bug 1083: Fix infinite loop in decompress_data

[elinks.git] / src / config / conf.c

/* Config file manipulation */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h> /* OS/2 needs this after sys/types.h */
#ifdef HAVE_FCNTL_H
#include <fcntl.h> /* OS/2 needs this after sys/types.h */
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include "elinks.h"

#include "config/conf.h"
#include "config/dialogs.h"
#include "config/home.h"
#include "config/kbdbind.h"
#include "config/options.h"
#include "config/opttypes.h"
#include "intl/gettext/libintl.h"
#include "osdep/osdep.h"
#include "terminal/terminal.h"
#include "util/error.h"
#include "util/memory.h"
#include "util/secsave.h"
#include "util/string.h"


/* Config file has only very simple grammar:
 *
 * /set *option *= *value/
 * /bind *keymap *keystroke *= *action/
 * /include *file/
 * /#.*$/
 *
 * Where option consists from any number of categories separated by dots and
 * name of the option itself. Both category and option name consists from
 * [a-zA-Z0-9_-*] - using uppercase letters is not recommended, though. '*' is
 * reserved and is used only as escape character in place of '.' originally in
 * option name.
 *
 * Value can consist from:
 * - number (it will be converted to int/long)
 * - enum (like on, off; true, fake, last_url; etc ;) - in planning state yet
 * - string - "blah blah" (keymap, keystroke and action and file looks like that too)
 *
 * "set" command is parsed first, and then type-specific function is called,
 * with option as one parameter and value as a second. Usually it just assigns
 * value to an option, but sometimes you may want to first create the option
 * ;). Then this will come handy. */

struct conf_parsing_state {
        /** This part may be copied to a local variable as a bookmark
         * and restored later.  So it must not contain any pointers
         * that would have to be freed in that situation.  */
        struct conf_parsing_pos {
                /** Points to the next character to be parsed from the
                 * configuration file.  */
                unsigned char *look;

                /** The line number corresponding to #look.  This is
                 * shown in error messages.  */
                int line;
        } pos;

        /** When ELinks is rewriting the configuration file, @c mirrored
         * indicates the end of the part that has already been copied
         * to the mirror string.  Otherwise, @c mirrored is not used.
         *
         * @invariant @c mirrored @<= @c pos.look */
        unsigned char *mirrored;

        /** File name for error messages.  If NULL then do not display
         * error messages.  */
        const unsigned char *filename;
};

/** Tell the user about an error in the configuration file.
 * @return @a err, for convenience.  */
static enum parse_error
show_parse_error(const struct conf_parsing_state *state, enum parse_error err)
{
        static const unsigned char error_msg[][40] = {
                "no error",        /* ERROR_NONE */
                "unknown command", /* ERROR_COMMAND */
                "parse error",     /* ERROR_PARSE */
                "unknown option",  /* ERROR_OPTION */
                "bad value",       /* ERROR_VALUE */
                "no memory left",  /* ERROR_NOMEM */
        };

        if (state->filename) {
                fprintf(stderr, "%s:%d: %s\n",
                        state->filename, state->pos.line, error_msg[err]);
        }
        return err;
}

/** Skip comments and whitespace.  */
static void
skip_white(struct conf_parsing_pos *pos)
{
        unsigned char *start = pos->look;

        while (*start) {
                while (isspace(*start)) {
                        if (*start == '\n') {
                                pos->line++;
                        }
                        start++;
                }

                if (*start == '#') {
                        start += strcspn(start, "\n");
                } else {
                        pos->look = start;
                        return;
                }
        }

        pos->look = start;
}

/** Skip a quoted string.
 * This function allows "mismatching quotes' because str_rd() does so.  */
static void
skip_quoted(struct conf_parsing_pos *pos)
{
        assert(isquote(*pos->look));
        if_assert_failed return;
        pos->look++;

        for (;;) {
                if (!*pos->look)
                        return;
                if (isquote(*pos->look)) {
                        pos->look++;
                        return;
                }
                if (*pos->look == '\\' && pos->look[1])
                        pos->look++;
                if (*pos->look == '\n')
                        pos->line++;
                pos->look++;
        }
}

