input/csv: update TODO comments

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

/*
 * This file is part of the libsigrok project.
 *
 * Copyright (C) 2013 Marc Schink <sigrok-dev@marcschink.de>
 * Copyright (C) 2019 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/>.
 */

#include "config.h"

#include <glib.h>
#include <stdlib.h>
#include <string.h>

#include <libsigrok/libsigrok.h>
#include "libsigrok-internal.h"
#include "scpi.h"       /* String un-quote for channel name from header line. */

#define LOG_PREFIX "input/csv"

#define CHUNK_SIZE      (4 * 1024 * 1024)

/*
 * The CSV input module has the following options:
 *
 * column_formats: Specifies the data formats and channel counts for the
 *     input file's text columns. Accepts a comma separated list of tuples
 *     with: an optional column repeat count ('*' as a wildcard meaning
 *     "all remaining columns", only applicable to the last field), a format
 *     specifying character ('x' hexadecimal, 'o' octal, 'b' binary, 'l'
 *     single-bit logic), and an optional bit count (translating to: logic
 *     channels communicated in that column). This "column_formats" option
 *     is most versatile, other forms of specifying the column layout only
 *     exist for backwards compatibility.
 *
 * single_column: Specifies the column number which contains the logic data
 *     for single-column mode. All logic data is taken from several bits
 *     which all are kept within that one column. Only exists for backwards
 *     compatibility, see "column_formats" for more flexibility.
 *
 * first_column: Specifies the number of the first column with logic data
 *     in simple multi-column mode. Only exists for backwards compatibility,
 *     see "column_formats" for more flexibility.
 *
 * logic_channels: Specifies the number of logic channels. Is required in
 *     simple single-column mode. Is optional in simple multi-column mode
 *     (and defaults to all remaining columns). Only exists for backwards
 *     compatibility, see "column_formats" for more flexibility.
 *
 * single_format: Specifies the format of the input text in simple single-
 *     column mode. Available formats are: 'bin' (default), 'hex' and 'oct'.
 *     Simple multi-column mode always uses single-bit data per column.
 *     Only exists for backwards compatibility, see "column_formats" for
 *     more flexibility.
 *
 * start_line: Specifies at which line to start processing the input file.
 *     Allows to skip leading lines which neither are header nor data lines.
 *     By default all of the input file gets processed.
 *
 * header: Boolean option, controls whether the first processed line is used
 *     to determine channel names. Off by default. Generic channel names are
 *     used in the absence of header line content.
 *
 * samplerate: Specifies the samplerate of the input data. Defaults to 0.
 *     User specs take precedence over data which optionally gets derived
 *     from input data.
 *
 * column_separator: Specifies the sequence which separates the text file
 *     columns. Cannot be empty. Defaults to comma.
 *
 * comment_leader: Specifies the sequence which starts comments that run
 *     up to the end of the current text line. Can be empty to disable
 *     comment support. Defaults to semicolon.
 *
 * Typical examples of using these options:
 * - ... -I csv:column_formats=*l ...
 *   All columns are single-bit logic data. Identical to the previous
 *   multi-column mode (the default when no options were given at all).
 * - ... -I csv:column_formats=3-,*l ...
 *   Ignore the first three columns, get single-bit logic data from all
 *   remaining lines (multi-column mode with first-column above 1).
 * - ... -I csv:column_formats=3-,4l,x8 ...
 *   Ignore the first three columns, get single-bit logic data from the
 *   next four columns, then eight-bit data in hex format from the next
 *   column. More columns may follow in the input text but won't get
 *   processed. (Mix of previous multi-column as well as single-column
 *   modes.)
 * - ... -I csv:column_formats=4x8,b16,5l ...
 *   Get eight-bit data in hex format from the first four columns, then
 *   sixteen-bit data in binary format, then five times single-bit data.
 * - ... -I csv:single_column=2:single_format=bin:logic_channels=8 ...
 *   Get eight logic bits in binary format from column 2. (Simple
 *   single-column mode, corresponds to the "-,b8" format.)
 * - ... -I csv:first_column=6:logic_channels=4 ...
 *   Get four single-bit logic channels from columns 6 to 9 respectively.
 *   (Simple multi-column mode, corresponds to the "5-,4b" format.)
 * - ... -I csv:start_line=20:header=yes:...
 *   Skip the first 19 text lines. Use line 20 to derive channel names.
 *   Data starts at line 21.
 */

/*
 * TODO
 *
 * - Add support for analog input data? (optional)
 *   - Extend the set of supported column types. Just grab a double
 *     value from floating point format input text.
 *   - Optionally get precision ('digits') from the column's format spec?
 *     From the position which is "bit count" for logic channels?
 * - Optionally get sample rate from timestamp column. Just best-effort
 *   approach, not necessarily reliable. Users can always specify rates.
 * - Add a test suite for input modules in general, and CSV in specific?
 *   Becomes more important with the multitude of options and their
 *   interaction. Could cover edge cases (BOM presence, line termination
 *   absence, etc) and auto-stuff as well (channel names, channel counts,
 *   samplerates, etc).
 */

