path: root/src/xkbcomp/rules.c

/************************************************************
 * Copyright (c) 1996 by Silicon Graphics Computer Systems, Inc.
 *
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting
 * documentation, and that the name of Silicon Graphics not be
 * used in advertising or publicity pertaining to distribution
 * of the software without specific prior written permission.
 * Silicon Graphics makes no representation about the suitability
 * of this software for any purpose. It is provided "as is"
 * without any express or implied warranty.
 *
 * SILICON GRAPHICS DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
 * SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL SILICON
 * GRAPHICS BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION  WITH
 * THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 ********************************************************/

/*
 * Copyright © 2012 Ran Benita <ran234@gmail.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */

#include "xkbcomp-priv.h"
#include "rules.h"
#include "include.h"
#include "scanner-utils.h"

/*
 * The rules file
 * ==============
 * The purpose of this file is to map between configuration values that
 * are easy for a user to specify and understand, and the configuration
 * values xkbcomp uses and understands.
 * xkbcomp uses the xkb_component_names struct, which maps directly to
 * include statements of the appropriate sections, called for short
 * KcCGST (see keycodes.c, types.c, compat.c, symbols.c; geometry.c was
 * removed). These are not really intuitive or straight-forward for
 * the uninitiated.
 * Instead, the user passes in a xkb_rule_names struct, which consists
 * of the name of a rules file (in Linux this is usually "evdev"), a
 * keyboard model (e.g. "pc105"), a set of layouts (which will end up
 * in different groups, e.g. "us,fr"), variants (used to alter/augment
 * the respective layout, e.g. "intl,dvorak"), and a set of options
 * (used to tweak some general behavior of the keyboard, e.g.
 * "ctrl:nocaps,compose:menu" to make the Caps Lock key act like Ctrl
 * and the Menu key like Compose). We call these RMLVO.
 *
 * Format of the file
 * ------------------
 * The file consists of rule sets, each consisting of rules (one per
 * line), which match the MLVO values on the left hand side, and, if
 * the values match to the values the user passed in, results in the
 * values on the right hand side being added to the resulting KcCGST.
 * Since some values are related and repeated often, it is possible
 * to group them together and refer to them by a group name in the
 * rules.
 * Along with matching values by simple string equality, and for
 * membership in a group defined previously, rules may also contain
 * "wildcard" values - "*" - which always match. These usually appear
 * near the end.
 *
 * Grammer
 * -------
 * (It might be helpful to look at a file like rules/evdev along with
 * this grammer. Comments, whitespace, etc. are not shown.)
 *
 * File         ::= { "!" (Group | RuleSet) }
 *
 * Group        ::= GroupName "=" { GroupElement } "\n"
 * GroupName    ::= "$"<ident>
 * GroupElement ::= <ident>
 *
 * RuleSet      ::= Mapping { Rule }
 *
 * Mapping      ::= { Mlvo } "=" { Kccgst } "\n"
 * Mlvo         ::= "model" | "option" | ("layout" | "variant") [ Index ]
 * Index        ::= "[" 1..XKB_NUM_GROUPS "]"
 * Kccgst       ::= "keycodes" | "symbols" | "types" | "compat" | "geometry"
 *
 * Rule         ::= { MlvoValue } "=" { KccgstValue } "\n"
 * MlvoValue    ::= "*" | GroupName | <ident>
 * KccgstValue  ::= <ident>
 *
 * Notes:
 * - The order of values in a Rule must be the same as the Mapping it
 *   follows. The mapping line determines the meaning of the values in
 *   the rules which follow in the RuleSet.
 * - If a Rule is matched, %-expansion is performed on the KccgstValue,
 *   as follows:
 *   %m, %l, %v:
 *      The model, layout or variant, if only one was given (e.g.
 *      %l for "us,il" is invalid).
 *   %l[1], %v[1]:
 *      Layout or variant for the specified group Index, if more than
 *      one was given (e.g. %l[1] for "us" is invalid).
 *   %+m, %+l, %+v, %+l[1], %+v[1]
 *      As above, but prefixed with '+'. Similarly, '|', '-', '_' may be
 *      used instead of '+'.
 *   %(m), %(l), %(l[1]), %(v), %(v[1]):
 *      As above, but prefixed by '(' and suffixed by ')'.
 *   In case the expansion is invalid, as described above, it is
 *   skipped (the rest of the string is still processed); this includes
 *   the prefix and suffix (that's why you shouldn't use e.g. "(%v[1])").
 */

