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#include "wp_format_table.h"
#include <stdio.h>
#include <string.h>

static uint16_t
format_table_le16(const uint8_t *p)
{
    return (uint16_t)((uint16_t)p[0] | ((uint16_t)p[1] << 8));
}

void
wp_format_table_clear(WpFormatTableInfo *table)
{
    if (table != NULL) {
        memset(table, 0, sizeof(*table));
    }
}

bool
wp_format_table_decode_payload(const uint8_t *payload,
                               uint16_t payload_length,
                               uint8_t sub_code,
                               WpFormatTableInfo *out_table)
{
    WpFormatTableInfo table;
    size_t i;
    bool in_group = false;
    size_t current_group_words = 0U;
    bool have_previous_in_group = false;
    uint16_t previous_in_group = 0U;

    wp_format_table_clear(out_table);
    if (payload == NULL || out_table == NULL) {
        return false;
    }

    memset(&table, 0, sizeof(table));
    table.is_present = true;
    table.sub_code = sub_code;
    table.payload_bytes = payload_length;
    table.word_count = payload_length / 2U;
    table.odd_payload_byte = (payload_length & 1U) != 0U;
    if (table.odd_payload_byte) {
        table.odd_payload_tail = payload[payload_length - 1U];
    }

    for (i = 0U; i < table.word_count; ++i) {
        uint16_t value = format_table_le16(payload + i * 2U);

        if (table.stored_word_count < WP_FORMAT_TABLE_MAX_STORED_WORDS) {
            table.stored_words[table.stored_word_count++] = value;
        }

        if (value == 0xffffU) {
            table.sentinel_word_count++;
            if (in_group) {
                if (current_group_words > table.longest_group_words) {
                    table.longest_group_words = current_group_words;
                }
                current_group_words = 0U;
                in_group = false;
                have_previous_in_group = false;
            }
            continue;
        }

        table.usable_word_count++;
        if (value == 0U) {
            table.zero_word_count++;
        }
        if (!in_group) {
            table.group_count++;
            in_group = true;
            current_group_words = 0U;
            have_previous_in_group = false;
        }
        current_group_words++;

        if (!table.has_values) {
            table.has_values = true;
            table.first_value_index = (uint16_t)i;
            table.first_value = value;
            table.min_value = value;
            table.max_value = value;
        } else {
            if (value < table.min_value) {
                table.min_value = value;
            }
            if (value > table.max_value) {
                table.max_value = value;
            }
        }
        table.last_value_index = (uint16_t)i;
        table.last_value = value;

        if (have_previous_in_group) {
            if (value < previous_in_group) {
                table.nonmonotonic_step_count++;
            } else if (value > previous_in_group) {
                uint16_t step = (uint16_t)(value - previous_in_group);

                if (!table.has_positive_step) {
                    table.has_positive_step = true;
                    table.first_positive_step = step;
                    table.min_positive_step = step;
                    table.max_positive_step = step;
                } else {
                    if (step < table.min_positive_step) {
                        table.min_positive_step = step;
                    }
                    if (step > table.max_positive_step) {
                        table.max_positive_step = step;
                    }
                }
                table.positive_step_count++;
            }
        }
        previous_in_group = value;
        have_previous_in_group = true;
    }

    if (in_group && current_group_words > table.longest_group_words) {
        table.longest_group_words = current_group_words;
    }

    *out_table = table;
    return true;
}

bool
wp_format_table_decode_record(const WpRecord *rec,
                              WpFormatTableInfo *out_table)
{
    wp_format_table_clear(out_table);
    if (rec == NULL || rec->type != WP_CODE_VARIABLE_LENGTH ||
        rec->code != 0xd0U) {
        return false;
    }
    if (rec->data == NULL && rec->data_length != 0U) {
        return false;
    }
    return wp_format_table_decode_payload(rec->data,
                                          rec->data_length,
                                          rec->sub_code,
                                          out_table);
}

uint16_t
wp_format_table_recommended_span_step(const WpFormatTableInfo *table)
{
    if (table == NULL || !table->has_positive_step) {
        return 0U;
    }
    return table->first_positive_step;
}

bool
wp_format_table_describe(const WpFormatTableInfo *table,
                         char *out,
                         size_t out_size)
{
    if (out == NULL || out_size == 0U) {
        return false;
    }
    out[0] = '\0';
    if (table == NULL || !table->is_present) {
        return false;
    }

    if (table->has_values) {
        snprintf(out,
                 out_size,
                 "format-table words=%lu groups=%lu sentinels=%lu zeros=%lu first[%u]=%u last[%u]=%u max=%u step=%u nonmono=%lu odd=%s",
                 (unsigned long)table->word_count,
                 (unsigned long)table->group_count,
                 (unsigned long)table->sentinel_word_count,
                 (unsigned long)table->zero_word_count,
                 (unsigned)table->first_value_index,
                 (unsigned)table->first_value,
                 (unsigned)table->last_value_index,
                 (unsigned)table->last_value,
                 (unsigned)table->max_value,
                 (unsigned)wp_format_table_recommended_span_step(table),
                 (unsigned long)table->nonmonotonic_step_count,
                 table->odd_payload_byte ? "yes" : "no");
    } else {
        snprintf(out,
                 out_size,
                 "format-table words=%lu groups=0 sentinels=%lu odd=%s",
                 (unsigned long)table->word_count,
                 (unsigned long)table->sentinel_word_count,
                 table->odd_payload_byte ? "yes" : "no");
    }
    return true;
}
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