action is logged but no file is actually
+                        written.
+        :return: The path of the file written to.
+        """
+        shared_path = os.path.join(self.path, 'SHARED')
+        logger.info('creating %s', shared_path)
+        if dry_run:
+            return None
+        lines = []
+        for key in ('prefix', 'lib', 'headers', 'scripts', 'data'):
+            path = paths[key]
+            if os.path.isdir(paths[key]):
+                lines.append('%s=%s' % (key,  path))
+        for ns in paths.get('namespace', ()):
+            lines.append('namespace=%s' % ns)
+
+        with codecs.open(shared_path, 'w', encoding='utf-8') as f:
+            f.write('\n'.join(lines))
+        return shared_path
+
+    def get_distinfo_resource(self, path):
+        if path not in DIST_FILES:
+            raise DistlibException('invalid path for a dist-info file: '
+                                   '%r at %r' % (path, self.path))
+        finder = resources.finder_for_path(self.path)
+        if finder is None:
+            raise DistlibException('Unable to get a finder for %s' % self.path)
+        return finder.find(path)
+
+    def get_distinfo_file(self, path):
+        """
+        Returns a path located under the ``.dist-info`` directory. Returns a
+        string representing the path.
+
+        :parameter path: a ``'/'``-separated path relative to the
+                         ``.dist-info`` directory or an absolute path;
+                         If *path* is an absolute path and doesn't start
+                         with the ``.dist-info`` directory path,
+                         a :class:`DistlibException` is raised
+        :type path: str
+        :rtype: str
+        """
+        # Check if it is an absolute path  # XXX use relpath, add tests
+        if path.find(os.sep) >= 0:
+            # it's an absolute path?
+            distinfo_dirname, path = path.split(os.sep)[-2:]
+            if distinfo_dirname != self.path.split(os.sep)[-1]:
+                raise DistlibException(
+                    'dist-info file %r does not belong to the %r %s '
+                    'distribution' % (path, self.name, self.version))
+
+        # The file must be relative
+        if path not in DIST_FILES:
+            raise DistlibException('invalid path for a dist-info file: '
+                                   '%r at %r' % (path, self.path))
+
+        return os.path.join(self.path, path)
+
+    def list_distinfo_files(self):
+        """
+        Iterates over the ``RECORD`` entries and returns paths for each line if
+        the path is pointing to a file located in the ``.dist-info`` directory
+        or one of its subdirectories.
+
+        :returns: iterator of paths
+        """
+        base = os.path.dirname(self.path)
+        for path, checksum, size in self._get_records():
+            # XXX add separator or use real relpath algo
+            if not os.path.isabs(path):
+                path = os.path.join(base, path)
+            if path.startswith(self.path):
+                yield path
+
+    def __eq__(self, other):
+        return (isinstance(other, InstalledDistribution) and
+                self.path == other.path)
+
+    # See http://docs.python.org/reference/datamodel#object.__hash__
+    __hash__ = object.__hash__
+
+
+class EggInfoDistribution(BaseInstalledDistribution):
+    """Created with the *path* of the ``.egg-info`` directory or file provided
+    to the constructor. It reads the metadata contained in the file itself, or
+    if the given path happens to be a directory, the metadata is read from the
+    file ``PKG-INFO`` under that directory."""
+
+    requested = True    # as we have no way of knowing, assume it was
+    shared_locations = {}
+
+    def __init__(self, path, env=None):
+        def set_name_and_version(s, n, v):
+            s.name = n
+            s.key = n.lower()   # for case-insensitive comparisons
+            s.version = v
+
+        self.path = path
+        self.dist_path = env
+        if env and env._cache_enabled and path in env._cache_egg.path:
+            metadata = env._cache_egg.path[path].metadata
+            set_name_and_version(self, metadata.name, metadata.version)
+        else:
+            metadata = self._get_metadata(path)
+
+            # Need to be set before caching
+            set_name_and_version(self, metadata.name, metadata.version)
+
+            if env and env._cache_enabled:
+                env._cache_egg.add(self)
+        super(EggInfoDistribution, self).__init__(metadata, path, env)
+
+    def _get_metadata(self, path):
+        requires = None
+
+        def parse_requires_data(data):
+            """Create a list of dependencies from a requires.txt file.