/* Scanner / Lexer */

/* Values returned with some tokens, like yylval. */
union lvalue {
    struct sval string;
};

/*
 * Holds the location in the file of the last processed token,
 * like yylloc.
 */
struct location {
    int line, column;
};

enum rules_token {
    TOK_END_OF_FILE = 0,
    TOK_END_OF_LINE,
    TOK_IDENTIFIER,
    TOK_GROUP_NAME,
    TOK_BANG,
    TOK_EQUALS,
    TOK_STAR,
    TOK_ERROR
};

/* C99 is stupid. Just use the 1 variant when there are no args. */
#define scanner_error1(scanner, loc, msg) \
    log_warn(scanner->ctx, "rules/%s:%d:%d: " msg "\n", \
             scanner->file_name, loc->line, loc->column)
#define scanner_error(scanner, loc, fmt, ...) \
    log_warn(scanner->ctx, "rules/%s:%d:%d: " fmt "\n", \
             scanner->file_name, loc->line, loc->column, __VA_ARGS__)

static enum rules_token
lex(struct scanner *s, union lvalue *val, struct location *loc)
{
skip_more_whitespace_and_comments:
    /* Skip spaces. */
    while (chr(s, ' ') || chr(s, '\t'));

    /* Skip comments. */
    if (lit(s, "//")) {
        while (!eof(s) && !eol(s)) next(s);
    }

    /* New line. */
    if (eol(s)) {
        while (eol(s)) next(s);
        return TOK_END_OF_LINE;
    }

    /* Escaped line continuation. */
    if (chr(s, '\\')) {
        if (!eol(s)) {
            scanner_error1(s, loc,
                           "illegal new line escape; must appear at end of line");
            return TOK_ERROR;
        }
        next(s);
        goto skip_more_whitespace_and_comments;
    }

    /* See if we're done. */
    if (eof(s)) return TOK_END_OF_FILE;

    /* New token. */
    loc->line = s->line;
    loc->column = s->column;

    /* Operators and punctuation. */
    if (chr(s, '!')) return TOK_BANG;
    if (chr(s, '=')) return TOK_EQUALS;
    if (chr(s, '*')) return TOK_STAR;

    /* Group name. */
    if (chr(s, '$')) {
        val->string.start = s->s + s->pos;
        val->string.len = 0;
        while (isgraph(peek(s))) {
            next(s);
            val->string.len++;
        }
        if (val->string.len == 0) {
            scanner_error1(s, loc,
                           "unexpected character after \'$\'; expected name");
            return TOK_ERROR;
        }
        return TOK_GROUP_NAME;
    }

    /* Identifier. */
    if (isgraph(peek(s))) {
        val->string.start = s->s + s->pos;
        val->string.len = 0;
        while (isgraph(peek(s))) {
            next(s);
            val->string.len++;
        }
        return TOK_IDENTIFIER;
    }

    scanner_error1(s, loc, "unrecognized token");
    return TOK_ERROR;
}

/***====================================================================***/

enum rules_mlvo {
    MLVO_MODEL,
    MLVO_LAYOUT,
    MLVO_VARIANT,
    MLVO_OPTION,
    _MLVO_NUM_ENTRIES
};

#define SVAL_LIT(literal) { literal, sizeof(literal) - 1 }

static const struct sval rules_mlvo_svals[_MLVO_NUM_ENTRIES] = {
    [MLVO_MODEL] = SVAL_LIT("model"),
    [MLVO_LAYOUT] = SVAL_LIT("layout"),
    [MLVO_VARIANT] = SVAL_LIT("variant"),
    [MLVO_OPTION] = SVAL_LIT("option"),
};

enum rules_kccgst {
    KCCGST_KEYCODES,
    KCCGST_TYPES,
    KCCGST_COMPAT,
    KCCGST_SYMBOLS,
    KCCGST_GEOMETRY,
    _KCCGST_NUM_ENTRIES
};

static const struct sval rules_kccgst_svals[_KCCGST_NUM_ENTRIES] = {
    [KCCGST_KEYCODES] = SVAL_LIT("keycodes"),
    [KCCGST_TYPES] = SVAL_LIT("types"),
    [KCCGST_COMPAT] = SVAL_LIT("compat"),
    [KCCGST_SYMBOLS] = SVAL_LIT("symbols"),
    [KCCGST_GEOMETRY] = SVAL_LIT("geometry"),
};

