1 | """Helper to provide extensibility for pickle/cPickle.
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2 |
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3 | This is only useful to add pickle support for extension types defined in
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4 | C, not for instances of user-defined classes.
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5 | """
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6 |
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7 | from types import ClassType as _ClassType
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8 |
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9 | __all__ = ["pickle", "constructor",
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10 | "add_extension", "remove_extension", "clear_extension_cache"]
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11 |
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12 | dispatch_table = {}
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13 |
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14 | def pickle(ob_type, pickle_function, constructor_ob=None):
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15 | if type(ob_type) is _ClassType:
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16 | raise TypeError("copy_reg is not intended for use with classes")
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17 |
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18 | if not hasattr(pickle_function, '__call__'):
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19 | raise TypeError("reduction functions must be callable")
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20 | dispatch_table[ob_type] = pickle_function
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21 |
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22 | # The constructor_ob function is a vestige of safe for unpickling.
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23 | # There is no reason for the caller to pass it anymore.
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24 | if constructor_ob is not None:
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25 | constructor(constructor_ob)
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26 |
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27 | def constructor(object):
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28 | if not hasattr(object, '__call__'):
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29 | raise TypeError("constructors must be callable")
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30 |
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31 | # Example: provide pickling support for complex numbers.
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32 |
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33 | try:
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34 | complex
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35 | except NameError:
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36 | pass
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37 | else:
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38 |
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39 | def pickle_complex(c):
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40 | return complex, (c.real, c.imag)
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41 |
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42 | pickle(complex, pickle_complex, complex)
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43 |
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44 | # Support for pickling new-style objects
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45 |
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46 | def _reconstructor(cls, base, state):
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47 | if base is object:
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48 | obj = object.__new__(cls)
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49 | else:
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50 | obj = base.__new__(cls, state)
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51 | if base.__init__ != object.__init__:
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52 | base.__init__(obj, state)
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53 | return obj
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54 |
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55 | _HEAPTYPE = 1<<9
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56 |
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57 | # Python code for object.__reduce_ex__ for protocols 0 and 1
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58 |
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59 | def _reduce_ex(self, proto):
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60 | assert proto < 2
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61 | for base in self.__class__.__mro__:
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62 | if hasattr(base, '__flags__') and not base.__flags__ & _HEAPTYPE:
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63 | break
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64 | else:
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65 | base = object # not really reachable
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66 | if base is object:
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67 | state = None
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68 | else:
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69 | if base is self.__class__:
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70 | raise TypeError, "can't pickle %s objects" % base.__name__
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71 | state = base(self)
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72 | args = (self.__class__, base, state)
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73 | try:
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74 | getstate = self.__getstate__
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75 | except AttributeError:
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76 | if getattr(self, "__slots__", None):
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77 | raise TypeError("a class that defines __slots__ without "
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78 | "defining __getstate__ cannot be pickled")
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79 | try:
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80 | dict = self.__dict__
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81 | except AttributeError:
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82 | dict = None
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83 | else:
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84 | dict = getstate()
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85 | if dict:
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86 | return _reconstructor, args, dict
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87 | else:
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88 | return _reconstructor, args
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89 |
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90 | # Helper for __reduce_ex__ protocol 2
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91 |
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92 | def __newobj__(cls, *args):
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93 | return cls.__new__(cls, *args)
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94 |
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95 | def _slotnames(cls):
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96 | """Return a list of slot names for a given class.
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97 |
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98 | This needs to find slots defined by the class and its bases, so we
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99 | can't simply return the __slots__ attribute. We must walk down
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100 | the Method Resolution Order and concatenate the __slots__ of each
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101 | class found there. (This assumes classes don't modify their
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102 | __slots__ attribute to misrepresent their slots after the class is
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103 | defined.)
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104 | """
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105 |
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106 | # Get the value from a cache in the class if possible
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107 | names = cls.__dict__.get("__slotnames__")
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108 | if names is not None:
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109 | return names
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110 |
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111 | # Not cached -- calculate the value
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112 | names = []
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113 | if not hasattr(cls, "__slots__"):
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114 | # This class has no slots
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115 | pass
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116 | else:
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117 | # Slots found -- gather slot names from all base classes
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118 | for c in cls.__mro__:
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119 | if "__slots__" in c.__dict__:
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120 | slots = c.__dict__['__slots__']
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121 | # if class has a single slot, it can be given as a string
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122 | if isinstance(slots, basestring):
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123 | slots = (slots,)
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124 | for name in slots:
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125 | # special descriptors
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126 | if name in ("__dict__", "__weakref__"):
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127 | continue
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128 | # mangled names
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129 | elif name.startswith('__') and not name.endswith('__'):
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130 | names.append('_%s%s' % (c.__name__, name))
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131 | else:
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132 | names.append(name)
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133 |
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134 | # Cache the outcome in the class if at all possible
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135 | try:
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136 | cls.__slotnames__ = names
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137 | except:
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138 | pass # But don't die if we can't
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139 |
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140 | return names
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141 |
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142 | # A registry of extension codes. This is an ad-hoc compression
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143 | # mechanism. Whenever a global reference to <module>, <name> is about
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144 | # to be pickled, the (<module>, <name>) tuple is looked up here to see
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145 | # if it is a registered extension code for it. Extension codes are
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146 | # universal, so that the meaning of a pickle does not depend on
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147 | # context. (There are also some codes reserved for local use that
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148 | # don't have this restriction.) Codes are positive ints; 0 is
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149 | # reserved.
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150 |
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151 | _extension_registry = {} # key -> code
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152 | _inverted_registry = {} # code -> key
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153 | _extension_cache = {} # code -> object
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154 | # Don't ever rebind those names: cPickle grabs a reference to them when
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155 | # it's initialized, and won't see a rebinding.
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156 |
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157 | def add_extension(module, name, code):
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158 | """Register an extension code."""
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159 | code = int(code)
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160 | if not 1 <= code <= 0x7fffffff:
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161 | raise ValueError, "code out of range"
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162 | key = (module, name)
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163 | if (_extension_registry.get(key) == code and
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164 | _inverted_registry.get(code) == key):
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165 | return # Redundant registrations are benign
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166 | if key in _extension_registry:
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167 | raise ValueError("key %s is already registered with code %s" %
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168 | (key, _extension_registry[key]))
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169 | if code in _inverted_registry:
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170 | raise ValueError("code %s is already in use for key %s" %
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171 | (code, _inverted_registry[code]))
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172 | _extension_registry[key] = code
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173 | _inverted_registry[code] = key
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174 |
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175 | def remove_extension(module, name, code):
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176 | """Unregister an extension code. For testing only."""
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177 | key = (module, name)
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178 | if (_extension_registry.get(key) != code or
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179 | _inverted_registry.get(code) != key):
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180 | raise ValueError("key %s is not registered with code %s" %
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181 | (key, code))
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182 | del _extension_registry[key]
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183 | del _inverted_registry[code]
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184 | if code in _extension_cache:
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185 | del _extension_cache[code]
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186 |
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187 | def clear_extension_cache():
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188 | _extension_cache.clear()
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189 |
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190 | # Standard extension code assignments
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191 |
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192 | # Reserved ranges
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193 |
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194 | # First Last Count Purpose
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195 | # 1 127 127 Reserved for Python standard library
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196 | # 128 191 64 Reserved for Zope
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197 | # 192 239 48 Reserved for 3rd parties
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198 | # 240 255 16 Reserved for private use (will never be assigned)
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199 | # 256 Inf Inf Reserved for future assignment
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200 |
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201 | # Extension codes are assigned by the Python Software Foundation.
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