+
+            *data*: the contents of a setuptools-produced requires.txt file.
+            """
+            reqs = []
+            lines = data.splitlines()
+            for line in lines:
+                line = line.strip()
+                if line.startswith('['):
+                    logger.warning('Unexpected line: quitting requirement scan: %r',
+                                   line)
+                    break
+                r = parse_requirement(line)
+                if not r:
+                    logger.warning('Not recognised as a requirement: %r', line)
+                    continue
+                if r.extras:
+                    logger.warning('extra requirements in requires.txt are '
+                                   'not supported')
+                if not r.constraints:
+                    reqs.append(r.name)
+                else:
+                    cons = ', '.join('%s%s' % c for c in r.constraints)
+                    reqs.append('%s (%s)' % (r.name, cons))
+            return reqs
+
+        def parse_requires_path(req_path):
+            """Create a list of dependencies from a requires.txt file.
+
+            *req_path*: the path to a setuptools-produced requires.txt file.
+            """
+
+            reqs = []
+            try:
+                with codecs.open(req_path, 'r', 'utf-8') as fp:
+                    reqs = parse_requires_data(fp.read())
+            except IOError:
+                pass
+            return reqs
+
+        tl_path = tl_data = None
+        if path.endswith('.egg'):
+            if os.path.isdir(path):
+                p = os.path.join(path, 'EGG-INFO')
+                meta_path = os.path.join(p, 'PKG-INFO')
+                metadata = Metadata(path=meta_path, scheme='legacy')
+                req_path = os.path.join(p, 'requires.txt')
+                tl_path = os.path.join(p, 'top_level.txt')
+                requires = parse_requires_path(req_path)
+            else:
+                # FIXME handle the case where zipfile is not available
+                zipf = zipimport.zipimporter(path)
+                fileobj = StringIO(
+                    zipf.get_data('EGG-INFO/PKG-INFO').decode('utf8'))
+                metadata = Metadata(fileobj=fileobj, scheme='legacy')
+                try:
+                    data = zipf.get_data('EGG-INFO/requires.txt')
+                    tl_data = zipf.get_data('EGG-INFO/top_level.txt').decode('utf-8')
+                    requires = parse_requires_data(data.decode('utf-8'))
+                except IOError:
+                    requires = None
+        elif path.endswith('.egg-info'):
+            if os.path.isdir(path):
+                req_path = os.path.join(path, 'requires.txt')
+                requires = parse_requires_path(req_path)
+                path = os.path.join(path, 'PKG-INFO')
+                tl_path = os.path.join(path, 'top_level.txt')
+            metadata = Metadata(path=path, scheme='legacy')
+        else:
+            raise DistlibException('path must end with .egg-info or .egg, '
+                                   'got %r' % path)
+
+        if requires:
+            metadata.add_requirements(requires)
+        # look for top-level modules in top_level.txt, if present
+        if tl_data is None:
+            if tl_path is not None and os.path.exists(tl_path):
+                with open(tl_path, 'rb') as f:
+                    tl_data = f.read().decode('utf-8')
+        if not tl_data:
+            tl_data = []
+        else:
+            tl_data = tl_data.splitlines()
+        self.modules = tl_data
+        return metadata
+
+    def __repr__(self):
+        return '<EggInfoDistribution %r %s at %r>' % (
+            self.name, self.version, self.path)
+
+    def __str__(self):
+        return "%s %s" % (self.name, self.version)
+
+    def check_installed_files(self):
+        """
+        Checks that the hashes and sizes of the files in ``RECORD`` are
+        matched by the files themselves. Returns a (possibly empty) list of
+        mismatches. Each entry in the mismatch list will be a tuple consisting
+        of the path, 'exists', 'size' or 'hash' according to what didn't match
+        (existence is checked first, then size, then hash), the expected
+        value and the actual value.