/*
 * A broken-down version of xkb_rule_names (without the rules,
 * obviously).
 */
struct rule_names {
    struct sval model;
    darray_sval layouts;
    darray_sval variants;
    darray_sval options;
};

struct group {
    struct sval name;
    darray_sval elements;
};

struct mapping {
    int mlvo_at_pos[_MLVO_NUM_ENTRIES];
    unsigned int num_mlvo;
    unsigned int defined_mlvo_mask;
    xkb_layout_index_t layout_idx, variant_idx;
    int kccgst_at_pos[_KCCGST_NUM_ENTRIES];
    unsigned int num_kccgst;
    unsigned int defined_kccgst_mask;
    bool skip;
};

enum mlvo_match_type {
    MLVO_MATCH_NORMAL = 0,
    MLVO_MATCH_WILDCARD,
    MLVO_MATCH_GROUP,
};

struct rule {
    struct sval mlvo_value_at_pos[_MLVO_NUM_ENTRIES];
    enum mlvo_match_type match_type_at_pos[_MLVO_NUM_ENTRIES];
    unsigned int num_mlvo_values;
    struct sval kccgst_value_at_pos[_KCCGST_NUM_ENTRIES];
    unsigned int num_kccgst_values;
    bool skip;
};

/*
 * This is the main object used to match a given RMLVO against a rules
 * file and aggragate the results in a KcCGST. It goes through a simple
 * matching state machine, with tokens as transitions (see
 * matcher_match()).
 */
struct matcher {
    struct xkb_context *ctx;
    /* Input.*/
    struct rule_names rmlvo;
    struct location loc;
    union lvalue val;
    struct scanner scanner;
    darray(struct group) groups;
    /* Current mapping. */
    struct mapping mapping;
    /* Current rule. */
    struct rule rule;
    /* Output. */
    darray_char kccgst[_KCCGST_NUM_ENTRIES];
};

static struct sval
strip_spaces(struct sval v)
{
    while (v.len > 0 && isspace(v.start[0])) { v.len--; v.start++; }
    while (v.len > 0 && isspace(v.start[v.len - 1])) v.len--;
    return v;
}

static darray_sval
split_comma_separated_string(const char *s)
{
    darray_sval arr = darray_new();
    struct sval val = { NULL, 0 };

    /*
     * Make sure the array returned by this function always includes at
     * least one value, e.g. "" -> { "" } and "," -> { "", "" }.
     */

    if (!s) {
        darray_append(arr, val);
        return arr;
    }

    while (true) {
        val.start = s; val.len = 0;
        while (*s != '\0' && *s != ',') { s++; val.len++; }
        darray_append(arr, strip_spaces(val));
        if (*s == '\0') break;
        if (*s == ',') s++;
    }

    return arr;
}

static struct matcher *
matcher_new(struct xkb_context *ctx,
            const struct xkb_rule_names *rmlvo)
{
    struct matcher *m = calloc(1, sizeof(*m));
    if (!m)
        return NULL;

    m->ctx = ctx;
    m->rmlvo.model.start = rmlvo->model;
    m->rmlvo.model.len = rmlvo->model ? strlen(rmlvo->model) : 0;
    m->rmlvo.layouts = split_comma_separated_string(rmlvo->layout);
    m->rmlvo.variants = split_comma_separated_string(rmlvo->variant);
    m->rmlvo.options = split_comma_separated_string(rmlvo->options);

    return m;
}

static void
matcher_free(struct matcher *m)
{
    struct group *group;
    if (!m)
        return;
    darray_free(m->rmlvo.layouts);
    darray_free(m->rmlvo.variants);
    darray_free(m->rmlvo.options);
    darray_foreach(group, m->groups)
        darray_free(group->elements);
    darray_free(m->groups);
    free(m);
}