/** Skip the value of an option.
 *
 * This job is normally done by the reader function that corresponds
 * to the type of the option.  However, if ELinks does not recognize
 * the name of the option, it cannot look up the type and has to use
 * this function instead.  */
static void
skip_option_value(struct conf_parsing_pos *pos)
{
        if (isquote(*pos->look)) {
                /* Looks like OPT_STRING, OPT_CODEPAGE, OPT_LANGUAGE,
                 * or OPT_COLOR.  */
                skip_quoted(pos);
        } else {
                /* Looks like OPT_BOOL, OPT_INT, or OPT_LONG.  */
                while (isasciialnum(*pos->look) || *pos->look == '.'
                       || *pos->look == '+' || *pos->look == '-')
                        pos->look++;
        }
}

/** Skip to the next newline or comment that is not part of a quoted
 * string.  When ELinks hits a parse error in the configuration file,
 * it calls this in order to find the place where is should resume
 * parsing.  This is intended to prevent ELinks from treating words
 * in strings as commands.  */
static void
skip_to_unquoted_newline_or_comment(struct conf_parsing_pos *pos)
{
        while (*pos->look && *pos->look != '#' && *pos->look != '\n') {
                if (isquote(*pos->look))
                        skip_quoted(pos);
                else
                        pos->look++;
        }
}

/* Parse a command. Returns error code. */
/* If dynamic string credentials are supplied, we will mirror the command at
 * the end of the string; however, we won't load the option value to the tree,
 * and we will even write option value from the tree to the output string.
 * We will only possibly set or clear OPT_MUST_SAVE flag in the option.  */

static enum parse_error
parse_set(struct option *opt_tree, struct conf_parsing_state *state,
          struct string *mirror, int is_system_conf)
{
        const unsigned char *optname_orig;
        size_t optname_len;
        unsigned char *optname_copy;

        skip_white(&state->pos);
        if (!*state->pos.look) return show_parse_error(state, ERROR_PARSE);

        /* Option name */
        optname_orig = state->pos.look;
        while (isident(*state->pos.look) || *state->pos.look == '*'
               || *state->pos.look == '.' || *state->pos.look == '+')
                state->pos.look++;
        optname_len = state->pos.look - optname_orig;

        skip_white(&state->pos);

        /* Equal sign */
        if (*state->pos.look != '=')
                return show_parse_error(state, ERROR_PARSE);
        state->pos.look++; /* '=' */
        skip_white(&state->pos);
        if (!*state->pos.look)
                return show_parse_error(state, ERROR_VALUE);

        optname_copy = memacpy(optname_orig, optname_len);
        if (!optname_copy) return show_parse_error(state, ERROR_NOMEM);

        /* Option value */
        {
                struct option *opt;
                unsigned char *val;
                const struct conf_parsing_pos pos_before_value = state->pos;

                opt = mirror
                        ? get_opt_rec_real(opt_tree, optname_copy)
                        : get_opt_rec(opt_tree, optname_copy);
                mem_free(optname_copy);
                optname_copy = NULL;

                if (!opt || (opt->flags & OPT_HIDDEN)) {
                        show_parse_error(state, ERROR_OPTION);
                        skip_option_value(&state->pos);
                        return ERROR_OPTION;
                        /* TODO: Distinguish between two scenarios:
                         * - A newer version of ELinks has saved an
                         *   option that this version does not recognize.
                         *   The option must be preserved.  (This works.)
                         * - The user has added an option, saved
                         *   elinks.conf, restarted ELinks, deleted the
                         *   option, and is now saving elinks.conf again.
                         *   The option should be rewritten to "unset".
                         *   (This does not work yet.)
                         * In both cases, ELinks has no struct option
                         * for that name.  Possible fixes:
                         * - If the tree has OPT_AUTOCREATE, then
                         *   assume the user had created that option,
                         *   and rewrite it to "unset".  Otherwise,
                         *   keep it.
                         * - When the user deletes an option, just mark
                         *   it with OPT_DELETED, and keep it in memory
                         *   as long as OPT_TOUCHED is set.  */
                }

                if (!option_types[opt->type].read) {
                        show_parse_error(state, ERROR_VALUE);
                        skip_option_value(&state->pos);
                        return ERROR_VALUE;
                }

