Parser/asdl_c.py

#! /usr/bin/env python
"""Generate C code from an ASDL description."""

# TO DO
# handle fields that have a type but no name

import os, sys, traceback

import asdl

TABSIZE = 8
MAX_COL = 80

def get_c_type(name):
    """Return a string for the C name of the type.

    This function special cases the default types provided by asdl:
    identifier, string, int, bool.
    """
    # XXX ack!  need to figure out where Id is useful and where string
    if isinstance(name, asdl.Id):
        name = name.value
    if name in asdl.builtin_types:
        return name
    else:
        return "%s_ty" % name

def reflow_lines(s, depth):
    """Reflow the line s indented depth tabs.

    Return a sequence of lines where no line extends beyond MAX_COL
    when properly indented.  The first line is properly indented based
    exclusively on depth * TABSIZE.  All following lines -- these are
    the reflowed lines generated by this function -- start at the same
    column as the first character beyond the opening { in the first
    line.
    """
    size = MAX_COL - depth * TABSIZE
    if len(s) < size:
        return [s]

    lines = []
    cur = s
    padding = ""
    while len(cur) > size:
        i = cur.rfind(' ', 0, size)
        # XXX this should be fixed for real
        if i == -1 and 'GeneratorExp' in cur:
            i = size + 3
        assert i != -1, "Impossible line %d to reflow: %s" % (size, `s`)
        lines.append(padding + cur[:i])
        if len(lines) == 1:
            # find new size based on brace
            j = cur.find('{', 0, i)
            if j >= 0:
                j += 2 # account for the brace and the space after it
                size -= j
                padding = " " * j
            else:
                j = cur.find('(', 0, i)
                if j >= 0:
                    j += 1 # account for the paren (no space after it)
                    size -= j
                    padding = " " * j
        cur = cur[i+1:]
    else:
        lines.append(padding + cur)
    return lines

def is_simple(sum):
    """Return True if a sum is a simple.

    A sum is simple if its types have no fields, e.g.
    unaryop = Invert | Not | UAdd | USub
    """

    for t in sum.types:
        if t.fields:
            return False
    return True

class EmitVisitor(asdl.VisitorBase):
    """Visit that emits lines"""

    def __init__(self, file):
        self.file = file
        super(EmitVisitor, self).__init__()

    def emit(self, s, depth, reflow=1):
        # XXX reflow long lines?
        if reflow:
            lines = reflow_lines(s, depth)
        else:
            lines = [s]
        for line in lines:
            line = (" " * TABSIZE * depth) + line + "\n"
            self.file.write(line)

class TypeDefVisitor(EmitVisitor):
    def visitModule(self, mod):
        for dfn in mod.dfns:
            self.visit(dfn)

    def visitType(self, type, depth=0):
        self.visit(type.value, type.name, depth)

    def visitSum(self, sum, name, depth):
        if is_simple(sum):
            self.simple_sum(sum, name, depth)
        else:
            self.sum_with_constructors(sum, name, depth)

    def simple_sum(self, sum, name, depth):
        enum = []
        for i in range(len(sum.types)):
            type = sum.types[i]
            enum.append("%s=%d" % (type.name, i + 1))
        enums = ", ".join(enum)
        ctype = get_c_type(name)
        s = "typedef enum _%s { %s } %s;" % (name, enums, ctype)
        self.emit(s, depth)
        self.emit("", depth)

    def sum_with_constructors(self, sum, name, depth):
        ctype = get_c_type(name)
        s = "typedef struct _%(name)s *%(ctype)s;" % locals()
        self.emit(s, depth)
        self.emit("", depth)

    def visitProduct(self, product, name, depth):
        ctype = get_c_type(name)
        s = "typedef struct _%(name)s *%(ctype)s;" % locals()
        self.emit(s, depth)
        self.emit("", depth)

class StructVisitor(EmitVisitor):
    """Visitor to generate typdefs for AST."""

