srd.c

Go to the documentation of this file.

/*
 * This file is part of the libsigrokdecode project.
 *
 * Copyright (C) 2010 Uwe Hermann <uwe@hermann-uwe.de>
 * Copyright (C) 2013 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. */
#include "libsigrokdecode.h"
#include <glib.h>

/** @cond PRIVATE */

/* Python module search paths */
SRD_PRIV GSList *searchpaths = NULL;

/* session.c */
extern SRD_PRIV GSList *sessions;
extern SRD_PRIV int max_session_id;

/** @endcond */

/**
 * @mainpage libsigrokdecode API
 *
 * @section sec_intro Introduction
 *
 * The <a href="http://sigrok.org">sigrok</a> project aims at creating a
 * portable, cross-platform, Free/Libre/Open-Source signal analysis software
 * suite that supports various device types (such as logic analyzers,
 * oscilloscopes, multimeters, and more).
 *
 * <a href="http://sigrok.org/wiki/Libsigrokdecode">libsigrokdecode</a> is a
 * shared library written in C which provides the basic API for (streaming)
 * protocol decoding functionality.
 *
 * The <a href="http://sigrok.org/wiki/Protocol_decoders">protocol decoders</a>
 * are written in Python (>= 3.0).
 *
 * @section sec_api API reference
 *
 * See the "Modules" page for an introduction to various libsigrokdecode
 * related topics and the detailed API documentation of the respective
 * functions.
 *
 * You can also browse the API documentation by file, or review all
 * data structures.
 *
 * @section sec_mailinglists Mailing lists
 *
 * There is one mailing list for sigrok/libsigrokdecode: <a href="https://lists.sourceforge.net/lists/listinfo/sigrok-devel">sigrok-devel</a>.
 *
 * @section sec_irc IRC
 *
 * You can find the sigrok developers in the
 * <a href="ircs://irc.libera.chat/#sigrok">\#sigrok</a>
 * IRC channel on Libera.Chat.
 *
 * @section sec_website Website
 *
 * <a href="http://sigrok.org/wiki/Libsigrokdecode">sigrok.org/wiki/Libsigrokdecode</a>
 */

/**
 * @file
 *
 * Initializing and shutting down libsigrokdecode.
 */

/**
 * @defgroup grp_init Initialization
 *
 * Initializing and shutting down libsigrokdecode.
 *
 * Before using any of the libsigrokdecode functionality, srd_init() must
 * be called to initialize the library.
 *
 * When libsigrokdecode functionality is no longer needed, srd_exit() should
 * be called.
 *
 * @{
 */

static int searchpath_add_xdg_dir(const char *datadir)
{
        char *decdir;
        int ret;

        decdir = g_build_filename(datadir, PACKAGE_TARNAME, "decoders", NULL);

        if (g_file_test(decdir, G_FILE_TEST_IS_DIR))
                ret = srd_decoder_searchpath_add(decdir);
        else
                ret = SRD_OK; /* Just ignore non-existing directory. */

        g_free(decdir);

        return ret;
}

static void print_versions(void)
{
        GString *s;
        GSList *l, *l_orig, *m;
        char *str;
        const char *lib, *version;

        srd_dbg("libsigrokdecode %s/%s (rt: %s/%s).",
                SRD_PACKAGE_VERSION_STRING, SRD_LIB_VERSION_STRING,
                srd_package_version_string_get(), srd_lib_version_string_get());

        s = g_string_sized_new(200);
        g_string_append(s, "Libs: ");
        l_orig = srd_buildinfo_libs_get();
        for (l = l_orig; l; l = l->next) {
                m = l->data;
                lib = m->data;
                version = m->next->data;
                g_string_append_printf(s, "%s %s, ", lib, version);
                g_slist_free_full(m, g_free);
        }
        g_slist_free(l_orig);
        s->str[s->len - 2] = '.';
        s->str[s->len - 1] = '\0';
        srd_dbg("%s", s->str);
        g_string_free(s, TRUE);

        str = srd_buildinfo_host_get();
        srd_dbg("Host: %s.", str);
        g_free(str);
}

static int print_searchpaths(void)
{
        PyObject *py_paths, *py_path, *py_bytes;
        PyGILState_STATE gstate;
        GString *s;
        GSList *l;
        int i;

        s = g_string_sized_new(500);
        g_string_append(s, "Protocol decoder search paths:\n");
        for (l = searchpaths; l; l = l->next)
                g_string_append_printf(s, " - %s\n", (const char *)l->data);
        s->str[s->len - 1] = '\0';
        srd_dbg("%s", s->str);
        g_string_free(s, TRUE);

