command_py.c

/*
 * clippy (CLI preparator in python) wrapper for FRR command_graph
 * Copyright (C) 2016-2017  David Lamparter for NetDEF, Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; see the file COPYING; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

/* note: this wrapper is intended to be used as build-time helper.  while
 * it should be generally correct and proper, there may be the occasional
 * memory leak or SEGV for things that haven't been well-tested.
 */

/* This file is "exempt" from having
#include "config.h"
 * as the first include statement because Python.h also does environment
 * setup & these trample over each other.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <Python.h>
#include "structmember.h"
#include <string.h>
#include <stdlib.h>

#include "command_graph.h"
#include "clippy.h"

struct wrap_graph;
static PyObject *graph_to_pyobj(struct wrap_graph *graph,
				struct graph_node *gn);

/*
 * nodes are wrapped as follows:
 *  - instances can only be acquired from a graph
 *  - the same node will return the same wrapper object (they're buffered
 *    through "idx")
 *  - a reference is held onto the graph
 *  - fields are copied for easy access with PyMemberDef
 */
struct wrap_graph_node {
	PyObject_HEAD

		bool allowrepeat;
	const char *type;

	bool deprecated;
	bool hidden;
	const char *text;
	const char *desc;
	const char *varname;
	long long min, max;

	struct graph_node *node;
	struct wrap_graph *wgraph;
	size_t idx;
};

/*
 * graphs are wrapped as follows:
 *  - they can only be created by parsing a definition string
 *  - there's a table here for the wrapped nodes (nodewrappers), indexed
 *    by "idx" (corresponds to node's position in graph's table of nodes)
 *  - graphs do NOT hold references to nodes (would be circular)
 */
struct wrap_graph {
	PyObject_HEAD

		char *definition;
	struct graph *graph;
	struct wrap_graph_node **nodewrappers;
};

static PyObject *refuse_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
	PyErr_SetString(PyExc_ValueError,
			"cannot create instances of this type");
	return NULL;
}

#define member(name, type)                                                     \
	{                                                                      \
		(char *)#name, type, offsetof(struct wrap_graph_node, name),   \
			READONLY, (char *)#name " (" #type ")"                 \
	}
static PyMemberDef members_graph_node[] = {
	member(allowrepeat, T_BOOL), member(type, T_STRING),
	member(deprecated, T_BOOL),  member(hidden, T_BOOL),
	member(text, T_STRING),      member(desc, T_STRING),
	member(min, T_LONGLONG),     member(max, T_LONGLONG),
	member(varname, T_STRING),   {},
};
#undef member

/*
 * node.next() -- returns list of all "next" nodes.
 * this will include circles if the graph has them.
 */
static PyObject *graph_node_next(PyObject *self, PyObject *args)
{
	struct wrap_graph_node *wrap = (struct wrap_graph_node *)self;
	PyObject *pylist;

	if (wrap->node->data
	    && ((struct cmd_token *)wrap->node->data)->type == END_TKN)
		return PyList_New(0);
	pylist = PyList_New(vector_active(wrap->node->to));
	for (size_t i = 0; i < vector_active(wrap->node->to); i++) {
		struct graph_node *gn = vector_slot(wrap->node->to, i);
		PyList_SetItem(pylist, i, graph_to_pyobj(wrap->wgraph, gn));
	}
	return pylist;
};

