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Direktori : /opt/alt/python36/lib/python3.6/site-packages/pip/_vendor/cachecontrol/ |
Current File : //opt/alt/python36/lib/python3.6/site-packages/pip/_vendor/cachecontrol/filewrapper.py |
from io import BytesIO class CallbackFileWrapper(object): """ Small wrapper around a fp object which will tee everything read into a buffer, and when that file is closed it will execute a callback with the contents of that buffer. All attributes are proxied to the underlying file object. This class uses members with a double underscore (__) leading prefix so as not to accidentally shadow an attribute. """ def __init__(self, fp, callback): self.__buf = BytesIO() self.__fp = fp self.__callback = callback def __getattr__(self, name): # The vaguaries of garbage collection means that self.__fp is # not always set. By using __getattribute__ and the private # name[0] allows looking up the attribute value and raising an # AttributeError when it doesn't exist. This stop thigns from # infinitely recursing calls to getattr in the case where # self.__fp hasn't been set. # # [0] https://docs.python.org/2/reference/expressions.html#atom-identifiers fp = self.__getattribute__("_CallbackFileWrapper__fp") return getattr(fp, name) def __is_fp_closed(self): try: return self.__fp.fp is None except AttributeError: pass try: return self.__fp.closed except AttributeError: pass # We just don't cache it then. # TODO: Add some logging here... return False def _close(self): if self.__callback: self.__callback(self.__buf.getvalue()) # We assign this to None here, because otherwise we can get into # really tricky problems where the CPython interpreter dead locks # because the callback is holding a reference to something which # has a __del__ method. Setting this to None breaks the cycle # and allows the garbage collector to do it's thing normally. self.__callback = None def read(self, amt=None): data = self.__fp.read(amt) self.__buf.write(data) if self.__is_fp_closed(): self._close() return data def _safe_read(self, amt): data = self.__fp._safe_read(amt) if amt == 2 and data == b"\r\n": # urllib executes this read to toss the CRLF at the end # of the chunk. return data self.__buf.write(data) if self.__is_fp_closed(): self._close() return data