    def visitModule(self, mod):
        for dfn in mod.dfns:
            self.visit(dfn)

    def visitType(self, type, depth=0):
        self.visit(type.value, type.name, depth)

    def visitSum(self, sum, name, depth):
        if not is_simple(sum):
            self.sum_with_constructors(sum, name, depth)

    def sum_with_constructors(self, sum, name, depth):
        def emit(s, depth=depth):
            self.emit(s % sys._getframe(1).f_locals, depth)
        enum = []
        for i in range(len(sum.types)):
            type = sum.types[i]
            enum.append("%s_kind=%d" % (type.name, i + 1))

        emit("struct _%(name)s {")
        emit("enum { " + ", ".join(enum) + " } kind;", depth + 1)
        emit("union {", depth + 1)
        for t in sum.types:
            self.visit(t, depth + 2)
        emit("} v;", depth + 1)
        for field in sum.attributes:
            # rudimentary attribute handling
            type = str(field.type)
            assert type in asdl.builtin_types, type
            emit("%s %s;" % (type, field.name), depth + 1);
        emit("};")
        emit("")

    def visitConstructor(self, cons, depth):
        if cons.fields:
            self.emit("struct {", depth)
            for f in cons.fields:
                self.visit(f, depth + 1)
            self.emit("} %s;" % cons.name, depth)
            self.emit("", depth)
        else:
            # XXX not sure what I want here, nothing is probably fine
            pass

    def visitField(self, field, depth):
        # XXX need to lookup field.type, because it might be something
        # like a builtin...
        ctype = get_c_type(field.type)
        name = field.name
        if field.seq:
            self.emit("asdl_seq *%(name)s;" % locals(), depth)
        else:
            self.emit("%(ctype)s %(name)s;" % locals(), depth)

    def visitProduct(self, product, name, depth):
        self.emit("struct _%(name)s {" % locals(), depth)
        for f in product.fields:
            self.visit(f, depth + 1)
        self.emit("};", depth)
        self.emit("", depth)

class PrototypeVisitor(EmitVisitor):
    """Generate function prototypes for the .h file"""

    def visitModule(self, mod):
        for dfn in mod.dfns:
            self.visit(dfn)

    def visitType(self, type):
        self.visit(type.value, type.name)

    def visitSum(self, sum, name):
        if is_simple(sum):
            pass # XXX
        else:
            for t in sum.types:
                self.visit(t, name, sum.attributes)

    def get_args(self, fields):
        """Return list of C argument into, one for each field.

        Argument info is 3-tuple of a C type, variable name, and flag
        that is true if type can be NULL.
        """
        args = []
        unnamed = {}
        for f in fields:
            if f.name is None:
                name = f.type
                c = unnamed[name] = unnamed.get(name, 0) + 1
                if c > 1:
                    name = "name%d" % (c - 1)
            else:
                name = f.name
            # XXX should extend get_c_type() to handle this
            if f.seq:
                ctype = "asdl_seq *"
            else:
                ctype = get_c_type(f.type)
            args.append((ctype, name, f.opt or f.seq))
        return args

    def visitConstructor(self, cons, type, attrs):
        args = self.get_args(cons.fields)
        attrs = self.get_args(attrs)
        ctype = get_c_type(type)
        self.emit_function(cons.name, ctype, args, attrs)

    def emit_function(self, name, ctype, args, attrs, union=1):
        args = args + attrs
        if args:
            argstr = ", ".join(["%s %s" % (atype, aname)
                                for atype, aname, opt in args])
            argstr += ", PyArena *arena"
        else:
            argstr = "PyArena *arena"
        self.emit("%s %s(%s);" % (ctype, name, argstr), 0)

    def visitProduct(self, prod, name):
        self.emit_function(name, get_c_type(name),
                           self.get_args(prod.fields), [], union=0)

class FunctionVisitor(PrototypeVisitor):
    """Visitor to generate constructor functions for AST."""

    def emit_function(self, name, ctype, args, attrs, union=1):
        def emit(s, depth=0, reflow=1):
            self.emit(s, depth, reflow)
        argstr = ", ".join(["%s %s" % (atype, aname)
                            for atype, aname, opt in args + attrs])
        if argstr:
            argstr += ", PyArena *arena"
        else:
            argstr = "PyArena *arena"
        self.emit("%s" % ctype, 0)
        emit("%s(%s)" % (name, argstr))
        emit("{")
        emit("%s p;" % ctype, 1)
        for argtype, argname, opt in args:
            # XXX hack alert: false is allowed for a bool
            if not opt and not argtype == "bool":
                emit("if (!%s) {" % argname, 1)
                emit("PyErr_SetString(PyExc_ValueError,", 2)
                msg = "field %s is required for %s" % (argname, name)
                emit('                "%s");' % msg,
                     2, reflow=0)
                emit('return NULL;', 2)
                emit('}', 1)

