Viewing file:  c_generator.py (17.36 KB) -rw-r--r--
Select action/file-type:
 (+) |  (+) |  (+) | Code (+) | Session (+) |  (+) | SDB (+) |  (+) |  (+) |  (+) |  (+) |  (+) |
#------------------------------------------------------------------------------
# pycparser: c_generator.py
#
# C code generator from pycparser AST nodes.
#
# Eli Bendersky [https://eli.thegreenplace.net/]
# 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, reduce_parentheses=False):
""" Constructs C-code generator
reduce_parentheses:
if True, eliminates needless parentheses on binary operators
"""
# Statements start with indentation of self.indent_level spaces, using
# the _make_indent method.
self.indent_level = 0
self.reduce_parentheses = reduce_parentheses
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):
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_Pragma(self, n):
ret = '#pragma'
if n.string:
ret += ' ' + n.string
return ret
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):
if n.op == 'sizeof':
# Always parenthesize the argument of sizeof since it can be
# a name.
return 'sizeof(%s)' % self.visit(n.expr)
else:
operand = self._parenthesize_unless_simple(n.expr)
if n.op == 'p++':
return '%s++' % operand
elif n.op == 'p--':
return '%s--' % operand
else:
return '%s%s' % (n.op, operand)
# Precedence map of binary operators:
precedence_map = {
# Should be in sync with c_parser.CParser.precedence
# Higher numbers are stronger binding
'||': 0, # weakest binding
'&&': 1,
'|': 2,
'^': 3,
'&': 4,
'==': 5, '!=': 5,
'>': 6, '>=': 6, '<': 6, '<=': 6,
'>>': 7, '<<': 7,
'+': 8, '-': 8,
'*': 9, '/': 9, '%': 9 # strongest binding
}
def visit_BinaryOp(self, n):
# Note: all binary operators are left-to-right associative
#
# If `n.left.op` has a stronger or equally binding precedence in
# comparison to `n.op`, no parenthesis are needed for the left:
# e.g., `(a*b) + c` is equivalent to `a*b + c`, as well as
# `(a+b) - c` is equivalent to `a+b - c` (same precedence).
# If the left operator is weaker binding than the current, then
# parentheses are necessary:
# e.g., `(a+b) * c` is NOT equivalent to `a+b * c`.
lval_str = self._parenthesize_if(
n.left,
lambda d: not (self._is_simple_node(d) or
self.reduce_parentheses and isinstance(d, c_ast.BinaryOp) and
self.precedence_map[d.op] >= self.precedence_map[n.op]))
# If `n.right.op` has a stronger -but not equal- binding precedence,
# parenthesis can be omitted on the right:
# e.g., `a + (b*c)` is equivalent to `a + b*c`.
# If the right operator is weaker or equally binding, then parentheses
# are necessary:
# e.g., `a * (b+c)` is NOT equivalent to `a * b+c` and
# `a - (b+c)` is NOT equivalent to `a - b+c` (same precedence).
rval_str = self._parenthesize_if(
n.right,
lambda d: not (self._is_simple_node(d) or
self.reduce_parentheses and isinstance(d, c_ast.BinaryOp) and
self.precedence_map[d.op] > self.precedence_map[n.op]))
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, emit_declname=False) + ')'
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):
return self._generate_struct_union_enum(n, name='enum')
def visit_Alignas(self, n):
return '_Alignas({})'.format(self.visit(n.alignment))
def visit_Enumerator(self, n):
if not n.value:
return '{indent}{name},\n'.format(
indent=self._make_indent(),
name=n.name,
)
else:
return '{indent}{name} = {value},\n'.format(
indent=self._make_indent(),
name=n.name,
value=self.visit(n.value),
)
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)
elif isinstance(ext, c_ast.Pragma):
s += self.visit(ext) + '\n'
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_CompoundLiteral(self, n):
return '(' + self.visit(n.type) + '){' + self.visit(n.init) + '}'
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_StaticAssert(self, n):
s = '_Static_assert('
s += self.visit(n.cond)
if n.message:
s += ','
s += self.visit(n.message)
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_enum(n, 'struct')
def visit_Typename(self, n):
return self._generate_type(n.type)
def visit_Union(self, n):
return self._generate_struct_union_enum(n, 'union')
def visit_NamedInitializer(self, n):
s = ''
for name in n.name:
if isinstance(name, c_ast.ID):
s += '.' + name.name
else:
s += '[' + self.visit(name) + ']'
s += ' = ' + self._visit_expr(n.expr)
return s
def visit_FuncDecl(self, n):
return self._generate_type(n)
def visit_ArrayDecl(self, n):
return self._generate_type(n, emit_declname=False)
def visit_TypeDecl(self, n):
return self._generate_type(n, emit_declname=False)
def visit_PtrDecl(self, n):
return self._generate_type(n, emit_declname=False)
def _generate_struct_union_enum(self, n, name):
""" Generates code for structs, unions, and enums. name should be
'struct', 'union', or 'enum'.
"""
if name in ('struct', 'union'):
members = n.decls
body_function = self._generate_struct_union_body
else:
assert name == 'enum'
members = None if n.values is None else n.values.enumerators
body_function = self._generate_enum_body
s = name + ' ' + (n.name or '')
if members is not None:
# None means no members
# Empty sequence means an empty list of members
s += '\n'
s += self._make_indent()
self.indent_level += 2
s += '{\n'
s += body_function(members)
self.indent_level -= 2
s += self._make_indent() + '}'
return s
def _generate_struct_union_body(self, members):
return ''.join(self._generate_stmt(decl) for decl in members)
def _generate_enum_body(self, members):
# `[:-2] + '\n'` removes the final `,` from the enumerator list
return ''.join(self.visit(value) for value in members)[:-2] + '\n'
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)
elif typ in (c_ast.If,):
return indent + 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) + ' '
if n.align: s += self.visit(n.align[0]) + ' '
s += self._generate_type(n.type)
return s
def _generate_type(self, n, modifiers=[], emit_declname = True):
""" 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 and emit_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 += '['
if modifier.dim_quals:
nstr += ' '.join(modifier.dim_quals) + ' '
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 if nstr else '')
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, emit_declname = emit_declname)
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],
emit_declname = emit_declname)
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))
|