/* Single column formats. */
enum single_col_format {
        FORMAT_NONE,    /* Ignore this column. */
        FORMAT_BIN,     /* Bin digits for a set of bits (or just one bit). */
        FORMAT_HEX,     /* Hex digits for a set of bits. */
        FORMAT_OCT,     /* Oct digits for a set of bits. */
};

static const char *col_format_text[] = {
        [FORMAT_NONE] = "unknown",
        [FORMAT_BIN] = "binary",
        [FORMAT_HEX] = "hexadecimal",
        [FORMAT_OCT] = "octal",
};

static const char col_format_char[] = {
        [FORMAT_NONE] = '?',
        [FORMAT_BIN] = 'b',
        [FORMAT_HEX] = 'x',
        [FORMAT_OCT] = 'o',
};

struct column_details {
        size_t col_nr;
        enum single_col_format text_format;
        size_t channel_offset;
        size_t channel_count;
};

struct context {
        gboolean started;

        /* Current selected samplerate. */
        uint64_t samplerate;
        gboolean samplerate_sent;

        /* Number of logic channels. */
        size_t logic_channels;

        /* Column delimiter (actually separator), comment leader, EOL sequence. */
        GString *delimiter;
        GString *comment;
        char *termination;

        /* Format specs for input columns, and processing state. */
        size_t column_seen_count;
        const char *column_formats;
        size_t column_want_count;
        struct column_details *column_details;

        /* Line number to start processing. */
        size_t start_line;

        /*
         * Determines if the first line should be treated as header and used for
         * channel names in multi column mode.
         */
        gboolean use_header;
        gboolean header_seen;

        size_t sample_unit_size;        /**!< Byte count for a single sample. */
        uint8_t *sample_buffer;         /**!< Buffer for a single sample. */

        uint8_t *datafeed_buffer;       /**!< Queue for datafeed submission. */
        size_t datafeed_buf_size;
        size_t datafeed_buf_fill;

        /* Current line number. */
        size_t line_number;

        /* List of previously created sigrok channels. */
        GSList *prev_sr_channels;
};

/*
 * Primitive operations to handle sample sets:
 * - Keep a buffer for datafeed submission, capable of holding many
 *   samples (reduces call overhead, improves throughput).
 * - Have a "current sample set" pointer reference one position in that
 *   large samples buffer.
 * - Clear the current sample set before text line inspection, then set
 *   the bits which are found active in the current line of text input.
 *   Phrase the API such that call sites can be kept simple. Advance to
 *   the next sample set between lines, flush the larger buffer as needed
 *   (when it is full, or upon EOF).
 */

static void clear_logic_samples(struct context *inc)
{
        inc->sample_buffer = &inc->datafeed_buffer[inc->datafeed_buf_fill];
        memset(inc->sample_buffer, 0, inc->sample_unit_size);
}

static void set_logic_level(struct context *inc, size_t ch_idx, int on)
{
        size_t byte_idx, bit_idx;
        uint8_t bit_mask;

        if (ch_idx >= inc->logic_channels)
                return;
        if (!on)
                return;

        byte_idx = ch_idx / 8;
        bit_idx = ch_idx % 8;
        bit_mask = 1 << bit_idx;
        inc->sample_buffer[byte_idx] |= bit_mask;
}

static int flush_logic_samples(const struct sr_input *in)
{
        struct context *inc;
        struct sr_datafeed_packet packet;
        struct sr_datafeed_meta meta;
        struct sr_config *src;
        uint64_t samplerate;
        struct sr_datafeed_logic logic;
        int rc;

        inc = in->priv;
        if (!inc->datafeed_buf_fill)
                return SR_OK;

        if (inc->samplerate && !inc->samplerate_sent) {
                packet.type = SR_DF_META;
                packet.payload = &meta;
                samplerate = inc->samplerate;
                src = sr_config_new(SR_CONF_SAMPLERATE, g_variant_new_uint64(samplerate));
                meta.config = g_slist_append(NULL, src);
                sr_session_send(in->sdi, &packet);
                g_slist_free(meta.config);
                sr_config_free(src);
                inc->samplerate_sent = TRUE;
        }

        memset(&packet, 0, sizeof(packet));
        memset(&logic, 0, sizeof(logic));
        packet.type = SR_DF_LOGIC;
        packet.payload = &logic;
        logic.unitsize = inc->sample_unit_size;
        logic.length = inc->datafeed_buf_fill;
        logic.data = inc->datafeed_buffer;

        rc = sr_session_send(in->sdi, &packet);
        if (rc != SR_OK)
                return rc;

        inc->datafeed_buf_fill = 0;
        return SR_OK;
}

static int queue_logic_samples(const struct sr_input *in)
{
        struct context *inc;
        int rc;

        inc = in->priv;
        if (!inc->logic_channels)
                return SR_OK;

        inc->datafeed_buf_fill += inc->sample_unit_size;
        if (inc->datafeed_buf_fill == inc->datafeed_buf_size) {
                rc = flush_logic_samples(in);
                if (rc != SR_OK)
                        return rc;
        }
        return SR_OK;
}