/* C99 is stupid. Just use the 1 variant when there are no args. */
#define matcher_error1(matcher, msg) \
    log_warn(matcher->ctx, "rules/%s:%d:%d: " msg "\n", \
             matcher->scanner.file_name, matcher->loc.line, \
             matcher->loc.column)
#define matcher_error(matcher, fmt, ...) \
    log_warn(matcher->ctx, "rules/%s:%d:%d: " fmt "\n", \
             matcher->scanner.file_name, matcher->loc.line, \
             matcher->loc.column, __VA_ARGS__)

static void
matcher_group_start_new(struct matcher *m, struct sval name)
{
    struct group group = { .name = name, .elements = darray_new() };
    darray_append(m->groups, group);
}

static void
matcher_group_add_element(struct matcher *m, struct sval element)
{
    darray_append(darray_item(m->groups, darray_size(m->groups) - 1).elements,
                  element);
}

static void
matcher_mapping_start_new(struct matcher *m)
{
    unsigned int i;
    for (i = 0; i < _MLVO_NUM_ENTRIES; i++)
        m->mapping.mlvo_at_pos[i] = -1;
    for (i = 0; i < _KCCGST_NUM_ENTRIES; i++)
        m->mapping.kccgst_at_pos[i] = -1;
    m->mapping.layout_idx = m->mapping.variant_idx = XKB_LAYOUT_INVALID;
    m->mapping.num_mlvo = m->mapping.num_kccgst = 0;
    m->mapping.defined_mlvo_mask = 0;
    m->mapping.defined_kccgst_mask = 0;
    m->mapping.skip = false;
}

static int
extract_layout_index(const char *s, size_t max_len, xkb_layout_index_t *out)
{
    /* This function is pretty stupid, but works for now. */
    *out = XKB_LAYOUT_INVALID;
    if (max_len < 3)
        return -1;
    if (s[0] != '[' || !isdigit(s[1]) || s[2] != ']')
        return -1;
    if (s[1] - '0' < 1 || s[1] - '0' > XKB_MAX_GROUPS)
        return -1;
    /* To zero-based index. */
    *out = s[1] - '0' - 1;
    return 3;
}

static void
matcher_mapping_set_mlvo(struct matcher *m, struct sval ident)
{
    enum rules_mlvo mlvo;
    struct sval mlvo_sval;
    xkb_layout_index_t idx;
    int consumed;

    for (mlvo = 0; mlvo < _MLVO_NUM_ENTRIES; mlvo++) {
        mlvo_sval = rules_mlvo_svals[mlvo];

        if (svaleq_prefix(mlvo_sval, ident))
            break;
    }

    /* Not found. */
    if (mlvo >= _MLVO_NUM_ENTRIES) {
        matcher_error(m,
                      "invalid mapping: %.*s is not a valid value here; "
                      "ignoring rule set",
                      ident.len, ident.start);
        m->mapping.skip = true;
        return;
    }

    if (m->mapping.defined_mlvo_mask & (1 << mlvo)) {
        matcher_error(m,
                      "invalid mapping: %.*s appears twice on the same line; "
                      "ignoring rule set",
                      mlvo_sval.len, mlvo_sval.start);
        m->mapping.skip = true;
        return;
    }

    /* If there are leftovers still, it must be an index. */
    if (mlvo_sval.len < ident.len) {
        consumed = extract_layout_index(ident.start + mlvo_sval.len,
                                       ident.len - mlvo_sval.len, &idx);
        if ((int) (ident.len - mlvo_sval.len) != consumed) {
            matcher_error(m,
                          "invalid mapping:\" %.*s\" may only be followed by a valid group index; "
                          "ignoring rule set",
                          mlvo_sval.len, mlvo_sval.start);
            m->mapping.skip = true;
            return;
        }

        if (mlvo == MLVO_LAYOUT) {
            m->mapping.layout_idx = idx;
        }
        else if (mlvo == MLVO_VARIANT) {
            m->mapping.variant_idx = idx;
        }
        else {
            matcher_error(m,
                          "invalid mapping: \"%.*s\" cannot be followed by a group index; "
                          "ignoring rule set",
                          mlvo_sval.len, mlvo_sval.start);
            m->mapping.skip = true;
            return;
        }
    }

    m->mapping.mlvo_at_pos[m->mapping.num_mlvo] = mlvo;
    m->mapping.defined_mlvo_mask |= 1 << mlvo;
    m->mapping.num_mlvo++;
}

static void
matcher_mapping_set_kccgst(struct matcher *m, struct sval ident)
{
    enum rules_kccgst kccgst;
    struct sval kccgst_sval;

    for (kccgst = 0; kccgst < _KCCGST_NUM_ENTRIES; kccgst++) {
        kccgst_sval = rules_kccgst_svals[kccgst];

        if (svaleq(rules_kccgst_svals[kccgst], ident))
            break;
    }

    /* Not found. */
    if (kccgst >= _KCCGST_NUM_ENTRIES) {
        matcher_error(m,
                      "invalid mapping: %.*s is not a valid value here; "
                      "ignoring rule set",
                      ident.len, ident.start);
        m->mapping.skip = true;
        return;
    }