                val = option_types[opt->type].read(opt, &state->pos.look,
                                                   &state->pos.line);
                if (!val) {
                        /* The reader function failed.  Jump back to
                         * the beginning of the value and skip it with
                         * the generic code.  For the error message,
                         * use the line number at the beginning of the
                         * value, because the ending position is not
                         * interesting if there is an unclosed quote.  */
                        state->pos = pos_before_value;
                        show_parse_error(state, ERROR_VALUE);
                        skip_option_value(&state->pos);
                        return ERROR_VALUE;
                }

                if (!mirror) {
                        /* loading a configuration file */
                        if (!option_types[opt->type].set
                            || !option_types[opt->type].set(opt, val)) {
                                mem_free(val);
                                return show_parse_error(state, ERROR_VALUE);
                        }
                } else if (is_system_conf) {
                        /* scanning a file that will not be rewritten */
                        struct option *flagsite = indirect_option(opt);

                        if (!(flagsite->flags & OPT_DELETED)
                            && option_types[opt->type].equals
                            && option_types[opt->type].equals(opt, val))
                                flagsite->flags &= ~OPT_MUST_SAVE;
                        else
                                flagsite->flags |= OPT_MUST_SAVE;
                } else {
                        /* rewriting a configuration file */
                        struct option *flagsite = indirect_option(opt);

                        if (flagsite->flags & OPT_DELETED) {
                                /* Replace the "set" command with an
                                 * "unset" command.  */
                                add_to_string(mirror, "unset ");
                                add_bytes_to_string(mirror, optname_orig,
                                                    optname_len);
                                state->mirrored = state->pos.look;
                        } else if (option_types[opt->type].write) {
                                add_bytes_to_string(mirror, state->mirrored,
                                                    pos_before_value.look
                                                    - state->mirrored);
                                option_types[opt->type].write(opt, mirror);
                                state->mirrored = state->pos.look;
                        }
                        /* Remember that the option need not be
                         * written to the end of the file.  */
                        flagsite->flags &= ~OPT_MUST_SAVE;
                }
                mem_free(val);
        }

        return ERROR_NONE;
}

static enum parse_error
parse_unset(struct option *opt_tree, struct conf_parsing_state *state,
            struct string *mirror, int is_system_conf)
{
        const unsigned char *optname_orig;
        size_t optname_len;
        unsigned char *optname_copy;

        skip_white(&state->pos);
        if (!*state->pos.look) return show_parse_error(state, ERROR_PARSE);

        /* Option name */
        optname_orig = state->pos.look;
        while (isident(*state->pos.look) || *state->pos.look == '*'
               || *state->pos.look == '.' || *state->pos.look == '+')
                state->pos.look++;
        optname_len = state->pos.look - optname_orig;

        optname_copy = memacpy(optname_orig, optname_len);
        if (!optname_copy) return show_parse_error(state, ERROR_NOMEM);

        {
                struct option *opt;

                opt = get_opt_rec_real(opt_tree, optname_copy);
                mem_free(optname_copy);
                optname_copy = NULL;

                if (!opt || (opt->flags & OPT_HIDDEN)) {
                        /* The user wanted to delete the option, and
                         * it has already been deleted; this is not an
                         * error.  This might happen if a version of
                         * ELinks has a built-in URL rewriting rule,
                         * the user disables it, and a later version
                         * no longer has it.  */
                        return ERROR_NONE;
                }

                if (!mirror) {
                        /* loading a configuration file */
                        if (opt->flags & OPT_ALLOC) delete_option(opt);
                        else mark_option_as_deleted(opt);
                } else if (is_system_conf) {
                        /* scanning a file that will not be rewritten */
                        struct option *flagsite = indirect_option(opt);

                        if (flagsite->flags & OPT_DELETED)
                                flagsite->flags &= ~OPT_MUST_SAVE;
                        else
                                flagsite->flags |= OPT_MUST_SAVE;
                } else {
                        /* rewriting a configuration file */
                        struct option *flagsite = indirect_option(opt);