        gstate = PyGILState_Ensure();

        py_paths = PySys_GetObject("path");
        if (!py_paths)
                goto err;

        s = g_string_sized_new(500);
        g_string_append(s, "Python system search paths:\n");
        for (i = 0; i < PyList_Size(py_paths); i++) {
                py_path = PyList_GetItem(py_paths, i);
                py_bytes = PyUnicode_AsUTF8String(py_path);
                g_string_append_printf(s, " - %s\n", PyBytes_AsString(py_bytes));
                Py_DECREF(py_bytes);
        }
        s->str[s->len - 1] = '\0';
        srd_dbg("%s", s->str);
        g_string_free(s, TRUE);

        PyGILState_Release(gstate);

        return SRD_OK;

err:
        srd_err("Unable to query Python system search paths.");
        PyGILState_Release(gstate);

        return SRD_ERR_PYTHON;
}

/**
 * Initialize libsigrokdecode.
 *
 * This initializes the Python interpreter, and creates and initializes
 * a "sigrokdecode" Python module.
 *
 * Then, it searches for sigrok protocol decoders in the "decoders"
 * subdirectory of the the libsigrokdecode installation directory.
 * All decoders that are found are loaded into memory and added to an
 * internal list of decoders, which can be queried via srd_decoder_list().
 *
 * The caller is responsible for calling the clean-up function srd_exit(),
 * which will properly shut down libsigrokdecode and free its allocated memory.
 *
 * Multiple calls to srd_init(), without calling srd_exit() in between,
 * are not allowed.
 *
 * @param path Path to an extra directory containing protocol decoders
 *             which will be added to the Python sys.path. May be NULL.
 *
 * @return SRD_OK upon success, a (negative) error code otherwise.
 *         Upon Python errors, SRD_ERR_PYTHON is returned. If the decoders
 *         directory cannot be accessed, SRD_ERR_DECODERS_DIR is returned.
 *         If not enough memory could be allocated, SRD_ERR_MALLOC is returned.
 *
 * @since 0.1.0
 */
SRD_API int srd_init(const char *path)
{
        const char *const *sys_datadirs;
        const char *env_path;
        size_t i;
        int ret;

        if (max_session_id != -1) {
                srd_err("libsigrokdecode is already initialized.");
                return SRD_ERR;
        }

        print_versions();

        srd_dbg("Initializing libsigrokdecode.");

        /* Add our own module to the list of built-in modules. */
        PyImport_AppendInittab("sigrokdecode", PyInit_sigrokdecode);

        /* Initialize the Python interpreter. */
        Py_InitializeEx(0);

        /* Locations relative to the XDG system data directories. */
        sys_datadirs = g_get_system_data_dirs();
        for (i = g_strv_length((char **)sys_datadirs); i > 0; i--) {
                ret = searchpath_add_xdg_dir(sys_datadirs[i - 1]);
                if (ret != SRD_OK) {
                        Py_Finalize();
                        return ret;
                }
        }
#ifdef DECODERS_DIR
        /* Hardcoded decoders install location, if defined. */
        if ((ret = srd_decoder_searchpath_add(DECODERS_DIR)) != SRD_OK) {
                Py_Finalize();
                return ret;
        }
#endif
        /* Location relative to the XDG user data directory. */
        ret = searchpath_add_xdg_dir(g_get_user_data_dir());
        if (ret != SRD_OK) {
                Py_Finalize();
                return ret;
        }

        /* Path specified by the user. */
        if (path) {
                if ((ret = srd_decoder_searchpath_add(path)) != SRD_OK) {
                        Py_Finalize();
                        return ret;
                }
        }

        /* Environment variable overrides everything, for debugging. */
        /*
         * TODO
         * Is the comment still applicable and correct or up to date?
         * This implementation adds paths which were specified by the
         * env var. Which can shadow files in other locations, or can
         * extend the set of available decoders. Which need not only
         * serve for development, it is as beneficial to regular users.
         * Without shadowing all other files still are found.
         */
        if ((env_path = g_getenv("SIGROKDECODE_DIR"))) {
                if ((ret = srd_decoder_searchpath_add(env_path)) != SRD_OK) {
                        Py_Finalize();
                        return ret;
                }
        }
        env_path = g_getenv("SIGROKDECODE_PATH");
        if (env_path) {
                char **dir_list, **dir_iter, *dir_item;
                dir_list = g_strsplit(env_path, G_SEARCHPATH_SEPARATOR_S, 0);
                for (dir_iter = dir_list; *dir_iter; dir_iter++) {
                        dir_item = *dir_iter;
                        if (!dir_item || !*dir_item)
                                continue;
                        ret = srd_decoder_searchpath_add(dir_item);
                        if (ret != SRD_OK) {
                                Py_Finalize();
                                return ret;
                        }
                }
                g_strfreev(dir_list);
        }