    if (m->mapping.defined_kccgst_mask & (1 << kccgst)) {
        matcher_error(m,
                      "invalid mapping: %.*s appears twice on the same line; "
                      "ignoring rule set",
                      kccgst_sval.len, kccgst_sval.start);
        m->mapping.skip = true;
        return;
    }

    m->mapping.kccgst_at_pos[m->mapping.num_kccgst] = kccgst;
    m->mapping.defined_kccgst_mask |= 1 << kccgst;
    m->mapping.num_kccgst++;
}

static void
matcher_mapping_verify(struct matcher *m)
{
    if (m->mapping.num_mlvo == 0) {
        matcher_error1(m,
                       "invalid mapping: must have at least one value on the left hand side; "
                       "ignoring rule set");
        goto skip;
    }

    if (m->mapping.num_kccgst == 0) {
        matcher_error1(m,
                       "invalid mapping: must have at least one value on the right hand side; "
                       "ignoring rule set");
        goto skip;
    }

    /*
     * This following is very stupid, but this is how it works.
     * See the "Notes" section in the overview above.
     */

    if (m->mapping.defined_mlvo_mask & (1 << MLVO_LAYOUT)) {
        if (m->mapping.layout_idx == XKB_LAYOUT_INVALID) {
            if (darray_size(m->rmlvo.layouts) > 1)
                goto skip;
        }
        else {
            if (darray_size(m->rmlvo.layouts) == 1 ||
                m->mapping.layout_idx >= darray_size(m->rmlvo.layouts))
                goto skip;
        }
    }

    if (m->mapping.defined_mlvo_mask & (1 << MLVO_VARIANT)) {
        if (m->mapping.variant_idx == XKB_LAYOUT_INVALID) {
            if (darray_size(m->rmlvo.variants) > 1)
                goto skip;
        }
        else {
            if (darray_size(m->rmlvo.variants) == 1 ||
                m->mapping.variant_idx >= darray_size(m->rmlvo.variants))
                goto skip;
        }
    }

    return;

skip:
    m->mapping.skip = true;
}

static void
matcher_rule_start_new(struct matcher *m)
{
    memset(&m->rule, 0, sizeof(m->rule));
    m->rule.skip = m->mapping.skip;
}

static void
matcher_rule_set_mlvo_common(struct matcher *m, struct sval ident,
                             enum mlvo_match_type match_type)
{
    if (m->rule.num_mlvo_values + 1 > m->mapping.num_mlvo) {
        matcher_error1(m,
                       "invalid rule: has more values than the mapping line; "
                       "ignoring rule");
        m->rule.skip = true;
        return;
    }
    m->rule.match_type_at_pos[m->rule.num_mlvo_values] = match_type;
    m->rule.mlvo_value_at_pos[m->rule.num_mlvo_values] = ident;
    m->rule.num_mlvo_values++;
}

static void
matcher_rule_set_mlvo_wildcard(struct matcher *m)
{
    struct sval dummy = { NULL, 0 };
    matcher_rule_set_mlvo_common(m, dummy, MLVO_MATCH_WILDCARD);
}

static void
matcher_rule_set_mlvo_group(struct matcher *m, struct sval ident)
{
    matcher_rule_set_mlvo_common(m, ident, MLVO_MATCH_GROUP);
}

static void
matcher_rule_set_mlvo(struct matcher *m, struct sval ident)
{
    matcher_rule_set_mlvo_common(m, ident, MLVO_MATCH_NORMAL);
}

static void
matcher_rule_set_kccgst(struct matcher *m, struct sval ident)
{
    if (m->rule.num_kccgst_values + 1 > m->mapping.num_kccgst) {
        matcher_error1(m,
                       "invalid rule: has more values than the mapping line; "
                       "ignoring rule");
        m->rule.skip = true;
        return;
    }
    m->rule.kccgst_value_at_pos[m->rule.num_kccgst_values] = ident;
    m->rule.num_kccgst_values++;
}

static bool
match_group(struct matcher *m, struct sval group_name, struct sval to)
{
    struct group *group;
    struct sval *element;
    bool found = false;

    darray_foreach(group, m->groups) {
        if (svaleq(group->name, group_name)) {
            found = true;
            break;
        }
    }

    if (!found) {
        /*
         * rules/evdev intentionally uses some undeclared group names
         * in rules (e.g. commented group definitions which may be
         * uncommented if needed). So we continue silently.
         */
        return false;
    }

    darray_foreach(element, group->elements)
        if (svaleq(to, *element))
            return true;

    return false;
}

static bool
match_value(struct matcher *m, struct sval val, struct sval to,
          enum mlvo_match_type match_type)
{
    if (match_type == MLVO_MATCH_WILDCARD)
        return true;
    if (match_type == MLVO_MATCH_GROUP)
        return match_group(m, val, to);
    return svaleq(val, to);
}

