wsgi.py 文件源码

def get_input_stream(environ, safe_fallback=True):
    """Returns the input stream from the WSGI environment and wraps it
    in the most sensible way possible.  The stream returned is not the
    raw WSGI stream in most cases but one that is safe to read from
    without taking into account the content length.

    .. versionadded:: 0.9

    :param environ: the WSGI environ to fetch the stream from.
    :param safe: indicates whether the function should use an empty
                 stream as safe fallback or just return the original
                 WSGI input stream if it can't wrap it safely.  The
                 default is to return an empty string in those cases.
    """
    stream = environ['wsgi.input']
    content_length = get_content_length(environ)

    # A wsgi extension that tells us if the input is terminated.  In
    # that case we return the stream unchanged as we know we can safely
    # read it until the end.
    if environ.get('wsgi.input_terminated'):
        return stream

    # If we don't have a content length we fall back to an empty stream
    # in case of a safe fallback, otherwise we return the stream unchanged.
    # The non-safe fallback is not recommended but might be useful in
    # some situations.
    if content_length is None:
        return safe_fallback and _empty_stream or stream

    # Otherwise limit the stream to the content length
    return LimitedStream(stream, content_length)