[catapult] - Copy Telemetry's gsutilz over to third_party.

third_party/gsutil/gslib/file_part.py

+# -*- coding: utf-8 -*-
+# Copyright 2013 Google Inc. All Rights Reserved.
+#
+# Licensed 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.
+"""FilePart implementation for representing part of a file."""
+
+from __future__ import absolute_import
+
+import os
+
+
+class FilePart(file):
+  """Subclass of the file API for representing part of a file.
+
+  This class behaves as a contiguous subset of a given file (e.g., this object
+  will behave as though the desired part of the file was written to another
+  file, and the second file was opened).
+  """
+
+  # pylint: disable=super-init-not-called
+  def __init__(self, filename, offset, length):
+    """Initializes the FilePart.
+
+    Args:
+      filename: The name of the existing file, of which this object represents
+                a part.
+      offset: The position (in bytes) in the original file that corresponds to
+              the first byte of the FilePart.
+      length: The total number of bytes in the FilePart.
+    """
+    self._fp = open(filename, 'rb')
+    self.length = length
+    self._start = offset
+    self._end = self._start + self.length
+    self._fp.seek(self._start)
+
+  def __enter__(self):
+    pass
+
+  # pylint: disable=redefined-builtin
+  def __exit__(self, type, value, traceback):
+    self.close()
+
+  def tell(self):
+    return self._fp.tell() - self._start
+
+  def read(self, size=-1):
+    if size < 0:
+      size = self.length
+    size = min(size, self._end - self._fp.tell())  # Only read to our EOF
+    return self._fp.read(max(0, size))
+
+  def seek(self, offset, whence=os.SEEK_SET):
+    if whence == os.SEEK_END:
+      return self._fp.seek(offset + self._end)
+    elif whence == os.SEEK_CUR:
+      return self._fp.seek(offset, whence)
+    else:
+      return self._fp.seek(self._start + offset)
+
+  def close(self):
+    self._fp.close()
+
+  def flush(self, size=None):
+    raise NotImplementedError('flush is not implemented in FilePart.')
+
+  def fileno(self, size=None):
+    raise NotImplementedError('fileno is not implemented in FilePart.')
+
+  def isatty(self, size=None):
+    raise NotImplementedError('isatty is not implemented in FilePart.')
+
+  def next(self, size=None):
+    raise NotImplementedError('next is not implemented in FilePart.')
+
+  def readline(self, size=None):
+    raise NotImplementedError('readline is not implemented in FilePart.')
+
+  def readlines(self, size=None):
+    raise NotImplementedError('readlines is not implemented in FilePart.')
+
+  def xreadlines(self, size=None):
+    raise NotImplementedError('xreadlines is not implemented in FilePart.')
+
+  def truncate(self, size=None):
+    raise NotImplementedError('truncate is not implemented in FilePart.')
+
+  def write(self, size=None):
+    raise NotImplementedError('write is not implemented in FilePart.')
+
+  def writelines(self, size=None):
+    raise NotImplementedError('writelines is not implemented in FilePart.')