+        """
+        mismatches = []
+        record_path = os.path.join(self.path, 'installed-files.txt')
+        if os.path.exists(record_path):
+            for path, _, _ in self.list_installed_files():
+                if path == record_path:
+                    continue
+                if not os.path.exists(path):
+                    mismatches.append((path, 'exists', True, False))
+        return mismatches
+
+    def list_installed_files(self):
+        """
+        Iterates over the ``installed-files.txt`` entries and returns a tuple
+        ``(path, hash, size)`` for each line.
+
+        :returns: a list of (path, hash, size)
+        """
+
+        def _md5(path):
+            f = open(path, 'rb')
+            try:
+                content = f.read()
+            finally:
+                f.close()
+            return hashlib.md5(content).hexdigest()
+
+        def _size(path):
+            return os.stat(path).st_size
+
+        record_path = os.path.join(self.path, 'installed-files.txt')
+        result = []
+        if os.path.exists(record_path):
+            with codecs.open(record_path, 'r', encoding='utf-8') as f:
+                for line in f:
+                    line = line.strip()
+                    p = os.path.normpath(os.path.join(self.path, line))
+                    # "./" is present as a marker between installed files
+                    # and installation metadata files
+                    if not os.path.exists(p):
+                        logger.warning('Non-existent file: %s', p)
+                        if p.endswith(('.pyc', '.pyo')):
+                            continue
+                        #otherwise fall through and fail
+                    if not os.path.isdir(p):
+                        result.append((p, _md5(p), _size(p)))
+            result.append((record_path, None, None))
+        return result
+
+    def list_distinfo_files(self, absolute=False):
+        """
+        Iterates over the ``installed-files.txt`` entries and returns paths for
+        each line if the path is pointing to a file located in the
+        ``.egg-info`` directory or one of its subdirectories.
+
+        :parameter absolute: If *absolute* is ``True``, each returned path is
+                          transformed into a local absolute path. Otherwise the
+                          raw value from ``installed-files.txt`` is returned.
+        :type absolute: boolean
+        :returns: iterator of paths
+        """
+        record_path = os.path.join(self.path, 'installed-files.txt')
+        if os.path.exists(record_path):
+            skip = True
+            with codecs.open(record_path, 'r', encoding='utf-8') as f:
+                for line in f:
+                    line = line.strip()
+                    if line == './':
+                        skip = False
+                        continue
+                    if not skip:
+                        p = os.path.normpath(os.path.join(self.path, line))
+                        if p.startswith(self.path):
+                            if absolute:
+                                yield p
+                            else:
+                                yield line
+
+    def __eq__(self, other):
+        return (isinstance(other, EggInfoDistribution) and
+                self.path == other.path)
+
+    # See http://docs.python.org/reference/datamodel#object.__hash__
+    __hash__ = object.__hash__
+
+new_dist_class = InstalledDistribution
+old_dist_class = EggInfoDistribution
+
+
+class DependencyGraph(object):
+    """
+    Represents a dependency graph between distributions.
+
+    The dependency relationships are stored in an ``adjacency_list`` that maps
+    distributions to a list of ``(other, label)`` tuples where  ``other``
+    is a distribution and the edge is labeled with ``label`` (i.e. the version
+    specifier, if such was provided). Also, for more efficient traversal, for
+    every distribution ``x``, a list of predecessors is kept in
+    ``reverse_list[x]``. An edge from distribution ``a`` to
+    distribution ``b`` means that ``a`` depends on ``b``. If any missing
+    dependencies are found, they are stored in ``missing``, which is a
+    dictionary that maps distributions to a list of requirements that were not
+    provided by any other distributions.
+    """
+
+    def __init__(self):
+        self.adjacency_list = {}
+        self.reverse_list = {}
+        self.missing = {}
+
+    def add_distribution(self, distribution):
+        """Add the *distribution* to the graph.
