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107 lines
2.5 KiB
Python
107 lines
2.5 KiB
Python
"""
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Interface adapters for low-level readers.
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"""
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import abc
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import io
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import itertools
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from typing import BinaryIO, List
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from .abc import Traversable, TraversableResources
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class SimpleReader(abc.ABC):
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"""
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The minimum, low-level interface required from a resource
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provider.
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"""
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@property
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@abc.abstractmethod
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def package(self) -> str:
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"""
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The name of the package for which this reader loads resources.
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"""
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@abc.abstractmethod
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def children(self) -> List['SimpleReader']:
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"""
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Obtain an iterable of SimpleReader for available
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child containers (e.g. directories).
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"""
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@abc.abstractmethod
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def resources(self) -> List[str]:
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"""
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Obtain available named resources for this virtual package.
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"""
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@abc.abstractmethod
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def open_binary(self, resource: str) -> BinaryIO:
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"""
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Obtain a File-like for a named resource.
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"""
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@property
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def name(self):
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return self.package.split('.')[-1]
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class ResourceContainer(Traversable):
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"""
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Traversable container for a package's resources via its reader.
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"""
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def __init__(self, reader: SimpleReader):
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self.reader = reader
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def is_dir(self):
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return True
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def is_file(self):
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return False
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def iterdir(self):
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files = (ResourceHandle(self, name) for name in self.reader.resources)
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dirs = map(ResourceContainer, self.reader.children())
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return itertools.chain(files, dirs)
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def open(self, *args, **kwargs):
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raise IsADirectoryError()
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class ResourceHandle(Traversable):
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"""
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Handle to a named resource in a ResourceReader.
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"""
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def __init__(self, parent: ResourceContainer, name: str):
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self.parent = parent
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self.name = name # type: ignore
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def is_file(self):
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return True
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def is_dir(self):
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return False
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def open(self, mode='r', *args, **kwargs):
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stream = self.parent.reader.open_binary(self.name)
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if 'b' not in mode:
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stream = io.TextIOWrapper(stream, *args, **kwargs)
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return stream
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def joinpath(self, name):
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raise RuntimeError("Cannot traverse into a resource")
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class TraversableReader(TraversableResources, SimpleReader):
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"""
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A TraversableResources based on SimpleReader. Resource providers
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may derive from this class to provide the TraversableResources
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interface by supplying the SimpleReader interface.
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"""
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def files(self):
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return ResourceContainer(self)
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