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""" |
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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 |
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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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