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/*
* Copyright © 2013,2021 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.
*/
#ifndef COMPOSE_COMPOSE_H
#define COMPOSE_COMPOSE_H
#include "xkbcommon/xkbcommon-compose.h"
#include "utils.h"
#include "context.h"
/*
* The compose table data structure is a ternary search tree.
*
* Reference: https://www.drdobbs.com/database/ternary-search-trees/184410528
* Visualization: https://www.cs.usfca.edu/~galles/visualization/TST.html
*
* Short example. Given these sequences:
*
* <B> <C> : "first" dead_a
* <B> <D> <E> : "second" dead_b
* <A> <F> : "third" dead_c
*
* the tree would look like:
*
* -------- [<B>]---------
* | | #
* v V
* -- [<A>] -- [<C>] --------
* # | # | |
* v # -- [<D>] --
* -- [<F>] -- # | #
* # | # v
* # -- [<E>] --
* # | #
* #
*
* where:
* - [<X>] is a node for a sequence keysym <X>.
* - right arrows are `hikid` pointers.
* - left arrows are `lokid` pointers.
* - down arrows are `eqkid` pointers.
* - # is a nil pointer.
*
* The nodes are all kept in a contiguous array. Pointers are represented
* as integer offsets into this array. A nil pointer is represented as 0
* (which, helpfully, is the offset of an empty dummy node).
*
* Nodes without an eqkid are leaf nodes. Since a sequence cannot be a
* prefix of another, these are exactly the nodes which terminate the
* sequences (in a bijective manner).
*
* A leaf contains the result data of its sequence. The result keysym is
* contained in the node struct itself; the result UTF-8 string is a byte
* offset into an array of the form "\0first\0second\0third" (the initial
* \0 is so offset 0 points to an empty string).
*/
/* Fits in uint16_t, also a good idea to have some limit. */
#define MAX_COMPOSE_NODES 65535
struct compose_node {
xkb_keysym_t keysym;
/* Offset into xkb_compose_table::nodes or 0. */
uint16_t lokid;
/* Offset into xkb_compose_table::nodes or 0. */
uint16_t hikid;
union {
struct {
uint32_t _pad:31;
bool is_leaf:1;
};
struct {
uint32_t _pad:31;
bool is_leaf:1;
/* Offset into xkb_compose_table::nodes or 0. */
uint16_t eqkid;
} internal;
struct {
/* Offset into xkb_compose_table::utf8. */
uint32_t utf8:31;
bool is_leaf:1;
xkb_keysym_t keysym;
} leaf;
};
};
struct xkb_compose_table {
int refcnt;
enum xkb_compose_format format;
enum xkb_compose_compile_flags flags;
struct xkb_context *ctx;
char *locale;
darray_char utf8;
darray(struct compose_node) nodes;
};
#endif
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