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/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* libthai - Thai Language Support Library
* Copyright (C) 2001 Theppitak Karoonboonyanan <thep@linux.thai.net>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
/*
* thinp.c - Thai string input sequence filtering
* Created: 2001-08-04
* Author: Theppitak Karoonboonyanan <thep@linux.thai.net>
*/
#include <string.h>
#include <thai/thinp.h>
#include <thai/thctype.h>
#include <thai/tis.h>
#include <thai/wtt.h>
/**
* @brief Check for acceptance of input sequence
*
* @param c1 : previous character
* @param c2 : the newly input character
* @param s : strictness level
*
* @return non-zero if accepted, 0 otherwise
*
* Checks if, according to WTT 2.0 strictness level @a s, @a c2 is allowed
* after @a c1.
*/
int
th_isaccept (thchar_t c1, thchar_t c2, thstrict_t s)
{
switch (s) {
case ISC_PASSTHROUGH:
return 1;
case ISC_BASICCHECK:
return TACio_op (c1, c2) != RJ;
case ISC_STRICT:
{
WTTOp op = TACio_op (c1, c2);
return op != RJ && op != SR;
}
default:
return 0;
}
}
static const struct correction_t {
thchar_t c1, c2, to[3];
} corrections[] = {
{ TIS_RU, TIS_SARA_AA, { TIS_RU, TIS_LAKKHANGYAO, 0 } },
{ TIS_LU, TIS_SARA_AA, { TIS_LU, TIS_LAKKHANGYAO, 0 } },
{ TIS_NIKHAHIT, TIS_SARA_AA, { TIS_SARA_AM, 0, 0 } },
{ 0, 0, { 0, 0, 0 } }
};
static int
correct_ (thchar_t c_1, thchar_t c, thchar_t conv[3])
{
const struct correction_t *p;
for (p = corrections; p->c1; ++p) {
if (c_1 == (thchar_t) p->c1 && c == (thchar_t) p->c2) {
strcpy ((char *) conv, (const char *) p->to);
return 1;
}
}
return 0;
}
/**
* @brief Check and try to correct input sequence
*
* @param context : previous cell
* @param c : the newly input character
* @param conv : the storage for resulting correction info
*
* @returns 0 if the input is to be rejected
* non-zero otherwise.
*
* Given the previous cell as @a context, edit the input buffer using
* the given input @a c, maintaining WTT canonical order, and do some
* convenient correction in @a conv.
*/
int
th_validate (struct thcell_t context, thchar_t c, struct thinpconv_t *conv)
{
thchar_t prev_c = context.top ?
context.top :
(context.hilo ? context.hilo : context.base);
int ret;
/* SARA_AM, if present, is always the last char of the cell */
if (context.hilo == TIS_SARA_AM) {
prev_c = TIS_SARA_AM;
}
/* try predefined corrections */
ret = correct_ (prev_c, c, conv->conv);
if (ret) {
conv->offset = -1;
return 1;
}
/* normal cases, using Strict level */
if (th_isaccept (prev_c, c, ISC_STRICT)) {
conv->conv[0] = c; conv->conv[1] = 0;
conv->offset = 0;
return 1;
}
/* try correction by conversion */
switch (th_chlevel(c)) {
case 3:
case 2:
if (context.hilo && th_isaccept (context.hilo, c, ISC_STRICT)) {
/* hilo OK, replace top only */
conv->offset = 0;
conv->conv[0] = c; conv->conv[1] = 0;
if (context.top) {
--conv->offset;
}
return 1;
}
/* hilo not OK with c (hilo == SARA_AM falls here), or no hilo */
if (th_isaccept (context.base, c, ISC_STRICT)
&& (context.hilo != TIS_SARA_AM
|| th_isaccept (c, TIS_SARA_AM, ISC_STRICT)))
{
/* replace from hilo on, using new top */
int i = 0;
conv->offset = 0;
conv->conv[i++] = c;
if (context.hilo) {
--conv->offset;
if (context.hilo == TIS_SARA_AM) {
conv->conv[i++] = TIS_SARA_AM;
}
}
if (context.top) {
--conv->offset;
}
conv->conv[i] = 0;
return 1;
}
if (th_chlevel(c) == 2)
break;
/* fall through for level 3 */
case -1:
case 1:
if (th_isaccept (context.base, c, ISC_STRICT)) {
/* replace from hilo on; use new hilo + old top if OK */
int i = 0;
conv->offset = 0;
conv->conv[i++] = c;
if (context.hilo) {
--conv->offset;
}
if (context.top) {
--conv->offset;
if (th_isaccept (c, context.top, ISC_STRICT)) {
conv->conv[i++] = context.top;
}
}
conv->conv[i] = 0;
return 1;
}
break;
}
return 0;
}
/*
vi:ts=4:ai:expandtab
*/
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