[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 <ctype.h>
#include <glib.h>
#include <stdlib.h>
#include <string.h>
#include <strings.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). The 'a' format marks analog
 *     data, an optionally following number is the digits count (resolution).
 *     The 't' format marks timestamp values, which could help in automatic
 *     determination of the input stream's samplerate. This "column_formats"
 *     option is most versatile, other forms of specifying the column layout
 *     only exist for backwards compatibility, and are rather limited. They
 *     exclusively support logic input data in strictly adjacent columns,
 *     with further constraints on column layout for multi-bit data.
 *
 * 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.
 * - ... -I csv:column_formats=*a6 ...
 *   Each column contains an analog value with six significant digits
 *   after the decimal period.
 * - ... -I csv:column_formats=t,2a ...
 *   The first column contains timestamps, the next two columns contain
 *   analog values. The capture's samplerate could get determined from
 *   the timestamp values if not provided by the user by means of the
 *   'samplerate' option. This assumes a mere number in units of seconds,
 *   and equidistant rows, there is no fancy support for textual unit
 *   suffixes nor gaps in the stream of samples nor other non-linearity,
 *   just '-' ignore the column if the format is not supported).
 *
 * IMPORTANT! Make sure the .format_match() logic matches the default
 * values for the input module's options. Ideally the format match test
 * shall pass for all input data that is supported by default.
 */

/*
 * TODO
 *
 * - Unbreak analog data when submitted in the 'double' data type. This
 *   was observed with sigrok-cli screen output. Is analog.encoding->unitsize
 *   not handled appropriately? Is it a sigrok-cli or libsigrok issue?
 * - 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).
 */

typedef float csv_analog_t;     /* 'double' currently is flawed. */

/* 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. */
        FORMAT_ANALOG,  /* Floating point number for an analog channel. */
        FORMAT_TIME,    /* Timestamps. */
};

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

static const char col_format_char[] = {
        [FORMAT_NONE] = '?',
        [FORMAT_BIN] = 'b',
        [FORMAT_HEX] = 'x',
        [FORMAT_OCT] = 'o',
        [FORMAT_ANALOG] = 'a',
        [FORMAT_TIME] = 't',
};

static gboolean format_is_ignore(enum single_col_format fmt)
{
        return fmt == FORMAT_NONE;
}

static gboolean format_is_logic(enum single_col_format fmt)
{
        return fmt >= FORMAT_BIN && fmt <= FORMAT_OCT;
}

static gboolean format_is_analog(enum single_col_format fmt)
{
        return fmt == FORMAT_ANALOG;
}

static gboolean format_is_timestamp(enum single_col_format fmt)
{
        return fmt == FORMAT_TIME;
}

struct column_details {
        size_t col_nr;
        enum single_col_format text_format;
        size_t channel_offset;
        size_t channel_count;
        int analog_digits;
        GString **channel_names;
};

struct context {
        gboolean started;

        /* Current samplerate, optionally determined from input data. */
        uint64_t samplerate;
        uint64_t calc_samplerate;
        double prev_timestamp;
        gboolean samplerate_sent;

        /* Number of channels. */
        size_t logic_channels;
        size_t analog_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. */
        csv_analog_t *analog_sample_buffer;     /**!< Buffer for one set of analog values. */

        uint8_t *datafeed_buffer;       /**!< Queue for datafeed submission. */
        size_t datafeed_buf_size;
        size_t datafeed_buf_fill;
        /* "Striped" layout, M samples for N channels each. */
        csv_analog_t *analog_datafeed_buffer;   /**!< Queue for analog datafeed. */
        size_t analog_datafeed_buf_size;
        size_t analog_datafeed_buf_fill;
        int *analog_datafeed_digits;
        GSList **analog_datafeed_channels;

        /* Current line number. */
        size_t line_number;

        /* List of previously created sigrok channels. */
        GSList *prev_sr_channels;
        GSList **prev_df_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 int flush_samplerate(const struct sr_input *in)
{
        struct context *inc;

        inc = in->priv;
        if (!inc->calc_samplerate && inc->samplerate)
                inc->calc_samplerate = inc->samplerate;
        if (inc->calc_samplerate && !inc->samplerate_sent) {
                (void)sr_session_send_meta(in->sdi, SR_CONF_SAMPLERATE,
                        g_variant_new_uint64(inc->calc_samplerate));
                inc->samplerate_sent = TRUE;
        }

        return SR_OK;
}

static void clear_logic_samples(struct context *inc)
{
        if (!inc->logic_channels)
                return;
        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_logic logic;
        int rc;