/* Helpers for "column processing". */

static int split_column_format(const char *spec,
        size_t *column_count, enum single_col_format *format, size_t *bit_count)
{
        size_t count;
        char *endp, format_char;
        enum single_col_format format_code;

        if (!spec || !*spec)
                return SR_ERR_ARG;

        /* Get the (optional, decimal, default 1) column count. Accept '*'. */
        endp = NULL;
        if (*spec == '*') {
                count = 0;
                endp = (char *)&spec[1];
        } else {
                count = strtoul(spec, &endp, 10);
        }
        if (!endp)
                return SR_ERR_ARG;
        if (endp == spec)
                count = 1;
        if (column_count)
                *column_count = count;
        spec = endp;

        /* Get the (mandatory, single letter) type spec (-/xob/l). */
        format_char = *spec++;
        switch (format_char) {
        case '-':       /* Might conflict with number-parsing. */
        case '/':
                format_char = '-';
                format_code = FORMAT_NONE;
                break;
        case 'x':
                format_code = FORMAT_HEX;
                break;
        case 'o':
                format_code = FORMAT_OCT;
                break;
        case 'b':
        case 'l':
                format_code = FORMAT_BIN;
                break;
        default:        /* includes NUL */
                return SR_ERR_ARG;
        }
        if (format)
                *format = format_code;

        /* Get the (optional, decimal, default 1) bit count. */
        endp = NULL;
        count = strtoul(spec, &endp, 10);
        if (!endp)
                return SR_ERR_ARG;
        if (endp == spec)
                count = 1;
        if (format_char == '-')
                count = 0;
        if (format_char == 'l')
                count = 1;
        if (bit_count)
                *bit_count = count;
        spec = endp;

        /* Input spec must have been exhausted. */
        if (*spec)
                return SR_ERR_ARG;

        return SR_OK;
}

static int make_column_details_from_format(struct context *inc,
        const char *column_format)
{
        char **formats, *format;
        size_t format_count, column_count, bit_count;
        size_t auto_column_count;
        size_t format_idx, c, b, column_idx, channel_idx;
        enum single_col_format f;
        struct column_details *detail;
        int ret;

        /* Split the input spec, count involved columns and bits. */
        formats = g_strsplit(column_format, ",", 0);
        if (!formats) {
                sr_err("Cannot parse columns format %s (comma split).", column_format);
                return SR_ERR_ARG;
        }
        format_count = g_strv_length(formats);
        if (!format_count) {
                sr_err("Cannot parse columns format %s (field count).", column_format);
                g_strfreev(formats);
                return SR_ERR_ARG;
        }
        column_count = bit_count = 0;
        auto_column_count = 0;
        for (format_idx = 0; format_idx < format_count; format_idx++) {
                format = formats[format_idx];
                ret = split_column_format(format, &c, &f, &b);
                sr_dbg("fmt %s -> %zu cols, %s fmt, %zu bits, rc %d", format, c, col_format_text[f], b, ret);
                if (ret != SR_OK) {
                        sr_err("Cannot parse columns format %s (field split, %s).", column_format, format);
                        g_strfreev(formats);
                        return SR_ERR_ARG;
                }
                if (f && !c) {
                        /* User requested "auto-count", must be last format. */
                        if (formats[format_idx + 1]) {
                                sr_err("Auto column count must be last format field.");
                                g_strfreev(formats);
                                return SR_ERR_ARG;
                        }
                        auto_column_count = inc->column_seen_count - column_count;
                        c = auto_column_count;
                }
                column_count += c;
                bit_count += c * b;
        }
        sr_dbg("Column format %s -> %zu columns, %zu logic channels.",
                column_format, column_count, bit_count);

        /* Allocate and fill in "column processing" details. */
        inc->column_want_count = column_count;
        inc->column_details = g_malloc0_n(column_count, sizeof(inc->column_details[0]));
        column_idx = channel_idx = 0;
        for (format_idx = 0; format_idx < format_count; format_idx++) {
                format = formats[format_idx];
                (void)split_column_format(format, &c, &f, &b);
                if (f && !c)
                        c = auto_column_count;
                while (c-- > 0) {
                        detail = &inc->column_details[column_idx++];
                        detail->col_nr = column_idx;
                        detail->text_format = f;
                        if (detail->text_format) {
                                detail->channel_offset = channel_idx;
                                detail->channel_count = b;
                                channel_idx += b;
                        }
                        sr_dbg("detail -> col %zu, fmt %s, ch off/cnt %zu/%zu",
                                detail->col_nr, col_format_text[detail->text_format],
                                detail->channel_offset, detail->channel_count);
                }
        }
        inc->logic_channels = channel_idx;
        g_strfreev(formats);

        return SR_OK;
}

static const struct column_details *lookup_column_details(struct context *inc, size_t nr)
{
        if (!inc || !inc->column_details)
                return NULL;
        if (!nr || nr > inc->column_want_count)
                return NULL;
        return &inc->column_details[nr - 1];
}

/*
 * Primitive operations for text input: Strip comments off text lines.
 * Split text lines into columns. Process input text for individual
 * columns.
 */

static void strip_comment(char *buf, const GString *prefix)
{
        char *ptr;

        if (!prefix->len)
                return;

        if ((ptr = strstr(buf, prefix->str))) {
                *ptr = '\0';
                g_strstrip(buf);
        }
}

