[libsigrokdecode.git] / controller.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 "libsigrokdecode.h" /* First, so we avoid a _POSIX_C_SOURCE warning. */
#include "libsigrokdecode-internal.h"
#include "config.h"
#include <glib.h>
#include <inttypes.h>
#include <stdlib.h>

/**
 * @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 are two mailing lists for sigrok/libsigrokdecode: <a href="https://lists.sourceforge.net/lists/listinfo/sigrok-devel">sigrok-devel</a> and <a href="https://lists.sourceforge.net/lists/listinfo/sigrok-commits">sigrok-commits</a>.
 *
 * @section sec_irc IRC
 *
 * You can find the sigrok developers in the
 * <a href="irc://chat.freenode.net/sigrok">\#sigrok</a>
 * IRC channel on Freenode.
 *
 * @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.
 *
 * @{
 */

/* List of decoder instances. */
static GSList *di_list = NULL;

/* List of frontend callbacks to receive decoder output. */
static GSList *callbacks = NULL;

/** @cond PRIVATE */

/* decoder.c */
extern SRD_PRIV GSList *pd_list;

/* module_sigrokdecode.c */
extern PyMODINIT_FUNC PyInit_sigrokdecode(void);

/* type_logic.c */
extern SRD_PRIV PyTypeObject srd_logic_type;

/** @endcond */

/**
 * 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)
{
        int ret;
        char *env_path;

        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_Initialize();

        /* Installed decoders. */
        if ((ret = srd_decoder_searchpath_add(DECODERS_DIR)) != 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. */
        if ((env_path = getenv("SIGROKDECODE_DIR"))) {
                if ((ret = srd_decoder_searchpath_add(env_path)) != SRD_OK) {
                        Py_Finalize();
                        return ret;
                }
        }

        return SRD_OK;
}

/**
 * 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.");

        srd_decoder_unload_all();
        g_slist_free(pd_list);
        pd_list = NULL;

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

        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
 *
 * @since 0.1.0
 */
SRD_PRIV int srd_decoder_searchpath_add(const char *path)
{
        PyObject *py_cur_path, *py_item;
        GString *new_path;
        int wc_len, i;
        wchar_t *wc_new_path;
        char *item;

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

        new_path = g_string_sized_new(256);
        g_string_assign(new_path, path);
        py_cur_path = PySys_GetObject("path");
        for (i = 0; i < PyList_Size(py_cur_path); i++) {
                g_string_append(new_path, G_SEARCHPATH_SEPARATOR_S);
                py_item = PyList_GetItem(py_cur_path, i);
                if (!PyUnicode_Check(py_item))
                        /* Shouldn't happen. */
                        continue;
                if (py_str_as_str(py_item, &item) != SRD_OK)
                        continue;
                g_string_append(new_path, item);
                g_free(item);
        }

        /* Convert to wide chars. */
        wc_len = sizeof(wchar_t) * (new_path->len + 1);
        if (!(wc_new_path = g_try_malloc(wc_len))) {
                srd_dbg("malloc failed");
                return SRD_ERR_MALLOC;
        }
        mbstowcs(wc_new_path, new_path->str, wc_len);
        PySys_SetPath(wc_new_path);
        g_string_free(new_path, TRUE);
        g_free(wc_new_path);

        return SRD_OK;
}

/** @} */

/**
 * @defgroup grp_instances Decoder instances
 *
 * Decoder instance handling.
 *
 * @{
 */