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

        rc = flush_samplerate(in);
        if (rc != SR_OK)
                return rc;

        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;
}

static void set_analog_value(struct context *inc, size_t ch_idx, csv_analog_t value);

static void clear_analog_samples(struct context *inc)
{
        size_t idx;

        if (!inc->analog_channels)
                return;
        inc->analog_sample_buffer = &inc->analog_datafeed_buffer[inc->analog_datafeed_buf_fill];
        for (idx = 0; idx < inc->analog_channels; idx++)
                set_analog_value(inc, idx, 0.0);
}

static void set_analog_value(struct context *inc, size_t ch_idx, csv_analog_t value)
{
        if (ch_idx >= inc->analog_channels)
                return;
        if (!value)
                return;
        inc->analog_sample_buffer[ch_idx * inc->analog_datafeed_buf_size] = value;
}

static int flush_analog_samples(const struct sr_input *in)
{
        struct context *inc;
        struct sr_datafeed_packet packet;
        struct sr_datafeed_analog analog;
        struct sr_analog_encoding encoding;
        struct sr_analog_meaning meaning;
        struct sr_analog_spec spec;
        csv_analog_t *samples;
        size_t ch_idx;
        int digits;
        int rc;

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

        rc = flush_samplerate(in);
        if (rc != SR_OK)
                return rc;

        samples = inc->analog_datafeed_buffer;
        for (ch_idx = 0; ch_idx < inc->analog_channels; ch_idx++) {
                digits = inc->analog_datafeed_digits[ch_idx];
                sr_analog_init(&analog, &encoding, &meaning, &spec, digits);
                memset(&packet, 0, sizeof(packet));
                packet.type = SR_DF_ANALOG;
                packet.payload = &analog;
                analog.num_samples = inc->analog_datafeed_buf_fill;
                analog.data = samples;
                analog.meaning->channels = inc->analog_datafeed_channels[ch_idx];
                analog.meaning->mq = 0;
                analog.meaning->mqflags = 0;
                analog.meaning->unit = 0;
                analog.encoding->unitsize = sizeof(samples[0]);
                analog.encoding->is_signed = TRUE;
                analog.encoding->is_float = TRUE;
#ifdef WORDS_BIGENDIAN
                analog.encoding->is_bigendian = TRUE;
#else
                analog.encoding->is_bigendian = FALSE;
#endif
                analog.encoding->digits = spec.spec_digits;
                rc = sr_session_send(in->sdi, &packet);
                if (rc != SR_OK)
                        return rc;
                samples += inc->analog_datafeed_buf_size;
        }

        inc->analog_datafeed_buf_fill = 0;

        return SR_OK;
}

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

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

        inc->analog_datafeed_buf_fill++;
        if (inc->analog_datafeed_buf_fill == inc->analog_datafeed_buf_size) {
                rc = flush_analog_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 == '*') {
                /* Workaround, strtoul("*") won't always yield expected endp. */
                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 '-':
        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;
        case 'a':
                format_code = FORMAT_ANALOG;
                break;
        case 't':
                format_code = FORMAT_TIME;
                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 = format_is_analog(format_code) ? 3 : 1;
        if (format_is_ignore(format_code))
                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(const struct sr_input *in,
        const char *column_format, char **column_texts)
{
        struct context *inc;
        char **formats, *format;
        size_t format_count, column_count, logic_count, analog_count;
        size_t auto_column_count;
        size_t format_idx, c, b, column_idx, channel_idx, analog_idx;
        enum single_col_format f;
        struct column_details *detail;
        GString *channel_name;
        size_t create_idx;
        char *column;
        const char *caption;
        int channel_type, channel_sdi_nr;
        void *channel;
        int ret;

        inc = in->priv;
        inc->column_seen_count = g_strv_length(column_texts);