/**
 * @brief Splits a text line into a set of columns.
 *
 * @param[in] buf       The input text line to split.
 * @param[in] inc       The input module's context.
 *
 * @returns An array of strings, representing the columns' text.
 *
 * This routine splits a text line on previously determined separators.
 */
static char **split_line(char *buf, struct context *inc)
{
        return g_strsplit(buf, inc->delimiter->str, 0);
}

/**
 * @brief Parse a multi-bit field into several logic channels.
 *
 * @param[in] column    The input text, a run of bin/hex/oct digits.
 * @param[in] inc       The input module's context.
 * @param[in] details   The column processing details.
 *
 * @retval SR_OK        Success.
 * @retval SR_ERR       Invalid input data (empty, or format error).
 *
 * This routine modifies the logic levels in the current sample set,
 * based on the text input and a user provided format spec.
 */
static int parse_logic(const char *column, struct context *inc,
        const struct column_details *details)
{
        size_t length, ch_rem, ch_idx, ch_inc;
        const char *rdptr;
        char c;
        gboolean valid;
        const char *type_text;
        uint8_t bits;

        /*
         * Prepare to read the digits from the text end towards the start.
         * A digit corresponds to a variable number of channels (depending
         * on the value's radix). Prepare the mapping of text digits to
         * (a number of) logic channels.
         */
        length = strlen(column);
        if (!length) {
                sr_err("Column %zu in line %zu is empty.", details->col_nr,
                        inc->line_number);
                return SR_ERR;
        }
        rdptr = &column[length];
        ch_idx = details->channel_offset;
        ch_rem = details->channel_count;

        /*
         * Get another digit and derive up to four logic channels' state from
         * it. Make sure to not process more bits than the column has channels
         * associated with it.
         */
        while (rdptr > column && ch_rem) {
                /* Check for valid digits according to the input radix. */
                c = *(--rdptr);
                switch (details->text_format) {
                case FORMAT_BIN:
                        valid = g_ascii_isxdigit(c) && c < '2';
                        ch_inc = 1;
                        break;
                case FORMAT_OCT:
                        valid = g_ascii_isxdigit(c) && c < '8';
                        ch_inc = 3;
                        break;
                case FORMAT_HEX:
                        valid = g_ascii_isxdigit(c);
                        ch_inc = 4;
                        break;
                default:
                        valid = FALSE;
                        break;
                }
                if (!valid) {
                        type_text = col_format_text[details->text_format];
                        sr_err("Invalid text '%s' in %s type column %zu in line %zu.",
                                column, type_text, details->col_nr, inc->line_number);
                        return SR_ERR;
                }
                /* Use the digit's bits for logic channels' data. */
                bits = g_ascii_xdigit_value(c);
                switch (details->text_format) {
                case FORMAT_HEX:
                        if (ch_rem >= 4) {
                                ch_rem--;
                                set_logic_level(inc, ch_idx + 3, bits & (1 << 3));
                        }
                        /* FALLTHROUGH */
                case FORMAT_OCT:
                        if (ch_rem >= 3) {
                                ch_rem--;
                                set_logic_level(inc, ch_idx + 2, bits & (1 << 2));
                        }
                        if (ch_rem >= 2) {
                                ch_rem--;
                                set_logic_level(inc, ch_idx + 1, bits & (1 << 1));
                        }
                        /* FALLTHROUGH */
                case FORMAT_BIN:
                        ch_rem--;
                        set_logic_level(inc, ch_idx + 0, bits & (1 << 0));
                        break;
                case FORMAT_NONE:
                        /* ShouldNotHappen(TM), but silences compiler warning. */
                        return SR_ERR;
                }
                ch_idx += ch_inc;
        }
        /*
         * TODO Determine whether the availability of extra input data
         * for unhandled logic channels is worth warning here. In this
         * implementation users are in control, and can have the more
         * significant bits ignored (which can be considered a feature
         * and not really a limitation).
         */

        return SR_OK;
}

/**
 * @brief Parse routine which ignores the input text.
 *
 * This routine exists to unify dispatch code paths, mapping input file
 * columns' data types to their respective parse routines.
 */
static int parse_ignore(const char *column, struct context *inc,
        const struct column_details *details)
{
        (void)column;
        (void)inc;
        (void)details;
        return SR_OK;
}

typedef int (*col_parse_cb)(const char *column, struct context *inc,
        const struct column_details *details);

static const col_parse_cb col_parse_funcs[] = {
        [FORMAT_NONE] = parse_ignore,
        [FORMAT_BIN] = parse_logic,
        [FORMAT_OCT] = parse_logic,
        [FORMAT_HEX] = parse_logic,
};

static int init(struct sr_input *in, GHashTable *options)
{
        struct context *inc;
        size_t single_column, first_column, logic_channels;
        const char *s;
        enum single_col_format format;
        char format_char;