                        if (flagsite->flags & OPT_DELETED) {
                                /* The "unset" command is already in the file,
                                 * and unlike with "set", there is no value
                                 * to be updated.  */
                        } else if (option_types[opt->type].write) {
                                /* Replace the "unset" command with a
                                 * "set" command.  */
                                add_to_string(mirror, "set ");
                                add_bytes_to_string(mirror, optname_orig,
                                                    optname_len);
                                add_to_string(mirror, " = ");
                                option_types[opt->type].write(opt, mirror);
                                state->mirrored = state->pos.look;
                        }
                        /* Remember that the option need not be
                         * written to the end of the file.  */
                        flagsite->flags &= ~OPT_MUST_SAVE;
                }
        }

        return ERROR_NONE;
}

static enum parse_error
parse_bind(struct option *opt_tree, struct conf_parsing_state *state,
           struct string *mirror, int is_system_conf)
{
        unsigned char *keymap, *keystroke, *action;
        enum parse_error err = ERROR_NONE;
        struct conf_parsing_pos before_error;

        skip_white(&state->pos);
        if (!*state->pos.look) return show_parse_error(state, ERROR_PARSE);

        /* Keymap */
        before_error = state->pos;
        keymap = option_types[OPT_STRING].read(NULL, &state->pos.look,
                                               &state->pos.line);
        skip_white(&state->pos);
        if (!keymap || !*state->pos.look) {
                state->pos = before_error;
                return show_parse_error(state, ERROR_PARSE);
        }

        /* Keystroke */
        before_error = state->pos;
        keystroke = option_types[OPT_STRING].read(NULL, &state->pos.look,
                                                  &state->pos.line);
        skip_white(&state->pos);
        if (!keystroke || !*state->pos.look) {
                mem_free(keymap); mem_free_if(keystroke);
                state->pos = before_error;
                return show_parse_error(state, ERROR_PARSE);
        }

        /* Equal sign */
        skip_white(&state->pos);
        if (*state->pos.look != '=') {
                mem_free(keymap); mem_free(keystroke);
                return show_parse_error(state, ERROR_PARSE);
        }
        state->pos.look++; /* '=' */

        skip_white(&state->pos);
        if (!*state->pos.look) {
                mem_free(keymap); mem_free(keystroke);
                return show_parse_error(state, ERROR_PARSE);
        }

        /* Action */
        before_error = state->pos;
        action = option_types[OPT_STRING].read(NULL, &state->pos.look,
                                               &state->pos.line);
        if (!action) {
                mem_free(keymap); mem_free(keystroke);
                state->pos = before_error;
                return show_parse_error(state, ERROR_PARSE);
        }

        if (!mirror) {
                /* loading a configuration file */
                /* We don't bother to bind() if -default-keys. */
                if (!get_cmd_opt_bool("default-keys")
                    && bind_do(keymap, keystroke, action, is_system_conf)) {
                        /* bind_do() tried but failed. */
                        err = show_parse_error(state, ERROR_VALUE);
                } else {
                        err = ERROR_NONE;
                }
        } else if (is_system_conf) {
                /* scanning a file that will not be rewritten */
                /* TODO */
        } else {
                /* rewriting a configuration file */
                /* Mirror what we already have.  If the keystroke has
                 * been unbound, then act_str is simply "none" and
                 * this does not require special handling.  */
                unsigned char *act_str = bind_act(keymap, keystroke);

                if (act_str) {
                        add_bytes_to_string(mirror, state->mirrored,
                                            before_error.look - state->mirrored);
                        add_to_string(mirror, act_str);
                        mem_free(act_str);
                        state->mirrored = state->pos.look;
                } else {
                        err = show_parse_error(state, ERROR_VALUE);
                }
        }
        mem_free(keymap); mem_free(keystroke); mem_free(action);
        return err;
}

static int load_config_file(unsigned char *, unsigned char *, struct option *,
                            struct string *, int);

static enum parse_error
parse_include(struct option *opt_tree, struct conf_parsing_state *state,
              struct string *mirror, int is_system_conf)
{
        unsigned char *fname;
        struct string dumbstring;
        struct conf_parsing_pos before_error;

        if (!init_string(&dumbstring))
                return show_parse_error(state, ERROR_NOMEM);

        skip_white(&state->pos);
        if (!*state->pos.look) {
                done_string(&dumbstring);
                return show_parse_error(state, ERROR_PARSE);
        }