/**
 * Set one or more options in a decoder instance.
 *
 * Handled options are removed from the hash.
 *
 * @param di Decoder instance.
 * @param options A GHashTable of options to set.
 *
 * @return SRD_OK upon success, a (negative) error code otherwise.
 *
 * @since 0.1.0
 */
SRD_API int srd_inst_option_set(struct srd_decoder_inst *di,
                GHashTable *options)
{
        PyObject *py_dec_options, *py_dec_optkeys, *py_di_options, *py_optval;
        PyObject *py_optlist, *py_classval;
        Py_UNICODE *py_ustr;
        GVariant *value;
        unsigned long long int val_ull;
        gint64 val_int;
        int num_optkeys, ret, size, i;
        const char *val_str;
        char *dbg, *key;

        if (!PyObject_HasAttrString(di->decoder->py_dec, "options")) {
                /* Decoder has no options. */
                if (g_hash_table_size(options) == 0) {
                        /* No options provided. */
                        return SRD_OK;
                } else {
                        srd_err("Protocol decoder has no options.");
                        return SRD_ERR_ARG;
                }
                return SRD_OK;
        }

        ret = SRD_ERR_PYTHON;
        key = NULL;
        py_dec_options = py_dec_optkeys = py_di_options = py_optval = NULL;
        py_optlist = py_classval = NULL;
        py_dec_options = PyObject_GetAttrString(di->decoder->py_dec, "options");

        /* All of these are synthesized objects, so they're good. */
        py_dec_optkeys = PyDict_Keys(py_dec_options);
        num_optkeys = PyList_Size(py_dec_optkeys);
        if (!(py_di_options = PyObject_GetAttrString(di->py_inst, "options")))
                goto err_out;
        for (i = 0; i < num_optkeys; i++) {
                /* Get the default class value for this option. */
                py_str_as_str(PyList_GetItem(py_dec_optkeys, i), &key);
                if (!(py_optlist = PyDict_GetItemString(py_dec_options, key)))
                        goto err_out;
                if (!(py_classval = PyList_GetItem(py_optlist, 1)))
                        goto err_out;
                if (!PyUnicode_Check(py_classval) && !PyLong_Check(py_classval)) {
                        srd_err("Options of type %s are not yet supported.",
                                Py_TYPE(py_classval)->tp_name);
                        goto err_out;
                }

                if ((value = g_hash_table_lookup(options, key))) {
                        dbg = g_variant_print(value, TRUE);
                        srd_dbg("got option '%s' = %s", key, dbg);
                        g_free(dbg);
                        /* An override for this option was provided. */
                        if (PyUnicode_Check(py_classval)) {
                                if (!g_variant_is_of_type(value, G_VARIANT_TYPE_STRING)) {
                                        srd_err("Option '%s' requires a string value.", key);
                                        goto err_out;
                                }
                                val_str = g_variant_get_string(value, NULL);
                                if (!(py_optval = PyUnicode_FromString(val_str))) {
                                        /* Some UTF-8 encoding error. */
                                        PyErr_Clear();
                                        srd_err("Option '%s' requires a UTF-8 string value.", key);
                                        goto err_out;
                                }
                        } else if (PyLong_Check(py_classval)) {
                                if (!g_variant_is_of_type(value, G_VARIANT_TYPE_INT64)) {
                                        srd_err("Option '%s' requires an integer value.", key);
                                        goto err_out;
                                }
                                val_int = g_variant_get_int64(value);
                                if (!(py_optval = PyLong_FromLong(val_int))) {
                                        /* ValueError Exception */
                                        PyErr_Clear();
                                        srd_err("Option '%s' has invalid integer value.", key);
                                        goto err_out;
                                }
                        }
                        g_hash_table_remove(options, key);
                } else {
                        /* Use the class default for this option. */
                        if (PyUnicode_Check(py_classval)) {
                                /* Make a brand new copy of the string. */
                                py_ustr = PyUnicode_AS_UNICODE(py_classval);
                                size = PyUnicode_GET_SIZE(py_classval);
                                py_optval = PyUnicode_FromUnicode(py_ustr, size);
                        } else if (PyLong_Check(py_classval)) {
                                /* Make a brand new copy of the integer. */
                                val_ull = PyLong_AsUnsignedLongLong(py_classval);
                                if (val_ull == (unsigned long long)-1) {
                                        /* OverFlowError exception */
                                        PyErr_Clear();
                                        srd_err("Invalid integer value for %s: "
                                                "expected integer.", key);
                                        goto err_out;
                                }
                                if (!(py_optval = PyLong_FromUnsignedLongLong(val_ull)))
                                        goto err_out;
                        }
                }