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

        single_column = g_variant_get_uint32(g_hash_table_lookup(options, "single_column"));

        logic_channels = g_variant_get_uint32(g_hash_table_lookup(options, "logic_channels"));

        inc->delimiter = g_string_new(g_variant_get_string(
                        g_hash_table_lookup(options, "column_separator"), NULL));
        if (!inc->delimiter->len) {
                sr_err("Column separator cannot be empty.");
                return SR_ERR_ARG;
        }

        s = g_variant_get_string(g_hash_table_lookup(options, "single_format"), NULL);
        if (g_ascii_strncasecmp(s, "bin", 3) == 0) {
                format = FORMAT_BIN;
        } else if (g_ascii_strncasecmp(s, "hex", 3) == 0) {
                format = FORMAT_HEX;
        } else if (g_ascii_strncasecmp(s, "oct", 3) == 0) {
                format = FORMAT_OCT;
        } else {
                sr_err("Invalid single-column format: '%s'", s);
                return SR_ERR_ARG;
        }

        inc->comment = g_string_new(g_variant_get_string(
                        g_hash_table_lookup(options, "comment_leader"), NULL));
        if (g_string_equal(inc->comment, inc->delimiter)) {
                /*
                 * Using the same sequence as comment leader and column
                 * separator won't work. The user probably specified ';'
                 * as the column separator but did not adjust the comment
                 * leader. Try DWIM, drop comment strippin support here.
                 */
                sr_warn("Comment leader and column separator conflict, disabling comment support.");
                g_string_truncate(inc->comment, 0);
        }

        inc->samplerate = g_variant_get_uint64(g_hash_table_lookup(options, "samplerate"));

        first_column = g_variant_get_uint32(g_hash_table_lookup(options, "first_column"));

        inc->use_header = g_variant_get_boolean(g_hash_table_lookup(options, "header"));

        inc->start_line = g_variant_get_uint32(g_hash_table_lookup(options, "start_line"));
        if (inc->start_line < 1) {
                sr_err("Invalid start line %zu.", inc->start_line);
                return SR_ERR_ARG;
        }

        /*
         * Scan flexible, to get prefered format specs which describe
         * the input file's data formats. As well as some simple specs
         * for backwards compatibility and user convenience.
         *
         * This logic ends up with a copy of the format string, either
         * user provided or internally derived. Actual creation of the
         * column processing details gets deferred until the first line
         * of input data was seen. To support automatic determination of
         * e.g. channel counts from column counts.
         */
        s = g_variant_get_string(g_hash_table_lookup(options, "column_formats"), NULL);
        if (s && *s) {
                inc->column_formats = g_strdup(s);
                sr_dbg("User specified column_formats: %s.", s);
        } else if (single_column && logic_channels) {
                format_char = col_format_char[format];
                if (single_column == 1) {
                        inc->column_formats = g_strdup_printf("%c%zu",
                                format_char, logic_channels);
                } else {
                        inc->column_formats = g_strdup_printf("%zu-,%c%zu",
                                single_column - 1,
                                format_char, logic_channels);
                }
                sr_dbg("Backwards compat single_column, col %zu, fmt %s, bits %zu -> %s.",
                        single_column, col_format_text[format], logic_channels,
                        inc->column_formats);
        } else if (!single_column) {
                if (first_column > 1) {
                        inc->column_formats = g_strdup_printf("%zu-,%zul",
                                first_column - 1, logic_channels);
                } else {
                        inc->column_formats = g_strdup_printf("%zul",
                                logic_channels);
                }
                sr_dbg("Backwards compat multi-column, col %zu, chans %zu -> %s.",
                        first_column, logic_channels,
                        inc->column_formats);
        } else {
                sr_warn("Unknown or unsupported columns layout spec, assuming simple multi-column mode.");
                inc->column_formats = g_strdup("*l");
        }

        return SR_OK;
}

/*
 * Check the channel list for consistency across file re-import. See
 * the VCD input module for more details and motivation.
 */

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

        inc = in->priv;
        g_slist_free_full(inc->prev_sr_channels, sr_channel_free_cb);
        inc->prev_sr_channels = in->sdi->channels;
        in->sdi->channels = NULL;
}

static int 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->channels, sr_channel_free_cb);
        in->sdi->channels = inc->prev_sr_channels;
        inc->prev_sr_channels = NULL;

        return TRUE;
}

static const char *delim_set = "\r\n";

static const char *get_line_termination(GString *buf)
{
        const char *term;

        term = NULL;
        if (g_strstr_len(buf->str, buf->len, "\r\n"))
                term = "\r\n";
        else if (memchr(buf->str, '\n', buf->len))
                term = "\n";
        else if (memchr(buf->str, '\r', buf->len))
                term = "\r";

        return term;
}

static int initial_parse(const struct sr_input *in, GString *buf)
{
        struct context *inc;
        GString *channel_name;
        size_t num_columns, ch_idx, ch_name_idx, col_idx, col_nr;
        size_t line_number, line_idx;
        int ret;
        char **lines, *line, **columns, *column;
        const char *col_caption;
        gboolean got_caption;
        const struct column_details *detail;

        ret = SR_OK;
        inc = in->priv;
        columns = NULL;

        line_number = 0;
        if (inc->termination)
                lines = g_strsplit(buf->str, inc->termination, 0);
        else
                lines = g_strsplit_set(buf->str, delim_set, 0);
        for (line_idx = 0; (line = lines[line_idx]); line_idx++) {
                line_number++;
                if (inc->start_line > line_number) {
                        sr_spew("Line %zu skipped (before start).", line_number);
                        continue;
                }
                if (line[0] == '\0') {
                        sr_spew("Blank line %zu skipped.", line_number);
                        continue;
                }
                strip_comment(line, inc->comment);
                if (line[0] == '\0') {
                        sr_spew("Comment-only line %zu skipped.", line_number);
                        continue;
                }