        /* Split the input spec, count involved columns and channels. */
        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 = logic_count = analog_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;
                if (format_is_analog(f))
                        analog_count += c;
                else if (format_is_logic(f))
                        logic_count += c * b;
        }
        sr_dbg("Column format %s -> %zu columns, %zu logic, %zu analog channels.",
                column_format, column_count, logic_count, analog_count);

        /* Allocate and fill in "column processing" details. */
        inc->column_want_count = column_count;
        if (inc->column_seen_count < inc->column_want_count) {
                sr_err("Insufficient input text width for desired data amount, got %zu but want %zu columns.",
                        inc->column_seen_count, inc->column_want_count);
                g_strfreev(formats);
                return SR_ERR_ARG;
        }
        inc->logic_channels = logic_count;
        inc->analog_channels = analog_count;
        inc->analog_datafeed_digits = g_malloc0(inc->analog_channels * sizeof(inc->analog_datafeed_digits[0]));
        inc->analog_datafeed_channels = g_malloc0(inc->analog_channels * sizeof(inc->analog_datafeed_channels[0]));
        inc->column_details = g_malloc0_n(column_count, sizeof(inc->column_details[0]));
        column_idx = channel_idx = analog_idx = 0;
        channel_name = g_string_sized_new(64);
        for (format_idx = 0; format_idx < format_count; format_idx++) {
                /* Process a format field, which can span multiple columns. */
                format = formats[format_idx];
                (void)split_column_format(format, &c, &f, &b);
                if (f && !c)
                        c = auto_column_count;
                while (c-- > 0) {
                        /* Fill in a column's processing details. */
                        detail = &inc->column_details[column_idx++];
                        detail->col_nr = column_idx;
                        detail->text_format = f;
                        if (format_is_analog(detail->text_format)) {
                                detail->channel_offset = analog_idx;
                                detail->channel_count = 1;
                                detail->analog_digits = b;
                                analog_idx += detail->channel_count;
                        } else if (format_is_logic(detail->text_format)) {
                                detail->channel_offset = channel_idx;
                                detail->channel_count = b;
                                channel_idx += detail->channel_count;
                        } else if (format_is_ignore(detail->text_format)) {
                                /* EMPTY */
                                continue;
                        } else {
                                /*
                                 * Neither logic nor analog data, nor ignore.
                                 * Format was noted. No channel creation involved.
                                 */
                                continue;
                        }
                        /*
                         * Pick most appropriate channel names. Optionally
                         * use text from a header line (when requested by the
                         * user). In the absence of header text, channels are
                         * assigned rather generic names.
                         *
                         * Manipulation of the column's caption (when a header
                         * line is seen) is acceptable, because this header
                         * line won't get processed another time.
                         */
                        column = column_texts[detail->col_nr - 1];
                        if (inc->use_header && column && *column)
                                caption = sr_scpi_unquote_string(column);
                        else
                                caption = NULL;
                        if (!caption || !*caption)
                                caption = NULL;
                        /*
                         * Collect channel creation details here, but defer
                         * actual creation of the channels such that all
                         * logic channels can get created first and analog
                         * channels only get created afterwards.
                         */
                        detail->channel_names = g_malloc0(detail->channel_count * sizeof(detail->channel_names[0]));
                        for (create_idx = 0; create_idx < detail->channel_count; create_idx++) {
                                if (caption && detail->channel_count == 1) {
                                        g_string_assign(channel_name, caption);
                                } else if (caption) {
                                        g_string_printf(channel_name, "%s[%zu]",
                                                caption, create_idx);
                                } else {
                                        g_string_printf(channel_name, "%zu",
                                                detail->channel_offset + create_idx);
                                }
                                detail->channel_names[create_idx] = g_string_new_len(channel_name->str, channel_name->len);
                        }
                }
        }
        g_string_free(channel_name, TRUE);
        g_strfreev(formats);

