input/vcd: do propagate parse error in file header

[libsigrok.git] / src / input / vcd.c

/*
 * This file is part of the libsigrok project.
 *
 * Copyright (C) 2012 Petteri Aimonen <jpa@sr.mail.kapsi.fi>
 * Copyright (C) 2014 Bert Vermeulen <bert@biot.com>
 * Copyright (C) 2017-2020 Gerhard Sittig <gerhard.sittig@gmx.net>
 *
 * 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/>.
 */

/*
 * The VCD input module has the following options. See the options[]
 * declaration near the bottom of the input module's source file.
 *
 * numchannels: Maximum number of sigrok channels to create. VCD signals
 *   are detected in their order of declaration in the VCD file header,
 *   and mapped to sigrok channels.
 *
 * skip: Allows to skip data at the start of the input file. This can
 *   speed up operation on long captures.
 *   Value < 0: Skip until first timestamp that is listed in the file.
 *     (This is the default behaviour.)
 *   Value = 0: Do not skip, instead generate samples beginning from
 *     timestamp 0.
 *   Value > 0: Start at the given timestamp.
 *
 * downsample: Divide the samplerate by the given factor. This can
 *   speed up operation on long captures.
 *
 * compress: Trim idle periods which are longer than this value to span
 *   only this many timescale ticks. This can speed up operation on long
 *   captures (default 0, don't compress).
 *
 * Based on Verilog standard IEEE Std 1364-2001 Version C
 *
 * Supported features:
 * - $var with 'wire' and 'reg' types of scalar variables
 * - $timescale definition for samplerate
 * - multiple character variable identifiers
 * - same identifer used for multiple signals (identical values)
 * - vector variables (bit vectors)
 * - integer variables (analog signals with 0 digits, passed as single
 *   precision float number)
 * - real variables (analog signals, passed on with single precision,
 *   arbitrary digits value, not user adjustable)
 * - nested $scope, results in prefixed sigrok channel names
 *
 * Most important unsupported features:
 * - $dumpvars initial value declaration (is not an issue if generators
 *   provide sample data for the #0 timestamp, otherwise session data
 *   starts from zero values, and catches up when the signal changes its
 *   state to a supported value)
 *
 * Implementor's note: This input module specifically does _not_ use
 * glib routines where they would hurt performance. Lots of memory
 * allocations increase execution time not by percents but by huge
 * factors. This motivated this module's custom code for splitting
 * words on text lines, and pooling previously allocated buffers.
 *
 * TODO (in arbitrary order)
 * - Map VCD scopes to sigrok channel groups?
 *   - Does libsigrok support nested channel groups? Or is this feature
 *     exclusive to Pulseview?
 * - Check VCD input to VCD output behaviour. Verify that export and
 *   re-import results in identical data (well, VCD's constraints on
 *   timescale values is known to result in differences).
 * - Check the minimum timestamp delta in the input data set, suggest
 *   the downsample=N option to users for reduced resource consumption.
 *   Popular VCD file creation utilities love to specify insanely tiny
 *   timescale values in the pico or even femto seconds range. Which
 *   results in huge sample counts after import, and potentially even
 *   terminates the application due to resource exhaustion. This issue
 *   only will vanish when common libsigrok infrastructure no longer
 *   depends on constant rate streams of samples at discrete points
 *   in time. The current input module implementation has code in place
 *   to gather timestamp statistics, but the most appropriate condition
 *   when to notify users is yet to be found.
 * - Cleanup the implementation.
 *   - Consistent use of the glib API (where appropriate).
 *   - More appropriate variable/function identifiers.
 *   - More robust handling of multi-word input phrases and chunked
 *     input buffers? This implementation assumes that e.g. b[01]+
 *     patterns are complete when they start, and the signal identifier
 *     is available as well. Which may be true assuming that input data
 *     comes in complete text lines.
 *   - See if other input modules have learned lessons that we could
 *     benefit from here as well? Pointless BOM (done), line oriented
 *     processing with EOL variants and with optional last EOL, module
 *     state reset and file re-read (stable channels list), buffered
 *     session feed, synchronized feed for mixed signal sources, digits
 *     or formats support for analog input, single vs double precision,
 *     etc.
 *   - Re-consider logging. Verbosity levels should be acceptable,
 *     but volume is an issue. Drop duplicates, and drop messages from
 *     known good code paths.
 */

#include <config.h>

#include <glib.h>
#include <libsigrok/libsigrok.h>
#include "libsigrok-internal.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define LOG_PREFIX "input/vcd"

#define CHUNK_SIZE (4 * 1024 * 1024)
#define SCOPE_SEP '.'

struct context {
        struct vcd_user_opt {
                size_t maxchannels; /* sigrok channels (output) */
                uint64_t downsample;
                uint64_t compress;
                uint64_t skip_starttime;
                gboolean skip_specified;
        } options;
        gboolean use_skip;
        gboolean started;
        gboolean got_header;
        uint64_t prev_timestamp;
        uint64_t samplerate;
        size_t vcdsignals; /* VCD signals (input) */
        GSList *ignored_signals;
        gboolean data_after_timestamp;
        gboolean ignore_end_keyword;
        gboolean skip_until_end;
        GSList *channels;
        size_t unit_size;
        size_t logic_count;
        size_t analog_count;
        uint8_t *current_logic;
        float *current_floats;
        struct {
                size_t max_bits;
                size_t unit_size;
                uint8_t *value;
                size_t sig_count;
        } conv_bits;
        GString *scope_prefix;
        struct feed_queue_logic *feed_logic;
        struct split_state {
                size_t alloced;
                char **words;
                gboolean in_use;
        } split;
        struct ts_stats {
                size_t total_ts_seen;
                uint64_t last_ts_value;
                uint64_t last_ts_delta;
                size_t min_count;
                struct {
                        uint64_t delta;
                        size_t count;
                } min_items[2];
                uint32_t early_check_shift;
                size_t early_last_emitted;
        } ts_stats;
        struct vcd_prev {
                GSList *sr_channels;
                GSList *sr_groups;
        } prev;
};

struct vcd_channel {
        char *name;
        char *identifier;
        size_t size;
        enum sr_channeltype type;
        size_t array_index;
        size_t byte_idx;
        uint8_t bit_mask;
        char *base_name;
        size_t range_lower, range_upper;
        int submit_digits;
        struct feed_queue_analog *feed_analog;
};

static void free_channel(void *data)
{
        struct vcd_channel *vcd_ch;

        vcd_ch = data;
        if (!vcd_ch)
                return;

        g_free(vcd_ch->name);
        g_free(vcd_ch->identifier);
        g_free(vcd_ch->base_name);
        feed_queue_analog_free(vcd_ch->feed_analog);

        g_free(vcd_ch);
}

/*
 * Another timestamp delta was observed, update statistics: Update the
 * sorted list of minimum values, and increment the occurance counter.
 * Returns the position of the item's statistics slot, or returns a huge
 * invalid index when the current delta is larger than previously found
 * values.
 */
static size_t ts_stats_update_min(struct ts_stats *stats, uint64_t delta)
{
        size_t idx, copy_idx;

        /* Advance over previously recorded values which are smaller. */
        idx = 0;
        while (idx < stats->min_count && stats->min_items[idx].delta < delta)
                idx++;
        if (idx == ARRAY_SIZE(stats->min_items))
                return idx;

        /* Found the exact value that previously was registered? */
        if (stats->min_items[idx].delta == delta) {
                stats->min_items[idx].count++;
                return idx;
        }

        /* Allocate another slot, bubble up larger values as needed. */
        if (stats->min_count < ARRAY_SIZE(stats->min_items))
                stats->min_count++;
        for (copy_idx = stats->min_count - 1; copy_idx > idx; copy_idx--)
                stats->min_items[copy_idx] = stats->min_items[copy_idx - 1];

        /* Start tracking this value in the found or freed slot. */
        memset(&stats->min_items[idx], 0, sizeof(stats->min_items[idx]));
        stats->min_items[idx].delta = delta;
        stats->min_items[idx].count++;

        return idx;
}

/*
 * Intermediate check for extreme oversampling in the input data. Rate
 * limited emission of warnings to avoid noise, "late" emission of the
 * first potential message to avoid false positives, yet need to  emit
 * the messages early (*way* before EOF) to raise awareness.
 *
 * TODO
 * Tune the limits, improve perception and usefulness of these checks.
 * Need to start emitting messages soon enough to be seen by users. Yet
 * avoid unnecessary messages for valid input's idle/quiet phases. Slow
 * input transitions are perfectly legal before bursty phases are seen
 * in the input data. Needs the check become an option, on by default,
 * but suppressable by users?
 */
static void ts_stats_check_early(struct ts_stats *stats)
{
        static const struct {
                uint64_t delta;
                size_t count;
        } *cp, check_points[] = {
                {     100, 1000000, }, /* Still x100 after 1mio transitions. */
                {    1000,  100000, }, /* Still x1k after 100k transitions. */
                {   10000,   10000, }, /* Still x10k after 10k transitions. */
                { 1000000,    2500, }, /* Still x1m after 2.5k transitions. */
        };

        size_t cp_idx;
        uint64_t seen_delta, check_delta;
        size_t seen_count;

        /* Get the current minimum's value and count. */
        if (!stats->min_count)
                return;
        seen_delta = stats->min_items[0].delta;
        seen_count = stats->min_items[0].count;

        /* Emit at most one weak message per import. */
        if (stats->early_last_emitted)
                return;