                /* Reached first proper line. */
                break;
        }
        if (!line) {
                /* Not enough data for a proper line yet. */
                ret = SR_ERR_NA;
                goto out;
        }

        /* See how many columns the current line has. */
        columns = split_line(line, inc);
        if (!columns) {
                sr_err("Error while parsing line %zu.", line_number);
                ret = SR_ERR;
                goto out;
        }
        num_columns = g_strv_length(columns);
        if (!num_columns) {
                sr_err("Error while parsing line %zu.", line_number);
                ret = SR_ERR;
                goto out;
        }
        sr_dbg("DIAG Got %zu columns in text line: %s.", num_columns, line);

        /*
         * Track the observed number of columns in the input file. Do
         * process the previously gathered columns format spec now that
         * automatic channel count can be dealt with.
         */
        inc->column_seen_count = num_columns;
        ret = make_column_details_from_format(inc, inc->column_formats);
        if (ret != SR_OK) {
                sr_err("Cannot parse columns format using line %zu.", line_number);
                goto out;
        }

        /*
         * Assume all lines have equal length (column count). Bail out
         * early on suspicious or insufficient input data (check input
         * which became available here against previous user specs or
         * auto-determined properties, regardless of layout variant).
         */
        if (num_columns < inc->column_want_count) {
                sr_err("Insufficient input text width for desired data amount, got %zu but want %zu columns.",
                        num_columns, inc->column_want_count);
                ret = SR_ERR;
                goto out;
        }

        /*
         * Determine channel names. Optionally use text from a header
         * line (when requested by the user, and only works in multi
         * column mode). In the absence of header text, or in single
         * column mode, channels are assigned rather generic names.
         *
         * Manipulation of the column's caption is acceptable here, the
         * header line will never get processed another time.
         */
        channel_name = g_string_sized_new(64);
        for (col_idx = 0; col_idx < inc->column_want_count; col_idx++) {

                col_nr = col_idx + 1;
                detail = lookup_column_details(inc, col_nr);
                if (detail->text_format == FORMAT_NONE)
                        continue;
                column = columns[col_idx];
                col_caption = sr_scpi_unquote_string(column);
                got_caption = inc->use_header && *col_caption;
                sr_dbg("DIAG col %zu, ch count %zu, text %s.",
                        col_nr, detail->channel_count, col_caption);
                for (ch_idx = 0; ch_idx < detail->channel_count; ch_idx++) {
                        ch_name_idx = detail->channel_offset + ch_idx;
                        if (got_caption && detail->channel_count == 1)
                                g_string_assign(channel_name, col_caption);
                        else if (got_caption)
                                g_string_printf(channel_name, "%s[%zu]",
                                        col_caption, ch_idx);
                        else
                                g_string_printf(channel_name, "%zu", ch_name_idx);
                        sr_dbg("DIAG ch idx %zu, name %s.", ch_name_idx, channel_name->str);
                        sr_channel_new(in->sdi, ch_name_idx, SR_CHANNEL_LOGIC, TRUE,
                                channel_name->str);
                }
        }
        g_string_free(channel_name, TRUE);
        if (!check_header_in_reread(in)) {
                ret = SR_ERR_DATA;
                goto out;
        }

        /*
         * Calculate the minimum buffer size to store the set of samples
         * of all channels (unit size). Determine a larger buffer size
         * for datafeed submission that is a multiple of the unit size.
         * Allocate the larger buffer, the "sample buffer" will point
         * to a location within that large buffer later.
         */
        inc->sample_unit_size = (inc->logic_channels + 7) / 8;
        inc->datafeed_buf_size = CHUNK_SIZE;
        inc->datafeed_buf_size *= inc->sample_unit_size;
        inc->datafeed_buffer = g_malloc(inc->datafeed_buf_size);
        inc->datafeed_buf_fill = 0;

out:
        if (columns)
                g_strfreev(columns);
        g_strfreev(lines);

        return ret;
}

/*
 * Gets called from initial_receive(), which runs until the end-of-line
 * encoding of the input stream could get determined. Assumes that this
 * routine receives enough buffered initial input data to either see the
 * BOM when there is one, or that no BOM will follow when a text line
 * termination sequence was seen. Silently drops the UTF-8 BOM sequence
 * from the input buffer if one was seen. Does not care to protect
 * against multiple execution or dropping the BOM multiple times --
 * there should be at most one in the input stream.
 */
static void initial_bom_check(const struct sr_input *in)
{
        static const char *utf8_bom = "\xef\xbb\xbf";