                /*
                 * If we got here, py_optval holds a known good new reference
                 * to the instance option to set.
                 */
                if (PyDict_SetItemString(py_di_options, key, py_optval) == -1)
                        goto err_out;
                g_free(key);
                key = NULL;
        }

        ret = SRD_OK;

err_out:
        Py_XDECREF(py_optlist);
        Py_XDECREF(py_di_options);
        Py_XDECREF(py_dec_optkeys);
        Py_XDECREF(py_dec_options);
        g_free(key);
        if (PyErr_Occurred())
                srd_exception_catch("Stray exception in srd_inst_option_set().");

        return ret;
}

/* Helper GComparefunc for g_slist_find_custom() in srd_inst_probe_set_all() */
static gint compare_probe_id(const struct srd_probe *a, const char *probe_id)
{
        return strcmp(a->id, probe_id);
}

/**
 * Set all probes in a decoder instance.
 *
 * This function sets _all_ probes for the specified decoder instance, i.e.,
 * it overwrites any probes that were already defined (if any).
 *
 * @param di Decoder instance.
 * @param new_probes A GHashTable of probes to set. Key is probe name, value is
 *                   the probe number. Samples passed to this instance will be
 *                   arranged in this order.
 *
 * @return SRD_OK upon success, a (negative) error code otherwise.
 *
 * @since 0.1.0
 */
SRD_API int srd_inst_probe_set_all(struct srd_decoder_inst *di,
                GHashTable *new_probes)
{
        GVariant *probe_val;
        GList *l;
        GSList *sl;
        struct srd_probe *p;
        int *new_probemap, new_probenum;
        char *probe_id;
        int i, num_required_probes;

        srd_dbg("set probes called for instance %s with list of %d probes",
                di->inst_id, g_hash_table_size(new_probes));

        if (g_hash_table_size(new_probes) == 0)
                /* No probes provided. */
                return SRD_OK;

        if (di->dec_num_probes == 0) {
                /* Decoder has no probes. */
                srd_err("Protocol decoder %s has no probes to define.",
                        di->decoder->name);
                return SRD_ERR_ARG;
        }

        new_probemap = NULL;

        if (!(new_probemap = g_try_malloc(sizeof(int) * di->dec_num_probes))) {
                srd_err("Failed to g_malloc() new probe map.");
                return SRD_ERR_MALLOC;
        }

        /*
         * For now, map all indexes to probe -1 (can be overridden later).
         * This -1 is interpreted as an unspecified probe later.
         */
        for (i = 0; i < di->dec_num_probes; i++)
                new_probemap[i] = -1;

        for (l = g_hash_table_get_keys(new_probes); l; l = l->next) {
                probe_id = l->data;
                probe_val= g_hash_table_lookup(new_probes, probe_id);
                if (!g_variant_is_of_type(probe_val, G_VARIANT_TYPE_INT32)) {
                        /* Probe name was specified without a value. */
                        srd_err("No probe number was specified for %s.",
                                        probe_id);
                        g_free(new_probemap);
                        return SRD_ERR_ARG;
                }
                new_probenum = g_variant_get_int32(probe_val);
                if (!(sl = g_slist_find_custom(di->decoder->probes, probe_id,
                                (GCompareFunc)compare_probe_id))) {
                        /* Fall back on optional probes. */
                        if (!(sl = g_slist_find_custom(di->decoder->opt_probes,
                             probe_id, (GCompareFunc) compare_probe_id))) {
                                srd_err("Protocol decoder %s has no probe "
                                                "'%s'.", di->decoder->name, probe_id);
                                g_free(new_probemap);
                                return SRD_ERR_ARG;
                        }
                }
                p = sl->data;
                new_probemap[p->order] = new_probenum;
                srd_dbg("Setting probe mapping: %s (index %d) = probe %d.",
                        p->id, p->order, new_probenum);
        }