        /* Check arbitrary marks, emit rate limited warnings. */
        (void)seen_count;
        check_delta = seen_delta >> stats->early_check_shift;
        for (cp_idx = 0; cp_idx < ARRAY_SIZE(check_points); cp_idx++) {
                cp = &check_points[cp_idx];
                /* No other match can happen below. Done iterating. */
                if (stats->total_ts_seen > cp->count)
                        return;
                /* Advance to the next checkpoint description. */
                if (stats->total_ts_seen != cp->count)
                        continue;
                /* First occurance of that timestamp count. Check the value. */
                sr_dbg("TS early chk: total %zu, min delta %" PRIu64 " / %" PRIu64 ".",
                        cp->count, seen_delta, check_delta);
                if (check_delta < cp->delta)
                        return;
                sr_warn("Low change rate? (weak estimate, min TS delta %" PRIu64 " after %zu timestamps)",
                        seen_delta, stats->total_ts_seen);
                sr_warn("Consider using the downsample=N option, or increasing its value.");
                stats->early_last_emitted = stats->total_ts_seen;
                return;
        }
}

/* Reset the internal state of the timestamp tracker. */
static int ts_stats_prep(struct context *inc)
{
        struct ts_stats *stats;
        uint64_t down_sample_value;
        uint32_t down_sample_shift;

        stats = &inc->ts_stats;
        memset(stats, 0, sizeof(*stats));

        down_sample_value = inc->options.downsample;
        down_sample_shift = 0;
        while (down_sample_value >= 2) {
                down_sample_shift++;
                down_sample_value /= 2;
        }
        stats->early_check_shift = down_sample_shift;

        return SR_OK;
}

/* Inspect another timestamp that was received. */
static int ts_stats_check(struct ts_stats *stats, uint64_t curr_ts)
{
        uint64_t last_ts, delta;

        last_ts = stats->last_ts_value;
        stats->last_ts_value = curr_ts;
        stats->total_ts_seen++;
        if (stats->total_ts_seen < 2)
                return SR_OK;

        delta = curr_ts - last_ts;
        stats->last_ts_delta = delta;
        (void)ts_stats_update_min(stats, delta);

        ts_stats_check_early(stats);

        return SR_OK;
}

/* Postprocess internal timestamp tracker state. */
static int ts_stats_post(struct context *inc, gboolean ignore_terminal)
{
        struct ts_stats *stats;
        size_t min_idx;
        uint64_t delta, over_sample, over_sample_scaled, suggest_factor;
        enum sr_loglevel log_level;
        gboolean is_suspicious, has_downsample;

        stats = &inc->ts_stats;

        /*
         * Lookup the smallest timestamp delta which was found during
         * data import. Ignore the last delta if its timestamp was never
         * followed by data, and this was the only occurance. Absence of
         * result data is non-fatal here -- this code exclusively serves
         * to raise users' awareness of potential pitfalls, but does not
         * change behaviour of data processing.
         *
         * TODO Also filter by occurance count? To not emit warnings when
         * captured signals only change slowly by design. Only warn when
         * the sample rate and samples count product exceeds a threshold?
         * See below for the necessity (and potential) to adjust the log
         * message's severity and content.
         */
        min_idx = 0;
        if (ignore_terminal) do {
                if (min_idx >= stats->min_count)
                        break;
                delta = stats->last_ts_delta;
                if (stats->min_items[min_idx].delta != delta)
                        break;
                if (stats->min_items[min_idx].count != 1)
                        break;
                min_idx++;
        } while (0);
        if (min_idx >= stats->min_count)
                return SR_OK;

        /*
         * TODO Refine the condition whether to notify the user, and
         * which severity to use after having inspected all input data.
         * Any detail could get involved which previously was gathered
         * during data processing: total sample count, channel count
         * including their data type and bits width, the oversampling
         * factor (minimum observed "change rate"), or any combination
         * thereof. The current check is rather simple (unconditional
         * warning for ratios starting at 100, regardless of sample or
         * channel count).
         */
        over_sample = stats->min_items[min_idx].delta;
        over_sample_scaled = over_sample / inc->options.downsample;
        sr_dbg("TS post stats: oversample unscaled %" PRIu64 ", scaled %" PRIu64,
                over_sample, over_sample_scaled);
        if (over_sample_scaled < 10) {
                sr_dbg("TS post stats: Low oversampling ratio, good.");
                return SR_OK;
        }

        /*
         * Avoid constructing the message from several tiny pieces by
         * design, because this would be hard on translators. Stick with
         * complete sentences instead, and accept the redundancy in the
         * user's interest.
         */
        log_level = (over_sample_scaled > 20) ? SR_LOG_WARN : SR_LOG_INFO;
        is_suspicious = over_sample_scaled > 20;
        if (is_suspicious) {
                sr_log(log_level, LOG_PREFIX ": "
                        "Suspiciously low overall change rate (total min TS delta %" PRIu64 ").",
                        over_sample_scaled);
        } else {
                sr_log(log_level, LOG_PREFIX ": "
                        "Low overall change rate (total min TS delta %" PRIu64 ").",
                        over_sample_scaled);
        }
        has_downsample = inc->options.downsample > 1;
        suggest_factor = inc->options.downsample;
        while (over_sample_scaled >= 10) {
                suggest_factor *= 10;
                over_sample_scaled /= 10;
        }
        if (has_downsample) {
                sr_log(log_level, LOG_PREFIX ": "
                        "Suggest higher downsample value, like %" PRIu64 ".",
                        suggest_factor);
        } else {
                sr_log(log_level, LOG_PREFIX ": "
                        "Suggest to downsample, value like %" PRIu64 ".",
                        suggest_factor);
        }

        return SR_OK;
}

static void check_remove_bom(GString *buf)
{
        static const char *bom_text = "\xef\xbb\xbf";

        if (buf->len < strlen(bom_text))
                return;
        if (strncmp(buf->str, bom_text, strlen(bom_text)) != 0)
                return;
        g_string_erase(buf, 0, strlen(bom_text));
}

/*
 * Reads a single VCD section from input file and parses it to name/contents.
 * e.g. $timescale 1ps $end => "timescale" "1ps"
 */
static gboolean parse_section(GString *buf, char **name, char **contents)
{
        static const char *end_text = "$end";

        gboolean status;
        size_t pos, len;
        const char *grab_start, *grab_end;
        GString *sname, *scontent;

        /* Preset falsy return values. Gets updated below. */
        *name = *contents = NULL;
        status = FALSE;

        /* Skip any initial white-space. */
        pos = 0;
        while (pos < buf->len && g_ascii_isspace(buf->str[pos]))
                pos++;

        /* Section tag should start with $. */
        if (buf->str[pos++] != '$')
                return FALSE;

        /* Read the section tag. */
        grab_start = &buf->str[pos];
        while (pos < buf->len && !g_ascii_isspace(buf->str[pos]))
                pos++;
        grab_end = &buf->str[pos];
        sname = g_string_new_len(grab_start, grab_end - grab_start);

        /* Skip whitespace before content. */
        while (pos < buf->len && g_ascii_isspace(buf->str[pos]))
                pos++;

        /* Read the content up to the '$end' marker. */
        scontent = g_string_sized_new(128);
        grab_start = &buf->str[pos];
        grab_end = g_strstr_len(grab_start, buf->len - pos, end_text);
        if (grab_end) {
                /* Advance 'pos' to after '$end' and more whitespace. */
                pos = grab_end - buf->str;
                pos += strlen(end_text);
                while (pos < buf->len && g_ascii_isspace(buf->str[pos]))
                        pos++;

                /* Grab the (trimmed) content text. */
                while (grab_end > grab_start && g_ascii_isspace(grab_end[-1]))
                        grab_end--;
                len = grab_end - grab_start;
                g_string_append_len(scontent, grab_start, len);
                if (sname->len)
                        status = TRUE;

                /* Consume the input text which just was taken. */
                g_string_erase(buf, 0, pos);
        }

        /* Return section name and content if a section was seen. */
        *name = g_string_free(sname, !status);
        *contents = g_string_free(scontent, !status);

        return status;
}

/*
 * The glib routine which splits an input text into a list of words also
 * "provides empty strings" which application code then needs to remove.
 * And copies of the input text get allocated for all words.
 *
 * The repeated memory allocation is acceptable for small workloads like
 * parsing the header sections. But the heavy lifting for sample data is
 * done by DIY code to speedup execution. The use of glib routines would
 * severely hurt throughput. Allocated memory gets re-used while a strict
 * ping-pong pattern is assumed (each text line of input data enters and
 * leaves in a strict symmetrical manner, due to the organization of the
 * receive() routine and parse calls).
 */

/* Remove empty parts from an array returned by g_strsplit(). */
static void remove_empty_parts(gchar **parts)
{
        gchar **src, **dest;

        src = dest = parts;
        while (*src) {
                if (!**src) {
                        g_free(*src);
                } else {
                        if (dest != src)
                                *dest = *src;
                        dest++;
                }
                src++;
        }
        *dest = NULL;
}

static char **split_text_line(struct context *inc, char *text, size_t *count)
{
        struct split_state *state;
        size_t counted, alloced, wanted;
        char **words, *p, **new_words;

        state = &inc->split;

        if (count)
                *count = 0;

        if (state->in_use) {
                sr_dbg("coding error, split() called while \"in use\".");
                return NULL;
        }

        /*
         * Seed allocation when invoked for the first time. Assume
         * simple logic data, start with a few words per line. Will
         * automatically adjust with subsequent use.
         */
        if (!state->alloced) {
                alloced = 20;
                words = g_malloc(sizeof(words[0]) * alloced);
                if (!words)
                        return NULL;
                state->alloced = alloced;
                state->words = words;
        }