        /* Create channels in strict logic to analog order. */
        channel_type = SR_CHANNEL_LOGIC;
        for (column_idx = 0; column_idx < inc->column_want_count; column_idx++) {
                detail = &inc->column_details[column_idx];
                if (!format_is_logic(detail->text_format))
                        continue;
                for (create_idx = 0; create_idx < detail->channel_count; create_idx++) {
                        caption = detail->channel_names[create_idx]->str;
                        channel_sdi_nr = g_slist_length(in->sdi->channels);
                        sr_channel_new(in->sdi, channel_sdi_nr, channel_type, TRUE, caption);
                }
        }
        channel_type = SR_CHANNEL_ANALOG;
        for (column_idx = 0; column_idx < inc->column_want_count; column_idx++) {
                detail = &inc->column_details[column_idx];
                if (!format_is_analog(detail->text_format))
                        continue;
                caption = detail->channel_names[0]->str;
                channel_sdi_nr = g_slist_length(in->sdi->channels);
                channel = sr_channel_new(in->sdi, channel_sdi_nr, channel_type, TRUE, caption);
                channel_idx = channel_sdi_nr - inc->logic_channels;
                inc->analog_datafeed_digits[channel_idx] = detail->analog_digits;
                inc->analog_datafeed_channels[channel_idx] = g_slist_append(NULL, channel);
        }

        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);
        }
}

/**
 * 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);
}

/**
 * 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;
                default:
                        /* 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;
}

/**
 * Parse a floating point text into an analog value.
 *
 * @param[in] column    The input text, a floating point number.
 * @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 analog values in the current sample set,
 * based on the text input and a user provided format spec.
 */
static int parse_analog(const char *column, struct context *inc,
        const struct column_details *details)
{
        size_t length;
        double dvalue; float fvalue;
        csv_analog_t value;
        int ret;

        if (!format_is_analog(details->text_format))
                return SR_ERR_BUG;

        length = strlen(column);
        if (!length) {
                sr_err("Column %zu in line %zu is empty.", details->col_nr,
                        inc->line_number);
                return SR_ERR;
        }
        if (sizeof(value) == sizeof(double)) {
                ret = sr_atod_ascii(column, &dvalue);
                value = dvalue;
        } else if (sizeof(value) == sizeof(float)) {
                ret = sr_atof_ascii(column, &fvalue);
                value = fvalue;
        } else {
                ret = SR_ERR_BUG;
        }
        if (ret != SR_OK) {
                sr_err("Cannot parse analog text %s in column %zu in line %zu.",
                        column, details->col_nr, inc->line_number);
                return SR_ERR_DATA;
        }
        set_analog_value(inc, details->channel_offset, value);

        return SR_OK;
}

/**
 * Parse a timestamp text, auto-determine samplerate.
 *
 * @param[in] column    The input text, a floating point number.
 * @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 attempts to automatically determine the input data's
 * samplerate from text rows' timestamp values. Only simple formats are
 * supported, user provided values always take precedence.
 */
static int parse_timestamp(const char *column, struct context *inc,
        const struct column_details *details)
{
        double ts, rate;
        int ret;

        if (!format_is_timestamp(details->text_format))
                return SR_ERR_BUG;

        /*
         * Implementor's notes on timestamp interpretation. Use a simple
         * approach for improved maintainability which covers most cases
         * of input data. There is not much gain in adding complexity,
         * users can easily provide the rate when auto-detection fails.
         * - Bail out if samplerate is known already.
         * - Try to interpret the timestamp (simple float conversion).
         *   If conversion fails then clear all previous knowledge and
         *   bail out (non-fatal, perhaps warn). Silently ignore values
         *   of zero since those could be silent fails -- assume that
         *   genuine data contains at least two adjacent rows with useful
         *   timestamps for the feature to work reliably. Annoying users
         *   with "failed to detect" messages is acceptable here, since
         *   users expecting the feature to work should provide useful
         *   data, and there are easy ways to disable the detection or
         *   ignore the column.
         * - If there is no previous timestamp, keep the current value
         *   for later reference and bail out.
         * - If a previous timestamp was seen, determine the difference
         *   between them, and derive the samplerate. Update internal
         *   state (the value automatically gets sent to the datafeed),
         *   and clear previous knowledge. Subsequent calls will ignore
         *   following input data (see above, rate is known).
         *
         * TODO Potential future improvements:
         * - Prefer rationals over floats for improved precision and
         *   reduced rounding errors which result in odd rates.
         * - Support other formats ("2 ms" or similar)?
         */
        if (inc->calc_samplerate)
                return SR_OK;
        ret = sr_atod_ascii(column, &ts);
        if (ret != SR_OK)
                ts = 0.0;
        if (!ts) {
                sr_info("Cannot convert timestamp text %s in line %zu (or zero value).",
                        column, inc->line_number);
                inc->prev_timestamp = 0.0;
                return SR_OK;
        }
        if (!inc->prev_timestamp) {
                sr_dbg("First timestamp value %g in line %zu.",
                        ts, inc->line_number);
                inc->prev_timestamp = ts;
                return SR_OK;
        }
        sr_dbg("Second timestamp value %g in line %zu.", ts, inc->line_number);
        ts -= inc->prev_timestamp;
        sr_dbg("Timestamp difference %g in line %zu.",
                ts, inc->line_number);
        if (!ts) {
                sr_warn("Zero timestamp difference in line %zu.",
                        inc->line_number);
                inc->prev_timestamp = ts;
                return SR_OK;
        }
        rate = 1.0 / ts;
        rate += 0.5;
        rate = (uint64_t)rate;
        sr_dbg("Rate from timestamp %g in line %zu.", rate, inc->line_number);
        inc->calc_samplerate = rate;
        inc->prev_timestamp = 0.0;