        srd_dbg("Final probe map:");
        num_required_probes = g_slist_length(di->decoder->probes);
        for (i = 0; i < di->dec_num_probes; i++) {
                srd_dbg(" - index %d = probe %d (%s)", i, new_probemap[i],
                        (i < num_required_probes) ? "required" : "optional");
        }

        g_free(di->dec_probemap);
        di->dec_probemap = new_probemap;

        return SRD_OK;
}

/**
 * Create a new protocol decoder instance.
 *
 * @param decoder_id Decoder 'id' field.
 * @param options GHashtable of options which override the defaults set in
 *                the decoder class. May be NULL.
 *
 * @return Pointer to a newly allocated struct srd_decoder_inst, or
 *         NULL in case of failure.
 *
 * @since 0.1.0
 */
SRD_API struct srd_decoder_inst *srd_inst_new(const char *decoder_id,
                GHashTable *options)
{
        int i;
        struct srd_decoder *dec;
        struct srd_decoder_inst *di;
        char *inst_id;

        srd_dbg("Creating new %s instance.", decoder_id);

        if (!(dec = srd_decoder_get_by_id(decoder_id))) {
                srd_err("Protocol decoder %s not found.", decoder_id);
                return NULL;
        }

        if (!(di = g_try_malloc0(sizeof(struct srd_decoder_inst)))) {
                srd_err("Failed to g_malloc() instance.");
                return NULL;
        }

        di->decoder = dec;
        if (options) {
                inst_id = g_hash_table_lookup(options, "id");
                di->inst_id = g_strdup(inst_id ? inst_id : decoder_id);
                g_hash_table_remove(options, "id");
        } else
                di->inst_id = g_strdup(decoder_id);

        /*
         * Prepare a default probe map, where samples come in the
         * order in which the decoder class defined them.
         */
        di->dec_num_probes = g_slist_length(di->decoder->probes) +
                             g_slist_length(di->decoder->opt_probes);
        if (di->dec_num_probes) {
                if (!(di->dec_probemap =
                     g_try_malloc(sizeof(int) * di->dec_num_probes))) {
                        srd_err("Failed to g_malloc() probe map.");
                        g_free(di);
                        return NULL;
                }
                for (i = 0; i < di->dec_num_probes; i++)
                        di->dec_probemap[i] = i;
        }

        /* Create a new instance of this decoder class. */
        if (!(di->py_inst = PyObject_CallObject(dec->py_dec, NULL))) {
                if (PyErr_Occurred())
                        srd_exception_catch("failed to create %s instance: ",
                                            decoder_id);
                g_free(di->dec_probemap);
                g_free(di);
                return NULL;
        }

        if (options && srd_inst_option_set(di, options) != SRD_OK) {
                g_free(di->dec_probemap);
                g_free(di);
                return NULL;
        }

        /* Instance takes input from a frontend by default. */
        di_list = g_slist_append(di_list, di);

        return di;
}

/**
 * Stack a decoder instance on top of another.
 *
 * @param di_from The instance to move.
 * @param di_to The instance on top of which di_from will be stacked.
 *
 * @return SRD_OK upon success, a (negative) error code otherwise.
 *
 * @since 0.1.0
 */
SRD_API int srd_inst_stack(struct srd_decoder_inst *di_from,
                struct srd_decoder_inst *di_to)
{
        if (!di_from || !di_to) {
                srd_err("Invalid from/to instance pair.");
                return SRD_ERR_ARG;
        }

        if (g_slist_find(di_list, di_to)) {
                /* Remove from the unstacked list. */
                di_list = g_slist_remove(di_list, di_to);
        }