        /* Start with most recently allocated word list space. */
        alloced = state->alloced;
        words = state->words;
        counted = 0;

        /* As long as more input text remains ... */
        p = text;
        while (*p) {
                /* Resize word list if needed. Just double the size. */
                if (counted + 1 >= alloced) {
                        wanted = 2 * alloced;
                        new_words = g_realloc(words, sizeof(words[0]) * wanted);
                        if (!new_words) {
                                return NULL;
                        }
                        words = new_words;
                        alloced = wanted;
                        state->words = words;
                        state->alloced = alloced;
                }

                /* Skip leading spaces. */
                while (g_ascii_isspace(*p))
                        p++;
                if (!*p)
                        break;

                /* Add found word to word list. */
                words[counted++] = p;

                /* Find end of the word. Terminate loop upon EOS. */
                while (*p && !g_ascii_isspace(*p))
                        p++;
                if (!*p)
                        break;

                /* More text follows. Terminate the word. */
                *p++ = '\0';
        }

        /*
         * NULL terminate the word list. Provide its length so that
         * calling code need not re-iterate the list to get the count.
         */
        words[counted] = NULL;
        if (count)
                *count = counted;
        state->in_use = TRUE;

        return words;
}

static void free_text_split(struct context *inc, char **words)
{
        struct split_state *state;

        state = &inc->split;

        if (words && words != state->words) {
                sr_dbg("coding error, free() arg differs from split() result.");
        }

        /* "Double free" finally releases the memory. */
        if (!state->in_use) {
                g_free(state->words);
                state->words = NULL;
                state->alloced = 0;
        }

        /* Mark as no longer in use. */
        state->in_use = FALSE;
}

static gboolean have_header(GString *buf)
{
        static const char *enddef_txt = "$enddefinitions";
        static const char *end_txt = "$end";

        char *p, *p_stop;

        /* Search for "end of definitions" section keyword. */
        p = g_strstr_len(buf->str, buf->len, enddef_txt);
        if (!p)
                return FALSE;
        p += strlen(enddef_txt);

        /* Search for end of section (content expected to be empty). */
        p_stop = &buf->str[buf->len];
        p_stop -= strlen(end_txt);
        while (p < p_stop && g_ascii_isspace(*p))
                p++;
        if (strncmp(p, end_txt, strlen(end_txt)) != 0)
                return FALSE;
        p += strlen(end_txt);

        return TRUE;
}

static int parse_timescale(struct context *inc, char *contents)
{
        uint64_t p, q;

        /*
         * The standard allows for values 1, 10 or 100
         * and units s, ms, us, ns, ps and fs.
         */
        if (sr_parse_period(contents, &p, &q) != SR_OK) {
                sr_err("Parsing $timescale failed.");
                return SR_ERR_DATA;
        }

        inc->samplerate = q / p;
        sr_dbg("Samplerate: %" PRIu64, inc->samplerate);
        if (q % p != 0) {
                /* Does not happen unless time value is non-standard */
                sr_warn("Inexact rounding of samplerate, %" PRIu64 " / %" PRIu64 " to %" PRIu64 " Hz.",
                        q, p, inc->samplerate);
        }

        return SR_OK;
}

/*
 * Handle '$scope' and '$upscope' sections in the input file. Assume that
 * input signals have a "base name", which may be ambiguous within the
 * file. These names get declared within potentially nested scopes, which
 * this implementation uses to create longer but hopefully unique and
 * thus more usable sigrok channel names.
 *
 * Track the currently effective scopes in a string variable to simplify
 * the channel name creation. Start from an empty string, then append the
 * scope name and a separator when a new scope opens, and remove the last
 * scope name when a scope closes. This allows to simply prefix basenames
 * with the current scope to get a full name.
 *
 * It's an implementation detail to keep the trailing NUL here in the
 * GString member, to simplify the g_strconcat() call in the channel name
 * creation.
 *
 * TODO
 * - Check whether scope types must get supported, this implementation
 *   does not distinguish between 'module' and 'begin' and what else
 *   may be seen. The first word simply gets ignored.
 * - Check the allowed alphabet for scope names. This implementation
 *   assumes "programming language identifier" style (alphanumeric with
 *   underscores, plus brackets since we've seen them in example files).
 */
static int parse_scope(struct context *inc, char *contents, gboolean is_up)
{
        char *sep_pos, *name_pos;
        char **parts;
        size_t length;

        /*
         * The 'upscope' case, drop one scope level (if available). Accept
         * excess 'upscope' calls, assume that a previous 'scope' section
         * was ignored because it referenced our software package's name.
         */
        if (is_up) {
                /*
                 * Check for a second right-most separator (and position
                 * right behind that, which is the start of the last
                 * scope component), or fallback to the start of string.
                 * g_string_erase() from that positon to the end to drop
                 * the last component.
                 */
                name_pos = inc->scope_prefix->str;
                do {
                        sep_pos = strrchr(name_pos, SCOPE_SEP);
                        if (!sep_pos)
                                break;
                        *sep_pos = '\0';
                        sep_pos = strrchr(name_pos, SCOPE_SEP);
                        if (!sep_pos)
                                break;
                        name_pos = ++sep_pos;
                } while (0);
                length = name_pos - inc->scope_prefix->str;
                g_string_truncate(inc->scope_prefix, length);
                g_string_append_c(inc->scope_prefix, '\0');
                sr_dbg("$upscope, prefix now: \"%s\"", inc->scope_prefix->str);
                return SR_OK;
        }

        /*
         * The 'scope' case, add another scope level. But skip our own
         * package name, assuming that this is an artificial node which
         * was emitted by libsigrok's VCD output module.
         */
        sr_spew("$scope, got: \"%s\"", contents);
        parts = g_strsplit_set(contents, " \r\n\t", 0);
        remove_empty_parts(parts);
        length = g_strv_length(parts);
        if (length != 2) {
                sr_err("Unsupported 'scope' syntax: %s", contents);
                g_strfreev(parts);
                return SR_ERR_DATA;
        }
        name_pos = parts[1];
        if (strcmp(name_pos, PACKAGE_NAME) == 0) {
                sr_info("Skipping scope with application's package name: %s",
                        name_pos);
                *name_pos = '\0';
        }
        if (*name_pos) {
                /* Drop NUL, append scope name and separator, and re-add NUL. */
                g_string_truncate(inc->scope_prefix, inc->scope_prefix->len - 1);
                g_string_append_printf(inc->scope_prefix,
                        "%s%c%c", name_pos, SCOPE_SEP, '\0');
        }
        g_strfreev(parts);
        sr_dbg("$scope, prefix now: \"%s\"", inc->scope_prefix->str);

        return SR_OK;
}

/**
 * Parse a $var section which describes a VCD signal ("variable").
 *
 * @param[in] inc Input module context.
 * @param[in] contents Input text, content of $var section.
 */
static int parse_header_var(struct context *inc, char *contents)
{
        char **parts;
        size_t length;
        char *type, *size_txt, *id, *ref, *idx;
        gboolean is_reg, is_wire, is_real, is_int;
        gboolean is_str;
        enum sr_channeltype ch_type;
        size_t size, next_size;
        struct vcd_channel *vcd_ch;

        /*
         * Format of $var or $reg header specs:
         * $var type size identifier reference [opt-index] $end
         */
        parts = g_strsplit_set(contents, " \r\n\t", 0);
        remove_empty_parts(parts);
        length = g_strv_length(parts);
        if (length != 4 && length != 5) {
                sr_warn("$var section should have 4 or 5 items");
                g_strfreev(parts);
                return SR_ERR_DATA;
        }

        type = parts[0];
        size_txt = parts[1];
        id = parts[2];
        ref = parts[3];
        idx = parts[4];
        if (idx && !*idx)
                idx = NULL;
        is_reg = g_strcmp0(type, "reg") == 0;
        is_wire = g_strcmp0(type, "wire") == 0;
        is_real = g_strcmp0(type, "real") == 0;
        is_int = g_strcmp0(type, "integer") == 0;
        is_str = g_strcmp0(type, "string") == 0;

        if (is_reg || is_wire) {
                ch_type = SR_CHANNEL_LOGIC;
        } else if (is_real || is_int) {
                ch_type = SR_CHANNEL_ANALOG;
        } else if (is_str) {
                sr_warn("Skipping id %s, name '%s%s', unsupported type '%s'.",
                        id, ref, idx ? idx : "", type);
                inc->ignored_signals = g_slist_append(inc->ignored_signals,
                        g_strdup(id));
                g_strfreev(parts);
                return SR_OK;
        } else {
                sr_err("Unsupported signal type: '%s'", type);
                g_strfreev(parts);
                return SR_ERR_DATA;
        }

        size = strtol(size_txt, NULL, 10);
        if (ch_type == SR_CHANNEL_ANALOG) {
                if (is_real && size != 32 && size != 64) {
                        /*
                         * The VCD input module does not depend on the
                         * specific width of the floating point value.
                         * This is just for information. Upon value
                         * changes, a mere string gets converted to
                         * float, so we may not care at all.
                         *
                         * Strictly speaking we might warn for 64bit
                         * (double precision) declarations, because
                         * sigrok internally uses single precision
                         * (32bit) only.
                         */
                        sr_info("Unexpected real width: '%s'", size_txt);
                }
                /* Simplify code paths below, by assuming size 1. */
                size = 1;
        }
        if (!size) {
                sr_warn("Unsupported signal size: '%s'", size_txt);
                g_strfreev(parts);
                return SR_ERR_DATA;
        }
        if (inc->conv_bits.max_bits < size)
                inc->conv_bits.max_bits = size;
        next_size = inc->logic_count + inc->analog_count + size;
        if (inc->options.maxchannels && next_size > inc->options.maxchannels) {
                sr_warn("Skipping '%s%s', exceeds requested channel count %zu.",
                        ref, idx ? idx : "", inc->options.maxchannels);
                inc->ignored_signals = g_slist_append(inc->ignored_signals,
                        g_strdup(id));
                g_strfreev(parts);
                return SR_OK;
        }

