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"""
Interface adapters for low-level readers.
"""
import abc
import io
import itertools
from typing import BinaryIO, List
from .abc import Traversable, TraversableResources
class SimpleReader(abc.ABC):
"""
The minimum, low-level interface required from a resource
provider.
"""
@abc.abstractproperty
def package(self):
# type: () -> str
"""
The name of the package for which this reader loads resources.
"""
@abc.abstractmethod
def children(self):
# type: () -> List['SimpleReader']
"""
Obtain an iterable of SimpleReader for available
child containers (e.g. directories).
"""
@abc.abstractmethod
def resources(self):
# type: () -> List[str]
"""
Obtain available named resources for this virtual package.
"""
@abc.abstractmethod
def open_binary(self, resource):
# type: (str) -> BinaryIO
"""
Obtain a File-like for a named resource.
"""
@property
def name(self):
return self.package.split('.')[-1]
class ResourceHandle(Traversable):
"""
Handle to a named resource in a ResourceReader.
"""
def __init__(self, parent, name):
# type: (ResourceContainer, str) -> None
self.parent = parent
self.name = name # type: ignore
def is_file(self):
return True
def is_dir(self):
return False
def open(self, mode='r', *args, **kwargs):
stream = self.parent.reader.open_binary(self.name)
if 'b' not in mode:
stream = io.TextIOWrapper(stream, *args, **kwargs)
return stream
def joinpath(self, name):
raise RuntimeError("Cannot traverse into a resource")
class ResourceContainer(Traversable):
"""
Traversable container for a package's resources via its reader.
"""
def __init__(self, reader):
# type: (SimpleReader) -> None
self.reader = reader
def is_dir(self):
return True
def is_file(self):
return False
def iterdir(self):
files = (ResourceHandle(self, name) for name in self.reader.resources)
dirs = map(ResourceContainer, self.reader.children())
return itertools.chain(files, dirs)
def open(self, *args, **kwargs):
raise IsADirectoryError()
@staticmethod
def _flatten(compound_names):
for name in compound_names:
yield from name.split('/')
def joinpath(self, *descendants):
if not descendants:
return self
names = self._flatten(descendants)
target = next(names)
return next(
traversable for traversable in self.iterdir() if traversable.name == target
).joinpath(*names)
class TraversableReader(TraversableResources, SimpleReader):
"""
A TraversableResources based on SimpleReader. Resource providers
may derive from this class to provide the TraversableResources
interface by supplying the SimpleReader interface.
"""
def files(self):
return ResourceContainer(self)
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