/*
 * node.join() -- return FORK's JOIN node or None
 */
static PyObject *graph_node_join(PyObject *self, PyObject *args)
{
	struct wrap_graph_node *wrap = (struct wrap_graph_node *)self;

	if (!wrap->node->data
	    || ((struct cmd_token *)wrap->node->data)->type == END_TKN)
		Py_RETURN_NONE;

	struct cmd_token *tok = wrap->node->data;
	if (tok->type != FORK_TKN)
		Py_RETURN_NONE;

	return graph_to_pyobj(wrap->wgraph, tok->forkjoin);
};

static PyMethodDef methods_graph_node[] = {
	{"next", graph_node_next, METH_NOARGS, "outbound graph edge list"},
	{"join", graph_node_join, METH_NOARGS, "outbound join node"},
	{}};

static void graph_node_wrap_free(void *arg)
{
	struct wrap_graph_node *wrap = arg;
	wrap->wgraph->nodewrappers[wrap->idx] = NULL;
	Py_DECREF(wrap->wgraph);
}

static PyTypeObject typeobj_graph_node = {
	PyVarObject_HEAD_INIT(NULL, 0).tp_name = "_clippy.GraphNode",
	.tp_basicsize = sizeof(struct wrap_graph_node),
	.tp_flags = Py_TPFLAGS_DEFAULT,
	.tp_doc = "struct graph_node *",
	.tp_new = refuse_new,
	.tp_free = graph_node_wrap_free,
	.tp_members = members_graph_node,
	.tp_methods = methods_graph_node,
};

static PyObject *graph_to_pyobj(struct wrap_graph *wgraph,
				struct graph_node *gn)
{
	struct wrap_graph_node *wrap;
	size_t i;

	for (i = 0; i < vector_active(wgraph->graph->nodes); i++)
		if (vector_slot(wgraph->graph->nodes, i) == gn)
			break;
	if (i == vector_active(wgraph->graph->nodes)) {
		PyErr_SetString(PyExc_ValueError, "cannot find node in graph");
		return NULL;
	}
	if (wgraph->nodewrappers[i]) {
		PyObject *obj = (PyObject *)wgraph->nodewrappers[i];
		Py_INCREF(obj);
		return obj;
	}

	wrap = (struct wrap_graph_node *)typeobj_graph_node.tp_alloc(
		&typeobj_graph_node, 0);
	if (!wrap)
		return NULL;
	wgraph->nodewrappers[i] = wrap;
	Py_INCREF(wgraph);

	wrap->idx = i;
	wrap->wgraph = wgraph;
	wrap->node = gn;
	wrap->type = "NULL";
	wrap->allowrepeat = false;
	if (gn->data) {
		struct cmd_token *tok = gn->data;
		switch (tok->type) {
#define item(x)                                                                \
	case x:                                                                \
		wrap->type = #x;                                               \
		break /* no semicolon */

			item(WORD_TKN);	       // words
			item(VARIABLE_TKN);    // almost anything
			item(RANGE_TKN);       // integer range
			item(IPV4_TKN);	       // IPV4 addresses
			item(IPV4_PREFIX_TKN); // IPV4 network prefixes
			item(IPV6_TKN);	       // IPV6 prefixes
			item(IPV6_PREFIX_TKN); // IPV6 network prefixes
			item(MAC_TKN);	       // MAC address
			item(MAC_PREFIX_TKN);  // MAC address with mask

			/* plumbing types */
			item(FORK_TKN);
			item(JOIN_TKN);
			item(START_TKN);
			item(END_TKN);
			item(NEG_ONLY_TKN);
#undef item
		default:
			wrap->type = "???";
		}

		wrap->deprecated = (tok->attr == CMD_ATTR_DEPRECATED);
		wrap->hidden = (tok->attr == CMD_ATTR_HIDDEN);
		wrap->text = tok->text;
		wrap->desc = tok->desc;
		wrap->varname = tok->varname;
		wrap->min = tok->min;
		wrap->max = tok->max;
		wrap->allowrepeat = tok->allowrepeat;
	}

	return (PyObject *)wrap;
}

#define member(name, type)                                                     \
	{                                                                      \
		(char *)#name, type, offsetof(struct wrap_graph, name),        \
			READONLY, (char *)#name " (" #type ")"                 \
	}
static PyMemberDef members_graph[] = {
	member(definition, T_STRING),
	{},
};
#undef member

