Add FileIO, InputFile, and OutputFile abstract base classes

python/src/iceberg/io/base.py

@@ -0,0 +1,100 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+"""Base FileIO classes for implementing reading and writing table files
+
+The FileIO abstraction includes a subset of full filesystem implementations. Specifically,
+Iceberg needs to read or write a file at a given location (as a seekable stream), as well
+as check if a file exists. An implementation of the FileIO abstract base class is responsible
+for returning an InputFile instance, an OutputFile instance, and deleting a file given
+its location.
+"""
+
+from abc import ABC, abstractmethod
+from typing import Union
+
+
+class InputFile(ABC):
+    """A base class for InputFile implementations"""
+
+    def __init__(self, location: str):
+        self._location = location
+
+    @abstractmethod
+    def __len__(self) -> int:
+        """Returns the total length of the file, in bytes"""
+
+    @property
+    def location(self) -> str:
+        """The fully-qualified location of the input file"""
+        return self._location
+
+    @property
+    @abstractmethod
+    def exists(self) -> bool:
+        """Checks whether the file exists"""
+
+    @abstractmethod
+    def open(self):
+        """This method should return an instance of an seekable input stream."""
+
+
+class OutputFile(ABC):
+    """A base class for OutputFile implementations"""
+
+    def __init__(self, location: str):
+        self._location = location
+
+    @abstractmethod
+    def __len__(self) -> int:
+        """Returns the total length of the file, in bytes"""
+
+    @property
+    def location(self) -> str:
+        """The fully-qualified location of the output file"""
+        return self._location
+
+    @property
+    @abstractmethod
+    def exists(self) -> bool:
+        """Checks whether the file exists"""
+
+    @abstractmethod
+    def to_input_file(self) -> InputFile:
+        """Returns an InputFile for the location of this output file"""
+
+    @abstractmethod
+    def create(self, overwrite: bool = False):
+        """This method should return a file-like object.
+
+        Args:
+            overwrite(bool): If the file already exists at `self.location`
+            and `overwrite` is False a FileExistsError should be raised.
+        """
+
+
+class FileIO(ABC):
+    @abstractmethod
+    def new_input(self, location: str) -> InputFile:
+        """Get an InputFile instance to read bytes from the file at the given location"""
+
+    @abstractmethod
+    def new_output(self, location: str) -> OutputFile:
+        """Get an OutputFile instance to write bytes to the file at the given location"""
+
+    @abstractmethod
+    def delete(self, location: Union[str, InputFile, OutputFile]) -> None:
+        """Delete the file at the given path"""