#if PY_VERSION_HEX < 0x03090000
        /*
         * Initialize and acquire the Python GIL. In Python 3.7+ this
         * will be done implicitly as part of the Py_InitializeEx()
         * call above. PyEval_InitThreads() was deprecated in 3.9.
         */
        PyEval_InitThreads();
#endif

        /* Release the GIL (ignore return value, we don't need it here). */
        (void)PyEval_SaveThread();

        max_session_id = 0;

        print_searchpaths();

        return SRD_OK;
}

static void srd_session_destroy_cb(void *arg, void *ignored)
{
        (void)ignored; // Prevent unused warning
        srd_session_destroy((struct srd_session *)arg);
}

/**
 * Shutdown libsigrokdecode.
 *
 * This frees all the memory allocated for protocol decoders and shuts down
 * the Python interpreter.
 *
 * This function should only be called if there was a (successful!) invocation
 * of srd_init() before. Calling this function multiple times in a row, without
 * any successful srd_init() calls in between, is not allowed.
 *
 * @return SRD_OK upon success, a (negative) error code otherwise.
 *
 * @since 0.1.0
 */
SRD_API int srd_exit(void)
{
        srd_dbg("Exiting libsigrokdecode.");

        g_slist_foreach(sessions, srd_session_destroy_cb, NULL);
        g_slist_free(sessions);
        sessions = NULL;

        srd_decoder_unload_all();
        g_slist_free_full(searchpaths, g_free);
        searchpaths = NULL;

        /*
         * Acquire the GIL, otherwise Py_Finalize() might have issues.
         * Ignore the return value, we don't need it here.
         */
        if (Py_IsInitialized())
                (void)PyGILState_Ensure();

        /* Py_Finalize() returns void, any finalization errors are ignored. */
        Py_Finalize();

        /* Note: No need to release the GIL since Python is shut down now. */

        max_session_id = -1;

        return SRD_OK;
}

/**
 * Add an additional search directory for the protocol decoders.
 *
 * The specified directory is prepended (not appended!) to Python's sys.path,
 * in order to search for sigrok protocol decoders in the specified
 * directories first, and in the generic Python module directories (and in
 * the current working directory) last. This avoids conflicts if there are
 * Python modules which have the same name as a sigrok protocol decoder in
 * sys.path or in the current working directory.
 *
 * @param path Path to the directory containing protocol decoders which shall
 *             be added to the Python sys.path, or NULL.
 *
 * @return SRD_OK upon success, a (negative) error code otherwise.
 *
 * @private
 */
SRD_PRIV int srd_decoder_searchpath_add(const char *path)
{
        PyObject *py_cur_path, *py_item;
        PyGILState_STATE gstate;

        srd_dbg("Adding '%s' to module path.", path);

        gstate = PyGILState_Ensure();

        py_cur_path = PySys_GetObject("path");
        if (!py_cur_path)
                goto err;

        py_item = PyUnicode_FromString(path);
        if (!py_item) {
                srd_exception_catch("Failed to create Unicode object");
                goto err;
        }
        if (PyList_Insert(py_cur_path, 0, py_item) < 0) {
                srd_exception_catch("Failed to insert path element");
                Py_DECREF(py_item);
                goto err;
        }
        Py_DECREF(py_item);

        PyGILState_Release(gstate);

        searchpaths = g_slist_prepend(searchpaths, g_strdup(path));

        return SRD_OK;

err:
        PyGILState_Release(gstate);

        return SRD_ERR_PYTHON;
}

/**
 * Return the list of protocol decoder search paths.
 *
 * @return The list of search paths used when loading protocol decoders.
 *
 * @since 0.5.1
 */
SRD_API GSList *srd_searchpaths_get(void)
{
        GSList *paths = NULL;

        for (GSList *l = searchpaths; l; l = l->next)
                paths = g_slist_append(paths, g_strdup(l->data));

        return paths;
}

/** @} */