X-Git-Url: https://git.mdrn.pl/wolnelektury.git/blobdiff_plain/d0ab1d8908cadac9f51a17e2fe9e1193f14e28cc..0e87ae0739ed3e72301b7b718098f97a7f06a5d8:/apps/piston/decorator.py

diff --git a/apps/piston/decorator.py b/apps/piston/decorator.py
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+"""
+Decorator module, see
+http://www.phyast.pitt.edu/~micheles/python/documentation.html
+for the documentation and below for the licence.
+"""
+
+## The basic trick is to generate the source code for the decorated function
+## with the right signature and to evaluate it.
+## Uncomment the statement 'print >> sys.stderr, func_src'  in _decorator
+## to understand what is going on.
+
+__all__ = ["decorator", "new_wrapper", "getinfo"]
+
+import inspect, sys
+
+try:
+    set
+except NameError:
+    from sets import Set as set
+
+def getinfo(func):
+    """
+    Returns an info dictionary containing:
+    - name (the name of the function : str)
+    - argnames (the names of the arguments : list)
+    - defaults (the values of the default arguments : tuple)
+    - signature (the signature : str)
+    - doc (the docstring : str)
+    - module (the module name : str)
+    - dict (the function __dict__ : str)
+    
+    >>> def f(self, x=1, y=2, *args, **kw): pass
+
+    >>> info = getinfo(f)
+
+    >>> info["name"]
+    'f'
+    >>> info["argnames"]
+    ['self', 'x', 'y', 'args', 'kw']
+    
+    >>> info["defaults"]
+    (1, 2)
+
+    >>> info["signature"]
+    'self, x, y, *args, **kw'
+    """
+    assert inspect.ismethod(func) or inspect.isfunction(func)
+    regargs, varargs, varkwargs, defaults = inspect.getargspec(func)
+    argnames = list(regargs)
+    if varargs:
+        argnames.append(varargs)
+    if varkwargs:
+        argnames.append(varkwargs)
+    signature = inspect.formatargspec(regargs, varargs, varkwargs, defaults,
+                                      formatvalue=lambda value: "")[1:-1]
+    return dict(name=func.__name__, argnames=argnames, signature=signature,
+                defaults = func.func_defaults, doc=func.__doc__,
+                module=func.__module__, dict=func.__dict__,
+                globals=func.func_globals, closure=func.func_closure)
+
+# akin to functools.update_wrapper
+def update_wrapper(wrapper, model, infodict=None):
+    infodict = infodict or getinfo(model)
+    try:
+        wrapper.__name__ = infodict['name']
+    except: # Python version < 2.4
+        pass
+    wrapper.__doc__ = infodict['doc']
+    wrapper.__module__ = infodict['module']
+    wrapper.__dict__.update(infodict['dict'])
+    wrapper.func_defaults = infodict['defaults']
+    wrapper.undecorated = model
+    return wrapper
+
+def new_wrapper(wrapper, model):
+    """
+    An improvement over functools.update_wrapper. The wrapper is a generic
+    callable object. It works by generating a copy of the wrapper with the 
+    right signature and by updating the copy, not the original.
+    Moreovoer, 'model' can be a dictionary with keys 'name', 'doc', 'module',
+    'dict', 'defaults'.
+    """
+    if isinstance(model, dict):
+        infodict = model
+    else: # assume model is a function
+        infodict = getinfo(model)
+    assert not '_wrapper_' in infodict["argnames"], (
+        '"_wrapper_" is a reserved argument name!')
+    src = "lambda %(signature)s: _wrapper_(%(signature)s)" % infodict
+    funcopy = eval(src, dict(_wrapper_=wrapper))
+    return update_wrapper(funcopy, model, infodict)
+
+# helper used in decorator_factory
+def __call__(self, func):
+    infodict = getinfo(func)
+    for name in ('_func_', '_self_'):
+        assert not name in infodict["argnames"], (
+           '%s is a reserved argument name!' % name)
+    src = "lambda %(signature)s: _self_.call(_func_, %(signature)s)"
+    new = eval(src % infodict, dict(_func_=func, _self_=self))
+    return update_wrapper(new, func, infodict)
+
+def decorator_factory(cls):
+    """
+    Take a class with a ``.caller`` method and return a callable decorator
+    object. It works by adding a suitable __call__ method to the class;
+    it raises a TypeError if the class already has a nontrivial __call__
+    method.
+    """
+    attrs = set(dir(cls))
+    if '__call__' in attrs:
+        raise TypeError('You cannot decorate a class with a nontrivial '
+                        '__call__ method')
+    if 'call' not in attrs:
+        raise TypeError('You cannot decorate a class without a '
+                        '.call method')
+    cls.__call__ = __call__
+    return cls
+
+def decorator(caller):
+    """
+    General purpose decorator factory: takes a caller function as
+    input and returns a decorator with the same attributes.
+    A caller function is any function like this::
+
+     def caller(func, *args, **kw):
+         # do something
+         return func(*args, **kw)
+    
+    Here is an example of usage:
+
+    >>> @decorator
+    ... def chatty(f, *args, **kw):
+    ...     print "Calling %r" % f.__name__
+    ...     return f(*args, **kw)
+
+    >>> chatty.__name__
+    'chatty'
+    
+    >>> @chatty
+    ... def f(): pass
+    ...
+    >>> f()
+    Calling 'f'
+
+    decorator can also take in input a class with a .caller method; in this
+    case it converts the class into a factory of callable decorator objects.
+    See the documentation for an example.
+    """
+    if inspect.isclass(caller):
+        return decorator_factory(caller)
+    def _decorator(func): # the real meat is here
+        infodict = getinfo(func)
+        argnames = infodict['argnames']
+        assert not ('_call_' in argnames or '_func_' in argnames), (
+            'You cannot use _call_ or _func_ as argument names!')
+        src = "lambda %(signature)s: _call_(_func_, %(signature)s)" % infodict
+        # import sys; print >> sys.stderr, src # for debugging purposes
+        dec_func = eval(src, dict(_func_=func, _call_=caller))
+        return update_wrapper(dec_func, func, infodict)
+    return update_wrapper(_decorator, caller)
+
+if __name__ == "__main__":
+    import doctest; doctest.testmod()
+
+##########################     LEGALESE    ###############################
+      
+##   Redistributions of source code must retain the above copyright 
+##   notice, this list of conditions and the following disclaimer.
+##   Redistributions in bytecode form must reproduce the above copyright
+##   notice, this list of conditions and the following disclaimer in
+##   the documentation and/or other materials provided with the
+##   distribution. 
+
+##   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+##   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+##   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+##   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+##   HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+##   INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+##   BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+##   OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+##   ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
+##   TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+##   USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+##   DAMAGE.