--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/python3.8/site-packages/pip/_internal/cache.py	Mon Jul 27 03:47:31 2020 -0400
@@ -0,0 +1,329 @@
+"""Cache Management
+"""
+
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
+import hashlib
+import json
+import logging
+import os
+
+from pip._vendor.packaging.tags import interpreter_name, interpreter_version
+from pip._vendor.packaging.utils import canonicalize_name
+
+from pip._internal.exceptions import InvalidWheelFilename
+from pip._internal.models.link import Link
+from pip._internal.models.wheel import Wheel
+from pip._internal.utils.temp_dir import TempDirectory
+from pip._internal.utils.typing import MYPY_CHECK_RUNNING
+from pip._internal.utils.urls import path_to_url
+
+if MYPY_CHECK_RUNNING:
+    from typing import Optional, Set, List, Any, Dict
+
+    from pip._vendor.packaging.tags import Tag
+
+    from pip._internal.models.format_control import FormatControl
+
+logger = logging.getLogger(__name__)
+
+
+def _hash_dict(d):
+    # type: (Dict[str, str]) -> str
+    """Return a stable sha224 of a dictionary."""
+    s = json.dumps(d, sort_keys=True, separators=(",", ":"), ensure_ascii=True)
+    return hashlib.sha224(s.encode("ascii")).hexdigest()
+
+
+class Cache(object):
+    """An abstract class - provides cache directories for data from links
+
+
+        :param cache_dir: The root of the cache.
+        :param format_control: An object of FormatControl class to limit
+            binaries being read from the cache.
+        :param allowed_formats: which formats of files the cache should store.
+            ('binary' and 'source' are the only allowed values)
+    """
+
+    def __init__(self, cache_dir, format_control, allowed_formats):
+        # type: (str, FormatControl, Set[str]) -> None
+        super(Cache, self).__init__()
+        assert not cache_dir or os.path.isabs(cache_dir)
+        self.cache_dir = cache_dir or None
+        self.format_control = format_control
+        self.allowed_formats = allowed_formats
+
+        _valid_formats = {"source", "binary"}
+        assert self.allowed_formats.union(_valid_formats) == _valid_formats
+
+    def _get_cache_path_parts_legacy(self, link):
+        # type: (Link) -> List[str]
+        """Get parts of part that must be os.path.joined with cache_dir
+
+        Legacy cache key (pip < 20) for compatibility with older caches.
+        """
+
+        # We want to generate an url to use as our cache key, we don't want to
+        # just re-use the URL because it might have other items in the fragment
+        # and we don't care about those.
+        key_parts = [link.url_without_fragment]
+        if link.hash_name is not None and link.hash is not None:
+            key_parts.append("=".join([link.hash_name, link.hash]))
+        key_url = "#".join(key_parts)
+
+        # Encode our key url with sha224, we'll use this because it has similar
+        # security properties to sha256, but with a shorter total output (and
+        # thus less secure). However the differences don't make a lot of
+        # difference for our use case here.
+        hashed = hashlib.sha224(key_url.encode()).hexdigest()
+
+        # We want to nest the directories some to prevent having a ton of top
+        # level directories where we might run out of sub directories on some
+        # FS.
+        parts = [hashed[:2], hashed[2:4], hashed[4:6], hashed[6:]]
+
+        return parts
+
+    def _get_cache_path_parts(self, link):
+        # type: (Link) -> List[str]
+        """Get parts of part that must be os.path.joined with cache_dir
+        """
+
+        # We want to generate an url to use as our cache key, we don't want to
+        # just re-use the URL because it might have other items in the fragment
+        # and we don't care about those.
+        key_parts = {"url": link.url_without_fragment}
+        if link.hash_name is not None and link.hash is not None:
+            key_parts[link.hash_name] = link.hash
+        if link.subdirectory_fragment:
+            key_parts["subdirectory"] = link.subdirectory_fragment
+
+        # Include interpreter name, major and minor version in cache key
+        # to cope with ill-behaved sdists that build a different wheel
+        # depending on the python version their setup.py is being run on,
+        # and don't encode the difference in compatibility tags.
+        # https://github.com/pypa/pip/issues/7296
+        key_parts["interpreter_name"] = interpreter_name()
+        key_parts["interpreter_version"] = interpreter_version()
+
+        # Encode our key url with sha224, we'll use this because it has similar
+        # security properties to sha256, but with a shorter total output (and
+        # thus less secure). However the differences don't make a lot of
+        # difference for our use case here.
+        hashed = _hash_dict(key_parts)
+
+        # We want to nest the directories some to prevent having a ton of top
+        # level directories where we might run out of sub directories on some
+        # FS.
+        parts = [hashed[:2], hashed[2:4], hashed[4:6], hashed[6:]]
+
+        return parts
+
+    def _get_candidates(self, link, canonical_package_name):
+        # type: (Link, Optional[str]) -> List[Any]
+        can_not_cache = (
+            not self.cache_dir or
+            not canonical_package_name or
+            not link
+        )
+        if can_not_cache:
+            return []
+
+        formats = self.format_control.get_allowed_formats(
+            canonical_package_name
+        )
+        if not self.allowed_formats.intersection(formats):
+            return []
+
+        candidates = []
+        path = self.get_path_for_link(link)
+        if os.path.isdir(path):
+            for candidate in os.listdir(path):
+                candidates.append((candidate, path))
+        # TODO remove legacy path lookup in pip>=21
+        legacy_path = self.get_path_for_link_legacy(link)
+        if os.path.isdir(legacy_path):
+            for candidate in os.listdir(legacy_path):
+                candidates.append((candidate, legacy_path))
+        return candidates
+
+    def get_path_for_link_legacy(self, link):
+        # type: (Link) -> str
+        raise NotImplementedError()
+
+    def get_path_for_link(self, link):
+        # type: (Link) -> str
+        """Return a directory to store cached items in for link.
