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c_generator.py
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#------------------------------------------------------------------------------ # pycparser: c_generator.py # # C code generator from pycparser AST nodes. # # Copyright (C) 2008-2015, Eli Bendersky # License: BSD #------------------------------------------------------------------------------ from . import c_ast class CGenerator(object): """ Uses the same visitor pattern as c_ast.NodeVisitor, but modified to return a value from each visit method, using string accumulation in generic_visit. """ def __init__(self): # Statements start with indentation of self.indent_level spaces, using # the _make_indent method # self.indent_level = 0 def _make_indent(self): return ' ' * self.indent_level def visit(self, node): method = 'visit_' + node.__class__.__name__ return getattr(self, method, self.generic_visit)(node) def generic_visit(self, node): #~ print('generic:', type(node)) if node is None: return '' else: return ''.join(self.visit(c) for c_name, c in node.children()) def visit_Constant(self, n): return n.value def visit_ID(self, n): return n.name def visit_ArrayRef(self, n): arrref = self._parenthesize_unless_simple(n.name) return arrref + '[' + self.visit(n.subscript) + ']' def visit_StructRef(self, n): sref = self._parenthesize_unless_simple(n.name) return sref + n.type + self.visit(n.field) def visit_FuncCall(self, n): fref = self._parenthesize_unless_simple(n.name) return fref + '(' + self.visit(n.args) + ')' def visit_UnaryOp(self, n): operand = self._parenthesize_unless_simple(n.expr) if n.op == 'p++': return '%s++' % operand elif n.op == 'p--': return '%s--' % operand elif n.op == 'sizeof': # Always parenthesize the argument of sizeof since it can be # a name. return 'sizeof(%s)' % self.visit(n.expr) else: return '%s%s' % (n.op, operand) def visit_BinaryOp(self, n): lval_str = self._parenthesize_if(n.left, lambda d: not self._is_simple_node(d)) rval_str = self._parenthesize_if(n.right, lambda d: not self._is_simple_node(d)) return '%s %s %s' % (lval_str, n.op, rval_str) def visit_Assignment(self, n): rval_str = self._parenthesize_if( n.rvalue, lambda n: isinstance(n, c_ast.Assignment)) return '%s %s %s' % (self.visit(n.lvalue), n.op, rval_str) def visit_IdentifierType(self, n): return ' '.join(n.names) def _visit_expr(self, n): if isinstance(n, c_ast.InitList): return '{' + self.visit(n) + '}' elif isinstance(n, c_ast.ExprList): return '(' + self.visit(n) + ')' else: return self.visit(n) def visit_Decl(self, n, no_type=False): # no_type is used when a Decl is part of a DeclList, where the type is # explicitly only for the first declaration in a list. # s = n.name if no_type else self._generate_decl(n) if n.bitsize: s += ' : ' + self.visit(n.bitsize) if n.init: s += ' = ' + self._visit_expr(n.init) return s def visit_DeclList(self, n): s = self.visit(n.decls[0]) if len(n.decls) > 1: s += ', ' + ', '.join(self.visit_Decl(decl, no_type=True) for decl in n.decls[1:]) return s def visit_Typedef(self, n): s = '' if n.storage: s += ' '.join(n.storage) + ' ' s += self._generate_type(n.type) return s def visit_Cast(self, n): s = '(' + self._generate_type(n.to_type) + ')' return s + ' ' + self._parenthesize_unless_simple(n.expr) def visit_ExprList(self, n): visited_subexprs = [] for expr in n.exprs: visited_subexprs.append(self._visit_expr(expr)) return ', '.join(visited_subexprs) def visit_InitList(self, n): visited_subexprs = [] for expr in n.exprs: visited_subexprs.append(self._visit_expr(expr)) return ', '.join(visited_subexprs) def visit_Enum(self, n): s = 'enum' if n.name: s += ' ' + n.name if n.values: s += ' {' for i, enumerator in enumerate(n.values.enumerators): s += enumerator.name if enumerator.value: s += ' = ' + self.visit(enumerator.value) if i != len(n.values.enumerators) - 1: s += ', ' s += '}' return s def visit_FuncDef(self, n): decl = self.visit(n.decl) self.indent_level = 0 body = self.visit(n.body) if n.param_decls: knrdecls = ';\n'.join(self.visit(p) for p in n.param_decls) return decl + '\n' + knrdecls + ';\n' + body + '\n' else: return decl + '\n' + body + '\n' def visit_FileAST(self, n): s = '' for ext in n.ext: if isinstance(ext, c_ast.FuncDef): s += self.visit(ext) else: s += self.visit(ext) + ';\n' return s def visit_Compound(self, n): s = self._make_indent() + '{\n' self.indent_level += 2 if n.block_items: s += ''.join(self._generate_stmt(stmt) for stmt in n.block_items) self.indent_level -= 2 s += self._make_indent() + '}\n' return s def visit_EmptyStatement(self, n): return ';' def visit_ParamList(self, n): return ', '.join(self.visit(param) for param in n.params) def visit_Return(self, n): s = 'return' if n.expr: s += ' ' + self.visit(n.expr) return s + ';' def visit_Break(self, n): return 'break;' def visit_Continue(self, n): return 'continue;' def visit_TernaryOp(self, n): s = self._visit_expr(n.cond) + ' ? ' s += self._visit_expr(n.iftrue) + ' : ' s += self._visit_expr(n.iffalse) return s def visit_If(self, n): s = 'if (' if n.cond: s += self.visit(n.cond) s += ')\n' s += self._generate_stmt(n.iftrue, add_indent=True) if n.iffalse: s += self._make_indent() + 'else\n' s += self._generate_stmt(n.iffalse, add_indent=True) return s def visit_For(self, n): s = 'for (' if n.init: s += self.visit(n.init) s += ';' if n.cond: s += ' ' + self.visit(n.cond) s += ';' if n.next: s += ' ' + self.visit(n.next) s += ')\n' s += self._generate_stmt(n.stmt, add_indent=True) return s def visit_While(self, n): s = 'while (' if n.cond: s += self.visit(n.cond) s += ')\n' s += self._generate_stmt(n.stmt, add_indent=True) return s def visit_DoWhile(self, n): s = 'do\n' s += self._generate_stmt(n.stmt, add_indent=True) s += self._make_indent() + 'while (' if n.cond: s += self.visit(n.cond) s += ');' return s def visit_Switch(self, n): s = 'switch (' + self.visit(n.cond) + ')\n' s += self._generate_stmt(n.stmt, add_indent=True) return s def visit_Case(self, n): s = 'case ' + self.visit(n.expr) + ':\n' for stmt in n.stmts: s += self._generate_stmt(stmt, add_indent=True) return s def visit_Default(self, n): s = 'default:\n' for stmt in n.stmts: s += self._generate_stmt(stmt, add_indent=True) return s def visit_Label(self, n): return n.name + ':\n' + self._generate_stmt(n.stmt) def visit_Goto(self, n): return 'goto ' + n.name + ';' def visit_EllipsisParam(self, n): return '...' def visit_Struct(self, n): return self._generate_struct_union(n, 'struct') def visit_Typename(self, n): return self._generate_type(n.type) def visit_Union(self, n): return self._generate_struct_union(n, 'union') def visit_NamedInitializer(self, n): s = '' for name in n.name: if isinstance(name, c_ast.ID): s += '.' + name.name elif isinstance(name, c_ast.Constant): s += '[' + name.value + ']' s += ' = ' + self.visit(n.expr) return s def visit_FuncDecl(self, n): return self._generate_type(n) def _generate_struct_union(self, n, name): """ Generates code for structs and