        /* Stack on top of source di. */
        di_from->next_di = g_slist_append(di_from->next_di, di_to);

        return SRD_OK;
}

/**
 * Find a decoder instance by its instance ID.
 *
 * Only the bottom level of instances are searched -- instances already stacked
 * on top of another one will not be found.
 *
 * @param inst_id The instance ID to be found.
 *
 * @return Pointer to struct srd_decoder_inst, or NULL if not found.
 *
 * @since 0.1.0
 */
SRD_API struct srd_decoder_inst *srd_inst_find_by_id(const char *inst_id)
{
        GSList *l;
        struct srd_decoder_inst *tmp, *di;

        di = NULL;
        for (l = di_list; l; l = l->next) {
                tmp = l->data;
                if (!strcmp(tmp->inst_id, inst_id)) {
                        di = tmp;
                        break;
                }
        }

        return di;
}

/**
 * Find a decoder instance by its Python object.
 *
 * I.e. find that instance's instantiation of the sigrokdecode.Decoder class.
 * This will recurse to find the instance anywhere in the stack tree.
 *
 * @param stack Pointer to a GSList of struct srd_decoder_inst, indicating the
 *              stack to search. To start searching at the bottom level of
 *              decoder instances, pass NULL.
 * @param obj The Python class instantiation.
 *
 * @return Pointer to struct srd_decoder_inst, or NULL if not found.
 *
 * @private
 *
 * @since 0.1.0
 */
SRD_PRIV struct srd_decoder_inst *srd_inst_find_by_obj(const GSList *stack,
                const PyObject *obj)
{
        const GSList *l;
        struct srd_decoder_inst *tmp, *di;

        di = NULL;
        for (l = stack ? stack : di_list; di == NULL && l != NULL; l = l->next) {
                tmp = l->data;
                if (tmp->py_inst == obj)
                        di = tmp;
                else if (tmp->next_di)
                        di = srd_inst_find_by_obj(tmp->next_di, obj);
        }

        return di;
}

/** @private */
SRD_PRIV int srd_inst_start(struct srd_decoder_inst *di, PyObject *args)
{
        PyObject *py_name, *py_res;
        GSList *l;
        struct srd_decoder_inst *next_di;

        srd_dbg("Calling start() method on protocol decoder instance %s.",
                di->inst_id);

        if (!(py_name = PyUnicode_FromString("start"))) {
                srd_err("Unable to build Python object for 'start'.");
                srd_exception_catch("Protocol decoder instance %s: ",
                                    di->inst_id);
                return SRD_ERR_PYTHON;
        }

        if (!(py_res = PyObject_CallMethodObjArgs(di->py_inst,
                                                  py_name, args, NULL))) {
                srd_exception_catch("Protocol decoder instance %s: ",
                                    di->inst_id);
                return SRD_ERR_PYTHON;
        }

        Py_DecRef(py_res);
        Py_DecRef(py_name);

        /*
         * Start all the PDs stacked on top of this one. Pass along the
         * metadata all the way from the bottom PD, even though it's only
         * applicable to logic data for now.
         */
        for (l = di->next_di; l; l = l->next) {
                next_di = l->data;
                srd_inst_start(next_di, args);
        }

        return SRD_OK;
}

/**
 * Run the specified decoder function.
 *
 * @param start_samplenum The starting sample number for the buffer's sample
 *                        set, relative to the start of capture.
 * @param di The decoder instance to call. Must not be NULL.
 * @param inbuf The buffer to decode. Must not be NULL.
 * @param inbuflen Length of the buffer. Must be > 0.
 *
 * @return SRD_OK upon success, a (negative) error code otherwise.
 *
 * @private
 *
 * @since 0.1.0
 */
SRD_PRIV int srd_inst_decode(uint64_t start_samplenum,
                const struct srd_decoder_inst *di, const uint8_t *inbuf,
                uint64_t inbuflen)
{
        PyObject *py_res;
        srd_logic *logic;
        uint64_t end_samplenum;

        srd_dbg("Calling decode() on instance %s with %d bytes starting "
                "at sample %d.", di->inst_id, inbuflen, start_samplenum);