+
+        :type distribution: :class:`distutils2.database.InstalledDistribution`
+                            or :class:`distutils2.database.EggInfoDistribution`
+        """
+        self.adjacency_list[distribution] = []
+        self.reverse_list[distribution] = []
+        #self.missing[distribution] = []
+
+    def add_edge(self, x, y, label=None):
+        """Add an edge from distribution *x* to distribution *y* with the given
+        *label*.
+
+        :type x: :class:`distutils2.database.InstalledDistribution` or
+                 :class:`distutils2.database.EggInfoDistribution`
+        :type y: :class:`distutils2.database.InstalledDistribution` or
+                 :class:`distutils2.database.EggInfoDistribution`
+        :type label: ``str`` or ``None``
+        """
+        self.adjacency_list[x].append((y, label))
+        # multiple edges are allowed, so be careful
+        if x not in self.reverse_list[y]:
+            self.reverse_list[y].append(x)
+
+    def add_missing(self, distribution, requirement):
+        """
+        Add a missing *requirement* for the given *distribution*.
+
+        :type distribution: :class:`distutils2.database.InstalledDistribution`
+                            or :class:`distutils2.database.EggInfoDistribution`
+        :type requirement: ``str``
+        """
+        logger.debug('%s missing %r', distribution, requirement)
+        self.missing.setdefault(distribution, []).append(requirement)
+
+    def _repr_dist(self, dist):
+        return '%s %s' % (dist.name, dist.version)
+
+    def repr_node(self, dist, level=1):
+        """Prints only a subgraph"""
+        output = [self._repr_dist(dist)]
+        for other, label in self.adjacency_list[dist]:
+            dist = self._repr_dist(other)
+            if label is not None:
+                dist = '%s [%s]' % (dist, label)
+            output.append('    ' * level + str(dist))
+            suboutput = self.repr_node(other, level + 1)
+            subs = suboutput.split('\n')
+            output.extend(subs[1:])
+        return '\n'.join(output)
+
+    def to_dot(self, f, skip_disconnected=True):
+        """Writes a DOT output for the graph to the provided file *f*.
+
+        If *skip_disconnected* is set to ``True``, then all distributions
+        that are not dependent on any other distribution are skipped.
+
+        :type f: has to support ``file``-like operations
+        :type skip_disconnected: ``bool``
+        """
+        disconnected = []
+
+        f.write("digraph dependencies {\n")
+        for dist, adjs in self.adjacency_list.items():
+            if len(adjs) == 0 and not skip_disconnected:
+                disconnected.append(dist)
+            for other, label in adjs:
+                if not label is None:
+                    f.write('"%s" -> "%s" [label="%s"]\n' %
+                            (dist.name, other.name, label))
+                else:
+                    f.write('"%s" -> "%s"\n' % (dist.name, other.name))
+        if not skip_disconnected and len(disconnected) > 0:
+            f.write('subgraph disconnected {\n')
+            f.write('label = "Disconnected"\n')
+            f.write('bgcolor = red\n')
+
+            for dist in disconnected:
+                f.write('"%s"' % dist.name)
+                f.write('\n')
+            f.write('}\n')
+        f.write('}\n')
+
+    def topological_sort(self):
+        """
+        Perform a topological sort of the graph.
+        :return: A tuple, the first element of which is a topologically sorted
+                 list of distributions, and the second element of which is a
+                 list of distributions that cannot be sorted because they have
+                 circular dependencies and so form a cycle.
+        """
+        result = []
+        # Make a shallow copy of the adjacency list
+        alist = {}
+        for k, v in self.adjacency_list.items():
+            alist[k] = v[:]
+        while True:
+            # See what we can remove in this run
+            to_remove = []
+            for k, v in list(alist.items())[:]:
+                if not v:
+                    to_remove.append(k)
+                    del alist[k]
+            if not to_remove:
+                # What's left in alist (if anything) is a cycle.