        return SR_OK;
}

/**
 * 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,
        [FORMAT_ANALOG] = parse_analog,
        [FORMAT_TIME] = parse_timestamp,
};

/*
 * BEWARE! Implementor's notes. Sync with feature set and default option
 * values required during maintenance of the input module implementation.
 *
 * When applications invoke .format_match() routines, trying automatic
 * determination of an input file's format handler, then no options are
 * in effect. Because specifying options requires selection of an input
 * module to pass the options to, which obsoletes the format-match check.
 *
 * Which means that we only need to deal with the default format here,
 * which happens to be the simple multi-column format without header
 * lines or leading garbage. Which means that the check can be rather
 * strict, resulting in high levels of confidence upon match, never
 * "accidently" winning for unreadable or unsupported-by-default formats.
 *
 * This .format_match() logic only needs to become more involved when
 * default option values change, or when automatic detection of column
 * data types improves. Then the supported-by-default types of input
 * data must be considered acceptable here in the format-match check
 * as well.
 *
 * Notice that the format check cannot re-use regular processing logic
 * when their implementation assumes proper input data and wll generate
 * diagnostics for unexpected input data. Failure to match the format is
 * non-fatal here, mismatch must remain silent. It's up to applications
 * how large a chunk of data gets passed here (start of the file's
 * content). But inspection of the first few hundred bytes will usually
 * be GoodEnough(TM) for the format-match purpose. Notice that filenames
 * need not necessarily be available to the format-match routine.
 *
 * This implementation errs on the safe side. Users can always select
 * the CSV input module when automatic format detection fails.
 */
static int format_match(GHashTable *metadata, unsigned int *confidence)
{
        const int match_confidence = 100;
        const char *default_extension = ".csv";
        const char *line_termination = "\n";
        const char *comment_leader = ";";
        const char *column_separator = ",";
        const char *binary_charset = "01";

        const char *fn;
        GString *buf;
        size_t fn_len;
        GString *tmpbuf;
        gboolean status;
        size_t line_idx, col_idx;
        char *rdptr, **lines, *line;
        char **cols, *col;

        /* Get the application provided input data properties. */
        fn = g_hash_table_lookup(metadata, GINT_TO_POINTER(SR_INPUT_META_FILENAME));
        buf = g_hash_table_lookup(metadata, GINT_TO_POINTER(SR_INPUT_META_HEADER));

        /* Filenames are a strong hint. Use then when available. */
        if (fn && *fn && (fn_len = strlen(fn)) >= strlen(default_extension)) {
                if (strcasecmp(&fn[fn_len - strlen(default_extension)], default_extension) == 0) {
                        *confidence = 10;
                        return SR_OK;
                }
        }