        if (in->buf->len < strlen(utf8_bom))
                return;
        if (strncmp(in->buf->str, utf8_bom, strlen(utf8_bom)) != 0)
                return;
        g_string_erase(in->buf, 0, strlen(utf8_bom));
}

static int initial_receive(const struct sr_input *in)
{
        struct context *inc;
        GString *new_buf;
        int len, ret;
        char *p;
        const char *termination;

        initial_bom_check(in);

        inc = in->priv;

        termination = get_line_termination(in->buf);
        if (!termination)
                /* Don't have a full line yet. */
                return SR_ERR_NA;

        p = g_strrstr_len(in->buf->str, in->buf->len, termination);
        if (!p)
                /* Don't have a full line yet. */
                return SR_ERR_NA;
        len = p - in->buf->str - 1;
        new_buf = g_string_new_len(in->buf->str, len);
        g_string_append_c(new_buf, '\0');

        inc->termination = g_strdup(termination);

        if (in->buf->str[0] != '\0')
                ret = initial_parse(in, new_buf);
        else
                ret = SR_OK;

        g_string_free(new_buf, TRUE);

        return ret;
}

static int process_buffer(struct sr_input *in, gboolean is_eof)
{
        struct context *inc;
        gsize num_columns;
        size_t line_idx, col_idx, col_nr;
        const struct column_details *details;
        col_parse_cb parse_func;
        int ret;
        char *p, **lines, *line, **columns, *column;

        inc = in->priv;
        if (!inc->started) {
                std_session_send_df_header(in->sdi);
                inc->started = TRUE;
        }

        /*
         * Consider empty input non-fatal. Keep accumulating input until
         * at least one full text line has become available. Grab the
         * maximum amount of accumulated data that consists of full text
         * lines, and process what has been received so far, leaving not
         * yet complete lines for the next invocation.
         *
         * Enforce that all previously buffered data gets processed in
         * the "EOF" condition. Do not insist in the presence of the
         * termination sequence for the last line (may often be missing
         * on Windows). A present termination sequence will just result
         * in the "execution of an empty line", and does not harm.
         */
        if (!in->buf->len)
                return SR_OK;
        if (is_eof) {
                p = in->buf->str + in->buf->len;
        } else {
                p = g_strrstr_len(in->buf->str, in->buf->len, inc->termination);
                if (!p)
                        return SR_ERR;
                *p = '\0';
                p += strlen(inc->termination);
        }
        g_strstrip(in->buf->str);

        ret = SR_OK;
        lines = g_strsplit(in->buf->str, inc->termination, 0);
        for (line_idx = 0; (line = lines[line_idx]); line_idx++) {
                inc->line_number++;
                if (inc->line_number < inc->start_line) {
                        sr_spew("Line %zu skipped (before start).", inc->line_number);
                        continue;
                }
                if (line[0] == '\0') {
                        sr_spew("Blank line %zu skipped.", inc->line_number);
                        continue;
                }

                /* Remove trailing comment. */
                strip_comment(line, inc->comment);
                if (line[0] == '\0') {
                        sr_spew("Comment-only line %zu skipped.", inc->line_number);
                        continue;
                }

                /* Skip the header line, its content was used as the channel names. */
                if (inc->use_header && !inc->header_seen) {
                        sr_spew("Header line %zu skipped.", inc->line_number);
                        inc->header_seen = TRUE;
                        continue;
                }

                /* Split the line into columns, check for minimum length. */
                columns = split_line(line, inc);
                if (!columns) {
                        sr_err("Error while parsing line %zu.", inc->line_number);
                        g_strfreev(lines);
                        return SR_ERR;
                }
                num_columns = g_strv_length(columns);
                if (num_columns < inc->column_want_count) {
                        sr_err("Insufficient column count %zu in line %zu.",
                                num_columns, inc->line_number);
                        g_strfreev(columns);
                        g_strfreev(lines);
                        return SR_ERR;
                }

                /* Have the columns of the current text line processed. */
                clear_logic_samples(inc);
                for (col_idx = 0; col_idx < inc->column_want_count; col_idx++) {
                        column = columns[col_idx];
                        col_nr = col_idx + 1;
                        details = lookup_column_details(inc, col_nr);
                        if (!details || !details->text_format)
                                continue;
                        parse_func = col_parse_funcs[details->text_format];
                        if (!parse_func)
                                continue;
                        ret = parse_func(column, inc, details);
                        if (ret != SR_OK) {
                                g_strfreev(columns);
                                g_strfreev(lines);
                                return SR_ERR;
                        }
                }

                /* Send sample data to the session bus (buffered). */
                ret = queue_logic_samples(in);
                if (ret != SR_OK) {
                        sr_err("Sending samples failed.");
                        g_strfreev(columns);
                        g_strfreev(lines);
                        return SR_ERR;
                }

                g_strfreev(columns);
        }
        g_strfreev(lines);
        g_string_erase(in->buf, 0, p - in->buf->str);

        return ret;
}

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

        g_string_append_len(in->buf, buf->str, buf->len);

        inc = in->priv;
        if (!inc->column_seen_count) {
                ret = initial_receive(in);
                if (ret == SR_ERR_NA)
                        /* Not enough data yet. */
                        return SR_OK;
                else if (ret != SR_OK)
                        return SR_ERR;