        vcd_ch = g_malloc0(sizeof(*vcd_ch));
        vcd_ch->identifier = g_strdup(id);
        vcd_ch->name = g_strconcat(inc->scope_prefix->str, ref, idx, NULL);
        vcd_ch->size = size;
        vcd_ch->type = ch_type;
        switch (ch_type) {
        case SR_CHANNEL_LOGIC:
                vcd_ch->array_index = inc->logic_count;
                vcd_ch->byte_idx = vcd_ch->array_index / 8;
                vcd_ch->bit_mask = 1 << (vcd_ch->array_index % 8);
                inc->logic_count += size;
                break;
        case SR_CHANNEL_ANALOG:
                vcd_ch->array_index = inc->analog_count++;
                /* TODO: Use proper 'digits' value for this input module. */
                vcd_ch->submit_digits = is_real ? 2 : 0;
                break;
        }
        inc->vcdsignals++;
        sr_spew("VCD signal %zu '%s' ID '%s' (size %zu), sr type %s, idx %zu.",
                inc->vcdsignals, vcd_ch->name,
                vcd_ch->identifier, vcd_ch->size,
                vcd_ch->type == SR_CHANNEL_ANALOG ? "A" : "L",
                vcd_ch->array_index);
        inc->channels = g_slist_append(inc->channels, vcd_ch);
        g_strfreev(parts);

        return SR_OK;
}

/**
 * Construct the name of the nth sigrok channel for a VCD signal.
 *
 * Uses the VCD signal name for scalar types and single-bit signals.
 * Uses "signal.idx" for multi-bit VCD signals without a range spec in
 * their declaration. Uses "signal[idx]" when a range is known and was
 * verified.
 *
 * @param[in] vcd_ch The VCD signal's description.
 * @param[in] idx The sigrok channel's index within the VCD signal's group.
 *
 * @return An allocated text buffer which callers need to release, #NULL
 *   upon failure to create a sigrok channel name.
 */
static char *get_channel_name(struct vcd_channel *vcd_ch, size_t idx)
{
        char *open_pos, *close_pos, *check_pos, *endptr;
        gboolean has_brackets, has_range;
        size_t upper, lower, tmp;
        char *ch_name;

        /* Handle simple scalar types, and single-bit logic first. */
        if (vcd_ch->size <= 1)
                return g_strdup(vcd_ch->name);

        /*
         * If not done before: Search for a matching pair of brackets in
         * the right-most position at the very end of the string. Get the
         * two colon separated numbers between the brackets, which are
         * the range limits for array indices into the multi-bit signal.
         * Grab the "base name" of the VCD signal.
         *
         * Notice that arrays can get nested. Earlier path components can
         * be indexed as well, that's why we need the right-most range.
         * This implementation does not handle bit vectors of size 1 here
         * by explicit logic. The check for a [0:0] range would even fail.
         * But the case of size 1 is handled above, and "happens to" give
         * the expected result (just the VCD signal name).
         *
         * This implementation also deals with range limits in the reverse
         * order, as well as ranges which are not 0-based (like "[4:7]").
         */
        if (!vcd_ch->base_name) {
                has_range = TRUE;
                open_pos = strrchr(vcd_ch->name, '[');
                close_pos = strrchr(vcd_ch->name, ']');
                if (close_pos && close_pos[1])
                        close_pos = NULL;
                has_brackets = open_pos && close_pos && close_pos > open_pos;
                if (!has_brackets)
                        has_range = FALSE;
                if (has_range) {
                        check_pos = &open_pos[1];
                        endptr = NULL;
                        upper = strtoul(check_pos, &endptr, 10);
                        if (!endptr || *endptr != ':')
                                has_range = FALSE;
                }
                if (has_range) {
                        check_pos = &endptr[1];
                        endptr = NULL;
                        lower = strtoul(check_pos, &endptr, 10);
                        if (!endptr || endptr != close_pos)
                                has_range = FALSE;
                }
                if (has_range && lower > upper) {
                        tmp = lower;
                        lower = upper;
                        upper = tmp;
                }
                if (has_range) {
                        if (lower >= upper)
                                has_range = FALSE;
                        if (upper + 1 - lower != vcd_ch->size)
                                has_range = FALSE;
                }
                if (has_range) {
                        /* Temporarily patch the VCD channel's name. */
                        *open_pos = '\0';
                        vcd_ch->base_name = g_strdup(vcd_ch->name);
                        *open_pos = '[';
                        vcd_ch->range_lower = lower;
                        vcd_ch->range_upper = upper;
                }
        }
        has_range = vcd_ch->range_lower + vcd_ch->range_upper;
        if (has_range && idx >= vcd_ch->size)
                has_range = FALSE;
        if (!has_range)
                return g_strdup_printf("%s.%zu", vcd_ch->name, idx);

        /*
         * Create a sigrok channel name with just the bit's index in
         * brackets. This avoids "name[7:0].3" results, instead results
         * in "name[3]".
         */
        ch_name = g_strdup_printf("%s[%zu]",
                vcd_ch->base_name, vcd_ch->range_lower + idx);
        return ch_name;
}

/*
 * Create (analog or logic) sigrok channels for the VCD signals. Create
 * multiple sigrok channels for vector input since sigrok has no concept
 * of multi-bit signals. Create a channel group for the vector's bits
 * though to reflect that they form a unit. This is beneficial when UIs
 * support optional "collapsed" displays of channel groups (like
 * "parallel bus, hex output").
 *
 * Defer channel creation until after completion of parsing the input
 * file header. Make sure to create all logic channels first before the
 * analog channels get created. This avoids issues with the mapping of
 * channel indices to bitmap positions in the sample buffer.
 */
static void create_channels(const struct sr_input *in,
        struct sr_dev_inst *sdi, enum sr_channeltype ch_type)
{
        struct context *inc;
        size_t ch_idx;
        GSList *l;
        struct vcd_channel *vcd_ch;
        size_t size_idx;
        char *ch_name;
        struct sr_channel_group *cg;
        struct sr_channel *ch;

        inc = in->priv;

        ch_idx = 0;
        if (ch_type > SR_CHANNEL_LOGIC)
                ch_idx += inc->logic_count;
        if (ch_type > SR_CHANNEL_ANALOG)
                ch_idx += inc->analog_count;
        for (l = inc->channels; l; l = l->next) {
                vcd_ch = l->data;
                if (vcd_ch->type != ch_type)
                        continue;
                cg = NULL;
                if (vcd_ch->size != 1)
                        cg = sr_channel_group_new(sdi, vcd_ch->name, NULL);
                for (size_idx = 0; size_idx < vcd_ch->size; size_idx++) {
                        ch_name = get_channel_name(vcd_ch, size_idx);
                        sr_dbg("sigrok channel idx %zu, name %s, type %s, en %d.",
                                ch_idx, ch_name,
                                ch_type == SR_CHANNEL_ANALOG ? "A" : "L", TRUE);
                        ch = sr_channel_new(sdi, ch_idx, ch_type, TRUE, ch_name);
                        g_free(ch_name);
                        ch_idx++;
                        if (cg)
                                cg->channels = g_slist_append(cg->channels, ch);
                }
        }
}

static void create_feeds(const struct sr_input *in)
{
        struct context *inc;
        GSList *l;
        struct vcd_channel *vcd_ch;
        size_t ch_idx;
        struct sr_channel *ch;

        inc = in->priv;

        /* Create one feed for logic data. */
        if (inc->logic_count) {
                inc->unit_size = (inc->logic_count + 7) / 8;
                inc->feed_logic = feed_queue_logic_alloc(in->sdi,
                        CHUNK_SIZE / inc->unit_size, inc->unit_size);
        }

        /* Create one feed per analog channel. */
        for (l = inc->channels; l; l = l->next) {
                vcd_ch = l->data;
                if (vcd_ch->type != SR_CHANNEL_ANALOG)
                        continue;
                ch_idx = vcd_ch->array_index;
                ch_idx += inc->logic_count;
                ch = g_slist_nth_data(in->sdi->channels, ch_idx);
                vcd_ch->feed_analog = feed_queue_analog_alloc(in->sdi,
                        CHUNK_SIZE / sizeof(float),
                        vcd_ch->submit_digits, ch);
        }
}

/*
 * Keep track of a previously created channel list, in preparation of
 * re-reading the input file. Gets called from reset()/cleanup() paths.
 */
static void keep_header_for_reread(const struct sr_input *in)
{
        struct context *inc;

        inc = in->priv;

        g_slist_free_full(inc->prev.sr_groups, sr_channel_group_free_cb);
        inc->prev.sr_groups = in->sdi->channel_groups;
        in->sdi->channel_groups = NULL;

        g_slist_free_full(inc->prev.sr_channels, sr_channel_free_cb);
        inc->prev.sr_channels = in->sdi->channels;
        in->sdi->channels = NULL;
}

