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Viewing changes to bzrlib/decorators.py

  • Committer: Robert Collins
  • Date: 2007-07-04 08:08:13 UTC
  • mfrom: (2572 +trunk)
  • mto: This revision was merged to the branch mainline in revision 2587.
  • Revision ID: robertc@robertcollins.net-20070704080813-wzebx0r88fvwj5rq
Merge bzr.dev.

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bzrlib/decorators.py
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__all__ = ['needs_read_lock',
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           'needs_write_lock',
 
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           'use_fast_decorators',
 
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           'use_pretty_decorators',
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           ]
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def needs_read_lock(unbound):
 
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def _get_parameters(func):
 
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    """Recreate the parameters for a function using introspection.
 
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    :return: (function_params, calling_params)
 
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        function_params: is a string representing the parameters of the
 
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            function. (such as "a, b, c=None, d=1")
 
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            This is used in the function declaration.
 
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        calling_params: is another string representing how you would call the
 
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            function with the correct parameters. (such as "a, b, c=c, d=d")
 
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            Assuming you sued function_params in the function declaration, this
 
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            is the parameters to put in the function call.
 
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        For example:
 
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        def wrapper(%(function_params)s):
 
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            return original(%(calling_params)s)
 
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    """
 
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    # "import inspect" should stay in local scope. 'inspect' takes a long time
 
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    # to import the first time. And since we don't always need it, don't import
 
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    # it globally.
 
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    import inspect
 
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    args, varargs, varkw, defaults = inspect.getargspec(func)
 
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    formatted = inspect.formatargspec(args, varargs=varargs,
 
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                                      varkw=varkw,
 
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                                      defaults=defaults)
 
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    if defaults is None:
 
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        args_passed = args
 
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    else:
 
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        first_default = len(args) - len(defaults)
 
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        args_passed = args[:first_default]
 
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        for arg in args[first_default:]:
 
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            args_passed.append("%s=%s" % (arg, arg))
 
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    if varargs is not None:
 
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        args_passed.append('*' + varargs)
 
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    if varkw is not None:
 
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        args_passed.append('**' + varkw)
 
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    args_passed = ', '.join(args_passed)
 
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    return formatted[1:-1], args_passed
 
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def _pretty_needs_read_lock(unbound):
 
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    """Decorate unbound to take out and release a read lock.
 
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    This decorator can be applied to methods of any class with lock_read() and
 
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    unlock() methods.
 
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    Typical usage:
 
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    class Branch(...):
 
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        @needs_read_lock
 
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        def branch_method(self, ...):
 
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            stuff
 
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    """
 
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    # This compiles a function with a similar name, but wrapped with
 
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    # lock_read/unlock calls. We use dynamic creation, because we need the
 
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    # internal name of the function to be modified so that --lsprof will see
 
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    # the correct name.
 
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    # TODO: jam 20070111 Modify this template so that the generated function
 
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    #       has the same argument signature as the original function, which
 
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    #       will help commands like epydoc.
 
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    #       This seems possible by introspecting foo.func_defaults, and
 
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    #       foo.func_code.co_argcount and foo.func_code.co_varnames
 
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    template = """\
 
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def %(name)s_read_locked(%(params)s):
 
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    self.lock_read()
 
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    try:
 
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        return unbound(%(passed_params)s)
 
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    finally:
 
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        self.unlock()
 
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read_locked = %(name)s_read_locked
 
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"""
 
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    params, passed_params = _get_parameters(unbound)
 
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    variables = {'name':unbound.__name__,
 
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                 'params':params,
 
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                 'passed_params':passed_params,
 
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                }
 
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    func_def = template % variables
 
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    exec func_def in locals()
 
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    read_locked.__doc__ = unbound.__doc__
 
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    read_locked.__name__ = unbound.__name__
 
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    return read_locked
 
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def _fast_needs_read_lock(unbound):
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    """Decorate unbound to take out and release a read lock.
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    This decorator can be applied to methods of any class with lock_read() and
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    return read_locked
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def needs_write_lock(unbound):
 
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def _pretty_needs_write_lock(unbound):
 
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    """Decorate unbound to take out and release a write lock."""
 
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    template = """\
 
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def %(name)s_write_locked(%(params)s):
 
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    self.lock_write()
 
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    try:
 
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        return unbound(%(passed_params)s)
 
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    finally:
 
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        self.unlock()
 
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write_locked = %(name)s_write_locked
 
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"""
 
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    params, passed_params = _get_parameters(unbound)
 
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    variables = {'name':unbound.__name__,
 
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                 'params':params,
 
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                 'passed_params':passed_params,
 
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                }
 
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    func_def = template % variables
 
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    exec func_def in locals()
 
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    write_locked.__doc__ = unbound.__doc__
 
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    write_locked.__name__ = unbound.__name__
 
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    return write_locked
 
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def _fast_needs_write_lock(unbound):
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    """Decorate unbound to take out and release a write lock."""
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    def write_locked(self, *args, **kwargs):
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        self.lock_write()
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    write_locked.__name__ = unbound.__name__
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    return write_locked
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# Default is more functionality, 'bzr' the commandline will request fast
 
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# versions.
 
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needs_read_lock = _pretty_needs_read_lock
 
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needs_write_lock = _pretty_needs_write_lock
 
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def use_fast_decorators():
 
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    """Change the default decorators to be fast loading ones.
 
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    The alternative is to have decorators that do more work to produce
 
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    nice-looking decorated functions, but this slows startup time.
 
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    """
 
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    global needs_read_lock, needs_write_lock
 
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    needs_read_lock = _fast_needs_read_lock
 
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    needs_write_lock = _fast_needs_write_lock
 
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def use_pretty_decorators():
 
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    """Change the default decorators to be pretty ones."""
 
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    global needs_read_lock, needs_write_lock
 
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    needs_read_lock = _pretty_needs_read_lock
 
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    needs_write_lock = _pretty_needs_write_lock