posix.py 文件源码

def _read(self, N):
        # Starting with Python 3 open with buffering=0 returns a FileIO object.
        # FileIO.read behaves like read(2) and not like fread(3) and thus we
        # have to handle the case that read returns less data as requested here
        # more carefully.
        data = b("")
        while len(data) < N:
            try:
                d = self.__file.read(N - len(data))
            except IOError, e:
                # read(2) has been interrupted by a signal; redo the read
                if e.errno == errno.EINTR:
                    continue
                raise

            if d is None:
                # __file is in non-blocking mode and no data is available
                return data
            if len(d) == 0:
                # __file is in blocking mode and arrived at EOF
                return data

            data += d
        return data