/******************************************************

  The CFrame

 ******************************************************/

/*
 * The purpose of a CFrame is to allow any callable to be run as
 * a tasklet.
 * A CFrame does not appear in tracebacks, but it does
 * play a role in frame chains. 
 * 
 * For simplicity, it mimicks the fields which slp_transfer needs
 * to do a proper switch, and the standard frame fields have
 * been slightly rearranged, to keep the size of CFrame small.
 * I have looked through all reachable C extensions to find out
 * which fields need to be present.
 *
 * The tasklet holds either a frame or a cframe and knows
 * how to handle them.
 *
 * XXX in a later, thunk-based implementation, CFrames should
 * vanish and be replaced by special thunks, which don't mess
 * with the frame chain.
 */

#include "Python.h"

#ifdef STACKLESS
#include "stackless_impl.h"
#include "pickling/prickelpit.h"

static PyCFrameObject *free_list = NULL;
static int numfree = 0;		/* number of cframes currently in free_list */
#define MAXFREELIST 200		/* max value for numfree */

static void
cframe_dealloc(PyCFrameObject *cf)
{
 	PyObject_GC_UnTrack(cf);
	Py_XDECREF(cf->f_back);
	Py_XDECREF(cf->ob1);
	Py_XDECREF(cf->ob2);
	Py_XDECREF(cf->ob3);
	if (numfree < MAXFREELIST) {
		++numfree;
		cf->f_back = (PyFrameObject *) free_list;
		free_list = cf;
	}
	else
		PyObject_GC_Del(cf);
}

static int
cframe_traverse(PyCFrameObject *cf, visitproc visit, void *arg)
{
	int err;

#define VISIT(o) if (o) {if ((err = visit((PyObject *)(o), arg))) return err;}

	VISIT(cf->f_back);
	VISIT(cf->ob1);
	VISIT(cf->ob2);
	VISIT(cf->ob3);
#undef VISIT
	return 0;
}

/* clearing a cframe while the object still exists */

static void
cframe_clear(PyCFrameObject *cf)
{
#define ZAP(x) \
	if (x != NULL) { \
		PyObject *_hold = (PyObject *) x; \
		x = NULL; \
		Py_XDECREF(_hold); \
	}
	ZAP(cf->f_back);
	ZAP(cf->ob1);
	ZAP(cf->ob2);
	ZAP(cf->ob3);
#undef ZAP
}


PyCFrameObject *
slp_cframe_new(PyFrame_ExecFunc *exec, unsigned int linked)
{
	PyThreadState *ts = PyThreadState_GET();
	PyCFrameObject *cf;
	PyFrameObject *back;

	if (free_list == NULL) {
		cf = PyObject_GC_NewVar(PyCFrameObject, &PyCFrame_Type, 0);
		if (cf == NULL)
			return NULL;
	}
	else {
		assert(numfree > 0);
		--numfree;
		cf = free_list;
		free_list = (PyCFrameObject *) free_list->f_back;
		_Py_NewReference((PyObject *) cf);
	}

        back = ts->frame;
	if (!linked)
		back = NULL;
        Py_XINCREF(back);
	cf->f_execute = exec;
	cf->f_back = back;
	cf->ob1 = cf->ob2 = cf->ob3 = NULL;
	cf->i = cf->n = 0;
	_PyObject_GC_TRACK(cf);
        return cf;
}

/* pickling support for cframes */

#define cframetuplefmt "iSOll"
#define cframetuplenewfmt "iSO!ll:cframe"


static PyObject *
cframe_reduce(PyCFrameObject *cf)
{
    PyObject *res = NULL, *exec_name = NULL;
    PyObject *params = NULL;
    int valid = 1;
    
    if ((exec_name = slp_find_execname((PyFrameObject *) cf, &valid)) == NULL)
	    return NULL;

    params = slp_into_tuple_with_nulls(&cf->ob1, 3);
    if (params == NULL) goto err_exit;

    res = Py_BuildValue ("(O()(" cframetuplefmt "))",
			 cf->ob_type,
			 valid,
			 exec_name,
			 params,
			 cf->i,
			 cf->n);
    
err_exit:
    Py_XDECREF(exec_name);
    Py_XDECREF(params);
    return res;
}

static PyObject *
cframe_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
	static char *kwlist[] = {NULL};

	if (!PyArg_ParseTupleAndKeywords(args, kwds, ":cframe", kwlist))
		return NULL;
	return (PyObject *) slp_cframe_new(NULL, 0);
}

/* note that args is a tuple, although we use METH_O */

static PyObject *
cframe_setstate(PyObject *self, PyObject *args)
{
	PyCFrameObject *cf = (PyCFrameObject *) self;
	int valid;
	PyObject *exec_name = NULL;
	PyFrame_ExecFunc *good_func, *bad_func;
	PyObject *params;
	long i, n;

        if (!PyArg_ParseTuple (args, cframetuplenewfmt,
			       &valid,
			       &exec_name,
			       &PyTuple_Type, &params,
			       &i,
			       &n))
	        return NULL;
    
	if (slp_find_execfuncs(cf->ob_type, exec_name, &good_func, &bad_func))
		return NULL;

        if (PyTuple_GET_SIZE(params)-1 != 3)
		VALUE_ERROR("bad argument for cframe unpickling", NULL);

