Function rewriteConfigRewriteLine

app/redis-6.2.6/src/config.c:1228–1261

Rewrite the specified configuration option with the new "line". * It progressively uses lines of the file that were already used for the same * configuration option in the old version of the file, removing that line from * the map of options -> line numbers. * * If there are lines associated with a given configuration option and * "force" is non-zero, the line is appended to the configuratio

 * "line" is either used, or freed, so the caller does not need to free it
 * in any way. */
void rewriteConfigRewriteLine(struct rewriteConfigState *state, const char *option, sds line, int force) {
    sds o = sdsnew(option);
    list *l = dictFetchValue(state->option_to_line,o);

    rewriteConfigMarkAsProcessed(state,option);

    if (!l && !force && !state->force_all) {
        /* Option not used previously, and we are not forced to use it. */
        sdsfree(line);
        sdsfree(o);
        return;
    }

    if (l) {
        listNode *ln = listFirst(l);
        int linenum = (long) ln->value;

        /* There are still lines in the old configuration file we can reuse
         * for this option. Replace the line with the new one. */
        listDelNode(l,ln);
        if (listLength(l) == 0) dictDelete(state->option_to_line,o);
        sdsfree(state->lines[linenum]);
        state->lines[linenum] = line;
    } else {
        /* Append a new line. */
        if (!state->has_tail) {
            rewriteConfigAppendLine(state,
                sdsnew(REDIS_CONFIG_REWRITE_SIGNATURE));
            state->has_tail = 1;
        }
        rewriteConfigAppendLine(state,line);
    }
    sdsfree(o);
}

/* Write the long long 'bytes' value as a string in a way that is parsable
 * inside redis.conf. If possible uses the GB, MB, KB notation. */