/*
 * Check whether the input file is being re-read, and refuse operation
 * when essential parameters of the acquisition have changed in ways
 * that are unexpected to calling applications. Gets called after the
 * file header got parsed (again).
 *
 * Changing the channel list across re-imports of the same file is not
 * supported, by design and for valid reasons, see bug #1215 for details.
 * Users are expected to start new sessions when they change these
 * essential parameters in the acquisition's setup. When we accept the
 * re-read file, then make sure to keep using the previous channel list,
 * applications may still reference them.
 */
static gboolean check_header_in_reread(const struct sr_input *in)
{
        struct context *inc;

        if (!in)
                return FALSE;
        inc = in->priv;
        if (!inc)
                return FALSE;
        if (!inc->prev.sr_channels)
                return TRUE;

        if (sr_channel_lists_differ(inc->prev.sr_channels, in->sdi->channels)) {
                sr_err("Channel list change not supported for file re-read.");
                return FALSE;
        }

        g_slist_free_full(in->sdi->channel_groups, sr_channel_group_free_cb);
        in->sdi->channel_groups = inc->prev.sr_groups;
        inc->prev.sr_groups = NULL;

        g_slist_free_full(in->sdi->channels, sr_channel_free_cb);
        in->sdi->channels = inc->prev.sr_channels;
        inc->prev.sr_channels = NULL;

        return TRUE;
}

/* Parse VCD file header sections (rate and variables declarations). */
static int parse_header(const struct sr_input *in, GString *buf)
{
        struct context *inc;
        gboolean enddef_seen, header_valid;
        char *name, *contents;
        size_t size;
        int ret;

        inc = in->priv;

        /* Parse sections until complete header was seen. */
        enddef_seen = FALSE;
        header_valid = TRUE;
        name = contents = NULL;
        inc->conv_bits.max_bits = 1;
        while (parse_section(buf, &name, &contents)) {
                sr_dbg("Section '%s', contents '%s'.", name, contents);

                if (g_strcmp0(name, "enddefinitions") == 0) {
                        enddef_seen = TRUE;
                        goto done_section;
                }
                if (g_strcmp0(name, "timescale") == 0) {
                        if (parse_timescale(inc, contents) != SR_OK)
                                header_valid = FALSE;
                        goto done_section;
                }
                if (g_strcmp0(name, "scope") == 0) {
                        if (parse_scope(inc, contents, FALSE) != SR_OK)
                                header_valid = FALSE;
                        goto done_section;
                }
                if (g_strcmp0(name, "upscope") == 0) {
                        if (parse_scope(inc, NULL, TRUE) != SR_OK)
                                header_valid = FALSE;
                        goto done_section;
                }
                if (g_strcmp0(name, "var") == 0) {
                        if (parse_header_var(inc, contents) != SR_OK)
                                header_valid = FALSE;
                        goto done_section;
                }

done_section:
                g_free(name);
                name = NULL;
                g_free(contents);
                contents = NULL;

                if (enddef_seen)
                        break;
        }
        g_free(name);
        g_free(contents);

        inc->got_header = enddef_seen && header_valid;
        if (!inc->got_header)
                return SR_ERR_DATA;

        /* Create sigrok channels here, late, logic before analog. */
        create_channels(in, in->sdi, SR_CHANNEL_LOGIC);
        create_channels(in, in->sdi, SR_CHANNEL_ANALOG);
        if (!check_header_in_reread(in))
                return SR_ERR_DATA;
        create_feeds(in);

        /*
         * Allocate space for text to number conversion, and buffers to
         * hold current sample values before submission to the session
         * feed. Allocate one buffer for all logic bits, and another for
         * all floating point values of all analog channels.
         *
         * The buffers get updated when the VCD input stream communicates
         * value changes. Upon reception of VCD timestamps, the buffer can
         * provide the previously received values, to "fill in the gaps"
         * in the generation of a continuous stream of samples for the
         * sigrok session.
         */
        size = (inc->conv_bits.max_bits + 7) / 8;
        inc->conv_bits.unit_size = size;
        inc->conv_bits.value = g_malloc0(size);
        if (!inc->conv_bits.value)
                return SR_ERR_MALLOC;

        size = (inc->logic_count + 7) / 8;
        inc->unit_size = size;
        inc->current_logic = g_malloc0(size);
        if (inc->unit_size && !inc->current_logic)
                return SR_ERR_MALLOC;
        size = sizeof(inc->current_floats[0]) * inc->analog_count;
        inc->current_floats = g_malloc0(size);
        if (size && !inc->current_floats)
                return SR_ERR_MALLOC;
        for (size = 0; size < inc->analog_count; size++)
                inc->current_floats[size] = 0.;

        ret = ts_stats_prep(inc);
        if (ret != SR_OK)
                return ret;

        return SR_OK;
}

/*
 * Add N copies of previously received values to the session, before
 * subsequent value changes will update the data buffer. Locally buffer
 * sample data to minimize the number of send() calls.
 */
static void add_samples(const struct sr_input *in, size_t count, gboolean flush)
{
        struct context *inc;
        GSList *ch_list;
        struct vcd_channel *vcd_ch;
        struct feed_queue_analog *q;
        float value;

        inc = in->priv;

        if (inc->logic_count) {
                feed_queue_logic_submit(inc->feed_logic,
                        inc->current_logic, count);
                if (flush)
                        feed_queue_logic_flush(inc->feed_logic);
        }
        for (ch_list = inc->channels; ch_list; ch_list = ch_list->next) {
                vcd_ch = ch_list->data;
                if (vcd_ch->type != SR_CHANNEL_ANALOG)
                        continue;
                q = vcd_ch->feed_analog;
                if (!q)
                        continue;
                value = inc->current_floats[vcd_ch->array_index];
                feed_queue_analog_submit(q, value, count);
                if (flush)
                        feed_queue_analog_flush(q);
        }
}

static gint vcd_compare_id(gconstpointer a, gconstpointer b)
{
        return strcmp((const char *)a, (const char *)b);
}

static gboolean is_ignored(struct context *inc, const char *id)
{
        GSList *ignored;

        ignored = g_slist_find_custom(inc->ignored_signals, id, vcd_compare_id);
        return ignored != NULL;
}

/*
 * Get an analog channel's value from a bit pattern (VCD 'integer' type).
 * The implementation assumes a maximum integer width (64bit), the API
 * doesn't (beyond the return data type). The use of SR_CHANNEL_ANALOG
 * channels may further constraint the number of significant digits
 * (current asumption: float -> 23bit).
 */
static float get_int_val(uint8_t *in_bits_data, size_t in_bits_count)
{
        uint64_t int_value;
        size_t byte_count, byte_idx;
        float flt_value; /* typeof(inc->current_floats[0]) */

        /* Convert bit pattern to integer number (limited range). */
        int_value = 0;
        byte_count = (in_bits_count + 7) / 8;
        for (byte_idx = 0; byte_idx < byte_count; byte_idx++) {
                if (byte_idx >= sizeof(int_value))
                        break;
                int_value |= *in_bits_data++ << (byte_idx * 8);
        }
        flt_value = int_value;

        return flt_value;
}

/*
 * Set a logic channel's level depending on the VCD signal's identifier
 * and parsed value. Multi-bit VCD values will affect several sigrok
 * channels. One VCD signal name can translate to several sigrok channels.
 */
static void process_bits(struct context *inc, char *identifier,
        uint8_t *in_bits_data, size_t in_bits_count)
{
        size_t size;
        gboolean have_int;
        GSList *l;
        struct vcd_channel *vcd_ch;
        float int_val;
        size_t bit_idx;
        uint8_t *in_bit_ptr, in_bit_mask;
        uint8_t *out_bit_ptr, out_bit_mask;
        uint8_t bit_val;

        size = 0;
        have_int = FALSE;
        int_val = 0;
        for (l = inc->channels; l; l = l->next) {
                vcd_ch = l->data;
                if (g_strcmp0(identifier, vcd_ch->identifier) != 0)
                        continue;
                if (vcd_ch->type == SR_CHANNEL_ANALOG) {
                        /* Special case for 'integer' VCD signal types. */
                        size = vcd_ch->size; /* Flag for "VCD signal found". */
                        if (!have_int) {
                                int_val = get_int_val(in_bits_data, in_bits_count);
                                have_int = TRUE;
                        }
                        inc->current_floats[vcd_ch->array_index] = int_val;
                        continue;
                }
                if (vcd_ch->type != SR_CHANNEL_LOGIC)
                        continue;
                sr_spew("Processing %s data, id '%s', ch %zu sz %zu",
                        (size == 1) ? "bit" : "vector",
                        identifier, vcd_ch->array_index, vcd_ch->size);

                /* Found our (logic) channel. Setup in/out bit positions. */
                size = vcd_ch->size;
                in_bit_ptr = in_bits_data;
                in_bit_mask = 1 << 0;
                out_bit_ptr = &inc->current_logic[vcd_ch->byte_idx];
                out_bit_mask = vcd_ch->bit_mask;

                /*
                 * Pass VCD input bit(s) to sigrok logic bits. Conversion
                 * must be done repeatedly because one VCD signal name
                 * can translate to several sigrok channels, and shifting
                 * a previously computed bit field to another channel's
                 * position in the buffer would be nearly as expensive,
                 * and certain would increase complexity of the code.
                 */
                for (bit_idx = 0; bit_idx < size; bit_idx++) {
                        /* Get the bit value from input data. */
                        bit_val = 0;
                        if (bit_idx < in_bits_count) {
                                bit_val = *in_bit_ptr & in_bit_mask;
                                in_bit_mask <<= 1;
                                if (!in_bit_mask) {
                                        in_bit_mask = 1 << 0;
                                        in_bit_ptr++;
                                }
                        }
                        /* Manipulate the sample buffer data image. */
                        if (bit_val)
                                *out_bit_ptr |= out_bit_mask;
                        else
                                *out_bit_ptr &= ~out_bit_mask;
                        /* Update output position after bitmap update. */
                        out_bit_mask <<= 1;
                        if (!out_bit_mask) {
                                out_bit_mask = 1 << 0;
                                out_bit_ptr++;
                        }
                }
        }
        if (!size && !is_ignored(inc, identifier))
                sr_warn("VCD signal not found for ID '%s'.", identifier);
}