        emit("p = (%s)PyArena_Malloc(arena, sizeof(*p));" % ctype, 1);
        emit("if (!p) {", 1)
        emit("PyErr_NoMemory();", 2)
        emit("return NULL;", 2)
        emit("}", 1)
        if union:
            self.emit_body_union(name, args, attrs)
        else:
            self.emit_body_struct(name, args, attrs)
        emit("return p;", 1)
        emit("}")
        emit("")

    def emit_body_union(self, name, args, attrs):
        def emit(s, depth=0, reflow=1):
            self.emit(s, depth, reflow)
        emit("p->kind = %s_kind;" % name, 1)
        for argtype, argname, opt in args:
            emit("p->v.%s.%s = %s;" % (name, argname, argname), 1)
        for argtype, argname, opt in attrs:
            emit("p->%s = %s;" % (argname, argname), 1)

    def emit_body_struct(self, name, args, attrs):
        def emit(s, depth=0, reflow=1):
            self.emit(s, depth, reflow)
        for argtype, argname, opt in args:
            emit("p->%s = %s;" % (argname, argname), 1)
        assert not attrs

class PickleVisitor(EmitVisitor):

    def visitModule(self, mod):
        for dfn in mod.dfns:
            self.visit(dfn)

    def visitType(self, type):
        self.visit(type.value, type.name)

    def visitSum(self, sum, name):
        pass

    def visitProduct(self, sum, name):
        pass

    def visitConstructor(self, cons, name):
        pass

    def visitField(self, sum):
        pass

class MarshalPrototypeVisitor(PickleVisitor):

    def prototype(self, sum, name):
        ctype = get_c_type(name)
        self.emit("static int marshal_write_%s(PyObject **, int *, %s);"
                  % (name, ctype), 0)

    visitProduct = visitSum = prototype

class PyTypesDeclareVisitor(PickleVisitor):

    def visitProduct(self, prod, name):
        self.emit("PyTypeObject *%s_type;" % name, 0)
        self.emit("static PyObject* ast2obj_%s(void*);" % name, 0)
        if prod.fields:
            self.emit("char *%s_fields[]={" % name,0)
            for f in prod.fields:
                self.emit('"%s",' % f.name, 1)
            self.emit("};", 0)
        
    def visitSum(self, sum, name):
        self.emit("PyTypeObject *%s_type;" % name, 0)
        if sum.attributes:
            self.emit("char *%s_attributes[] = {" % name, 0)
            for a in sum.attributes:
                self.emit('"%s",' % a.name, 1)
            self.emit("};", 0)
        ptype = "void*"
        if is_simple(sum):
            ptype = get_c_type(name)
            tnames = []
            for t in sum.types:
                tnames.append(str(t.name)+"_singleton")
            tnames = ", *".join(tnames)
            self.emit("static PyObject *%s;" % tnames, 0)
        self.emit("static PyObject* ast2obj_%s(%s);" % (name, ptype), 0)
        for t in sum.types:
            self.visitConstructor(t, name)
            
    def visitConstructor(self, cons, name):
        self.emit("PyTypeObject *%s_type;" % cons.name, 0)
        if cons.fields:
            self.emit("char *%s_fields[]={" % cons.name, 0)
            for t in cons.fields:
                self.emit('"%s",' % t.name, 1)
            self.emit("};",0)

class PyTypesVisitor(PickleVisitor):

    def visitModule(self, mod):
        self.emit("""
static PyTypeObject* make_type(char *type, PyTypeObject* base, char**fields, int num_fields)
{
    PyObject *fnames, *result;
    int i;
    if (num_fields) {
        fnames = PyTuple_New(num_fields);
        if (!fnames) return NULL;
    } else {
        fnames = Py_None;
        Py_INCREF(Py_None);
    }
    for(i=0; i < num_fields; i++) {
        PyObject *field = PyString_FromString(fields[i]);
        if (!field) {
            Py_DECREF(fnames);
            return NULL;
        }
        PyTuple_SET_ITEM(fnames, i, field);
    }
    result = PyObject_CallFunction((PyObject*)&PyType_Type, "s(O){sOss}", 
                    type, base, "_fields", fnames, "__module__", "_ast");
    Py_DECREF(fnames);
    return (PyTypeObject*)result;
}

