Source code for tornado.util

"""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 inspect
import sys
import zlib


[docs]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
[docs]class GzipDecompressor(object): """Streaming gzip decompressor. The interface is like that of `zlib.decompressobj` (without 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)
[docs] def decompress(self, value): """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. """ return self.decompressobj.decompress(value)
[docs] 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()
[docs]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 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]) # 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 type('') is not type(b''): def u(s): return s bytes_type = bytes unicode_type = str basestring_type = str else: def u(s): return s.decode('unicode_escape') bytes_type = str unicode_type = unicode basestring_type = basestring 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 """)
[docs]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, **kwargs): base = cls.configurable_base() args = {} if cls is base: impl = cls.configured_class() if base.__impl_kwargs: args.update(base.__impl_kwargs) else: impl = cls args.update(kwargs) instance = super(Configurable, cls).__new__(impl) # initialize vs __init__ chosen for compatiblity with AsyncHTTPClient # singleton magic. If we get rid of that we can switch to __init__ # here too. instance.initialize(**args) return instance @classmethod
[docs] 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
[docs] def configurable_default(cls): """Returns the implementation class to be used if none is configured.""" raise NotImplementedError()
[docs] def initialize(self): """Initialize a `Configurable` subclass instance. Configurable classes should use `initialize` instead of ``__init__``. """
@classmethod
[docs] def configure(cls, impl, **kwargs): """Sets the class to use when the base class is instantiated. Keyword arguments will be saved and added to the arguments passed to the constructor. This can be used to set global defaults for some parameters. """ base = cls.configurable_base() if isinstance(impl, (unicode_type, bytes_type)): impl = import_object(impl) if impl is not None and not issubclass(impl, cls): raise ValueError("Invalid subclass of %s" % cls) base.__impl_class = impl base.__impl_kwargs = kwargs
@classmethod
[docs] def configured_class(cls): """Returns the currently configured class.""" base = cls.configurable_base() if cls.__impl_class is None: base.__impl_class = cls.configurable_default() return base.__impl_class
@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]
[docs]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 = inspect.getargspec(func).args.index(self.name) except ValueError: # Not a positional parameter self.arg_pos = None
[docs] 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)
[docs] 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
def doctests(): import doctest return doctest.DocTestSuite()