/*
 * Set an analog channel's value from a floating point number. One
 * VCD signal name can translate to several sigrok channels.
 */
static void process_real(struct context *inc, char *identifier, float real_val)
{
        gboolean found;
        GSList *l;
        struct vcd_channel *vcd_ch;

        found = FALSE;
        for (l = inc->channels; l; l = l->next) {
                vcd_ch = l->data;
                if (vcd_ch->type != SR_CHANNEL_ANALOG)
                        continue;
                if (g_strcmp0(identifier, vcd_ch->identifier) != 0)
                        continue;

                /* Found our (analog) channel. */
                found = TRUE;
                sr_spew("Processing real data, id '%s', ch %zu, val %.16g",
                        identifier, vcd_ch->array_index, real_val);
                inc->current_floats[vcd_ch->array_index] = real_val;
        }
        if (!found && !is_ignored(inc, identifier))
                sr_warn("VCD signal not found for ID '%s'.", identifier);
}

/*
 * Converts a bit position's text character to a number value.
 *
 * TODO Check for complete coverage of Verilog's standard logic values
 * (IEEE-1364). The set is said to be “01XZHUWL-”, which only a part of
 * is handled here. What would be the complete mapping?
 * - 0/L -> bit value 0
 * - 1/H -> bit value 1
 * - X "don't care" -> TODO
 * - Z "high impedance" -> TODO
 * - W "weak(?)" -> TODO
 * - U "undefined" -> TODO
 * - '-' "TODO" -> TODO
 *
 * For simplicity, this input module implementation maps "known low"
 * values to 0, and "known high" values to 1. All other values will
 * end up assuming "low" (return number 0), while callers might warn.
 * It's up to users to provide compatible input data, or accept the
 * warnings. Silently accepting unknown input data is not desirable.
 */
static uint8_t vcd_char_to_value(char bit_char, int *warn)
{

        bit_char = g_ascii_tolower(bit_char);

        /* Convert the "undisputed" variants. */
        if (bit_char == '0' || bit_char == 'l')
                return 0;
        if (bit_char == '1' || bit_char == 'h')
                return 1;

        /* Convert the "uncertain" variants. */
        if (warn)
                *warn = 1;
        if (bit_char == 'x' || bit_char == 'z')
                return 0;
        if (bit_char == 'u')
                return 0;
        if (bit_char == '-')
                return 0;

        /* Unhandled input text. */
        return ~0;
}

/*
 * Check the validity of a VCD string value. It's essential to reliably
 * accept valid data which the community uses in the field, yet robustly
 * reject invalid data for users' awareness. Since IEEE 1800-2017 would
 * not discuss the representation of this data type, it's assumed to not
 * be an official feature of the VCD file format. This implementation is
 * an educated guess after inspection of other arbitrary implementations,
 * not backed by any specification or public documentation.
 *
 * A quick summary of the implemented assumptions: Must be a sequence of
 * ASCII printables. Must not contain whitespace. Might contain escape
 * sequences: A backslash followed by a single character, like '\n' or
 * '\\'. Or a backslash and the letter x followed by two hex digits,
 * like '\x20'. Or a backslash followed by three octal digits, like
 * '\007'. As an exception also accepts a single digit '\0' but only at
 * the text end. The string value may be empty, but must not be NULL.
 *
 * This implementation assumes an ASCII based platform for simplicity
 * and readability. Should be a given on sigrok supported platforms.
 */
static gboolean vcd_string_valid(const char *s)
{
        char c;

        if (!s)
                return FALSE;

        while (*s) {
                c = *s++;
                /* Reject non-printable ASCII chars including DEL. */
                if (c < ' ')
                        return FALSE;
                if (c > '~')
                        return FALSE;
                /* Deeper inspection of escape sequences. */
                if (c == '\\') {
                        c = *s++;
                        switch (c) {
                        case 'a': /* BEL, bell aka "alarm" */
                        case 'b': /* BS, back space */
                        case 't': /* TAB, tabulator */
                        case 'n': /* NL, newline */
                        case 'v': /* VT, vertical tabulator */
                        case 'f': /* FF, form feed */
                        case 'r': /* CR, carriage return */
                        case '"': /* double quotes */
                        case '\'': /* tick, single quote */
                        case '?': /* question mark */
                        case '\\': /* backslash */
                                continue;
                        case 'x': /* \xNN two hex digits */
                                c = *s++;
                                if (!g_ascii_isxdigit(c))
                                        return FALSE;
                                c = *s++;
                                if (!g_ascii_isxdigit(c))
                                        return FALSE;
                                continue;
                        case '0': /* \NNN three octal digits */
                        case '1':
                        case '2':
                        case '3':
                        case '4':
                        case '5':
                        case '6':
                        case '7':
                                /* Special case '\0' at end of text. */
                                if (c == '0' && !*s)
                                        return TRUE;
                                /*
                                 * First digit was covered by the outer
                                 * switch(). Two more digits to check.
                                 */
                                c = *s++;
                                if (!g_ascii_isdigit(c) || c > '7')
                                        return FALSE;
                                c = *s++;
                                if (!g_ascii_isdigit(c) || c > '7')
                                        return FALSE;
                                continue;
                        default:
                                return FALSE;
                        }
                }
        }

        return TRUE;
}

/* Parse one text line of the data section. */
static int parse_textline(const struct sr_input *in, char *lines)
{
        struct context *inc;
        int ret;
        char **words;
        size_t word_count, word_idx;
        char *curr_word, *next_word, curr_first;
        gboolean is_timestamp, is_section;
        gboolean is_real, is_multibit, is_singlebit, is_string;
        uint64_t timestamp;
        char *identifier, *endptr;
        size_t count;

        inc = in->priv;

        /*
         * Split the caller's text lines into a list of space separated
         * words. Note that some of the branches consume the very next
         * words as well, and assume that both adjacent words will be
         * available when the first word is seen. This constraint applies
         * to bit vector data, multi-bit integers and real (float) data,
         * as well as single-bit data with whitespace before its
         * identifier (if that's valid in VCD, we'd accept it here).
         * The fact that callers always pass complete text lines should
         * make this assumption acceptable.
         */
        ret = SR_OK;
        words = split_text_line(inc, lines, &word_count);
        for (word_idx = 0; word_idx < word_count; word_idx++) {
                /*
                 * Make the next two words available, to simpilify code
                 * paths below. The second word is optional here.
                 */
                curr_word = words[word_idx];
                if (!curr_word && !curr_word[0])
                        continue;
                curr_first = g_ascii_tolower(curr_word[0]);
                next_word = words[word_idx + 1];
                if (next_word && !next_word[0])
                        next_word = NULL;

                /*
                 * Optionally skip some sections that can be interleaved
                 * with data (and may or may not be supported by this
                 * input module). If the section is not skipped but the
                 * $end keyword needs to get tracked, specifically handle
                 * this case, for improved robustness (still reject files
                 * which happen to use invalid syntax).
                 */
                if (inc->skip_until_end) {
                        if (strcmp(curr_word, "$end") == 0) {
                                /* Done with unhandled/unknown section. */
                                sr_dbg("done skipping until $end");
                                inc->skip_until_end = FALSE;
                        } else {
                                sr_spew("skipping word: %s", curr_word);
                        }
                        continue;
                }
                if (inc->ignore_end_keyword) {
                        if (strcmp(curr_word, "$end") == 0) {
                                sr_dbg("done ignoring $end keyword");
                                inc->ignore_end_keyword = FALSE;
                                continue;
                        }
                }

                /*
                 * There may be $keyword sections inside the data part of
                 * the input file. Do inspect some of the sections' content
                 * but ignore their surrounding keywords. Silently skip
                 * unsupported section types (which transparently covers
                 * $comment sections).
                 */
                is_section = curr_first == '$' && curr_word[1];
                if (is_section) {
                        gboolean inspect_data;

                        inspect_data = FALSE;
                        inspect_data |= g_strcmp0(curr_word, "$dumpvars") == 0;
                        inspect_data |= g_strcmp0(curr_word, "$dumpon") == 0;
                        inspect_data |= g_strcmp0(curr_word, "$dumpoff") == 0;
                        if (inspect_data) {
                                /* Ignore keywords, yet parse contents. */
                                sr_dbg("%s section, will parse content", curr_word);
                                inc->ignore_end_keyword = TRUE;
                        } else {
                                /* Ignore section from here up to $end. */
                                sr_dbg("%s section, will skip until $end", curr_word);
                                inc->skip_until_end = TRUE;
                        }
                        continue;
                }

                /*
                 * Numbers prefixed by '#' are timestamps, which translate
                 * to sigrok sample numbers. Apply optional downsampling,
                 * and apply the 'skip' logic. Check the recent timestamp
                 * for plausibility. Submit the corresponding number of
                 * samples of previously accumulated data values to the
                 * session feed.
                 */
                is_timestamp = curr_first == '#' && g_ascii_isdigit(curr_word[1]);
                if (is_timestamp) {
                        endptr = NULL;
                        timestamp = strtoull(&curr_word[1], &endptr, 10);
                        if (!endptr || *endptr) {
                                sr_err("Invalid timestamp: %s.", curr_word);
                                ret = SR_ERR_DATA;
                                break;
                        }
                        sr_spew("Got timestamp: %" PRIu64, timestamp);
                        ret = ts_stats_check(&inc->ts_stats, timestamp);
                        if (ret != SR_OK)
                                break;
                        if (inc->options.downsample > 1) {
                                timestamp /= inc->options.downsample;
                                sr_spew("Downsampled timestamp: %" PRIu64, timestamp);
                        }