	/* mark this frame as coming from unpickling */
	Py_INCREF(Py_None);
	cf->f_back = (PyFrameObject *) Py_None;
	cf->f_execute = valid ? good_func : bad_func;
	slp_from_tuple_with_nulls(&cf->ob1, params);
	cf->i = i;
	cf->n = n;
	Py_INCREF(cf);
	return (PyObject *) cf;
}

static PyMethodDef cframe_methods[] = {
	{"__reduce__",	  (PyCFunction)cframe_reduce, METH_NOARGS, NULL},
	{"__reduce_ex__", (PyCFunction)cframe_reduce, METH_VARARGS, NULL},
	{"__setstate__",  (PyCFunction)cframe_setstate, METH_O, NULL},
	{NULL, NULL}
};


static PyObject * run_cframe(PyFrameObject *f, PyObject *retval)
{
	PyThreadState *ts = PyThreadState_GET();
	PyCFrameObject *cf = (PyCFrameObject*) f;
	PyTaskletObject *task = ts->st.current;
	int done = cf->i;

	ts->frame = f;

	if (retval == NULL || done)
	    goto exit_run_cframe;

	if (cf->ob2 == NULL)
		cf->ob2 = PyTuple_New(0);
	Py_DECREF(retval);
	STACKLESS_PROPOSE_ALL();
	retval = PyObject_Call(cf->ob1, cf->ob2, cf->ob3);
	STACKLESS_ASSERT();
	cf->i = 1; /* mark ourself as done */

	if (STACKLESS_UNWINDING(retval)) {
		/* try to shortcut */
		if (ts->st.current == task && ts->frame != NULL &&
		    ts->frame->f_back == (PyFrameObject *) cf) {
			Py_DECREF(ts->frame->f_back);
			ts->frame->f_back = cf->f_back;
			Py_DECREF(cf); /* the exec reference */
		}
		return retval;
	}
	/* pop frame */
exit_run_cframe:
	ts->frame = cf->f_back;
	Py_DECREF(cf);
	return retval;
}

DEF_INVALID_EXEC(run_cframe)

PyCFrameObject *
slp_cframe_newfunc(PyObject *func, PyObject *args, PyObject *kwds, unsigned int linked)
{
	PyCFrameObject *cf;

	if (func == NULL || !PyCallable_Check(func))
		TYPE_ERROR("cframe function must be a callable", NULL);
	cf = slp_cframe_new(run_cframe, linked);
	if (cf == NULL)
		return NULL;
	Py_INCREF(func);
	cf->ob1 = func;
	Py_INCREF(args);
	cf->ob2 = args;
	Py_XINCREF(kwds);
	cf->ob3 = kwds;
	return cf;
}

static PyMemberDef cframe_memberlist[] = {
	{"f_back",	T_OBJECT,   offsetof(PyCFrameObject, f_back),	RO},
	{"ob1",		T_OBJECT,   offsetof(PyCFrameObject, ob1),	RO},
	{"ob2",		T_OBJECT,   offsetof(PyCFrameObject, ob2),	RO},
	{"ob3",		T_OBJECT,   offsetof(PyCFrameObject, ob3),	RO},
	{"i",		T_LONG,	    offsetof(PyCFrameObject, i),	RO},
	{"n",		T_LONG,	    offsetof(PyCFrameObject, n),	RO},
	{NULL}  /* Sentinel */
};

PyTypeObject PyCFrame_Type = {
	PyObject_HEAD_INIT(&PyType_Type)
	0,
	"stackless.cframe",
	sizeof(PyCFrameObject),
	0,
	(destructor)cframe_dealloc,		/* tp_dealloc */
	0,					/* tp_print */
	0,					/* tp_getattr */
	0,					/* tp_setattr */
	0,					/* tp_compare */
	0,					/* tp_repr */
	0,					/* tp_as_number */
	0,					/* tp_as_sequence */
	0,					/* tp_as_mapping */
	0,					/* tp_hash */
	0,					/* tp_call */
	0,					/* tp_str */
	PyObject_GenericGetAttr,		/* tp_getattro */
	PyObject_GenericSetAttr,		/* tp_setattro */
	0,					/* tp_as_buffer */
	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC, /* tp_flags */
	0,					/* tp_doc */
	(traverseproc)cframe_traverse,		/* tp_traverse */
	(inquiry) cframe_clear,			/* tp_clear */
	0,					/* tp_richcompare */
	0,					/* tp_weaklistoffset */
	0,					/* tp_iter */
	0,					/* tp_iternext */
	cframe_methods,				/* tp_methods */
	cframe_memberlist,			/* tp_members */
	0,					/* tp_getset */
	0,					/* tp_base */
	0,					/* tp_dict */
	0,					/* tp_descr_get */
	0,					/* tp_descr_set */
	0,					/* tp_dictoffset */
	0,					/* tp_init */
	0,					/* tp_alloc */
	cframe_new,				/* tp_new */
	_PyObject_Del,				/* tp_free */
};

int init_cframetype(void)
{
	/* register the cframe exec func */
	return slp_register_execute(&PyCFrame_Type, "run_cframe", 
				    run_cframe, REF_INVALID_EXEC(run_cframe));
}

/* Clear out the free list */

void
slp_cstack_fini(void)
{
	while (free_list != NULL) {
		PyCFrameObject *cf = free_list;
		free_list = (PyCFrameObject *) free_list->f_back;
		PyObject_GC_Del(cf);
		--numfree;
	}
	assert(numfree == 0);
}

#endif