        /*
         * Check file content for compatibility with the input module's
         * default format. Which translates to:
         * - Must be at least one text line worth of input data. Ignore
         *   incomplete lines at the end of the available buffer.
         * - Must be LF terminated text lines, optional CR-LF sequence.
         *   (Drop CR-only for simplicity since that's rare and users
         *   can override the automatic detection.)
         * - Strip comments and skip empty lines.
         * - Data lines must be binary input (potentially multiple bits
         *   per column which then get ignored). Presence of comma is
         *   optional but then must be followed by another data column.
         * - No other content is acceptable, there neither are ignored
         *   columns nor analog data nor timestamps in the default layout.
         *   (See the above "sync format match with default options"
         *   comment though during maintenance!)
         * Run the check on a copy to not affect the caller's buffer.
         */
        if (!buf || !buf->len || !buf->str || !*buf->str)
                return SR_ERR;
        rdptr = g_strstr_len(buf->str, buf->len, line_termination);
        if (!rdptr)
                return SR_ERR;
        tmpbuf = g_string_new_len(buf->str, rdptr + 1 - buf->str);
        tmpbuf->str[tmpbuf->len - 1] = '\0';
        status = TRUE;
        *confidence = match_confidence;
        lines = g_strsplit(tmpbuf->str, line_termination, 0);
        for (line_idx = 0; status && (line = lines[line_idx]); line_idx++) {
                rdptr = strstr(line, comment_leader);
                if (rdptr)
                        *rdptr = '\0';
                line = g_strstrip(line);
                if (!line || !*line)
                        continue;
                cols = g_strsplit(line, column_separator, 0);
                if (!cols) {
                        status = FALSE;
                        break;
                }
                for (col_idx = 0; status && (col = cols[col_idx]); col_idx++) {
                        if (strspn(col, binary_charset) != strlen(col)) {
                                status = FALSE;
                                break;
                        }
                }
                g_strfreev(cols);
        }
        g_strfreev(lines);
        g_string_free(tmpbuf, TRUE);

        if (!status)
                return SR_ERR;

        return SR_OK;
}

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 release_df_channels(struct context *inc, GSList **l)
{
        size_t idx;

        if (!inc->analog_channels || !l)
                return;
        for (idx = 0; idx < inc->analog_channels; idx++)
                g_slist_free(l[idx]);
        g_free(l);
}

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;

        release_df_channels(inc, inc->prev_df_channels);
        inc->prev_df_channels = inc->analog_datafeed_channels;
        inc->analog_datafeed_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;

        release_df_channels(inc, inc->analog_datafeed_channels);
        inc->analog_datafeed_channels = inc->prev_df_channels;
        inc->prev_df_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;
        size_t num_columns;
        size_t line_number, line_idx;
        int ret;
        char **lines, *line, **columns;

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

        /* Search for the first line to process (header or data). */
        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;
        }

        /* Get the number of columns in the line. */
        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("Got %zu columns in text line: %s.", num_columns, line);

        /*
         * Interpret the user provided column format specs. This might
         * involve inspection of the now received input text, to support
         * e.g. automatic detection of channel counts in the absence of
         * user provided specs. Optionally a header line is used to get
         * channels' names.
         *
         * Check the then created channels for consistency across .reset
         * and .receive sequences (file re-load).
         */
        ret = make_column_details_from_format(in, inc->column_formats, columns);
        if (ret != SR_OK) {
                sr_err("Cannot parse columns format using line %zu.", line_number);
                goto out;
        }
        if (!check_header_in_reread(in)) {
                ret = SR_ERR_DATA;
                goto out;
        }

        /*
         * Allocate buffer memory for datafeed submission of sample data.
         * 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.
         *
         * TODO Move channel creation here, and just store required
         * parameters in the format parser above? Could simplify the
         * arrangement that logic and analog channels get created in
         * strict sequence in their respective groups.
         */
        if (inc->logic_channels) {
                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);
                if (!inc->datafeed_buffer) {
                        sr_err("Cannot allocate datafeed send buffer (logic).");
                        ret = SR_ERR_MALLOC;
                        goto out;
                }
                inc->datafeed_buf_fill = 0;
        }

        if (inc->analog_channels) {
                size_t sample_size, sample_count;
                sample_size = sizeof(inc->analog_datafeed_buffer[0]);
                inc->analog_datafeed_buf_size = CHUNK_SIZE;
                inc->analog_datafeed_buf_size /= sample_size;
                inc->analog_datafeed_buf_size /= inc->analog_channels;
                sample_count = inc->analog_channels * inc->analog_datafeed_buf_size;
                inc->analog_datafeed_buffer = g_malloc0(sample_count * sample_size);
                if (!inc->analog_datafeed_buffer) {
                        sr_err("Cannot allocate datafeed send buffer (analog).");
                        ret = SR_ERR_MALLOC;
                        goto out;
                }
                inc->analog_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 *processed_up_to;
        char **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) {
                processed_up_to = in->buf->str + in->buf->len;
        } else {
                processed_up_to = g_strrstr_len(in->buf->str, in->buf->len,
                        inc->termination);
                if (!processed_up_to)
                        return SR_OK;
                *processed_up_to = '\0';
                processed_up_to += strlen(inc->termination);
        }