/*
 * This function performs %-expansion on @value (see overview above),
 * and appends the result to @to.
 */
static bool
append_expanded_kccgst_value(struct matcher *m, darray_char *to,
                             struct sval value)
{
    unsigned int i;
    size_t original_size = darray_size(*to);
    const char *s = value.start;
    xkb_layout_index_t idx;
    int consumed;
    enum rules_mlvo mlv;
    struct sval expanded;
    char pfx, sfx;

    /*
     * Appending  bar to  foo ->  foo (not an error if this happens)
     * Appending +bar to  foo ->  foo+bar
     * Appending  bar to +foo ->  bar+foo
     * Appending +bar to +foo -> +foo+bar
     */
    if (!darray_empty(*to) && s[0] != '+' && s[0] != '|') {
        if (darray_item(*to, 0) == '+' || darray_item(*to, 0) == '|')
            darray_prepend_items_nullterminate(*to, value.start, value.len);
        return true;
    }

    /*
     * Some ugly hand-lexing here, but going through the scanner is more
     * trouble than it's worth, and the format is ugly on its own merit.
     */
    for (i = 0; i < value.len; ) {
        /* Check if that's a start of an expansion. */
        if (s[i] != '%') {
            /* Just a normal character. */
            darray_append_items_nullterminate(*to, &s[i++], 1);
            continue;
        }
        if (++i >= value.len) goto error;

        pfx = sfx = 0;

        /* Check for prefix. */
        if (s[i] == '(' || s[i] == '+' || s[i] == '|' ||
            s[i] == '_' || s[i] == '-') {
            pfx = s[i];
            if (s[i] == '(') sfx = ')';
            if (++i >= value.len) goto error;
        }

        /* Mandatory model/layout/variant specifier. */
        switch (s[i++]) {
        case 'm': mlv = MLVO_MODEL; break;
        case 'l': mlv = MLVO_LAYOUT; break;
        case 'v': mlv = MLVO_VARIANT; break;
        default: goto error;
        }

        /* Check for index. */
        idx = XKB_LAYOUT_INVALID;
        if (i < value.len) {
            if (s[i] == '[') {
                if (mlv != MLVO_LAYOUT && mlv != MLVO_VARIANT) {
                    matcher_error1(m,
                                   "invalid index in %%-expansion; "
                                   "may only index layout or variant");
                    goto error;
                }

                consumed = extract_layout_index(s + i, value.len - i, &idx);
                if (consumed == -1) goto error;
                i += consumed;
            }
            else {
                idx = XKB_LAYOUT_INVALID;
            }
        }

        /* Check for suffix, if there supposed to be one. */
        if (sfx != 0) {
            if (i >= value.len) goto error;
            if (s[i++] != sfx) goto error;
        }

        /* Get the expanded value. */
        expanded.len = 0;

        if (mlv == MLVO_LAYOUT) {
            if (idx != XKB_LAYOUT_INVALID &&
                idx < darray_size(m->rmlvo.layouts) &&
                darray_size(m->rmlvo.layouts) > 1)
                expanded = darray_item(m->rmlvo.layouts, idx);
            else if (idx == XKB_LAYOUT_INVALID &&
                     darray_size(m->rmlvo.layouts) == 1)
                expanded = darray_item(m->rmlvo.layouts, 0);
        }
        else if (mlv == MLVO_VARIANT) {
            if (idx != XKB_LAYOUT_INVALID &&
                idx < darray_size(m->rmlvo.variants) &&
                darray_size(m->rmlvo.variants) > 1)
                expanded = darray_item(m->rmlvo.variants, idx);
            else if (idx == XKB_LAYOUT_INVALID &&
                     darray_size(m->rmlvo.variants) == 1)
                expanded = darray_item(m->rmlvo.variants, 0);
        }
        else if (mlv == MLVO_MODEL) {
            expanded = m->rmlvo.model;
        }