        /* File name */
        before_error = state->pos;
        fname = option_types[OPT_STRING].read(NULL, &state->pos.look,
                                              &state->pos.line);
        if (!fname) {
                done_string(&dumbstring);
                state->pos = before_error;
                return show_parse_error(state, ERROR_PARSE);
        }

        /* We want load_config_file() to watermark stuff, but not to load
         * anything, polluting our beloved options tree - thus, we will feed it
         * with some dummy string which we will destroy later; still better
         * than cloning whole options tree or polluting interface with another
         * rarely-used option ;). */
        /* XXX: We should try CONFDIR/<file> when proceeding
         * CONFDIR/<otherfile> ;). --pasky */
        if (load_config_file(fname[0] == '/' ? (unsigned char *) ""
                                             : elinks_home,
                             fname, opt_tree, 
                             mirror ? &dumbstring : NULL, 1)) {
                done_string(&dumbstring);
                mem_free(fname);
                return show_parse_error(state, ERROR_VALUE);
        }

        done_string(&dumbstring);
        mem_free(fname);
        return ERROR_NONE;
}


struct parse_handler {
        const unsigned char *command;
        enum parse_error (*handler)(struct option *opt_tree,
                                    struct conf_parsing_state *state,
                                    struct string *mirror, int is_system_conf);
};

static const struct parse_handler parse_handlers[] = {
        { "set", parse_set },
        { "unset", parse_unset },
        { "bind", parse_bind },
        { "include", parse_include },
        { NULL, NULL }
};


static enum parse_error
parse_config_command(struct option *options, struct conf_parsing_state *state,
                     struct string *mirror, int is_system_conf)
{
        const struct parse_handler *handler;

        /* If we're mirroring, then everything up to this point must
         * have already been mirrored.  */
        assert(mirror == NULL || state->mirrored == state->pos.look);
        if_assert_failed return show_parse_error(state, ERROR_PARSE);

        for (handler = parse_handlers; handler->command;
             handler++) {
                int cmdlen = strlen(handler->command);

                if (!strncmp(state->pos.look, handler->command, cmdlen)
                    && isspace(state->pos.look[cmdlen])) {
                        enum parse_error err;

                        state->pos.look += cmdlen;
                        err = handler->handler(options, state, mirror,
                                               is_system_conf);
                        if (mirror) {
                                /* Mirror any characters that the handler
                                 * consumed but did not already mirror.  */
                                add_bytes_to_string(mirror, state->mirrored,
                                                    state->pos.look - state->mirrored);
                                state->mirrored = state->pos.look;
                        }
                        return err;
                }
        }

        return show_parse_error(state, ERROR_COMMAND);
}

#ifdef CONFIG_EXMODE
enum parse_error
parse_config_exmode_command(unsigned char *cmd)
{
        struct conf_parsing_state state = {{ 0 }};

        state.pos.look = cmd;
        state.pos.line = 0;
        state.mirrored = NULL; /* not read because mirror is NULL too */
        state.filename = NULL; /* prevent error messages */

        return parse_config_command(config_options, &state, NULL, 0);
}
#endif /* CONFIG_EXMODE */

void
parse_config_file(struct option *options, unsigned char *name,
                  unsigned char *file, struct string *mirror,
                  int is_system_conf)
{
        struct conf_parsing_state state = {{ 0 }};
        int error_occurred = 0;

        state.pos.look = file;
        state.pos.line = 1;
        state.mirrored = file;
        if (!mirror && get_cmd_opt_int("verbose") >= VERBOSE_WARNINGS)
                state.filename = name;

        while (state.pos.look && *state.pos.look) {
                enum parse_error err = ERROR_NONE;

                /* Skip all possible comments and whitespace. */
                skip_white(&state.pos);

                /* Mirror what we already have */
                if (mirror) {
                        add_bytes_to_string(mirror, state.mirrored,
                                            state.pos.look - state.mirrored);
                        state.mirrored = state.pos.look;
                }

