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file_io.py
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#!/usr/bin/env python3
# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
import errno
import logging
import os
import shutil
from collections import OrderedDict
from typing import (
IO,
Any,
Callable,
Dict,
List,
MutableMapping,
Optional,
Union,
)
from urllib.parse import urlparse
import portalocker # type: ignore
from fvcore.common.download import download
__all__ = ["PathManager", "get_cache_dir", "file_lock"]
def get_cache_dir(cache_dir: Optional[str] = None) -> str:
"""
Returns a default directory to cache static files
(usually downloaded from Internet), if None is provided.
Args:
cache_dir (None or str): if not None, will be returned as is.
If None, returns the default cache directory as:
1) $FVCORE_CACHE, if set
2) otherwise ~/.torch/fvcore_cache
"""
if cache_dir is None:
cache_dir = os.path.expanduser(
os.getenv("FVCORE_CACHE", "~/.torch/fvcore_cache")
)
return cache_dir
def file_lock(path: str): # type: ignore
"""
A file lock. Once entered, it is guaranteed that no one else holds the
same lock. Others trying to enter the lock will block for 30 minutes and
raise an exception.
This is useful to make sure workers don't cache files to the same location.
Args:
path (str): a path to be locked. This function will create a lock named
`path + ".lock"`
Examples:
filename = "/path/to/file"
with file_lock(filename):
if not os.path.isfile(filename):
do_create_file()
"""
dirname = os.path.dirname(path)
try:
os.makedirs(dirname, exist_ok=True)
except OSError:
# makedir is not atomic. Exceptions can happen when multiple workers try
# to create the same dir, despite exist_ok=True.
# When this happens, we assume the dir is created and proceed to creating
# the lock. If failed to create the directory, the next line will raise
# exceptions.
pass
return portalocker.Lock(path + ".lock", timeout=1800) # type: ignore
class PathHandler:
"""
PathHandler is a base class that defines common I/O functionality for a URI
protocol. It routes I/O for a generic URI which may look like "protocol://*"
or a canonical filepath "/foo/bar/baz".
"""
_strict_kwargs_check = True
def _check_kwargs(self, kwargs: Dict[str, Any]) -> None:
"""
Checks if the given arguments are empty. Throws a ValueError if strict
kwargs checking is enabled and args are non-empty. If strict kwargs
checking is disabled, only a warning is logged.
Args:
kwargs (Dict[str, Any])
"""
if self._strict_kwargs_check:
if len(kwargs) > 0:
raise ValueError("Unused arguments: {}".format(kwargs))
else:
logger = logging.getLogger(__name__)
for k, v in kwargs.items():
logger.warning("{}={} argument ignored".format(k, v))
def _get_supported_prefixes(self) -> List[str]:
"""
Returns:
List[str]: the list of URI prefixes this PathHandler can support
"""
raise NotImplementedError()
def _get_local_path(self, path: str, **kwargs: Any) -> str:
"""
Get a filepath which is compatible with native Python I/O such as `open`
and `os.path`.
If URI points to a remote resource, this function may download and cache
the resource to local disk. In this case, this function is meant to be
used with read-only resources.
Args:
path (str): A URI supported by this PathHandler
Returns:
local_path (str): a file path which exists on the local file system
"""
raise NotImplementedError()
def _open(
self, path: str, mode: str = "r", buffering: int = -1, **kwargs: Any
) -> Union[IO[str], IO[bytes]]:
"""
Open a stream to a URI, similar to the built-in `open`.
Args:
path (str): A URI supported by this PathHandler
mode (str): Specifies the mode in which the file is opened. It defaults
to 'r'.
buffering (int): An optional integer used to set the buffering policy.
Pass 0 to switch buffering off and an integer >= 1 to indicate the
size in bytes of a fixed-size chunk buffer. When no buffering
argument is given, the default buffering policy depends on the
underlying I/O implementation.
Returns:
file: a file-like object.
"""
raise NotImplementedError()
def _copy(
self,
src_path: str,
dst_path: str,
overwrite: bool = False,
**kwargs: Any,
) -> bool:
"""
Copies a source path to a destination path.
Args:
src_path (str): A URI supported by this PathHandler
dst_path (str): A URI supported by this PathHandler
overwrite (bool): Bool flag for forcing overwrite of existing file
Returns:
status (bool): True on success
"""
raise NotImplementedError()
def _exists(self, path: str, **kwargs: Any) -> bool:
"""
Checks if there is a resource at the given URI.