                        /*
                         * Skip < 0 => skip until first timestamp.
                         * Skip = 0 => don't skip
                         * Skip > 0 => skip until timestamp >= skip.
                         */
                        if (inc->options.skip_specified && !inc->use_skip) {
                                sr_dbg("Seeding skip from user spec %" PRIu64,
                                        inc->options.skip_starttime);
                                inc->prev_timestamp = inc->options.skip_starttime;
                                inc->use_skip = TRUE;
                        }
                        if (!inc->use_skip) {
                                sr_dbg("Seeding skip from first timestamp");
                                inc->options.skip_starttime = timestamp;
                                inc->prev_timestamp = timestamp;
                                inc->use_skip = TRUE;
                                continue;
                        }
                        if (inc->options.skip_starttime && timestamp < inc->options.skip_starttime) {
                                sr_spew("Timestamp skipped, before user spec");
                                inc->prev_timestamp = inc->options.skip_starttime;
                                continue;
                        }
                        if (timestamp == inc->prev_timestamp) {
                                /*
                                 * Ignore repeated timestamps (e.g. sigrok
                                 * outputs these). Can also happen when
                                 * downsampling makes distinct input values
                                 * end up at the same scaled down value.
                                 * Also transparently covers the initial
                                 * timestamp.
                                 */
                                sr_spew("Timestamp is identical to previous timestamp");
                                continue;
                        }
                        if (timestamp < inc->prev_timestamp) {
                                sr_err("Invalid timestamp: %" PRIu64 " (leap backwards).", timestamp);
                                ret = SR_ERR_DATA;
                                break;
                        }
                        if (inc->options.compress) {
                                /* Compress long idle periods */
                                count = timestamp - inc->prev_timestamp;
                                if (count > inc->options.compress) {
                                        sr_dbg("Long idle period, compressing");
                                        count = timestamp - inc->options.compress;
                                        inc->prev_timestamp = count;
                                }
                        }

                        /* Generate samples from prev_timestamp up to timestamp - 1. */
                        count = timestamp - inc->prev_timestamp;
                        sr_spew("Got a new timestamp, feeding %zu samples", count);
                        add_samples(in, count, FALSE);
                        inc->prev_timestamp = timestamp;
                        inc->data_after_timestamp = FALSE;
                        continue;
                }
                inc->data_after_timestamp = TRUE;

                /*
                 * Data values come in different formats, are associated
                 * with channel identifiers, and correspond to the period
                 * of time from the most recent timestamp to the next
                 * timestamp.
                 *
                 * Supported input data formats are:
                 * - S<value> <sep> <id> (value not used, VCD type 'string').
                 * - R<value> <sep> <id> (analog channel, VCD type 'real').
                 * - B<value> <sep> <id> (analog channel, VCD type 'integer').
                 * - B<value> <sep> <id> (logic channels, VCD bit vectors).
                 * - <value> <id> (logic channel, VCD single-bit values).
                 *
                 * Input values can be:
                 * - Floating point numbers.
                 * - Bit strings (which covers multi-bit aka integers
                 *   as well as vectors).
                 * - Single bits.
                 *
                 * Things to note:
                 * - Individual bits can be 0/1 which is supported by
                 *   libsigrok, or x or z which is treated like 0 here
                 *   (sigrok lacks support for ternary logic, neither is
                 *   there support for the full IEEE set of values).
                 * - Single-bit values typically won't be separated from
                 *   the signal identifer, multi-bit values and floats
                 *   are separated (will reference the next word). This
                 *   implementation silently accepts separators for
                 *   single-bit values, too.
                 */
                is_real = curr_first == 'r' && curr_word[1];
                is_multibit = curr_first == 'b' && curr_word[1];
                is_singlebit = curr_first == '0' || curr_first == '1';
                is_singlebit |= curr_first == 'l' || curr_first == 'h';
                is_singlebit |= curr_first == 'x' || curr_first == 'z';
                is_singlebit |= curr_first == 'u' || curr_first == '-';
                is_string = curr_first == 's';
                if (is_real) {
                        char *real_text;
                        float real_val;

                        real_text = &curr_word[1];
                        identifier = next_word;
                        word_idx++;
                        if (!*real_text || !identifier || !*identifier) {
                                sr_err("Unexpected real format.");
                                ret = SR_ERR_DATA;
                                break;
                        }
                        sr_spew("Got real data %s for id '%s'.",
                                real_text, identifier);
                        if (sr_atof_ascii(real_text, &real_val) != SR_OK) {
                                sr_err("Cannot convert value: %s.", real_text);
                                ret = SR_ERR_DATA;
                                break;
                        }
                        process_real(inc, identifier, real_val);
                        continue;
                }
                if (is_multibit) {
                        char *bits_text_start;
                        size_t bit_count;
                        char *bits_text, bit_char;
                        uint8_t bit_value;
                        uint8_t *value_ptr, value_mask;
                        GString *bits_val_text;

                        /* TODO
                         * Fold in single-bit code path here? To re-use
                         * the X/Z support. Current redundancy is few so
                         * there is little pressure to unify code paths.
                         * Also multi-bit handling is often different
                         * from single-bit handling, so the "unified"
                         * path would often check for special cases. So
                         * we may never unify code paths at all here.
                         */
                        bits_text = &curr_word[1];
                        identifier = next_word;
                        word_idx++;

                        if (!*bits_text || !identifier || !*identifier) {
                                sr_err("Unexpected integer/vector format.");
                                ret = SR_ERR_DATA;
                                break;
                        }
                        sr_spew("Got integer/vector data %s for id '%s'.",
                                bits_text, identifier);

                        /*
                         * Accept a bit string of arbitrary length (sort
                         * of, within the limits of the previously setup
                         * conversion buffer). The input text omits the
                         * leading zeroes, hence we convert from end to
                         * the start, to get the significant bits. There
                         * should only be errors for invalid input, or
                         * for input that is rather strange (data holds
                         * more bits than the signal's declaration in
                         * the header suggested). Silently accept data
                         * that fits in the conversion buffer, and has
                         * more significant bits than the signal's type
                         * (that'd be non-sence yet acceptable input).
                         */
                        bits_text_start = bits_text;
                        bits_text += strlen(bits_text);
                        bit_count = bits_text - bits_text_start;
                        if (bit_count > inc->conv_bits.max_bits) {
                                sr_err("Value exceeds conversion buffer: %s",
                                        bits_text_start);
                                ret = SR_ERR_DATA;
                                break;
                        }
                        memset(inc->conv_bits.value, 0, inc->conv_bits.unit_size);
                        value_ptr = &inc->conv_bits.value[0];
                        value_mask = 1 << 0;
                        inc->conv_bits.sig_count = 0;
                        while (bits_text > bits_text_start) {
                                inc->conv_bits.sig_count++;
                                bit_char = *(--bits_text);
                                bit_value = vcd_char_to_value(bit_char, NULL);
                                if (bit_value == 0) {
                                        /* EMPTY */
                                } else if (bit_value == 1) {
                                        *value_ptr |= value_mask;
                                } else {
                                        inc->conv_bits.sig_count = 0;
                                        break;
                                }
                                value_mask <<= 1;
                                if (!value_mask) {
                                        value_ptr++;
                                        value_mask = 1 << 0;
                                }
                        }
                        if (!inc->conv_bits.sig_count) {
                                sr_err("Unexpected vector format: %s",
                                        bits_text_start);
                                ret = SR_ERR_DATA;
                                break;
                        }
                        if (sr_log_loglevel_get() >= SR_LOG_SPEW) {
                                bits_val_text = sr_hexdump_new(inc->conv_bits.value,
                                        value_ptr - inc->conv_bits.value + 1);
                                sr_spew("Vector value: %s.", bits_val_text->str);
                                sr_hexdump_free(bits_val_text);
                        }

                        process_bits(inc, identifier,
                                inc->conv_bits.value, inc->conv_bits.sig_count);
                        continue;
                }
                if (is_singlebit) {
                        char *bits_text, bit_char;
                        uint8_t bit_value;

                        /* Get the value text, and signal identifier. */
                        bits_text = &curr_word[0];
                        bit_char = *bits_text;
                        if (!bit_char) {
                                sr_err("Bit value missing.");
                                ret = SR_ERR_DATA;
                                break;
                        }
                        identifier = ++bits_text;
                        if (!*identifier) {
                                identifier = next_word;
                                word_idx++;
                        }
                        if (!identifier || !*identifier) {
                                sr_err("Identifier missing.");
                                ret = SR_ERR_DATA;
                                break;
                        }

                        /* Convert value text to single-bit number. */
                        bit_value = vcd_char_to_value(bit_char, NULL);
                        if (bit_value != 0 && bit_value != 1) {
                                sr_err("Unsupported bit value '%c'.", bit_char);
                                ret = SR_ERR_DATA;
                                break;
                        }
                        inc->conv_bits.value[0] = bit_value;
                        process_bits(inc, identifier, inc->conv_bits.value, 1);
                        continue;
                }
                if (is_string) {
                        const char *str_value;

