moving CGenerator from examples/c-to-c.py into its own class in pycparser/. c-to-c remains as a shell example over it

2 files changed, 384 insertions, 3 deletions

diff --git a/pycparser/c_generator.py b/pycparser/c_generator.py
new file mode 100644
index 0000000..a646683
--- /dev/null
+++ b/pycparser/c_generator.py
@@ -0,0 +1,381 @@
+#------------------------------------------------------------------------------
+# pycparser: c_generator.py
+#
+# C code generator from pycparser AST nodes.
+#
+# Copyright (C) 2008-2012, 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):
+        self.output = ''
+        
+        # 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 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_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 delaration 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:
+            if isinstance(n.init, c_ast.ExprList):
+                s += ' = {' + self.visit(n.init) + '}'
+            else:
+                s += ' = ' + self.visit(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:
+            if isinstance(expr, c_ast.ExprList):
+                visited_subexprs.append('{' + self.visit(expr) + '}')
+            else:
+                visited_subexprs.append(self.visit(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
+        # The body is a Compound node
+        body = self.visit(n.body)
+        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(n.cond) + ' ? '
+        s += self.visit(n.iftrue) + ' : '
+        s += self.visit(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'
+        s += self._generate_stmt(n.stmt, add_indent=True)
+        return s
+    
+    def visit_Default(self, n):
+        return 'default:\n' + self._generate_stmt(n.stmt, add_indent=True)
+
+    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 _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):
+            # 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):
+                    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(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))
+
+
diff --git a/pycparser/c_parser.py b/pycparser/c_parser.py
index 77f1e34..7205842 100644
--- a/pycparser/c_parser.py
+++ b/pycparser/c_parser.py
@@ -1,11 +1,11 @@
-#-----------------------------------------------------------------
+#------------------------------------------------------------------------------
 # pycparser: c_parser.py
 #
 # CParser class: Parser and AST builder for the C language
 #
-# Copyright (C) 2008-2011, Eli Bendersky
+# Copyright (C) 2008-2012, Eli Bendersky
 # License: BSD
-#-----------------------------------------------------------------
+#------------------------------------------------------------------------------
 import re
 
 import ply.yacc