                /* Second chance to escape from the hell. */
                if (!*state.pos.look) break;

                err = parse_config_command(options, &state, mirror,
                                           is_system_conf);
                switch (err) {
                case ERROR_NONE:
                        break;

                case ERROR_COMMAND:
                case ERROR_PARSE:
                        /* Jump over this crap we can't understand. */
                        skip_to_unquoted_newline_or_comment(&state.pos);

                        /* Mirror what we already have */
                        if (mirror) {
                                add_bytes_to_string(mirror, state.mirrored,
                                                    state.pos.look - state.mirrored);
                                state.mirrored = state.pos.look;
                        }

                        /* fall through */
                default:
                        error_occurred = 1;
                        break;
                }
        }

        if (!error_occurred || !state.filename) return;

        /* If an error occurred make sure that the user is notified and is able
         * to see it. First sound the bell. Then, if the text viewer is going to
         * be started, sleep for a while so the message will be visible before
         * ELinks starts drawing to on the screen and overwriting any error
         * messages. This should not be necessary for terminals supporting the
         * alternate screen mode but better to be safe. (debian bug 305017) */

        fputc('\a', stderr);

        if (get_cmd_opt_bool("dump")
            || get_cmd_opt_bool("source"))
                return;

        sleep(1);
}



static unsigned char *
read_config_file(unsigned char *name)
{
#define FILE_BUF        1024
        unsigned char cfg_buffer[FILE_BUF];
        struct string string;
        int fd;
        ssize_t r;

        fd = open(name, O_RDONLY | O_NOCTTY);
        if (fd < 0) return NULL;
        set_bin(fd);

        if (!init_string(&string)) return NULL;

        while ((r = safe_read(fd, cfg_buffer, FILE_BUF)) > 0) {
                int i;

                /* Clear problems ;). */
                for (i = 0; i < r; i++)
                        if (!cfg_buffer[i])
                                cfg_buffer[i] = ' ';

                add_bytes_to_string(&string, cfg_buffer, r);
        }

        if (r < 0) done_string(&string);
        close(fd);

        return string.source;
#undef FILE_BUF
}

/* Return 0 on success. */
static int
load_config_file(unsigned char *prefix, unsigned char *name,
                 struct option *options, struct string *mirror,
                 int is_system_conf)
{
        unsigned char *config_str, *config_file;

        config_file = straconcat(prefix, STRING_DIR_SEP, name,
                                 (unsigned char *) NULL);
        if (!config_file) return 1;

        config_str = read_config_file(config_file);
        if (!config_str) {
                mem_free(config_file);
                config_file = straconcat(prefix, STRING_DIR_SEP, ".", name,
                                         (unsigned char *) NULL);
                if (!config_file) return 2;

                config_str = read_config_file(config_file);
                if (!config_str) {
                        mem_free(config_file);
                        return 3;
                }
        }

        parse_config_file(options, config_file, config_str, mirror,
                          is_system_conf);

        mem_free(config_str);
        mem_free(config_file);

        return 0;
}

static void
load_config_from(unsigned char *file, struct option *tree)
{
        load_config_file(CONFDIR, file, tree, NULL, 1);
        load_config_file(empty_string_or_(elinks_home), file, tree, NULL, 0);
}

void
load_config(void)
{
        load_config_from(get_cmd_opt_str("config-file"),
                         config_options);
}


static int indentation = 2;
/* 0 -> none, 1 -> only option full name+type, 2 -> only desc, 3 -> both */
static int comments = 3;

static inline unsigned char *
conf_i18n(unsigned char *s, int i18n)
{
        if (i18n) return gettext(s);
        return s;
}

static void
add_indent_to_string(struct string *string, int depth)
{
        if (!depth) return;

        add_xchar_to_string(string, ' ', depth * indentation);
}

struct string *
wrap_option_desc(struct string *out, const unsigned char *src,
                 const struct string *indent, int maxwidth)
{
        const unsigned char *last_space = NULL;
        const unsigned char *uncopied = src;
        int width = 0;