unions. name should be either 'struct' or union. """ s = name + ' ' + (n.name or '') if n.decls: s += '\n' s += self._make_indent() self.indent_level += 2 s += '{\n' for decl in n.decls: s += self._generate_stmt(decl) self.indent_level -= 2 s += self._make_indent() + '}' return s def _generate_stmt(self, n, add_indent=False): """ Generation from a statement node. This method exists as a wrapper for individual visit_* methods to handle different treatment of some statements in this context. """ typ = type(n) if add_indent: self.indent_level += 2 indent = self._make_indent() if add_indent: self.indent_level -= 2 if typ in ( c_ast.Decl, c_ast.Assignment, c_ast.Cast, c_ast.UnaryOp, c_ast.BinaryOp, c_ast.TernaryOp, c_ast.FuncCall, c_ast.ArrayRef, c_ast.StructRef, c_ast.Constant, c_ast.ID, c_ast.Typedef, c_ast.ExprList): # These can also appear in an expression context so no semicolon # is added to them automatically # return indent + self.visit(n) + ';\n' elif typ in (c_ast.Compound,): # No extra indentation required before the opening brace of a # compound - because it consists of multiple lines it has to # compute its own indentation. # return self.visit(n) else: return indent + self.visit(n) + '\n' def _generate_decl(self, n): """ Generation from a Decl node. """ s = '' if n.funcspec: s = ' '.join(n.funcspec) + ' ' if n.storage: s += ' '.join(n.storage) + ' ' s += self._generate_type(n.type) return s def _generate_type(self, n, modifiers=[]): """ Recursive generation from a type node. n is the type node. modifiers collects the PtrDecl, ArrayDecl and FuncDecl modifiers encountered on the way down to a TypeDecl, to allow proper generation from it. """ typ = type(n) #~ print(n, modifiers) if typ == c_ast.TypeDecl: s = '' if n.quals: s += ' '.join(n.quals) + ' ' s += self.visit(n.type) nstr = n.declname if n.declname else '' # Resolve modifiers. # Wrap in parens to distinguish pointer to array and pointer to # function syntax. # for i, modifier in enumerate(modifiers): if isinstance(modifier, c_ast.ArrayDecl): if (i != 0 and isinstance(modifiers[i - 1], c_ast.PtrDecl)): nstr = '(' + nstr + ')' nstr += '[' + self.visit(modifier.dim) + ']' elif isinstance(modifier, c_ast.FuncDecl): if (i != 0 and isinstance(modifiers[i - 1], c_ast.PtrDecl)): nstr = '(' + nstr + ')' nstr += '(' + self.visit(modifier.args) + ')' elif isinstance(modifier, c_ast.PtrDecl): if modifier.quals: nstr = '* %s %s' % (' '.join(modifier.quals), nstr) else: nstr = '*' + nstr if nstr: s += ' ' + nstr return s elif typ == c_ast.Decl: return self._generate_decl(n.type) elif typ == c_ast.Typename: return self._generate_type(n.type) elif typ == c_ast.IdentifierType: return ' '.join(n.names) + ' ' elif typ in (c_ast.ArrayDecl, c_ast.PtrDecl, c_ast.FuncDecl): return self._generate_type(n.type, modifiers + [n]) else: return self.visit(n) def _parenthesize_if(self, n, condition): """ Visits 'n' and returns its string representation, parenthesized if the condition function applied to the node returns True. """ s = self._visit_expr(n) if condition(n): return '(' + s + ')' else: return s def _parenthesize_unless_simple(self, n): """ Common use case for _parenthesize_if """ return self._parenthesize_if(n, lambda d: not self._is_simple_node(d)) def _is_simple_node(self, n): """ Returns True for nodes that are "simple" - i.e. nodes that always have higher precedence than operators. """ return isinstance(n,( c_ast.Constant, c_ast.ID, c_ast.ArrayRef, c_ast.StructRef, c_ast.FuncCall))