Args:
path (str): A URI supported by this PathHandler
Returns:
bool: true if the path exists
"""
raise NotImplementedError()
def _isfile(self, path: str, **kwargs: Any) -> bool:
"""
Checks if the resource at the given URI is a file.
Args:
path (str): A URI supported by this PathHandler
Returns:
bool: true if the path is a file
"""
raise NotImplementedError()
def _isdir(self, path: str, **kwargs: Any) -> bool:
"""
Checks if the resource at the given URI is a directory.
Args:
path (str): A URI supported by this PathHandler
Returns:
bool: true if the path is a directory
"""
raise NotImplementedError()
def _ls(self, path: str, **kwargs: Any) -> List[str]:
"""
List the contents of the directory at the provided URI.
Args:
path (str): A URI supported by this PathHandler
Returns:
List[str]: list of contents in given path
"""
raise NotImplementedError()
def _mkdirs(self, path: str, **kwargs: Any) -> None:
"""
Recursive directory creation function. Like mkdir(), but makes all
intermediate-level directories needed to contain the leaf directory.
Similar to the native `os.makedirs`.
Args:
path (str): A URI supported by this PathHandler
"""
raise NotImplementedError()
def _rm(self, path: str, **kwargs: Any) -> None:
"""
Remove the file (not directory) at the provided URI.
Args:
path (str): A URI supported by this PathHandler
"""
raise NotImplementedError()
class NativePathHandler(PathHandler):
"""
Handles paths that can be accessed using Python native system calls. This
handler uses `open()` and `os.*` calls on the given path.
"""
def _get_local_path(self, path: str, **kwargs: Any) -> str:
self._check_kwargs(kwargs)
return path
def _open(
self,
path: str,
mode: str = "r",
buffering: int = -1,
encoding: Optional[str] = None,
errors: Optional[str] = None,
newline: Optional[str] = None,
closefd: bool = True,
opener: Optional[Callable] = None,
**kwargs: Any,
) -> Union[IO[str], IO[bytes]]:
"""
Open a path.
Args:
path (str): A URI supported by this PathHandler
mode (str): Specifies the mode in which the file is opened. It defaults
to 'r'.
buffering (int): An optional integer used to set the buffering policy.
Pass 0 to switch buffering off and an integer >= 1 to indicate the
size in bytes of a fixed-size chunk buffer. When no buffering
argument is given, the default buffering policy works as follows:
* Binary files are buffered in fixed-size chunks; the size of
the buffer is chosen using a heuristic trying to determine the
underlying device’s “block size” and falling back on
io.DEFAULT_BUFFER_SIZE. On many systems, the buffer will
typically be 4096 or 8192 bytes long.
encoding (Optional[str]): the name of the encoding used to decode or
encode the file. This should only be used in text mode.
errors (Optional[str]): an optional string that specifies how encoding
and decoding errors are to be handled. This cannot be used in binary
mode.
newline (Optional[str]): controls how universal newlines mode works
(it only applies to text mode). It can be None, '', '\n', '\r',
and '\r\n'.
closefd (bool): If closefd is False and a file descriptor rather than
a filename was given, the underlying file descriptor will be kept
open when the file is closed. If a filename is given closefd must
be True (the default) otherwise an error will be raised.
opener (Optional[Callable]): A custom opener can be used by passing
a callable as opener. The underlying file descriptor for the file
object is then obtained by calling opener with (file, flags).
opener must return an open file descriptor (passing os.open as opener
results in functionality similar to passing None).
See https://docs.python.org/3/library/functions.html#open for details.
Returns:
file: a file-like object.
"""
self._check_kwargs(kwargs)
return open( # type: ignore
path,
mode,
buffering=buffering,
encoding=encoding,
errors=errors,
newline=newline,
closefd=closefd,
opener=opener,
)
def _copy(
self,
src_path: str,
dst_path: str,
overwrite: bool = False,
**kwargs: Any,
) -> bool:
"""
Copies a source path to a destination path.