/* graph.first() - root node */
static PyObject *graph_first(PyObject *self, PyObject *args)
{
	struct wrap_graph *gwrap = (struct wrap_graph *)self;
	struct graph_node *gn = vector_slot(gwrap->graph->nodes, 0);
	return graph_to_pyobj(gwrap, gn);
};

static PyMethodDef methods_graph[] = {
	{"first", graph_first, METH_NOARGS, "first graph node"},
	{}};

static PyObject *graph_parse(PyTypeObject *type, PyObject *args,
			     PyObject *kwds);

static void graph_wrap_free(void *arg)
{
	struct wrap_graph *wgraph = arg;

	graph_delete_graph(wgraph->graph);
	free(wgraph->nodewrappers);
	free(wgraph->definition);
}

static PyTypeObject typeobj_graph = {
	PyVarObject_HEAD_INIT(NULL, 0).tp_name = "_clippy.Graph",
	.tp_basicsize = sizeof(struct wrap_graph),
	.tp_flags = Py_TPFLAGS_DEFAULT,
	.tp_doc = "struct graph *",
	.tp_new = graph_parse,
	.tp_free = graph_wrap_free,
	.tp_members = members_graph,
	.tp_methods = methods_graph,
};

/* top call / entrypoint for python code */
static PyObject *graph_parse(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
	const char *def, *doc = NULL;
	struct wrap_graph *gwrap;
	static const char *kwnames[] = {"cmddef", "doc", NULL};

	gwrap = (struct wrap_graph *)typeobj_graph.tp_alloc(&typeobj_graph, 0);
	if (!gwrap)
		return NULL;

	if (!PyArg_ParseTupleAndKeywords(args, kwds, "s|s", (char **)kwnames,
					 &def, &doc))
		return NULL;

	struct graph *graph = graph_new();
	struct cmd_token *token = cmd_token_new(START_TKN, 0, NULL, NULL);
	graph_new_node(graph, token, (void (*)(void *)) & cmd_token_del);

	struct cmd_element cmd = {.string = def, .doc = doc};
	cmd_graph_parse(graph, &cmd);
	cmd_graph_names(graph);

	gwrap->graph = graph;
	gwrap->definition = strdup(def);
	gwrap->nodewrappers = calloc(vector_active(graph->nodes),
				     sizeof(gwrap->nodewrappers[0]));
	return (PyObject *)gwrap;
}

static PyMethodDef clippy_methods[] = {
	{"parse", clippy_parse, METH_VARARGS, "Parse a C file"},
	{NULL, NULL, 0, NULL}};

#if PY_MAJOR_VERSION >= 3
static struct PyModuleDef pymoddef_clippy = {
	PyModuleDef_HEAD_INIT,
	"_clippy",
	NULL, /* docstring */
	-1,
	clippy_methods,
};
#define modcreate() PyModule_Create(&pymoddef_clippy)
#define initret(val) return val;
#else
#define modcreate() Py_InitModule("_clippy", clippy_methods)
#define initret(val)                                                           \
	do {                                                                   \
		if (!val)                                                      \
			Py_FatalError("initialization failure");               \
		return;                                                        \
	} while (0)
#endif

#pragma GCC diagnostic ignored "-Wstrict-aliasing"
PyMODINIT_FUNC command_py_init(void)
{
	PyObject *pymod;

	if (PyType_Ready(&typeobj_graph_node) < 0)
		initret(NULL);
	if (PyType_Ready(&typeobj_graph) < 0)
		initret(NULL);

	pymod = modcreate();
	if (!pymod)
		initret(NULL);

	Py_INCREF(&typeobj_graph_node);
	PyModule_AddObject(pymod, "GraphNode", (PyObject *)&typeobj_graph_node);
	Py_INCREF(&typeobj_graph);
	PyModule_AddObject(pymod, "Graph", (PyObject *)&typeobj_graph);
	if (!elf_py_init(pymod))
		initret(NULL);
	initret(pymod);
}