        /* TODO: multibyte or fullwidth characters */
        for (; *src; src++, width++) {
                if (*src == '\n') {
                        last_space = src;
                        goto split;
                }

                if (*src == ' ') last_space = src;

                if (width >= maxwidth && last_space) {
split:
                        if (!add_string_to_string(out, indent))
                                return NULL;
                        if (!add_bytes_to_string(out, uncopied,
                                                 last_space - uncopied))
                                return NULL;
                        if (!add_char_to_string(out, '\n'))
                                return NULL;
                        uncopied = last_space + 1;
                        width = src - uncopied;
                        last_space = NULL;
                }
        }
        if (*uncopied) {
                if (!add_string_to_string(out, indent))
                        return NULL;
                if (!add_to_string(out, uncopied))
                        return NULL;
                if (!add_char_to_string(out, '\n'))
                        return NULL;
        }
        return out;
}

static void
output_option_desc_as_comment(struct string *out, const struct option *option,
                              int i18n, int depth)
{
        unsigned char *desc_i18n = conf_i18n(option->desc, i18n);
        struct string indent;

        if (!init_string(&indent)) return;

        add_indent_to_string(&indent, depth);
        if (!add_to_string(&indent, "#  ")) goto out_of_memory;
        if (!wrap_option_desc(out, desc_i18n, &indent, 80 - indent.length))
                goto out_of_memory;

out_of_memory:
        done_string(&indent);
}

static void
smart_config_output_fn(struct string *string, struct option *option,
                       unsigned char *path, int depth, int do_print_comment,
                       int action, int i18n)
{
        if (option->type == OPT_ALIAS)
                return;

        switch (action) {
                case 0:
                        if (!(comments & 1)) break;

                        add_indent_to_string(string, depth);

                        add_to_string(string, "## ");
                        if (path) {
                                add_to_string(string, path);
                                add_char_to_string(string, '.');
                        }
                        add_to_string(string, option->name);
                        add_char_to_string(string, ' ');
                        add_to_string(string, option_types[option->type].help_str);
                        add_char_to_string(string, '\n');
                        break;

                case 1:
                        if (!(comments & 2)) break;

                        if (!option->desc || !do_print_comment)
                                break;

                        output_option_desc_as_comment(string, option,
                                                      i18n, depth);
                        break;

                case 2:

                        add_indent_to_string(string, depth);
                        if (option->flags & OPT_DELETED) {
                                add_to_string(string, "un");
                        }
                        add_to_string(string, "set ");
                        if (path) {
                                add_to_string(string, path);
                                add_char_to_string(string, '.');
                        }
                        add_to_string(string, option->name);
                        if (!(option->flags & OPT_DELETED)) {
                                add_to_string(string, " = ");
                                /* OPT_ALIAS won't ever. OPT_TREE won't reach action 2.
                                 * OPT_SPECIAL makes no sense in the configuration
                                 * context. */
                                assert(option_types[option->type].write);
                                option_types[option->type].write(option, string);
                        }
                        add_char_to_string(string, '\n');
                        if (do_print_comment) add_char_to_string(string, '\n');
                        break;

                case 3:
                        if (do_print_comment < 2)
                                add_char_to_string(string, '\n');
                        break;
        }
}


static void
add_cfg_header_to_string(struct string *string, unsigned char *text)
{
        int n = strlen(text) + 2;

        int_bounds(&n, 10, 80);

        add_to_string(string, "\n\n\n");
        add_xchar_to_string(string, '#', n);
        add_to_string(string, "\n# ");
        add_to_string(string, text);
        add_to_string(string, "#\n\n");
}

unsigned char *
create_config_string(unsigned char *prefix, unsigned char *name,
                     struct option *options)
{
        struct string config;
        /* Don't write headers if nothing will be added anyway. */
        struct string tmpstring;
        int origlen;
        int savestyle = get_opt_int("config.saving_style");
        int i18n = get_opt_bool("config.i18n");

        if (!init_string(&config)) return NULL;

        prepare_mustsave_flags(options->value.tree,
                               savestyle == 1 || savestyle == 2);