        /* If we didn't get one, skip silently. */
        if (expanded.len <= 0)
            continue;

        if (pfx != 0)
            darray_append_items_nullterminate(*to, &pfx, 1);
        darray_append_items_nullterminate(*to, expanded.start, expanded.len);
        if (sfx != 0)
            darray_append_items_nullterminate(*to, &sfx, 1);
    }

    return true;

error:
    matcher_error1(m, "invalid %%-expansion in value; not used");
    darray_resize(*to, original_size);
    return false;
}

static void
matcher_rule_verify(struct matcher *m)
{
    if (m->rule.num_mlvo_values != m->mapping.num_mlvo ||
        m->rule.num_kccgst_values != m->mapping.num_kccgst) {
        matcher_error1(m,
                       "invalid rule: must have same number of values as mapping line;"
                       "ignoring rule");
        m->rule.skip = true;
    }
}

static void
matcher_rule_apply_if_matches(struct matcher *m)
{
    unsigned int i;
    enum rules_mlvo mlvo;
    enum rules_kccgst kccgst;
    struct sval value, *option;
    enum mlvo_match_type match_type;
    bool matched = false;
    xkb_layout_index_t idx;

    for (i = 0; i < m->mapping.num_mlvo; i++) {
        mlvo = m->mapping.mlvo_at_pos[i];
        value = m->rule.mlvo_value_at_pos[i];
        match_type = m->rule.match_type_at_pos[i];

        if (mlvo == MLVO_MODEL) {
            matched = match_value(m, value, m->rmlvo.model, match_type);
        }
        else if (mlvo == MLVO_LAYOUT) {
            idx = m->mapping.layout_idx;
            idx = (idx == XKB_LAYOUT_INVALID ? 0 : idx);
            matched = match_value(m, value,
                                  darray_item(m->rmlvo.layouts, idx),
                                  match_type);
        }
        else if (mlvo == MLVO_VARIANT) {
            idx = m->mapping.layout_idx;
            idx = (idx == XKB_LAYOUT_INVALID ? 0 : idx);
            matched = match_value(m, value,
                                  darray_item(m->rmlvo.variants, idx),
                                  match_type);
        }
        else if (mlvo == MLVO_OPTION) {
            darray_foreach(option, m->rmlvo.options) {
                matched = match_value(m, value, *option, match_type);
                if (matched)
                    break;
            }
        }

        if (!matched)
            return;
    }

    for (i = 0; i < m->mapping.num_kccgst; i++) {
        kccgst = m->mapping.kccgst_at_pos[i];
        value = m->rule.kccgst_value_at_pos[i];
        append_expanded_kccgst_value(m, &m->kccgst[kccgst], value);
    }

    /*
     * If a rule matches in a rule set, the rest of the set should be
     * skipped. However, rule sets matching against options may contain
     * several legitimate rules, so they are processed entirely.
     */
    if (!(m->mapping.defined_mlvo_mask & (1 << MLVO_OPTION)))
        m->mapping.skip = true;
}

static enum rules_token
gettok(struct matcher *m)
{
    return lex(&m->scanner, &m->val, &m->loc);
}

static bool
matcher_match(struct matcher *m, const char *string, size_t len,
              const char *file_name, struct xkb_component_names *out)
{
    enum rules_token tok;

    if (!m)
        return false;

    scanner_init(&m->scanner, m->ctx, string, len, file_name);

initial:
    switch (tok = gettok(m)) {
    case TOK_BANG:
        goto bang;
    case TOK_END_OF_LINE:
        goto initial;
    case TOK_END_OF_FILE:
        goto finish;
    default:
        goto unexpected;
    }

bang:
    switch (tok = gettok(m)) {
    case TOK_GROUP_NAME:
        matcher_group_start_new(m, m->val.string);
        goto group_name;
    case TOK_IDENTIFIER:
        matcher_mapping_start_new(m);
        matcher_mapping_set_mlvo(m, m->val.string);
        goto mapping_mlvo;
    default:
        goto unexpected;
    }

group_name:
    switch (tok = gettok(m)) {
    case TOK_EQUALS:
        goto group_element;
    default:
        goto unexpected;
    }

group_element:
    switch (tok = gettok(m)) {
    case TOK_IDENTIFIER:
        matcher_group_add_element(m, m->val.string);
        goto group_element;
    case TOK_END_OF_LINE:
        goto initial;
    default:
        goto unexpected;
    }