static int add_attributes(PyTypeObject* type, char**attrs, int num_fields)
{
    int i;
    PyObject *s, *l = PyList_New(num_fields);
    if (!l) return 0;
    for(i=0; i < num_fields; i++) {
        s = PyString_FromString(attrs[i]);
        if (!s) {
            Py_DECREF(l);
            return 0;
        }
        PyList_SET_ITEM(l, i, s);
    }
    return PyObject_SetAttrString((PyObject*)type, "_attributes", l) >=0;
}

static PyObject* ast2obj_list(asdl_seq *seq, PyObject* (*func)(void*))
{
    int i, n = asdl_seq_LEN(seq);
    PyObject *result = PyList_New(n);
    PyObject *value;
    if (!result)
        return NULL;
    for (i = 0; i < n; i++) {
        value = func(asdl_seq_GET(seq, i));
        if (!value) {
            Py_DECREF(result);
            return NULL;
        }
        PyList_SET_ITEM(result, i, value);
    }
    return result;
}

static PyObject* ast2obj_object(void *o)
{
    if (!o)
        o = Py_None;
    Py_INCREF((PyObject*)o);
    return (PyObject*)o;
}
#define ast2obj_identifier ast2obj_object
#define ast2obj_string ast2obj_object
static PyObject* ast2obj_bool(bool b)
{
    return PyBool_FromLong(b);
}

static PyObject* ast2obj_int(bool b)
{
    return PyInt_FromLong(b);
}
""", 0, reflow=False)

        self.emit("static int initialized;", 0)
        self.emit("static int init_types(void)",0)
        self.emit("{", 0)
        self.emit("if (initialized) return 1;", 1)
        self.emit('AST_type = make_type("AST", &PyBaseObject_Type, NULL, 0);', 1)
        for dfn in mod.dfns:
            self.visit(dfn)
        self.emit("initialized = 1;", 1)
        self.emit("return 1;", 1);
        self.emit("}", 0)

    def visitProduct(self, prod, name):
        if prod.fields:
            fields = name.value+"_fields"
        else:
            fields = "NULL"
        self.emit('%s_type = make_type("%s", AST_type, %s, %d);' % 
                        (name, name, fields, len(prod.fields)), 1)
        self.emit("if (!%s_type) return 0;" % name, 1)
        
    def visitSum(self, sum, name):
        self.emit('%s_type = make_type("%s", AST_type, NULL, 0);' % (name, name), 1)
        self.emit("if (!%s_type) return 0;" % name, 1)
        if sum.attributes:
            self.emit("if (!add_attributes(%s_type, %s_attributes, %d)) return 0;" % 
                            (name, name, len(sum.attributes)), 1)
        else:
            self.emit("if (!add_attributes(%s_type, NULL, 0)) return 0;" % name, 1)
        simple = is_simple(sum)
        for t in sum.types:
            self.visitConstructor(t, name, simple)
            
    def visitConstructor(self, cons, name, simple):
        if cons.fields:
            fields = cons.name.value+"_fields"
        else:
            fields = "NULL"
        self.emit('%s_type = make_type("%s", %s_type, %s, %d);' % 
                            (cons.name, cons.name, name, fields, len(cons.fields)), 1)
        self.emit("if (!%s_type) return 0;" % cons.name, 1)
        if simple:
            self.emit("%s_singleton = PyType_GenericNew(%s_type, NULL, NULL);" %
                             (cons.name, cons.name), 1)
            self.emit("if (!%s_singleton) return 0;" % cons.name, 1)
                             
class ASTModuleVisitor(PickleVisitor):

    def visitModule(self, mod):
        self.emit("PyMODINIT_FUNC", 0)
        self.emit("init_ast(void)", 0)
        self.emit("{", 0)
        self.emit("PyObject *m, *d;", 1)
        self.emit("if (!init_types()) return;", 1)
        self.emit('m = Py_InitModule3("_ast", NULL, NULL);', 1)
        self.emit("if (!m) return;", 1)
        self.emit("d = PyModule_GetDict(m);", 1)
        self.emit('if (PyDict_SetItemString(d, "AST", (PyObject*)AST_type) < 0) return;', 1)
        self.emit('if (PyModule_AddIntConstant(m, "PyCF_ONLY_AST", PyCF_ONLY_AST) < 0)', 1)
        self.emit("return;", 2)
        for dfn in mod.dfns:
            self.visit(dfn)
        self.emit("}", 0)