        /* Return an error upon unusable input. */
        if (!di) {
                srd_dbg("empty decoder instance");
                return SRD_ERR_ARG;
        }
        if (!inbuf) {
                srd_dbg("NULL buffer pointer");
                return SRD_ERR_ARG;
        }
        if (inbuflen == 0) {
                srd_dbg("empty buffer");
                return SRD_ERR_ARG;
        }

        /*
         * Create new srd_logic object. Each iteration around the PD's loop
         * will fill one sample into this object.
         */
        logic = PyObject_New(srd_logic, &srd_logic_type);
        Py_INCREF(logic);
        logic->di = (struct srd_decoder_inst *)di;
        logic->start_samplenum = start_samplenum;
        logic->itercnt = 0;
        logic->inbuf = (uint8_t *)inbuf;
        logic->inbuflen = inbuflen;
        logic->sample = PyList_New(2);
        Py_INCREF(logic->sample);

        Py_IncRef(di->py_inst);
        end_samplenum = start_samplenum + inbuflen / di->data_unitsize;
        if (!(py_res = PyObject_CallMethod(di->py_inst, "decode",
                                           "KKO", logic->start_samplenum,
                                           end_samplenum, logic))) {
                srd_exception_catch("Protocol decoder instance %s: ",
                                    di->inst_id);
                return SRD_ERR_PYTHON;
        }
        Py_DecRef(py_res);

        return SRD_OK;
}

/** @private */
SRD_PRIV void srd_inst_free(struct srd_decoder_inst *di)
{
        GSList *l;
        struct srd_pd_output *pdo;

        srd_dbg("Freeing instance %s", di->inst_id);

        Py_DecRef(di->py_inst);
        g_free(di->inst_id);
        g_free(di->dec_probemap);
        g_slist_free(di->next_di);
        for (l = di->pd_output; l; l = l->next) {
                pdo = l->data;
                g_free(pdo->proto_id);
                g_free(pdo);
        }
        g_slist_free(di->pd_output);
        g_free(di);
}

/** @private */
SRD_PRIV void srd_inst_free_all(GSList *stack)
{
        GSList *l;
        struct srd_decoder_inst *di;

        di = NULL;
        for (l = stack ? stack : di_list; di == NULL && l != NULL; l = l->next) {
                di = l->data;
                if (di->next_di)
                        srd_inst_free_all(di->next_di);
                srd_inst_free(di);
        }
        if (!stack) {
                g_slist_free(di_list);
                di_list = NULL;
        }
}

/** @} */

/**
 * @defgroup grp_session Session handling
 *
 * Starting and handling decoding sessions.
 *
 * @{
 */

/**
 * Start a decoding session.
 *
 * Decoders, instances and stack must have been prepared beforehand.
 *
 * @param num_probes The number of probes which the incoming feed will contain.
 * @param unitsize The number of bytes per sample in the incoming feed.
 * @param samplerate The samplerate of the incoming feed.
 *
 * @return SRD_OK upon success, a (negative) error code otherwise.
 *
 * @since 0.1.0
 */
SRD_API int srd_session_start(int num_probes, int unitsize, uint64_t samplerate)
{
        PyObject *args;
        GSList *d;
        struct srd_decoder_inst *di;
        int ret;

        ret = SRD_OK;

        srd_dbg("Calling start() on all instances with %d probes, "
                "unitsize %d samplerate %d.", num_probes, unitsize, samplerate);

        /*
         * Currently only one item of metadata is passed along to decoders,
         * samplerate. This can be extended as needed.
         */
        if (!(args = Py_BuildValue("{s:l}", "samplerate", (long)samplerate))) {
                srd_err("Unable to build Python object for metadata.");
                return SRD_ERR_PYTHON;
        }

