initial commit

pyctr/common.py

@@ -0,0 +1,82 @@
+# This file is a part of ninfs.
+#
+# Copyright (c) 2017-2019 Ian Burgwin
+# This file is licensed under The MIT License (MIT).
+# You can find the full license text in LICENSE.md in the root of this project.
+
+from functools import wraps
+from io import BufferedIOBase
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    # this is a lazy way to make type checkers stop complaining
+    from typing import BinaryIO
+    BufferedIOBase = BinaryIO
+
+
+class PyCTRError(Exception):
+    """Common base class for all PyCTR errors."""
+
+
+def _raise_if_closed(method):
+    @wraps(method)
+    def decorator(self: '_ReaderOpenFileBase', *args, **kwargs):
+        if self._reader.closed:
+            self.closed = True
+        if self.closed:
+            raise ValueError('I/O operation on closed file')
+        return method(self, *args, **kwargs)
+    return decorator
+
+
+class _ReaderOpenFileBase(BufferedIOBase):
+    """Base class for all open files for Reader classes."""
+
+    _seek = 0
+    _info = None
+    closed = False
+
+    def __init__(self, reader, path):
+        self._reader = reader
+        self._path = path
+
+    def __repr__(self):
+        return f'<{type(self).__name__} path={self._path!r} info={self._info!r} reader={self._reader!r}>'
+
+    @_raise_if_closed
+    def read(self, size: int = -1) -> bytes:
+        if size == -1:
+            size = self._info.size - self._seek
+        data = self._reader.get_data(self._info, self._seek, size)
+        self._seek += len(data)
+        return data
+
+    read1 = read  # probably make this act like read1 should, but this for now enables some other things to work
+
+    @_raise_if_closed
+    def seek(self, seek: int, whence: int = 0) -> int:
+        if whence == 0:
+            if seek < 0:
+                raise ValueError(f'negative seek value {seek}')
+            self._seek = min(seek, self._info.size)
+        elif whence == 1:
+            self._seek = max(self._seek + seek, 0)
+        elif whence == 2:
+            self._seek = max(self._info.size + seek, 0)
+        return self._seek
+
+    @_raise_if_closed
+    def tell(self) -> int:
+        return self._seek
+
+    @_raise_if_closed
+    def readable(self) -> bool:
+        return True
+
+    @_raise_if_closed
+    def writable(self) -> bool:
+        return False
+
+    @_raise_if_closed
+    def seekable(self) -> bool:
+        return True