                /* sdi is ready, notify frontend. */
                in->sdi_ready = TRUE;
                return SR_OK;
        }

        ret = process_buffer(in, FALSE);

        return ret;
}

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

        if (in->sdi_ready)
                ret = process_buffer(in, TRUE);
        else
                ret = SR_OK;
        if (ret != SR_OK)
                return ret;

        ret = flush_logic_samples(in);
        if (ret != SR_OK)
                return ret;

        inc = in->priv;
        if (inc->started)
                std_session_send_df_end(in->sdi);

        return ret;
}

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

        keep_header_for_reread(in);

        inc = in->priv;

        g_free(inc->termination);
        inc->termination = NULL;
        g_free(inc->datafeed_buffer);
        inc->datafeed_buffer = NULL;
}

static int reset(struct sr_input *in)
{
        struct context *inc = in->priv;

        cleanup(in);
        inc->started = FALSE;
        g_string_truncate(in->buf, 0);

        return SR_OK;
}

enum option_index {
        OPT_COL_FMTS,
        OPT_SINGLE_COL,
        OPT_FIRST_COL,
        OPT_NUM_LOGIC,
        OPT_FORMAT,
        OPT_START,
        OPT_HEADER,
        OPT_RATE,
        OPT_DELIM,
        OPT_COMMENT,
        OPT_MAX,
};

static struct sr_option options[] = {
        [OPT_COL_FMTS] = {
                "column_formats", "Column format specs",
                "Specifies text columns data types: comma separated list of [<cols>]<fmt>[<bits>], with -/x/o/b/l format specifiers.",
                NULL, NULL,
        },
        [OPT_SINGLE_COL] = {
                "single_column", "Single column",
                "Enable single-column mode, exclusively use text from the specified column (number starting at 1).",
                NULL, NULL,
        },
        [OPT_FIRST_COL] = {
                "first_column", "First column",
                "Number of the first column with logic data in simple multi-column mode (number starting at 1, default 1).",
                NULL, NULL,
        },
        [OPT_NUM_LOGIC] = {
                "logic_channels", "Number of logic channels",
                "Logic channel count, required in simple single-column mode, defaults to \"all remaining columns\" in simple multi-column mode. Obsoleted by 'column_formats'.",
                NULL, NULL,
        },
        [OPT_FORMAT] = {
                "single_format", "Data format for simple single-column mode.",
                "The number format of single-column mode input data: bin, hex, oct.",
                NULL, NULL,
        },
        [OPT_START] = {
                "start_line", "Start line",
                "The line number at which to start processing input text (default: 1).",
                NULL, NULL,
        },
        [OPT_HEADER] = {
                "header", "Get channel names from first line.",
                "Use the first processed line's column captions (when available) as channel names.",
                NULL, NULL,
        },
        [OPT_RATE] = {
                "samplerate", "Samplerate (Hz)",
                "The input data's sample rate in Hz.",
                NULL, NULL,
        },
        [OPT_DELIM] = {
                "column_separator", "Column separator",
                "The sequence which separates text columns. Non-empty text, comma by default.",
                NULL, NULL,
        },
        [OPT_COMMENT] = {
                "comment_leader", "Comment leader character",
                "The text which starts comments at the end of text lines.",
                NULL, NULL,
        },
        [OPT_MAX] = ALL_ZERO,
};

static const struct sr_option *get_options(void)
{
        GSList *l;

        if (!options[0].def) {
                options[OPT_COL_FMTS].def = g_variant_ref_sink(g_variant_new_string(""));
                options[OPT_SINGLE_COL].def = g_variant_ref_sink(g_variant_new_uint32(0));
                options[OPT_FIRST_COL].def = g_variant_ref_sink(g_variant_new_uint32(1));
                options[OPT_NUM_LOGIC].def = g_variant_ref_sink(g_variant_new_uint32(0));
                options[OPT_FORMAT].def = g_variant_ref_sink(g_variant_new_string("bin"));
                l = NULL;
                l = g_slist_append(l, g_variant_ref_sink(g_variant_new_string("bin")));
                l = g_slist_append(l, g_variant_ref_sink(g_variant_new_string("hex")));
                l = g_slist_append(l, g_variant_ref_sink(g_variant_new_string("oct")));
                options[OPT_FORMAT].values = l;
                options[OPT_START].def = g_variant_ref_sink(g_variant_new_uint32(1));
                options[OPT_HEADER].def = g_variant_ref_sink(g_variant_new_boolean(FALSE));
                options[OPT_RATE].def = g_variant_ref_sink(g_variant_new_uint64(0));
                options[OPT_DELIM].def = g_variant_ref_sink(g_variant_new_string(","));
                options[OPT_COMMENT].def = g_variant_ref_sink(g_variant_new_string(";"));
        }

        return options;
}

SR_PRIV struct sr_input_module input_csv = {
        .id = "csv",
        .name = "CSV",
        .desc = "Comma-separated values",
        .exts = (const char*[]){"csv", NULL},
        .options = get_options,
        .init = init,
        .receive = receive,
        .end = end,
        .cleanup = cleanup,
        .reset = reset,
};