+                break
+            # Remove from the adjacency list of others
+            for k, v in alist.items():
+                alist[k] = [(d, r) for d, r in v if d not in to_remove]
+            logger.debug('Moving to result: %s',
+                         ['%s (%s)' % (d.name, d.version) for d in to_remove])
+            result.extend(to_remove)
+        return result, list(alist.keys())
+
+    def __repr__(self):
+        """Representation of the graph"""
+        output = []
+        for dist, adjs in self.adjacency_list.items():
+            output.append(self.repr_node(dist))
+        return '\n'.join(output)
+
+
+def make_graph(dists, scheme='default'):
+    """Makes a dependency graph from the given distributions.
+
+    :parameter dists: a list of distributions
+    :type dists: list of :class:`distutils2.database.InstalledDistribution` and
+                 :class:`distutils2.database.EggInfoDistribution` instances
+    :rtype: a :class:`DependencyGraph` instance
+    """
+    scheme = get_scheme(scheme)
+    graph = DependencyGraph()
+    provided = {}  # maps names to lists of (version, dist) tuples
+
+    # first, build the graph and find out what's provided
+    for dist in dists:
+        graph.add_distribution(dist)
+
+        for p in dist.provides:
+            name, version = parse_name_and_version(p)
+            logger.debug('Add to provided: %s, %s, %s', name, version, dist)
+            provided.setdefault(name, []).append((version, dist))
+
+    # now make the edges
+    for dist in dists:
+        requires = (dist.run_requires | dist.meta_requires |
+                    dist.build_requires | dist.dev_requires)
+        for req in requires:
+            try:
+                matcher = scheme.matcher(req)
+            except UnsupportedVersionError:
+                # XXX compat-mode if cannot read the version
+                logger.warning('could not read version %r - using name only',
+                               req)
+                name = req.split()[0]
+                matcher = scheme.matcher(name)
+
+            name = matcher.key   # case-insensitive
+
+            matched = False
+            if name in provided:
+                for version, provider in provided[name]:
+                    try:
+                        match = matcher.match(version)
+                    except UnsupportedVersionError:
+                        match = False
+
+                    if match:
+                        graph.add_edge(dist, provider, req)
+                        matched = True
+                        break
+            if not matched:
+                graph.add_missing(dist, req)
+    return graph
+
+
+def get_dependent_dists(dists, dist):
+    """Recursively generate a list of distributions from *dists* that are
+    dependent on *dist*.
+
+    :param dists: a list of distributions
+    :param dist: a distribution, member of *dists* for which we are interested
+    """
+    if dist not in dists:
+        raise DistlibException('given distribution %r is not a member '
+                               'of the list' % dist.name)
+    graph = make_graph(dists)
+
+    dep = [dist]  # dependent distributions
+    todo = graph.reverse_list[dist]  # list of nodes we should inspect
+
+    while todo:
+        d = todo.pop()
+        dep.append(d)
+        for succ in graph.reverse_list[d]:
+            if succ not in dep:
+                todo.append(succ)
+
+    dep.pop(0)  # remove dist from dep, was there to prevent infinite loops
+    return dep
+
+
+def get_required_dists(dists, dist):
+    """Recursively generate a list of distributions from *dists* that are
+    required by *dist*.
+
+    :param dists: a list of distributions
+    :param dist: a distribution, member of *dists* for which we are interested
+    """
+    if dist not in dists:
+        raise DistlibException('given distribution %r is not a member '
+                               'of the list' % dist.name)
+    graph = make_graph(dists)
+
+    req = []  # required distributions
+    todo = graph.adjacency_list[dist]  # list of nodes we should inspect
+
+    while todo:
+        d = todo.pop()[0]
+        req.append(d)
+        for pred in graph.adjacency_list[d]:
+            if pred not in req:
+                todo.append(pred)
+
+    return req
+
+
+def make_dist(name, version, **kwargs):
+    """
+    A convenience method for making a dist given just a name and version.
+    """
+    summary = kwargs.pop('summary', 'Placeholder for summary')
+    md = Metadata(**kwargs)
+    md.name = name
+    md.version = version
+    md.summary = summary or 'Placeholder for summary'
+    return Distribution(md)