Args:
src_path (str): A URI supported by this PathHandler
dst_path (str): A URI supported by this PathHandler
overwrite (bool): Bool flag for forcing overwrite of existing file
Returns:
status (bool): True on success
"""
self._check_kwargs(kwargs)
if os.path.exists(dst_path) and not overwrite:
logger = logging.getLogger(__name__)
logger.error("Destination file {} already exists.".format(dst_path))
return False
try:
shutil.copyfile(src_path, dst_path)
return True
except Exception as e:
logger = logging.getLogger(__name__)
logger.error("Error in file copy - {}".format(str(e)))
return False
def _exists(self, path: str, **kwargs: Any) -> bool:
self._check_kwargs(kwargs)
return os.path.exists(path)
def _isfile(self, path: str, **kwargs: Any) -> bool:
self._check_kwargs(kwargs)
return os.path.isfile(path)
def _isdir(self, path: str, **kwargs: Any) -> bool:
self._check_kwargs(kwargs)
return os.path.isdir(path)
def _ls(self, path: str, **kwargs: Any) -> List[str]:
self._check_kwargs(kwargs)
return os.listdir(path)
def _mkdirs(self, path: str, **kwargs: Any) -> None:
self._check_kwargs(kwargs)
try:
os.makedirs(path, exist_ok=True)
except OSError as e:
# EEXIST it can still happen if multiple processes are creating the dir
if e.errno != errno.EEXIST:
raise
def _rm(self, path: str, **kwargs: Any) -> None:
self._check_kwargs(kwargs)
os.remove(path)
class HTTPURLHandler(PathHandler):
"""
Download URLs and cache them to disk.
"""
def __init__(self) -> None:
self.cache_map: Dict[str, str] = {}
def _get_supported_prefixes(self) -> List[str]:
return ["http://", "https://", "ftp://"]
def _get_local_path(self, path: str, **kwargs: Any) -> str:
"""
This implementation downloads the remote resource and caches it locally.
The resource will only be downloaded if not previously requested.
"""
self._check_kwargs(kwargs)
if path not in self.cache_map or not os.path.exists(
self.cache_map[path]
):
logger = logging.getLogger(__name__)
parsed_url = urlparse(path)
dirname = os.path.join(
get_cache_dir(), os.path.dirname(parsed_url.path.lstrip("/"))
)
filename = path.split("/")[-1]
cached = os.path.join(dirname, filename)
with file_lock(cached):
if not os.path.isfile(cached):
logger.info("Downloading {} ...".format(path))
cached = download(path, dirname, filename=filename)
logger.info("URL {} cached in {}".format(path, cached))
self.cache_map[path] = cached
return self.cache_map[path]
def _open(
self, path: str, mode: str = "r", buffering: int = -1, **kwargs: Any
) -> Union[IO[str], IO[bytes]]:
"""
Open a remote HTTP path. The resource is first downloaded and cached
locally.
Args:
path (str): A URI supported by this PathHandler
mode (str): Specifies the mode in which the file is opened. It defaults
to 'r'.
buffering (int): Not used for this PathHandler.
Returns:
file: a file-like object.
"""
self._check_kwargs(kwargs)
assert mode in (
"r",
"rb",
), "{} does not support open with {} mode".format(
self.__class__.__name__, mode
)
assert (
buffering == -1
), f"{self.__class__.__name__} does not support the `buffering` argument"
local_path = self._get_local_path(path)
return open(local_path, mode)
class PathManager:
"""
A class for users to open generic paths or translate generic paths to file names.
"""
_PATH_HANDLERS: MutableMapping[str, PathHandler] = OrderedDict()
_NATIVE_PATH_HANDLER = NativePathHandler()
@staticmethod
def __get_path_handler(path: str) -> PathHandler:
"""
Finds a PathHandler that supports the given path. Falls back to the native
PathHandler if no other handler is found.
Args:
path (str): URI path to resource
Returns:
handler (PathHandler)
"""
for p in PathManager._PATH_HANDLERS.keys():
if path.startswith(p):
return PathManager._PATH_HANDLERS[p]
return PathManager._NATIVE_PATH_HANDLER
@staticmethod
def open(
path: str, mode: str = "r", buffering: int = -1, **kwargs: Any
) -> Union[IO[str], IO[bytes]]:
"""
Open a stream to a URI, similar to the built-in `open`.
Args:
path (str): A URI supported by this PathHandler
mode (str): Specifies the mode in which the file is opened. It defaults
to 'r'.
buffering (int): An optional integer used to set the buffering policy.
Pass 0 to switch buffering off and an integer >= 1 to indicate the
size in bytes of a fixed-size chunk buffer. When no buffering
argument is given, the default buffering policy depends on the
underlying I/O implementation.
Returns:
file: a file-like object.
"""
return PathManager.__get_path_handler(path)._open( # type: ignore
path, mode, buffering=buffering, **kwargs
)
@staticmethod
def copy(
src_path: str, dst_path: str, overwrite: bool = False, **kwargs: Any
) -> bool:
"""
Copies a source path to a destination path.