        /* Split input text lines and process their columns. */
        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);
                clear_analog_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);
                ret += queue_analog_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, processed_up_to - 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);
        ret += flush_analog_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, save_ctx;

        /* Keep channel references between file re-imports. */
        keep_header_for_reread(in);

        /* Release dynamically allocated resources. */
        inc = in->priv;

        g_free(inc->termination);
        inc->termination = NULL;
        g_free(inc->datafeed_buffer);
        inc->datafeed_buffer = NULL;
        g_free(inc->analog_datafeed_buffer);
        inc->analog_datafeed_buffer = NULL;
        g_free(inc->analog_datafeed_digits);
        inc->analog_datafeed_digits = NULL;
        /* analog_datafeed_channels was released in keep_header_for_reread() */
        /* TODO Release channel names (before releasing details). */
        g_free(inc->column_details);
        inc->column_details = NULL;

        /* Clear internal state, but keep what .init() has provided. */
        save_ctx = *inc;
        memset(inc, 0, sizeof(*inc));
        inc->samplerate = save_ctx.samplerate;
        inc->delimiter = save_ctx.delimiter;
        inc->comment = save_ctx.comment;
        inc->column_formats = save_ctx.column_formats;
        inc->start_line = save_ctx.start_line;
        inc->use_header = save_ctx.use_header;
        inc->prev_sr_channels = save_ctx.prev_sr_channels;
        inc->prev_df_channels = save_ctx.prev_df_channels;
}

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

        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_SINGLE_FMT,
        OPT_START_LINE,
        OPT_HEADER,
        OPT_SAMPLERATE,
        OPT_COL_SEP,
        OPT_COMMENT,
        OPT_MAX,
};

static struct sr_option options[] = {
        [OPT_COL_FMTS] = {
                "column_formats", "Column format specs",
                "Text columns data types. A comma separated list of [<cols>]<fmt>[<bits>] items. * for all remaining columns. - ignores columns, x/o/b/l logic data, a (and digits) analog data, t timestamps.",
                NULL, NULL,
        },
        [OPT_SINGLE_COL] = {
                "single_column", "Single column",
                "Simple single-column mode, exclusively use text from the specified column (number starting at 1). Obsoleted by 'column_formats=4-,x16'.",
                NULL, NULL,
        },
        [OPT_FIRST_COL] = {
                "first_column", "First column",
                "First column with logic data in simple multi-column mode (number starting at 1, default 1). Obsoleted by 'column_formats=4-,*l'.",
                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=8l'.",
                NULL, NULL,
        },
        [OPT_SINGLE_FMT] = {
                "single_format", "Data format for simple single-column mode.",
                "The input text number format of simple single-column mode: bin, hex, oct. Obsoleted by 'column_formats=x8'.",
                NULL, NULL,
        },
        [OPT_START_LINE] = {
                "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. Enabled by default.",
                NULL, NULL,
        },
        [OPT_SAMPLERATE] = {
                "samplerate", "Samplerate (Hz)",
                "The input data's sample rate in Hz. No default value.",
                NULL, NULL,
        },
        [OPT_COL_SEP] = {
                "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, semicolon by default.",
                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_SINGLE_FMT].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_SINGLE_FMT].values = l;
                options[OPT_START_LINE].def = g_variant_ref_sink(g_variant_new_uint32(1));
                options[OPT_HEADER].def = g_variant_ref_sink(g_variant_new_boolean(TRUE));
                options[OPT_SAMPLERATE].def = g_variant_ref_sink(g_variant_new_uint64(0));
                options[OPT_COL_SEP].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},
        .metadata = { SR_INPUT_META_FILENAME, 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,
};