mapping_mlvo:
    switch (tok = gettok(m)) {
    case TOK_IDENTIFIER:
        if (!m->mapping.skip)
            matcher_mapping_set_mlvo(m, m->val.string);
        goto mapping_mlvo;
    case TOK_EQUALS:
        goto mapping_kccgst;
    default:
        goto unexpected;
    }

mapping_kccgst:
    switch (tok = gettok(m)) {
    case TOK_IDENTIFIER:
        if (!m->mapping.skip)
            matcher_mapping_set_kccgst(m, m->val.string);
        goto mapping_kccgst;
    case TOK_END_OF_LINE:
        if (!m->mapping.skip)
            matcher_mapping_verify(m);
        goto rule_mlvo_first;
    default:
        goto unexpected;
    }

rule_mlvo_first:
    switch (tok = gettok(m)) {
    case TOK_BANG:
        goto bang;
    case TOK_END_OF_LINE:
        goto rule_mlvo_first;
    case TOK_END_OF_FILE:
        goto finish;
    default:
        matcher_rule_start_new(m);
        goto rule_mlvo_no_tok;
    }

rule_mlvo:
    tok = gettok(m);
rule_mlvo_no_tok:
    switch (tok) {
    case TOK_IDENTIFIER:
        if (!m->rule.skip)
            matcher_rule_set_mlvo(m, m->val.string);
        goto rule_mlvo;
    case TOK_STAR:
        if (!m->rule.skip)
            matcher_rule_set_mlvo_wildcard(m);
        goto rule_mlvo;
    case TOK_GROUP_NAME:
        if (!m->rule.skip)
            matcher_rule_set_mlvo_group(m, m->val.string);
        goto rule_mlvo;
    case TOK_EQUALS:
        goto rule_kccgst;
    default:
        goto unexpected;
    }

rule_kccgst:
    switch (tok = gettok(m)) {
    case TOK_IDENTIFIER:
        if (!m->rule.skip)
            matcher_rule_set_kccgst(m, m->val.string);
        goto rule_kccgst;
    case TOK_END_OF_LINE:
        if (!m->rule.skip)
            matcher_rule_verify(m);
        if (!m->rule.skip)
            matcher_rule_apply_if_matches(m);
        goto rule_mlvo_first;
    default:
        goto unexpected;
    }

unexpected:
    switch (tok) {
    case TOK_ERROR:
        goto error;
    default:
        goto state_error;
    }

finish:
    if (darray_empty(m->kccgst[KCCGST_KEYCODES]) ||
        darray_empty(m->kccgst[KCCGST_TYPES]) ||
        darray_empty(m->kccgst[KCCGST_COMPAT]) ||
        /* darray_empty(m->kccgst[KCCGST_GEOMETRY]) || */
        darray_empty(m->kccgst[KCCGST_SYMBOLS]))
        goto error;

    out->keycodes = darray_mem(m->kccgst[KCCGST_KEYCODES], 0);
    out->types = darray_mem(m->kccgst[KCCGST_TYPES], 0);
    out->compat = darray_mem(m->kccgst[KCCGST_COMPAT], 0);
    /* out->geometry = darray_mem(m->kccgst[KCCGST_GEOMETRY], 0); */
    darray_free(m->kccgst[KCCGST_GEOMETRY]);
    out->symbols = darray_mem(m->kccgst[KCCGST_SYMBOLS], 0);

    return true;

state_error:
    matcher_error1(m, "unexpected token");
error:
    return false;
}

bool
xkb_components_from_rules(struct xkb_context *ctx,
                          const struct xkb_rule_names *rmlvo,
                          struct xkb_component_names *out)
{
    bool ret = false;
    FILE *file;
    char *path;
    const char *string;
    size_t size;
    struct matcher *matcher;

    file = FindFileInXkbPath(ctx, rmlvo->rules, FILE_TYPE_RULES, &path);
    if (!file)
        goto err_out;

    ret = map_file(file, &string, &size);
    if (!ret) {
        log_err(ctx, "Couldn't read rules file: %s\n", strerror(errno));
        goto err_file;
    }

    matcher = matcher_new(ctx, rmlvo);
    ret = matcher_match(matcher, string, size, rmlvo->rules, out);
    if (!ret)
        log_err(ctx, "No components returned from XKB rules \"%s\"\n", path);
    matcher_free(matcher);

    unmap_file(string, size);
err_file:
    free(path);
    fclose(file);
err_out:
    return ret;
}