# Django 2.2.9.dev20191202104323 文档

# django.core.files.base 源代码

    import os
    from io import BytesIO, StringIO, UnsupportedOperation

    from django.core.files.utils import FileProxyMixin
    from django.utils.functional import cached_property

    class File(FileProxyMixin):
        DEFAULT_CHUNK_SIZE = 64 * 2 ** 10

        def __init__(self, file, name=None):
            self.file = file
            if name is None:
                name = getattr(file, 'name', None)
            self.name = name
            if hasattr(file, 'mode'):
                self.mode = file.mode

        def __str__(self):
            return self.name or ''

        def __repr__(self):
            return "<%s: %s>" % (self.__class__.__name__, self or "None")

        def __bool__(self):
            return bool(self.name)

        def __len__(self):
            return self.size

        @cached_property
        def size(self):
            if hasattr(self.file, 'size'):
                return self.file.size
            if hasattr(self.file, 'name'):
                try:
                    return os.path.getsize(self.file.name)
                except (OSError, TypeError):
                    pass
            if hasattr(self.file, 'tell') and hasattr(self.file, 'seek'):
                pos = self.file.tell()
                self.file.seek(0, os.SEEK_END)
                size = self.file.tell()
                self.file.seek(pos)
                return size
            raise AttributeError("Unable to determine the file's size.")

        def chunks(self, chunk_size=None):
            """
            Read the file and yield chunks of ``chunk_size`` bytes (defaults to
            ``File.DEFAULT_CHUNK_SIZE``).
            """
            chunk_size = chunk_size or self.DEFAULT_CHUNK_SIZE
            try:
                self.seek(0)
            except (AttributeError, UnsupportedOperation):
                pass

            while True:
                data = self.read(chunk_size)
                if not data:
                    break
                yield data

        def multiple_chunks(self, chunk_size=None):
            """
            Return ``True`` if you can expect multiple chunks.

            NB: If a particular file representation is in memory, subclasses should
            always return ``False`` -- there's no good reason to read from memory in
            chunks.
            """
            return self.size > (chunk_size or self.DEFAULT_CHUNK_SIZE)

        def __iter__(self):
            # Iterate over this file-like object by newlines
            buffer_ = None
            for chunk in self.chunks():
                for line in chunk.splitlines(True):
                    if buffer_:
                        if endswith_cr(buffer_) and not equals_lf(line):
                            # Line split after a \r newline; yield buffer_.
                            yield buffer_
                            # Continue with line.
                        else:
                            # Line either split without a newline (line
                            # continues after buffer_) or with \r\n
                            # newline (line == b'\n').
                            line = buffer_ + line
                        # buffer_ handled, clear it.
                        buffer_ = None

                    # If this is the end of a \n or \r\n line, yield.
                    if endswith_lf(line):
                        yield line
                    else:
                        buffer_ = line

            if buffer_ is not None:
                yield buffer_

        def __enter__(self):
            return self

        def __exit__(self, exc_type, exc_value, tb):
            self.close()

        def open(self, mode=None):
            if not self.closed:
                self.seek(0)
            elif self.name and os.path.exists(self.name):
                self.file = open(self.name, mode or self.mode)
            else:
                raise ValueError("The file cannot be reopened.")
            return self

        def close(self):
            self.file.close()

    class ContentFile(File):
        """
        A File-like object that takes just raw content, rather than an actual file.
        """
        def __init__(self, content, name=None):
            stream_class = StringIO if isinstance(content, str) else BytesIO
            super().__init__(stream_class(content), name=name)
            self.size = len(content)

        def __str__(self):
            return 'Raw content'

        def __bool__(self):
            return True

        def open(self, mode=None):
            self.seek(0)
            return self

        def close(self):
            pass

        def write(self, data):
            self.__dict__.pop('size', None)  # Clear the computed size.
            return self.file.write(data)

    def endswith_cr(line):
        """Return True if line (a text or bytestring) ends with '\r'."""
        return line.endswith('\r' if isinstance(line, str) else b'\r')

    def endswith_lf(line):
        """Return True if line (a text or bytestring) ends with '\n'."""
        return line.endswith('\n' if isinstance(line, str) else b'\n')

    def equals_lf(line):
        """Return True if line (a text or bytestring) equals '\n'."""
        return line == ('\n' if isinstance(line, str) else b'\n')