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1 # jseval.py
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2 # By Atul Varma <varmaa@toolness.com>
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3 #
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4 # This is a simple example of embedding the SpiderMonkey engine into
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5 # Python using ctypes.
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6
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7 import sys
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8 import ctypes
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9
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10 # Sample Python function to inject into JavaScript space.
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11 def displayMessage(msg):
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12 print msg
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13
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14 class JSEngine( object ):
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15 def __init__( self, dllpath ):
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16 self._dllpath = dllpath
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17
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18 class JSClass( ctypes.Structure ):
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19 _fields_ = [("name", ctypes.c_char_p),
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20 ("flags", ctypes.c_uint32),
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21 # Mandatory non-null members
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22 ("addProperty", ctypes.c_void_p),
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23 ("delProperty", ctypes.c_void_p),
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24 ("getProperty", ctypes.c_void_p),
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25 ("setProperty", ctypes.c_void_p),
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26 ("enumerate", ctypes.c_void_p),
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27 ("resolve", ctypes.c_void_p),
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28 ("convert", ctypes.c_void_p),
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29 ("finalize", ctypes.c_void_p),
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30 # Optionally non-null members
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31 ("getObjectOps", ctypes.c_void_p),
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32 ("checkAccess", ctypes.c_void_p),
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33 ("call", ctypes.c_void_p),
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34 ("construct", ctypes.c_void_p),
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35 ("xdrObject", ctypes.c_void_p),
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36 ("hasInstance", ctypes.c_void_p),
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37 ("mark", ctypes.c_void_p),
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38 ("reserveSlots", ctypes.c_void_p)
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39 ]
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40
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41 JSNativeFunction = ctypes.CFUNCTYPE(
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42 ctypes.c_int, # Return value
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43 ctypes.c_void_p, # Context
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44 ctypes.c_void_p, # Object
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45 ctypes.c_int, # argc
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46 ctypes.POINTER( ctypes.c_int ), # argv
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47 ctypes.POINTER( ctypes.c_int ), # retval
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48 )
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49
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50 def _initRuntime( self ):
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51 self.jsdll = ctypes.cdll.LoadLibrary(self._dllpath)
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52 self.runtime = self.jsdll.JS_Init( 32768 )
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53
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54 if self.runtime == 0:
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55 raise JSError( "JS_Init() failed." )
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56
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57 def _shutdownRuntime( self ):
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58 self.jsdll.JS_Finish( self.runtime )
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59 del self.runtime
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60 del self.jsdll
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61
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62 def _getNewContext( self ):
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63 context = self.jsdll.JS_NewContext(self.runtime, 8192)
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64 if context == 0:
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65 raise JSError( "JS_NewContext() failed." )
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66 return context
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67
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68 def _createGlobalClass( self, name ):
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69 globalClass = self.JSClass(
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70 name, 0,
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71 ctypes.cast( self.jsdll.JS_PropertyStub, ctypes.c_void_p ),
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72 ctypes.cast( self.jsdll.JS_PropertyStub, ctypes.c_void_p ),
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73 ctypes.cast( self.jsdll.JS_PropertyStub, ctypes.c_void_p ),
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74 ctypes.cast( self.jsdll.JS_PropertyStub, ctypes.c_void_p ),
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75 ctypes.cast( self.jsdll.JS_EnumerateStub, ctypes.c_void_p ),
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76 ctypes.cast( self.jsdll.JS_ResolveStub, ctypes.c_void_p ),
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77 ctypes.cast( self.jsdll.JS_ConvertStub, ctypes.c_void_p ),
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78 ctypes.cast( self.jsdll.JS_FinalizeStub, ctypes.c_void_p ),
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79 0, 0, 0, 0, 0, 0, 0, 0
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80 )
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81 return globalClass
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82
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83 def _createGlobalObject( self, context, globalClass ):
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84 globalObj = self.jsdll.JS_NewObject(
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85 context,
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86 ctypes.byref( globalClass ),
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87 0,
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88 0
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89 )
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90
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91 if not globalObj:
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92 raise JSError( "JS_NewObject() failed." )
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93
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94 return globalObj
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95
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96 def _installDisplayMessageFunction( self, context, globalObj ):
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97 def jsDisplayMessage( context, object, argc, argv, retval ):
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98 jsString = self.jsdll.JS_ValueToString( context, argv[0] )
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99 cString = ctypes.c_char_p( self.jsdll.JS_GetStringBytes( jsString ) )
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100 displayMessage( cString.value )
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101 retval[0] = 0
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102 return 1
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103
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104 retval = self.jsdll.JS_DefineFunction(
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105 context,
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106 globalObj,
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107 "displayMessage",
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108 self.JSNativeFunction( jsDisplayMessage ),
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109 1,
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110 0
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111 )
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112
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113 if retval == 0:
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114 raise JSError( "JS_DefineFunction() failed." )
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115
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116 def eval( self, scriptString ):
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117 """
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118 Evaluates the given string of JavaScript code and returns the
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119 result as a string.
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120
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121 The string must be ascii-encodable, as this function does not
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122 currently use JavaScript's unicode API.
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123 """
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124
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125 # For more information on what's going on here, see:
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126 #
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127 # http://developer.mozilla.org [continued on next line]
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128 # /en/docs/JavaScript_C_Engine_Embedder%27s_Guide
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129 # http://www.mozilla.org/js/spidermonkey/tutorial.html
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130
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131 script = scriptString.encode( "ascii" )
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132
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133 # We carefully set up and shutdown everything on each pass, to
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134 # make the world a happier place.
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135 self._initRuntime()
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136 context = self._getNewContext()
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137 name = ctypes.c_char_p( "enso" )
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138 globalClass = self._createGlobalClass( name )
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139 globalObj = self._createGlobalObject( context, globalClass )
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140 self._installDisplayMessageFunction( context, globalObj )
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141 builtins = self.jsdll.JS_InitStandardClasses( context, globalObj )
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142
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143 try:
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144 rval = ctypes.c_int()
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145
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146 ok = self.jsdll.JS_EvaluateScript(
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147 context,
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148 globalObj,
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149 script,
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150 len(script),
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151 "<string>",
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152 0,
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153 ctypes.byref( rval )
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154 )
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155
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156 if not ok:
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157 raise JSEvalError( "JS_EvaluateScript() failed." )
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158
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159 jsString = self.jsdll.JS_ValueToString( context, rval )
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160 cString = ctypes.c_char_p(
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161 self.jsdll.JS_GetStringBytes( jsString )
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162 )
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163 retval = cString.value
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164 finally:
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165 self.jsdll.JS_DestroyContext( context )
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166 self._shutdownRuntime()
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167
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168 return retval
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169
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170 class JSError( Exception ):
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171 pass
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172
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173 class JSEvalError( JSError ):
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174 pass
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175
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176 if __name__ == "__main__":
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177 args = sys.argv[1:]
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178 if len(args) < 1:
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179 print "usage: %s <path-to-spidermonkey-dll>" % sys.argv[0]
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180 sys.exit(1)
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181
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182 e = JSEngine(sys.argv[1])
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183
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184 e.eval("displayMessage('hi from spidermonkey! ' + Math.abs(-5));")
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