99 lines
2.9 KiB
Python
Executable file
99 lines
2.9 KiB
Python
Executable file
#-----------------------------------------------------------------
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# pycparser: cdecl.py
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#
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# Example of the CDECL tool using pycparser. CDECL "explains"
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# C type declarations in plain English.
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#
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# The AST generated by pycparser from the given declaration is
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# traversed recursively to build the explanation.
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# Note that the declaration must be a valid external declaration
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# in C. All the types used in it must be defined with typedef,
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# or parsing will fail. The definition can be arbitrary, it isn't
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# really used - by pycparser must know which tokens are types.
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#
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# For example:
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#
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# 'typedef int Node; const Node* (*ar)[10];'
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# =>
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# ar is a pointer to array[10] of pointer to const Node
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#
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# Copyright (C) 2008, Eli Bendersky
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# License: LGPL
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#-----------------------------------------------------------------
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import sys
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from pycparser import c_parser, c_ast
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def explain_c_declaration(c_decl):
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""" Parses the declaration in c_decl and returns a text
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explanation as a string.
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The last external node of the string is used, to allow
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earlier typedefs for used types.
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"""
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parser = c_parser.CParser()
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node = parser.parse(c_decl, filename='<stdin>')
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if ( not isinstance(node, c_ast.FileAST) or
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not isinstance(node.ext[-1], c_ast.Decl)):
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return "Last external node is invalid type"
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return _explain_decl_node(node.ext[-1])
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def _explain_decl_node(decl_node):
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""" Receives a c_ast.Decl note and returns its explanation in
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English.
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"""
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#~ print decl_node.show()
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storage = ' '.join(decl_node.storage) + ' ' if decl_node.storage else ''
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return (decl_node.name +
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" is a " +
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storage +
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_explain_type(decl_node.type))
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def _explain_type(decl):
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""" Recursively explains a type decl node
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"""
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typ = type(decl)
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if typ == c_ast.TypeDecl:
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quals = ' '.join(decl.quals) + ' ' if decl.quals else ''
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return quals + _explain_type(decl.type)
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elif typ == c_ast.Typename or typ == c_ast.Decl:
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return _explain_type(decl.type)
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elif typ == c_ast.IdentifierType:
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return ' '.join(decl.names)
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elif typ == c_ast.PtrDecl:
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quals = ' '.join(decl.quals) + ' ' if decl.quals else ''
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return quals + 'pointer to ' + _explain_type(decl.type)
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elif typ == c_ast.ArrayDecl:
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arr = 'array'
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if decl.dim: arr += '[%s]' % decl.dim.value
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return arr + " of " + _explain_type(decl.type)
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elif typ == c_ast.FuncDecl:
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if decl.args:
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params = [_explain_type(param) for param in decl.args.params]
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args = ', '.join(params)
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else:
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args = ''
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return ('function(%s) returning ' % (args) +
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_explain_type(decl.type))
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if __name__ == "__main__":
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if len(sys.argv) > 1:
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c_decl = sys.argv[1]
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else:
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c_decl = "char *(*(**foo[][8])())[];"
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print "Explaining the declaration:", c_decl
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print "\n", explain_c_declaration(c_decl)
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