Args:
src_path (str): A URI supported by this PathHandler
dst_path (str): A URI supported by this PathHandler
overwrite (bool): Bool flag for forcing overwrite of existing file
Returns:
status (bool): True on success
"""
# Copying across handlers is not supported.
assert PathManager.__get_path_handler( # type: ignore
src_path
) == PathManager.__get_path_handler(dst_path)
return PathManager.__get_path_handler(src_path)._copy(
src_path, dst_path, overwrite, **kwargs
)
@staticmethod
def get_local_path(path: str, **kwargs: Any) -> str:
"""
Get a filepath which is compatible with native Python I/O such as `open`
and `os.path`.
If URI points to a remote resource, this function may download and cache
the resource to local disk.
Args:
path (str): A URI supported by this PathHandler
Returns:
local_path (str): a file path which exists on the local file system
"""
return PathManager.__get_path_handler( # type: ignore
path
)._get_local_path(path, **kwargs)
@staticmethod
def exists(path: str, **kwargs: Any) -> bool:
"""
Checks if there is a resource at the given URI.
Args:
path (str): A URI supported by this PathHandler
Returns:
bool: true if the path exists
"""
return PathManager.__get_path_handler(path)._exists( # type: ignore
path, **kwargs
)
@staticmethod
def isfile(path: str, **kwargs: Any) -> bool:
"""
Checks if there the resource at the given URI is a file.
Args:
path (str): A URI supported by this PathHandler
Returns:
bool: true if the path is a file
"""
return PathManager.__get_path_handler(path)._isfile( # type: ignore
path, **kwargs
)
@staticmethod
def isdir(path: str, **kwargs: Any) -> bool:
"""
Checks if the resource at the given URI is a directory.
Args:
path (str): A URI supported by this PathHandler
Returns:
bool: true if the path is a directory
"""
return PathManager.__get_path_handler(path)._isdir( # type: ignore
path, **kwargs
)
@staticmethod
def ls(path: str, **kwargs: Any) -> List[str]:
"""
List the contents of the directory at the provided URI.
Args:
path (str): A URI supported by this PathHandler
Returns:
List[str]: list of contents in given path
"""
return PathManager.__get_path_handler(path)._ls( # type: ignore
path, **kwargs
)
@staticmethod
def mkdirs(path: str, **kwargs: Any) -> None:
"""
Recursive directory creation function. Like mkdir(), but makes all
intermediate-level directories needed to contain the leaf directory.
Similar to the native `os.makedirs`.
Args:
path (str): A URI supported by this PathHandler
"""
return PathManager.__get_path_handler(path)._mkdirs( # type: ignore
path, **kwargs
)
@staticmethod
def rm(path: str, **kwargs: Any) -> None:
"""
Remove the file (not directory) at the provided URI.
Args:
path (str): A URI supported by this PathHandler
"""
return PathManager.__get_path_handler(path)._rm( # type: ignore
path, **kwargs
)
@staticmethod
def register_handler(handler: PathHandler) -> None:
"""
Register a path handler associated with `handler._get_supported_prefixes`
URI prefixes.
Args:
handler (PathHandler)
"""
assert isinstance(handler, PathHandler), handler
for prefix in handler._get_supported_prefixes():
assert prefix not in PathManager._PATH_HANDLERS
PathManager._PATH_HANDLERS[prefix] = handler
# Sort path handlers in reverse order so longer prefixes take priority,
# eg: http://foo/bar before http://foo
PathManager._PATH_HANDLERS = OrderedDict(
sorted(
PathManager._PATH_HANDLERS.items(),
key=lambda t: t[0],
reverse=True,
)
)
@staticmethod
def set_strict_kwargs_checking(enable: bool) -> None:
"""
Toggles strict kwargs checking. If enabled, a ValueError is thrown if any
unused parameters are passed to a PathHandler function. If disabled, only
a warning is given.
With a centralized file API, there's a tradeoff of convenience and
correctness delegating arguments to the proper I/O layers. An underlying
`PathHandler` may support custom arguments which should not be statically
exposed on the `PathManager` function. For example, a custom `HTTPURLHandler`
may want to expose a `cache_timeout` argument for `open()` which specifies
how old a locally cached resource can be before it's refetched from the
remote server. This argument would not make sense for a `NativePathHandler`.
If strict kwargs checking is disabled, `cache_timeout` can be passed to
`PathManager.open` which will forward the arguments to the underlying
handler. By default, checking is enabled since it is innately unsafe:
multiple `PathHandler`s could reuse arguments with different semantic
meanings or types.
Args:
enable (bool)
"""
PathManager._NATIVE_PATH_HANDLER._strict_kwargs_check = enable
for handler in PathManager._PATH_HANDLERS.values():
handler._strict_kwargs_check = enable
PathManager.register_handler(HTTPURLHandler())