"""Miscellaneous utility functions and classes.
This module is used internally by Tornado. It is not necessarily expected
that the functions and classes defined here will be useful to other
applications, but they are documented here in case they are.
The one public-facing part of this module is the `Configurable` class
and its `~Configurable.configure` method, which becomes a part of the
interface of its subclasses, including `.AsyncHTTPClient`, `.IOLoop`,
and `.Resolver`.
"""
from __future__ import absolute_import, division, print_function, with_statement
import array
import os
import sys
import zlib
try:
xrange # py2
except NameError:
xrange = range # py3
# inspect.getargspec() raises DeprecationWarnings in Python 3.5.
# The two functions have compatible interfaces for the parts we need.
try:
from inspect import getfullargspec as getargspec # py3
except ImportError:
from inspect import getargspec # py2
[文档]class ObjectDict(dict):
"""Makes a dictionary behave like an object, with attribute-style access.
"""
def __getattr__(self, name):
try:
return self[name]
except KeyError:
raise AttributeError(name)
def __setattr__(self, name, value):
self[name] = value
[文档]class GzipDecompressor(object):
"""Streaming gzip decompressor.
The interface is like that of `zlib.decompressobj` (without some of the
optional arguments, but it understands gzip headers and checksums.
"""
def __init__(self):
# Magic parameter makes zlib module understand gzip header
# http://stackoverflow.com/questions/1838699/how-can-i-decompress-a-gzip-stream-with-zlib
# This works on cpython and pypy, but not jython.
self.decompressobj = zlib.decompressobj(16 + zlib.MAX_WBITS)
[文档] def decompress(self, value, max_length=None):
"""Decompress a chunk, returning newly-available data.
Some data may be buffered for later processing; `flush` must
be called when there is no more input data to ensure that
all data was processed.
If ``max_length`` is given, some input data may be left over
in ``unconsumed_tail``; you must retrieve this value and pass
it back to a future call to `decompress` if it is not empty.
"""
return self.decompressobj.decompress(value, max_length)
@property
def unconsumed_tail(self):
"""Returns the unconsumed portion left over
"""
return self.decompressobj.unconsumed_tail
[文档] def flush(self):
"""Return any remaining buffered data not yet returned by decompress.
Also checks for errors such as truncated input.
No other methods may be called on this object after `flush`.
"""
return self.decompressobj.flush()
# Fake unicode literal support: Python 3.2 doesn't have the u'' marker for
# literal strings, and alternative solutions like "from __future__ import
# unicode_literals" have other problems (see PEP 414). u() can be applied
# to ascii strings that include \u escapes (but they must not contain
# literal non-ascii characters).
if not isinstance(b'', type('')):
def u(s):
return s
unicode_type = str
basestring_type = str
else:
def u(s):
return s.decode('unicode_escape')
# These names don't exist in py3, so use noqa comments to disable
# warnings in flake8.
unicode_type = unicode # noqa
basestring_type = basestring # noqa
[文档]def import_object(name):
"""Imports an object by name.
import_object('x') is equivalent to 'import x'.
import_object('x.y.z') is equivalent to 'from x.y import z'.
>>> import tornado.escape
>>> import_object('tornado.escape') is tornado.escape
True
>>> import_object('tornado.escape.utf8') is tornado.escape.utf8
True
>>> import_object('tornado') is tornado
True
>>> import_object('tornado.missing_module')
Traceback (most recent call last):
...
ImportError: No module named missing_module
"""
if isinstance(name, unicode_type) and str is not unicode_type:
# On python 2 a byte string is required.
name = name.encode('utf-8')
if name.count('.') == 0:
return __import__(name, None, None)
parts = name.split('.')
obj = __import__('.'.join(parts[:-1]), None, None, [parts[-1]], 0)
try:
return getattr(obj, parts[-1])
except AttributeError:
raise ImportError("No module named %s" % parts[-1])
# Deprecated alias that was used before we dropped py25 support.
# Left here in case anyone outside Tornado is using it.
bytes_type = bytes
if sys.version_info > (3,):
exec("""
def raise_exc_info(exc_info):
raise exc_info[1].with_traceback(exc_info[2])
def exec_in(code, glob, loc=None):
if isinstance(code, str):
code = compile(code, '<string>', 'exec', dont_inherit=True)
exec(code, glob, loc)
""")
else:
exec("""
def raise_exc_info(exc_info):
raise exc_info[0], exc_info[1], exc_info[2]
def exec_in(code, glob, loc=None):
if isinstance(code, basestring):
# exec(string) inherits the caller's future imports; compile
# the string first to prevent that.
code = compile(code, '<string>', 'exec', dont_inherit=True)
exec code in glob, loc
""")
[文档]def errno_from_exception(e):
"""Provides the errno from an Exception object.
There are cases that the errno attribute was not set so we pull
the errno out of the args but if someone instantiates an Exception
without any args you will get a tuple error. So this function
abstracts all that behavior to give you a safe way to get the
errno.
"""
if hasattr(e, 'errno'):
return e.errno
elif e.args:
return e.args[0]
else:
return None
[文档]class Configurable(object):
"""Base class for configurable interfaces.
A configurable interface is an (abstract) class whose constructor
acts as a factory function for one of its implementation subclasses.
The implementation subclass as well as optional keyword arguments to
its initializer can be set globally at runtime with `configure`.