    def visitProduct(self, prod, name):
        self.addObj(name)
        
    def visitSum(self, sum, name):
        self.addObj(name)
        for t in sum.types:
            self.visitConstructor(t, name)
            
    def visitConstructor(self, cons, name):
        self.addObj(cons.name)
        
    def addObj(self, name):
        self.emit('if(PyDict_SetItemString(d, "%s", (PyObject*)%s_type) < 0) return;' % (name, name), 1)

_SPECIALIZED_SEQUENCES = ('stmt', 'expr')

def find_sequence(fields, doing_specialization):
    """Return True if any field uses a sequence."""
    for f in fields:
        if f.seq:
            if not doing_specialization:
                return True
            if str(f.type) not in _SPECIALIZED_SEQUENCES:
                return True
    return False

def has_sequence(types, doing_specialization):
    for t in types:
        if find_sequence(t.fields, doing_specialization):
            return True
    return False


class StaticVisitor(PickleVisitor):
    CODE = '''Very simple, always emit this static code.  Overide CODE'''

    def visit(self, object):
        self.emit(self.CODE, 0, reflow=False)

class ObjVisitor(PickleVisitor):

    def func_begin(self, name):
        ctype = get_c_type(name)
        self.emit("PyObject*", 0)
        self.emit("ast2obj_%s(void* _o)" % (name), 0)
        self.emit("{", 0)
        self.emit("%s o = (%s)_o;" % (ctype, ctype), 1)
        self.emit("PyObject *result = NULL, *value = NULL;", 1)
        self.emit('if (!o) {', 1)
        self.emit("Py_INCREF(Py_None);", 2)
        self.emit('return Py_None;', 2)
        self.emit("}", 1)
        self.emit('', 0)

    def func_end(self):
        self.emit("return result;", 1)
        self.emit("failed:", 0)
        self.emit("Py_XDECREF(value);", 1)
        self.emit("Py_XDECREF(result);", 1)
        self.emit("return NULL;", 1)
        self.emit("}", 0)
        self.emit("", 0)

    def visitSum(self, sum, name):
        if is_simple(sum):
            self.simpleSum(sum, name)
            return
        self.func_begin(name)
        self.emit("switch (o->kind) {", 1)
        for i in range(len(sum.types)):
            t = sum.types[i]
            self.visitConstructor(t, i + 1, name)
        self.emit("}", 1)
        for a in sum.attributes:
            self.emit("value = ast2obj_%s(o->%s);" % (a.type, a.name), 1)
            self.emit("if (!value) goto failed;", 1)
            self.emit('PyObject_SetAttrString(result, "%s", value);' % a.name, 1)
        self.func_end()
        
    def simpleSum(self, sum, name):
        self.emit("PyObject* ast2obj_%s(%s_ty o)" % (name, name), 0)
        self.emit("{", 0)
        self.emit("switch(o) {", 1)
        for t in sum.types:
            self.emit("case %s:" % t.name, 2)
            self.emit("Py_INCREF(%s_singleton);" % t.name, 3)
            self.emit("return %s_singleton;" % t.name, 3)
        self.emit("}", 1)
        self.emit("return NULL; /* cannot happen */", 1)
        self.emit("}", 0)

    def visitProduct(self, prod, name):
        self.func_begin(name)
        self.emit("result = PyType_GenericNew(%s_type, NULL, NULL);" % name, 1);
        self.emit("if (!result) return NULL;", 1)
        for field in prod.fields:
            self.visitField(field, name, 1, True)
        self.func_end()

    def visitConstructor(self, cons, enum, name):
        self.emit("case %s_kind:" % cons.name, 1)
        self.emit("result = PyType_GenericNew(%s_type, NULL, NULL);" % cons.name, 2);
        self.emit("if (!result) goto failed;", 2)
        for f in cons.fields:
            self.visitField(f, cons.name, 2, False)
        self.emit("break;", 2)

