1 # jseval.py

        2 # By Atul Varma <varmaa@toolness.com>

        3 #

        4 # This is a simple example of embedding the SpiderMonkey engine into

        5 # Python using ctypes.

        6 

        7 import sys

        8 import ctypes

        9 

       10 # Sample Python function to inject into JavaScript space.

       11 def displayMessage(msg):

       12     print msg

       13 

       14 class JSEngine( object ):

       15     def __init__( self, dllpath ):

       16         self._dllpath = dllpath

       17 

       18     class JSClass( ctypes.Structure ):

       19         _fields_ = [("name", ctypes.c_char_p),

       20                     ("flags", ctypes.c_uint32),

       21                     # Mandatory non-null members

       22                     ("addProperty", ctypes.c_void_p),

       23                     ("delProperty", ctypes.c_void_p),

       24                     ("getProperty", ctypes.c_void_p),

       25                     ("setProperty", ctypes.c_void_p),

       26                     ("enumerate", ctypes.c_void_p),

       27                     ("resolve", ctypes.c_void_p),

       28                     ("convert", ctypes.c_void_p),

       29                     ("finalize", ctypes.c_void_p),

       30                     # Optionally non-null members

       31                     ("getObjectOps", ctypes.c_void_p),

       32                     ("checkAccess", ctypes.c_void_p),

       33                     ("call", ctypes.c_void_p),

       34                     ("construct", ctypes.c_void_p),

       35                     ("xdrObject", ctypes.c_void_p),

       36                     ("hasInstance", ctypes.c_void_p),

       37                     ("mark", ctypes.c_void_p),

       38                     ("reserveSlots", ctypes.c_void_p)

       39                     ]

       40 

       41     JSNativeFunction = ctypes.CFUNCTYPE(

       42         ctypes.c_int, # Return value

       43         ctypes.c_void_p, # Context

       44         ctypes.c_void_p, # Object

       45         ctypes.c_int, # argc

       46         ctypes.POINTER( ctypes.c_int ), # argv

       47         ctypes.POINTER( ctypes.c_int ), # retval

       48         )

       49 

       50     def _initRuntime( self ):

       51         self.jsdll = ctypes.cdll.LoadLibrary(self._dllpath)

       52         self.runtime = self.jsdll.JS_Init( 32768 )

       53 

       54         if self.runtime == 0:

       55             raise JSError( "JS_Init() failed." )

       56 

       57     def _shutdownRuntime( self ):

       58         self.jsdll.JS_Finish( self.runtime )

       59         del self.runtime

       60         del self.jsdll

       61         

       62     def _getNewContext( self ):

       63         context = self.jsdll.JS_NewContext(self.runtime, 8192)

       64         if context == 0:

       65             raise JSError( "JS_NewContext() failed." )

       66         return context

       67 

       68     def _createGlobalClass( self, name ):

       69         globalClass = self.JSClass(

       70             name, 0,

       71             ctypes.cast( self.jsdll.JS_PropertyStub, ctypes.c_void_p ),

       72             ctypes.cast( self.jsdll.JS_PropertyStub, ctypes.c_void_p ),

       73             ctypes.cast( self.jsdll.JS_PropertyStub, ctypes.c_void_p ),

       74             ctypes.cast( self.jsdll.JS_PropertyStub, ctypes.c_void_p ),

       75             ctypes.cast( self.jsdll.JS_EnumerateStub, ctypes.c_void_p ),

       76             ctypes.cast( self.jsdll.JS_ResolveStub, ctypes.c_void_p ),

       77             ctypes.cast( self.jsdll.JS_ConvertStub, ctypes.c_void_p ),

       78             ctypes.cast( self.jsdll.JS_FinalizeStub, ctypes.c_void_p ),

       79             0, 0, 0, 0, 0, 0, 0, 0

       80             )

       81         return globalClass

       82 

       83     def _createGlobalObject( self, context, globalClass ):

       84         globalObj = self.jsdll.JS_NewObject(

       85             context,

       86             ctypes.byref( globalClass ),

       87             0,

       88             0

       89             )

       90 

       91         if not globalObj:

       92             raise JSError( "JS_NewObject() failed." )

       93 

       94         return globalObj

       95 

       96     def _installDisplayMessageFunction( self, context, globalObj ):

       97         def jsDisplayMessage( context, object, argc, argv, retval ):

       98             jsString = self.jsdll.JS_ValueToString( context, argv[0] )

       99             cString = ctypes.c_char_p( self.jsdll.JS_GetStringBytes( jsString ) )

      100             displayMessage( cString.value )

      101             retval[0] = 0

      102             return 1

      103 

      104         retval = self.jsdll.JS_DefineFunction(

      105             context,

      106             globalObj,

      107             "displayMessage",

      108             self.JSNativeFunction( jsDisplayMessage ),

      109             1,

      110             0

      111             )

      112 

      113         if retval == 0:

      114             raise JSError( "JS_DefineFunction() failed." )

      115         

      116     def eval( self, scriptString ):

      117         """

      118         Evaluates the given string of JavaScript code and returns the

      119         result as a string.

      120         

      121         The string must be ascii-encodable, as this function does not

      122         currently use JavaScript's unicode API.

      123         """

      124 

      125         # For more information on what's going on here, see:

      126         #

      127         # http://developer.mozilla.org  [continued on next line]

      128         #            /en/docs/JavaScript_C_Engine_Embedder%27s_Guide

      129         # http://www.mozilla.org/js/spidermonkey/tutorial.html

      130 

      131         script = scriptString.encode( "ascii" )

      132 

      133         # We carefully set up and shutdown everything on each pass, to

      134         # make the world a happier place.

      135         self._initRuntime()

      136         context = self._getNewContext()

      137         name = ctypes.c_char_p( "enso" )

      138         globalClass = self._createGlobalClass( name )

      139         globalObj = self._createGlobalObject( context, globalClass )

      140         self._installDisplayMessageFunction( context, globalObj )

      141         builtins = self.jsdll.JS_InitStandardClasses( context, globalObj )

      142 

      143         try:

      144             rval = ctypes.c_int()

      145 

      146             ok = self.jsdll.JS_EvaluateScript(

      147                 context,

      148                 globalObj,

      149                 script,

      150                 len(script),

      151                 "<string>",

      152                 0,

      153                 ctypes.byref( rval )

      154                 )

      155 

      156             if not ok:

      157                 raise JSEvalError( "JS_EvaluateScript() failed." )

      158 

      159             jsString = self.jsdll.JS_ValueToString( context, rval )

      160             cString = ctypes.c_char_p(

      161                 self.jsdll.JS_GetStringBytes( jsString )

      162                 )

      163             retval = cString.value

      164         finally:

      165             self.jsdll.JS_DestroyContext( context )

      166             self._shutdownRuntime()

      167 

      168         return retval

      169 

      170 class JSError( Exception ):

      171     pass

      172 

      173 class JSEvalError( JSError ):

      174     pass

      175 

      176 if __name__ == "__main__":

      177     args = sys.argv[1:]

      178     if len(args) < 1:

      179         print "usage: %s <path-to-spidermonkey-dll>" % sys.argv[0]

      180         sys.exit(1)

      181 

      182     e = JSEngine(sys.argv[1])

      183 

      184     e.eval("displayMessage('hi from spidermonkey! ' + Math.abs(-5));")