Python: Restrict code to stable ABI subset

[libsigrokdecode.git] / util.c

/*
 * This file is part of the libsigrokdecode project.
 *
 * Copyright (C) 2010 Uwe Hermann <uwe@hermann-uwe.de>
 * Copyright (C) 2012 Bert Vermeulen <bert@biot.com>
 *
 * 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 3 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.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <config.h>
#include "libsigrokdecode-internal.h" /* First, so we avoid a _POSIX_C_SOURCE warning. */

/**
 * Get the value of a Python object's attribute, returned as a newly
 * allocated char *.
 *
 * @param[in] py_obj The object to probe.
 * @param[in] attr Name of the attribute to retrieve.
 * @param[out] outstr ptr to char * storage to be filled in.
 *
 * @return SRD_OK upon success, a (negative) error code otherwise.
 *         The 'outstr' argument points to a g_malloc()ed string upon success.
 *
 * @private
 */
SRD_PRIV int py_attr_as_str(PyObject *py_obj, const char *attr, char **outstr)
{
	PyObject *py_str;
	int ret;

	if (!PyObject_HasAttrString(py_obj, attr)) {
		srd_dbg("Object has no attribute '%s'.", attr);
		return SRD_ERR_PYTHON;
	}

	if (!(py_str = PyObject_GetAttrString(py_obj, attr))) {
		srd_exception_catch("Failed to get attribute '%s'", attr);
		return SRD_ERR_PYTHON;
	}

	ret = py_str_as_str(py_str, outstr);
	Py_DECREF(py_str);

	return ret;
}

/**
 * Get the value of a Python dictionary item, returned as a newly
 * allocated char *.
 *
 * @param[in] py_obj The dictionary to probe.
 * @param[in] key Key of the item to retrieve.
 * @param[out] outstr Pointer to char * storage to be filled in.
 *
 * @return SRD_OK upon success, a (negative) error code otherwise.
 *         The 'outstr' argument points to a g_malloc()ed string upon success.
 *
 * @private
 */
SRD_PRIV int py_dictitem_as_str(PyObject *py_obj, const char *key,
				char **outstr)
{
	PyObject *py_value;

	if (!PyDict_Check(py_obj)) {
		srd_dbg("Object is not a dictionary.");
		return SRD_ERR_PYTHON;
	}

	if (!(py_value = PyDict_GetItemString(py_obj, key))) {
		srd_dbg("Dictionary has no attribute '%s'.", key);
		return SRD_ERR_PYTHON;
	}

	return py_str_as_str(py_value, outstr);
}

/**
 * Get the value of a Python unicode string object, returned as a newly
 * allocated char *.
 *
 * @param[in] py_str The unicode string object.
 * @param[out] outstr ptr to char * storage to be filled in.
 *
 * @return SRD_OK upon success, a (negative) error code otherwise.
 *         The 'outstr' argument points to a g_malloc()ed string upon success.
 *
 * @private
 */
SRD_PRIV int py_str_as_str(PyObject *py_str, char **outstr)
{
	PyObject *py_bytes;
	char *str;

	if (!PyUnicode_Check(py_str)) {
		srd_dbg("Object is not a string object.");
		return SRD_ERR_PYTHON;
	}

	py_bytes = PyUnicode_AsUTF8String(py_str);
	if (py_bytes) {
		str = g_strdup(PyBytes_AsString(py_bytes));
		Py_DECREF(py_bytes);
		if (str) {
			*outstr = str;
			return SRD_OK;
		}
	}
	srd_exception_catch("Failed to extract string");

	return SRD_ERR_PYTHON;
}

/**
 * Convert a Python list of unicode strings to a C string vector.
 * On success, a pointer to a newly allocated NULL-terminated array of
 * allocated C strings is written to @a out_strv. The caller must g_free()
 * each string and the array itself.
 *
 * @param[in] py_strseq The sequence object.
 * @param[out] out_strv Address of string vector to be filled in.
 *
 * @return SRD_OK upon success, a (negative) error code otherwise.
 *
 * @private
 */
SRD_PRIV int py_strseq_to_char(PyObject *py_strseq, char ***out_strv)
{
	PyObject *py_item, *py_bytes;
	char **strv, *str;
	ssize_t seq_len, i;

	if (!PySequence_Check(py_strseq)) {
		srd_err("Object does not provide sequence protocol.");
		return SRD_ERR_PYTHON;
	}

	seq_len = PySequence_Size(py_strseq);
	if (seq_len < 0) {
		srd_exception_catch("Failed to obtain sequence size");
		return SRD_ERR_PYTHON;
	}

	strv = g_try_new0(char *, seq_len + 1);
	if (!strv) {
		srd_err("Failed to allocate result string vector.");
		return SRD_ERR_MALLOC;
	}

	for (i = 0; i < seq_len; i++) {
		py_item = PySequence_GetItem(py_strseq, i);
		if (!py_item)
			goto err_out;

		if (!PyUnicode_Check(py_item)) {
			Py_DECREF(py_item);
			goto err_out;
		}
		py_bytes = PyUnicode_AsUTF8String(py_item);
		Py_DECREF(py_item);
		if (!py_bytes)
			goto err_out;

		str = g_strdup(PyBytes_AsString(py_bytes));
		Py_DECREF(py_bytes);
		if (!str)
			goto err_out;

		strv[i] = str;
	}
	*out_strv = strv;

	return SRD_OK;

err_out:
	g_strfreev(strv);
	srd_exception_catch("Failed to obtain string item");

	return SRD_ERR_PYTHON;
}