        /* Scaring. */
        if (savestyle == 2
            || load_config_file(prefix, name, options, &config, 0)
            || !config.length) {
                /* At first line, and in English, write ELinks version, may be
                 * of some help in future. Please keep that format for it.
                 * --Zas */
                add_to_string(&config, "## ELinks " VERSION " configuration file\n\n");
                assert(savestyle >= 0  && savestyle <= 3);
                switch (savestyle) {
                case 0:
                        add_to_string(&config, conf_i18n(N_(
                        "## This is ELinks configuration file. You can edit it manually,\n"
                        "## if you wish so; this file is edited by ELinks when you save\n"
                        "## options through UI, however only option values will be altered\n"
                        "## and all your formatting, own comments etc will be kept as-is.\n"),
                        i18n));
                        break;
                case 1: case 3:
                        add_to_string(&config, conf_i18n(N_(
                        "## This is ELinks configuration file. You can edit it manually,\n"
                        "## if you wish so; this file is edited by ELinks when you save\n"
                        "## options through UI, however only option values will be altered\n"
                        "## and missing options will be added at the end of file; if option\n"
                        "## is not written in this file, but in some file included from it,\n"
                        "## it is NOT counted as missing. Note that all your formatting,\n"
                        "## own comments and so on will be kept as-is.\n"), i18n));
                        break;
                case 2:
                        add_to_string(&config, conf_i18n(N_(
                        "## This is ELinks configuration file. You can edit it manually,\n"
                        "## if you wish so, but keep in mind that this file is overwritten\n"
                        "## by ELinks when you save options through UI and you are out of\n"
                        "## luck with your formatting and own comments then, so beware.\n"),
                        i18n));
                        break;
                }

                add_to_string(&config, "##\n");

                add_to_string(&config, conf_i18n(N_(
                        "## Obviously, if you don't like what ELinks is going to do with\n"
                        "## this file, you can change it by altering the config.saving_style\n"
                        "## option. Come on, aren't we friendly guys after all?\n"), i18n));
        }

        if (savestyle == 0) goto get_me_out;

        indentation = get_opt_int("config.indentation");
        comments = get_opt_int("config.comments");

        if (!init_string(&tmpstring)) goto get_me_out;

        add_cfg_header_to_string(&tmpstring,
                                 conf_i18n(N_("Automatically saved options\n"), i18n));

        origlen = tmpstring.length;
        smart_config_string(&tmpstring, 2, i18n, options->value.tree, NULL, 0,
                            smart_config_output_fn);
        if (tmpstring.length > origlen)
                add_string_to_string(&config, &tmpstring);
        done_string(&tmpstring);

        if (!init_string(&tmpstring)) goto get_me_out;

        add_cfg_header_to_string(&tmpstring,
                                 conf_i18n(N_("Automatically saved keybindings\n"), i18n));

        origlen = tmpstring.length;
        bind_config_string(&tmpstring);
        if (tmpstring.length > origlen)
                add_string_to_string(&config, &tmpstring);
        done_string(&tmpstring);

get_me_out:
        return config.source;
}

static int
write_config_file(unsigned char *prefix, unsigned char *name,
                  struct option *options, struct terminal *term)
{
        int ret = -1;
        struct secure_save_info *ssi;
        unsigned char *config_file = NULL;
        unsigned char *cfg_str = create_config_string(prefix, name, options);
        int prefixlen = strlen(prefix);
        int prefix_has_slash = (prefixlen && dir_sep(prefix[prefixlen - 1]));
        int name_has_slash = dir_sep(name[0]);
        unsigned char *slash = name_has_slash || prefix_has_slash ? "" : STRING_DIR_SEP;

        if (!cfg_str) return -1;

        if (name_has_slash && prefix_has_slash) name++;

        config_file = straconcat(prefix, slash, name, (unsigned char *) NULL);
        if (!config_file) goto free_cfg_str;

        ssi = secure_open(config_file);
        if (ssi) {
                secure_fputs(ssi, cfg_str);
                ret = secure_close(ssi);
                if (!ret)
                        untouch_options(options->value.tree);
        }

        write_config_dialog(term, config_file, secsave_errno, ret);
        mem_free(config_file);

free_cfg_str:
        mem_free(cfg_str);

        return ret;
}

int
write_config(struct terminal *term)
{
        assert(term);

        if (!elinks_home) {
                write_config_dialog(term, get_cmd_opt_str("config-file"),
                                    SS_ERR_DISABLED, 0);
                return -1;
        }

        return write_config_file(elinks_home, get_cmd_opt_str("config-file"),
                                 config_options, term);
}