        /* Run the start() method on all decoders receiving frontend data. */
        for (d = di_list; d; d = d->next) {
                di = d->data;
                di->data_num_probes = num_probes;
                di->data_unitsize = unitsize;
                di->data_samplerate = samplerate;
                if ((ret = srd_inst_start(di, args)) != SRD_OK)
                        break;
        }

        Py_DecRef(args);

        return ret;
}

/**
 * Send a chunk of logic sample data to a running decoder session.
 *
 * @param start_samplenum The sample number of the first sample in this chunk.
 * @param inbuf Pointer to sample data.
 * @param inbuflen Length in bytes of the buffer.
 *
 * @return SRD_OK upon success, a (negative) error code otherwise.
 *
 * @since 0.1.0
 */
SRD_API int srd_session_send(uint64_t start_samplenum, const uint8_t *inbuf,
                uint64_t inbuflen)
{
        GSList *d;
        int ret;

        srd_dbg("Calling decode() on all instances with starting sample "
                "number %" PRIu64 ", %" PRIu64 " bytes at 0x%p",
                start_samplenum, inbuflen, inbuf);

        for (d = di_list; d; d = d->next) {
                if ((ret = srd_inst_decode(start_samplenum, d->data, inbuf,
                                           inbuflen)) != SRD_OK)
                        return ret;
        }

        return SRD_OK;
}

/**
 * Register/add a decoder output callback function.
 *
 * The function will be called when a protocol decoder sends output back
 * to the PD controller (except for Python objects, which only go up the
 * stack).
 *
 * @param output_type The output type this callback will receive. Only one
 *                    callback per output type can be registered.
 * @param cb The function to call. Must not be NULL.
 * @param cb_data Private data for the callback function. Can be NULL.
 *
 * @since 0.1.0
 */
SRD_API int srd_pd_output_callback_add(int output_type,
                srd_pd_output_callback_t cb, void *cb_data)
{
        struct srd_pd_callback *pd_cb;

        srd_dbg("Registering new callback for output type %d.", output_type);

        if (!(pd_cb = g_try_malloc(sizeof(struct srd_pd_callback)))) {
                srd_err("Failed to g_malloc() struct srd_pd_callback.");
                return SRD_ERR_MALLOC;
        }

        pd_cb->output_type = output_type;
        pd_cb->cb = cb;
        pd_cb->cb_data = cb_data;
        callbacks = g_slist_append(callbacks, pd_cb);

        return SRD_OK;
}

/** @private */
SRD_PRIV struct srd_pd_callback *srd_pd_output_callback_find(int output_type)
{
        GSList *l;
        struct srd_pd_callback *tmp, *pd_cb;

        pd_cb = NULL;
        for (l = callbacks; l; l = l->next) {
                tmp = l->data;
                if (tmp->output_type == output_type) {
                        pd_cb = tmp;
                        break;
                }
        }

        return pd_cb;
}

/* This is the backend function to Python sigrokdecode.add() call. */
/** @private */
SRD_PRIV int srd_inst_pd_output_add(struct srd_decoder_inst *di,
                                    int output_type, const char *proto_id)
{
        struct srd_pd_output *pdo;

        srd_dbg("Instance %s creating new output type %d for %s.",
                di->inst_id, output_type, proto_id);

        if (!(pdo = g_try_malloc(sizeof(struct srd_pd_output)))) {
                srd_err("Failed to g_malloc() struct srd_pd_output.");
                return -1;
        }

        /* pdo_id is just a simple index, nothing is deleted from this list anyway. */
        pdo->pdo_id = g_slist_length(di->pd_output);
        pdo->output_type = output_type;
        pdo->di = di;
        pdo->proto_id = g_strdup(proto_id);
        di->pd_output = g_slist_append(di->pd_output, pdo);

        return pdo->pdo_id;
}

/** @} */