By using the constructor as the factory method, the interface
looks like a normal class, `isinstance` works as usual, etc. This
pattern is most useful when the choice of implementation is likely
to be a global decision (e.g. when `~select.epoll` is available,
always use it instead of `~select.select`), or when a
previously-monolithic class has been split into specialized
subclasses.
Configurable subclasses must define the class methods
`configurable_base` and `configurable_default`, and use the instance
method `initialize` instead of ``__init__``.
"""
__impl_class = None
__impl_kwargs = None
def __new__(cls, *args, **kwargs):
base = cls.configurable_base()
init_kwargs = {}
if cls is base:
impl = cls.configured_class()
if base.__impl_kwargs:
init_kwargs.update(base.__impl_kwargs)
else:
impl = cls
init_kwargs.update(kwargs)
instance = super(Configurable, cls).__new__(impl)
# initialize vs __init__ chosen for compatibility with AsyncHTTPClient
# singleton magic. If we get rid of that we can switch to __init__
# here too.
instance.initialize(*args, **init_kwargs)
return instance
@classmethod
[文档] def configurable_base(cls):
"""Returns the base class of a configurable hierarchy.
This will normally return the class in which it is defined.
(which is *not* necessarily the same as the cls classmethod parameter).
"""
raise NotImplementedError()
@classmethod
[文档] def configurable_default(cls):
"""Returns the implementation class to be used if none is configured."""
raise NotImplementedError()
[文档] def initialize(self):
"""Initialize a `Configurable` subclass instance.
Configurable classes should use `initialize` instead of ``__init__``.
.. versionchanged:: 4.2
Now accepts positional arguments in addition to keyword arguments.
"""
@classmethod
@classmethod
@classmethod
def _save_configuration(cls):
base = cls.configurable_base()
return (base.__impl_class, base.__impl_kwargs)
@classmethod
def _restore_configuration(cls, saved):
base = cls.configurable_base()
base.__impl_class = saved[0]
base.__impl_kwargs = saved[1]
[文档]class ArgReplacer(object):
"""Replaces one value in an ``args, kwargs`` pair.
Inspects the function signature to find an argument by name
whether it is passed by position or keyword. For use in decorators
and similar wrappers.
"""
def __init__(self, func, name):
self.name = name
try:
self.arg_pos = self._getargnames(func).index(name)
except ValueError:
# Not a positional parameter
self.arg_pos = None
def _getargnames(self, func):
try:
return getargspec(func).args
except TypeError:
if hasattr(func, 'func_code'):
# Cython-generated code has all the attributes needed
# by inspect.getargspec, but the inspect module only
# works with ordinary functions. Inline the portion of
# getargspec that we need here. Note that for static
# functions the @cython.binding(True) decorator must
# be used (for methods it works out of the box).
code = func.func_code
return code.co_varnames[:code.co_argcount]
raise
[文档] def get_old_value(self, args, kwargs, default=None):
"""Returns the old value of the named argument without replacing it.
Returns ``default`` if the argument is not present.
"""
if self.arg_pos is not None and len(args) > self.arg_pos:
return args[self.arg_pos]
else:
return kwargs.get(self.name, default)
[文档] def replace(self, new_value, args, kwargs):
"""Replace the named argument in ``args, kwargs`` with ``new_value``.
Returns ``(old_value, args, kwargs)``. The returned ``args`` and
``kwargs`` objects may not be the same as the input objects, or
the input objects may be mutated.
If the named argument was not found, ``new_value`` will be added
to ``kwargs`` and None will be returned as ``old_value``.
"""
if self.arg_pos is not None and len(args) > self.arg_pos:
# The arg to replace is passed positionally
old_value = args[self.arg_pos]
args = list(args) # *args is normally a tuple
args[self.arg_pos] = new_value
else:
# The arg to replace is either omitted or passed by keyword.
old_value = kwargs.get(self.name)
kwargs[self.name] = new_value
return old_value, args, kwargs
[文档]def timedelta_to_seconds(td):
"""Equivalent to td.total_seconds() (introduced in python 2.7)."""
return (td.microseconds + (td.seconds + td.days * 24 * 3600) * 10 ** 6) / float(10 ** 6)
def _websocket_mask_python(mask, data):
"""Websocket masking function.
`mask` is a `bytes` object of length 4; `data` is a `bytes` object of any length.
Returns a `bytes` object of the same length as `data` with the mask applied
as specified in section 5.3 of RFC 6455.
This pure-python implementation may be replaced by an optimized version when available.
"""
mask = array.array("B", mask)
unmasked = array.array("B", data)
for i in xrange(len(data)):
unmasked[i] = unmasked[i] ^ mask[i % 4]
if hasattr(unmasked, 'tobytes'):
# tostring was deprecated in py32. It hasn't been removed,
# but since we turn on deprecation warnings in our tests
# we need to use the right one.
return unmasked.tobytes()
else:
return unmasked.tostring()
if (os.environ.get('TORNADO_NO_EXTENSION') or
os.environ.get('TORNADO_EXTENSION') == '0'):
# These environment variables exist to make it easier to do performance
# comparisons; they are not guaranteed to remain supported in the future.
_websocket_mask = _websocket_mask_python
else:
try:
from tornado.speedups import websocket_mask as _websocket_mask
except ImportError:
if os.environ.get('TORNADO_EXTENSION') == '1':
raise
_websocket_mask = _websocket_mask_python
def doctests():
import doctest
return doctest.DocTestSuite()