122 lines
3.9 KiB
C
122 lines
3.9 KiB
C
/*
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* Copyright © 2013,2021 Ran Benita <ran234@gmail.com>
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*/
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#ifndef COMPOSE_COMPOSE_H
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#define COMPOSE_COMPOSE_H
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#include "xkbcommon/xkbcommon-compose.h"
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#include "utils.h"
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#include "context.h"
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/*
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* The compose table data structure is a ternary search tree.
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*
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* Reference: https://www.drdobbs.com/database/ternary-search-trees/184410528
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* Visualization: https://www.cs.usfca.edu/~galles/visualization/TST.html
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*
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* Short example. Given these sequences:
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*
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* <B> <C> : "first" dead_a
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* <B> <D> <E> : "second" dead_b
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* <A> <F> : "third" dead_c
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*
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* the tree would look like:
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*
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* -------- [<B>]---------
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* | | #
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* v V
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* -- [<A>] -- [<C>] --------
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* # | # | |
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* v # -- [<D>] --
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* -- [<F>] -- # | #
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* # | # v
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* # -- [<E>] --
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* # | #
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* #
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*
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* where:
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* - [<X>] is a node for a sequence keysym <X>.
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* - right arrows are `hikid` pointers.
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* - left arrows are `lokid` pointers.
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* - down arrows are `eqkid` pointers.
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* - # is a nil pointer.
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*
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* The nodes are all kept in a contiguous array. Pointers are represented
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* as integer offsets into this array. A nil pointer is represented as 0
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* (which, helpfully, is the offset of an empty dummy node).
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*
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* Nodes without an eqkid are leaf nodes. Since a sequence cannot be a
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* prefix of another, these are exactly the nodes which terminate the
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* sequences (in a bijective manner).
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*
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* A leaf contains the result data of its sequence. The result keysym is
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* contained in the node struct itself; the result UTF-8 string is a byte
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* offset into an array of the form "\0first\0second\0third" (the initial
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* \0 is so offset 0 points to an empty string).
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*/
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/* Fits in uint16_t, also a good idea to have some limit. */
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#define MAX_COMPOSE_NODES 65535
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struct compose_node {
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xkb_keysym_t keysym;
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/* Offset into xkb_compose_table::nodes or 0. */
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uint16_t lokid;
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/* Offset into xkb_compose_table::nodes or 0. */
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uint16_t hikid;
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union {
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struct {
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uint32_t _pad:31;
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bool is_leaf:1;
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};
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struct {
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uint32_t _pad:31;
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bool is_leaf:1;
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/* Offset into xkb_compose_table::nodes or 0. */
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uint16_t eqkid;
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} internal;
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struct {
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/* Offset into xkb_compose_table::utf8. */
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uint32_t utf8:31;
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bool is_leaf:1;
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xkb_keysym_t keysym;
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} leaf;
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};
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};
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struct xkb_compose_table {
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int refcnt;
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enum xkb_compose_format format;
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enum xkb_compose_compile_flags flags;
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struct xkb_context *ctx;
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char *locale;
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darray_char utf8;
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darray(struct compose_node) nodes;
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};
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#endif
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