+        """
+        raise NotImplementedError()
+
+    def get(
+        self,
+        link,            # type: Link
+        package_name,    # type: Optional[str]
+        supported_tags,  # type: List[Tag]
+    ):
+        # type: (...) -> Link
+        """Returns a link to a cached item if it exists, otherwise returns the
+        passed link.
+        """
+        raise NotImplementedError()
+
+    def cleanup(self):
+        # type: () -> None
+        pass
+
+
+class SimpleWheelCache(Cache):
+    """A cache of wheels for future installs.
+    """
+
+    def __init__(self, cache_dir, format_control):
+        # type: (str, FormatControl) -> None
+        super(SimpleWheelCache, self).__init__(
+            cache_dir, format_control, {"binary"}
+        )
+
+    def get_path_for_link_legacy(self, link):
+        # type: (Link) -> str
+        parts = self._get_cache_path_parts_legacy(link)
+        return os.path.join(self.cache_dir, "wheels", *parts)
+
+    def get_path_for_link(self, link):
+        # type: (Link) -> str
+        """Return a directory to store cached wheels for link
+
+        Because there are M wheels for any one sdist, we provide a directory
+        to cache them in, and then consult that directory when looking up
+        cache hits.
+
+        We only insert things into the cache if they have plausible version
+        numbers, so that we don't contaminate the cache with things that were
+        not unique. E.g. ./package might have dozens of installs done for it
+        and build a version of 0.0...and if we built and cached a wheel, we'd
+        end up using the same wheel even if the source has been edited.
+
+        :param link: The link of the sdist for which this will cache wheels.
+        """
+        parts = self._get_cache_path_parts(link)
+
+        # Store wheels within the root cache_dir
+        return os.path.join(self.cache_dir, "wheels", *parts)
+
+    def get(
+        self,
+        link,            # type: Link
+        package_name,    # type: Optional[str]
+        supported_tags,  # type: List[Tag]
+    ):
+        # type: (...) -> Link
+        candidates = []
+
+        if not package_name:
+            return link
+
+        canonical_package_name = canonicalize_name(package_name)
+        for wheel_name, wheel_dir in self._get_candidates(
+            link, canonical_package_name
+        ):
+            try:
+                wheel = Wheel(wheel_name)
+            except InvalidWheelFilename:
+                continue
+            if canonicalize_name(wheel.name) != canonical_package_name:
+                logger.debug(
+                    "Ignoring cached wheel {} for {} as it "
+                    "does not match the expected distribution name {}.".format(
+                        wheel_name, link, package_name
+                    )
+                )
+                continue
+            if not wheel.supported(supported_tags):
+                # Built for a different python/arch/etc
+                continue
+            candidates.append(
+                (
+                    wheel.support_index_min(supported_tags),
+                    wheel_name,
+                    wheel_dir,
+                )
+            )
+
+        if not candidates:
+            return link
+
+        _, wheel_name, wheel_dir = min(candidates)
+        return Link(path_to_url(os.path.join(wheel_dir, wheel_name)))
+
+
+class EphemWheelCache(SimpleWheelCache):
+    """A SimpleWheelCache that creates it's own temporary cache directory
+    """
+
+    def __init__(self, format_control):
+        # type: (FormatControl) -> None
+        self._temp_dir = TempDirectory(kind="ephem-wheel-cache")
+
+        super(EphemWheelCache, self).__init__(
+            self._temp_dir.path, format_control
+        )
+
+    def cleanup(self):
+        # type: () -> None
+        self._temp_dir.cleanup()
+
+
+class WheelCache(Cache):
+    """Wraps EphemWheelCache and SimpleWheelCache into a single Cache
+
+    This Cache allows for gracefully degradation, using the ephem wheel cache
+    when a certain link is not found in the simple wheel cache first.
+    """
+
+    def __init__(self, cache_dir, format_control):
+        # type: (str, FormatControl) -> None
+        super(WheelCache, self).__init__(
+            cache_dir, format_control, {'binary'}
+        )
+        self._wheel_cache = SimpleWheelCache(cache_dir, format_control)
+        self._ephem_cache = EphemWheelCache(format_control)
+
+    def get_path_for_link_legacy(self, link):
+        # type: (Link) -> str
+        return self._wheel_cache.get_path_for_link_legacy(link)
+
+    def get_path_for_link(self, link):
+        # type: (Link) -> str
+        return self._wheel_cache.get_path_for_link(link)
+
+    def get_ephem_path_for_link(self, link):
+        # type: (Link) -> str
+        return self._ephem_cache.get_path_for_link(link)
+
+    def get(
+        self,
+        link,            # type: Link
+        package_name,    # type: Optional[str]
+        supported_tags,  # type: List[Tag]
+    ):
+        # type: (...) -> Link
+        retval = self._wheel_cache.get(
+            link=link,
+            package_name=package_name,
+            supported_tags=supported_tags,
+        )
+        if retval is not link:
+            return retval
+
+        return self._ephem_cache.get(
+            link=link,
+            package_name=package_name,
+            supported_tags=supported_tags,
+        )
+
+    def cleanup(self):
+        # type: () -> None
+        self._wheel_cache.cleanup()
+        self._ephem_cache.cleanup()