                        str_value = &curr_word[1];
                        identifier = next_word;
                        word_idx++;
                        if (!vcd_string_valid(str_value)) {
                                sr_err("Invalid string data: %s", str_value);
                                ret = SR_ERR_DATA;
                                break;
                        }
                        if (!identifier || !*identifier) {
                                sr_err("String value without identifier.");
                                ret = SR_ERR_DATA;
                                break;
                        }
                        sr_spew("Got string data, id '%s', value \"%s\".",
                                identifier, str_value);
                        if (!is_ignored(inc, identifier)) {
                                sr_err("String value for identifier '%s'.",
                                        identifier);
                                ret = SR_ERR_DATA;
                                break;
                        }
                        continue;
                }

                /* Design choice: Consider unsupported input fatal. */
                sr_err("Unknown token '%s'.", curr_word);
                ret = SR_ERR_DATA;
                break;
        }
        free_text_split(inc, words);

        return ret;
}

static int process_buffer(struct sr_input *in, gboolean is_eof)
{
        struct context *inc;
        uint64_t samplerate;
        GVariant *gvar;
        int ret;
        char *rdptr, *endptr, *trimptr;
        size_t rdlen;

        inc = in->priv;

        if (!inc->got_header)
                return SR_ERR_DATA;

        /* Send feed header and samplerate (once) before sample data. */
        if (!inc->started) {
                std_session_send_df_header(in->sdi);

                samplerate = inc->samplerate / inc->options.downsample;
                if (samplerate) {
                        gvar = g_variant_new_uint64(samplerate);
                        sr_session_send_meta(in->sdi, SR_CONF_SAMPLERATE, gvar);
                }

                inc->started = TRUE;
        }

        /*
         * Workaround broken generators which output incomplete text
         * lines. Enforce the trailing line feed. Proper input is not
         * harmed by another empty line of input data.
         */
        if (is_eof)
                g_string_append_c(in->buf, '\n');

        /* Find and process complete text lines in the input data. */
        ret = SR_OK;
        rdptr = in->buf->str;
        while (TRUE) {
                rdlen = &in->buf->str[in->buf->len] - rdptr;
                endptr = g_strstr_len(rdptr, rdlen, "\n");
                if (!endptr)
                        break;
                trimptr = endptr;
                *endptr++ = '\0';
                while (g_ascii_isspace(*rdptr))
                        rdptr++;
                while (trimptr > rdptr && g_ascii_isspace(trimptr[-1]))
                        *(--trimptr) = '\0';
                if (!*rdptr) {
                        rdptr = endptr;
                        continue;
                }
                ret = parse_textline(in, rdptr);
                rdptr = endptr;
                if (ret != SR_OK)
                        break;
        }
        rdlen = rdptr - in->buf->str;
        g_string_erase(in->buf, 0, rdlen);

        return ret;
}

static int format_match(GHashTable *metadata, unsigned int *confidence)
{
        GString *buf, *tmpbuf;
        gboolean status;
        char *name, *contents;

        buf = g_hash_table_lookup(metadata,
                GINT_TO_POINTER(SR_INPUT_META_HEADER));
        tmpbuf = g_string_new_len(buf->str, buf->len);

        /*
         * If we can parse the first section correctly, then it is
         * assumed that the input is in VCD format.
         */
        check_remove_bom(tmpbuf);
        status = parse_section(tmpbuf, &name, &contents);
        g_string_free(tmpbuf, TRUE);
        g_free(name);
        g_free(contents);

        if (!status)
                return SR_ERR;

        *confidence = 1;
        return SR_OK;
}

static int init(struct sr_input *in, GHashTable *options)
{
        struct context *inc;
        GVariant *data;

        inc = g_malloc0(sizeof(*inc));

        data = g_hash_table_lookup(options, "numchannels");
        inc->options.maxchannels = g_variant_get_uint32(data);

        data = g_hash_table_lookup(options, "downsample");
        inc->options.downsample = g_variant_get_uint64(data);
        if (inc->options.downsample < 1)
                inc->options.downsample = 1;

        data = g_hash_table_lookup(options, "compress");
        inc->options.compress = g_variant_get_uint64(data);
        inc->options.compress /= inc->options.downsample;

        data = g_hash_table_lookup(options, "skip");
        if (data) {
                inc->options.skip_specified = TRUE;
                inc->options.skip_starttime = g_variant_get_uint64(data);
                if (inc->options.skip_starttime == ~UINT64_C(0)) {
                        inc->options.skip_specified = FALSE;
                        inc->options.skip_starttime = 0;
                }
                inc->options.skip_starttime /= inc->options.downsample;
        }

        in->sdi = g_malloc0(sizeof(*in->sdi));
        in->priv = inc;

        inc->scope_prefix = g_string_new("\0");

        return SR_OK;
}

static int receive(struct sr_input *in, GString *buf)
{
        struct context *inc;
        int ret;

        inc = in->priv;

        /* Collect all input chunks, potential deferred processing. */
        g_string_append_len(in->buf, buf->str, buf->len);
        if (!inc->got_header && in->buf->len == buf->len)
                check_remove_bom(in->buf);

        /* Must complete reception of the VCD header first. */
        if (!inc->got_header) {
                if (!have_header(in->buf))
                        return SR_OK;
                ret = parse_header(in, in->buf);
                if (ret != SR_OK)
                        return ret;
                /* sdi is ready, notify frontend. */
                in->sdi_ready = TRUE;
                return SR_OK;
        }

        /* Process sample data. */
        ret = process_buffer(in, FALSE);

        return ret;
}

static int end(struct sr_input *in)
{
        struct context *inc;
        int ret;
        size_t count;

        inc = in->priv;

        /* Must complete processing of previously received chunks. */
        if (in->sdi_ready)
                ret = process_buffer(in, TRUE);
        else
                ret = SR_OK;

        /* Flush most recently queued sample data when EOF is seen. */
        if (inc->got_header && ret == SR_OK) {
                count = inc->data_after_timestamp ? 1 : 0;
                add_samples(in, count, TRUE);
        }

        /* Optionally suggest downsampling after all input data was seen. */
        if (inc->got_header)
                (void)ts_stats_post(inc, !inc->data_after_timestamp);

        /* Must send DF_END when DF_HEADER was sent before. */
        if (inc->started)
                std_session_send_df_end(in->sdi);

        return ret;
}

static void cleanup(struct sr_input *in)
{
        struct context *inc;

        inc = in->priv;

        keep_header_for_reread(in);

        g_slist_free_full(inc->channels, free_channel);
        inc->channels = NULL;
        feed_queue_logic_free(inc->feed_logic);
        inc->feed_logic = NULL;
        g_free(inc->conv_bits.value);
        inc->conv_bits.value = NULL;
        g_free(inc->current_logic);
        inc->current_logic = NULL;
        g_free(inc->current_floats);
        inc->current_floats = NULL;
        g_string_free(inc->scope_prefix, TRUE);
        inc->scope_prefix = NULL;
        g_slist_free_full(inc->ignored_signals, g_free);
        inc->ignored_signals = NULL;
        free_text_split(inc, NULL);
}

static int reset(struct sr_input *in)
{
        struct context *inc;
        struct vcd_user_opt save;
        struct vcd_prev prev;

        inc = in->priv;

        /* Relase previously allocated resources. */
        cleanup(in);
        g_string_truncate(in->buf, 0);

        /* Restore part of the context, init() won't run again. */
        save = inc->options;
        prev = inc->prev;
        memset(inc, 0, sizeof(*inc));
        inc->options = save;
        inc->prev = prev;
        inc->scope_prefix = g_string_new("\0");

        return SR_OK;
}

enum vcd_option_t {
        OPT_NUM_CHANS,
        OPT_DOWN_SAMPLE,
        OPT_SKIP_COUNT,
        OPT_COMPRESS,
        OPT_MAX,
};

static struct sr_option options[] = {
        [OPT_NUM_CHANS] = {
                "numchannels", "Max number of sigrok channels",
                "The maximum number of sigrok channels to create for VCD input signals.",
                NULL, NULL,
        },
        [OPT_DOWN_SAMPLE] = {
                "downsample", "Downsampling factor",
                "Downsample the input file's samplerate, i.e. divide by the specified factor.",
                NULL, NULL,
        },
        [OPT_SKIP_COUNT] = {
                "skip", "Skip this many initial samples",
                "Skip samples until the specified timestamp. "
                "By default samples start at the first timestamp in the file. "
                "Value 0 creates samples starting at timestamp 0. "
                "Values above 0 only start processing at the given timestamp.",
                NULL, NULL,
        },
        [OPT_COMPRESS] = {
                "compress", "Compress idle periods",
                "Compress idle periods which are longer than the specified number of timescale ticks.",
                NULL, NULL,
        },
        [OPT_MAX] = ALL_ZERO,
};

static const struct sr_option *get_options(void)
{
        if (!options[0].def) {
                options[OPT_NUM_CHANS].def = g_variant_ref_sink(g_variant_new_uint32(0));
                options[OPT_DOWN_SAMPLE].def = g_variant_ref_sink(g_variant_new_uint64(1));
                options[OPT_SKIP_COUNT].def = g_variant_ref_sink(g_variant_new_uint64(~UINT64_C(0)));
                options[OPT_COMPRESS].def = g_variant_ref_sink(g_variant_new_uint64(0));
        }

        return options;
}

SR_PRIV struct sr_input_module input_vcd = {
        .id = "vcd",
        .name = "VCD",
        .desc = "Value Change Dump data",
        .exts = (const char*[]){"vcd", NULL},
        .metadata = { SR_INPUT_META_HEADER | SR_INPUT_META_REQUIRED },
        .options = get_options,
        .format_match = format_match,
        .init = init,
        .receive = receive,
        .end = end,
        .cleanup = cleanup,
        .reset = reset,
};