    def visitField(self, field, name, depth, product):
        def emit(s, d):
            self.emit(s, depth + d)
        if product:
            value = "o->%s" % field.name
        else:
            value = "o->v.%s.%s" % (name, field.name)
        self.set(field, value, depth)
        emit("if (!value) goto failed;", 0)
        emit('if (PyObject_SetAttrString(result, "%s", value) == -1)' % field.name, 0)
        emit("goto failed;", 1)
        emit("Py_DECREF(value);", 0)

    def emitSeq(self, field, value, depth, emit):
        emit("seq = %s;" % value, 0)
        emit("n = asdl_seq_LEN(seq);", 0)
        emit("value = PyList_New(n);", 0)
        emit("if (!value) goto failed;", 0)
        emit("for (i = 0; i < n; i++) {", 0)
        self.set("value", field, "asdl_seq_GET(seq, i)", depth + 1)
        emit("if (!value1) goto failed;", 1)
        emit("PyList_SET_ITEM(value, i, value1);", 1)
        emit("value1 = NULL;", 1)
        emit("}", 0)

    def set(self, field, value, depth):
        if field.seq:
            # XXX should really check for is_simple, but that requires a symbol table
            if field.type.value == "cmpop":
                # While the sequence elements are stored as void*,
                # ast2obj_cmpop expects an enum
                self.emit("{", depth)
                self.emit("int i, n = asdl_seq_LEN(%s);" % value, depth+1)
                self.emit("value = PyList_New(n);", depth+1)
                self.emit("if (!value) goto failed;", depth+1)
                self.emit("for(i = 0; i < n; i++)", depth+1)
                # This cannot fail, so no need for error handling
                self.emit("PyList_SET_ITEM(value, i, ast2obj_%s((%s_ty)asdl_seq_GET(%s, i)));" %
                                (field.type, field.type, value), depth+2, reflow=False)
                self.emit("}", depth)
            else:
                self.emit("value = ast2obj_list(%s, ast2obj_%s);" % (value, field.type), depth)
        else:
            ctype = get_c_type(field.type)
            self.emit("value = ast2obj_%s(%s);" % (field.type, value), depth, reflow=False)


class PartingShots(StaticVisitor):

    CODE = """
PyObject* PyAST_mod2obj(mod_ty t)
{
    init_types();
    return ast2obj_mod(t);
}
"""

class ChainOfVisitors:
    def __init__(self, *visitors):
        self.visitors = visitors

    def visit(self, object):
        for v in self.visitors:
            v.visit(object)
            v.emit("", 0)

def main(srcfile):
    argv0 = sys.argv[0]
    components = argv0.split(os.sep)
    argv0 = os.sep.join(components[-2:])
    auto_gen_msg = '/* File automatically generated by %s */\n' % argv0
    mod = asdl.parse(srcfile)
    if not asdl.check(mod):
        sys.exit(1)
    if INC_DIR:
        p = "%s/%s-ast.h" % (INC_DIR, mod.name)
    else:
        p = "%s-ast.h" % mod.name
    f = open(p, "wb")
    print >> f, auto_gen_msg
    print >> f, '#include "asdl.h"\n'
    c = ChainOfVisitors(TypeDefVisitor(f),
                        StructVisitor(f),
                        PrototypeVisitor(f),
                        )
    c.visit(mod)
    print >>f, "PyObject* PyAST_mod2obj(mod_ty t);"
    f.close()

    if SRC_DIR:
        p = "%s/%s-ast.c" % (SRC_DIR, mod.name)
    else:
        p = "%s-ast.c" % mod.name
    f = open(p, "wb")
    print >> f, auto_gen_msg
    print >> f, '#include "Python.h"'
    print >> f, '#include "%s-ast.h"' % mod.name
    print >> f
    print >>f, "PyTypeObject* AST_type;"
    v = ChainOfVisitors(
                        PyTypesDeclareVisitor(f),
                        PyTypesVisitor(f),
                        FunctionVisitor(f),
                        ObjVisitor(f),
                        ASTModuleVisitor(f),
                        PartingShots(f),
                        )
    v.visit(mod)
    f.close()

if __name__ == "__main__":
    import sys
    import getopt

    INC_DIR = ''
    SRC_DIR = ''
    opts, args = getopt.getopt(sys.argv[1:], "h:c:")
    for o, v in opts:
        if o == '-h':
            INC_DIR = v
        if o == '-c':
            SRC_DIR = v
    if len(args) != 1:
        print "Must specify single input file"
    main(args[0])