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/* Sentence handling.
Copyright (C) 2015-2016 Free Software Foundation, Inc.
Written by Daiki Ueno <ueno@gnu.org>, 2015.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
/* Specification. */
#include "sentence.h"
#include <stdlib.h>
#include <string.h>
#include "unistr.h"
/* The minimal number of white spaces which should follow after the
end of sentence. */
int sentence_end_required_spaces = 1;
/* This function works in a similar way to 'forward-sentence' in
Emacs, which basically does a regular expression matching of:
[.?!\u2026]
[]"'\u201d)}]*
\($\|[ \u00a0]$\|\t\|[ \u00a0]\{REQUIRED_SPACES\}\)
Since we are lacking a regular expression routine capable of
Unicode (though gnulib-lib/lib/regex.c provides a locale-dependent
version, we would rather avoid depending on it), apply a manually
constructed DFA, which consists of 8 states where 4 of them are a
terminal. */
const char *
sentence_end (const char *string, ucs4_t *ending_charp)
{
const char *str = string;
const char *str_limit = string + strlen (str);
/* States of the DFA, 0 to 7, where 3, 5, 6, and 7 are a terminal. */
int state = 0;
/* Previous character before an end marker. */
ucs4_t ending_char = 0xfffd;
/* Possible starting position of the match, and the next starting
position if the current match fails. */
const char *match_start = NULL, *match_next = NULL;
/* Number of spaces. */
int spaces = 0;
while (str <= str_limit)
{
ucs4_t uc;
size_t length;
length = u8_mbtouc (&uc, (const unsigned char *) str, str_limit - str);
if (state == 0)
{
switch (uc)
{
case '.': case '?': case '!': case 0x2026:
state = 1;
match_start = str;
match_next = str + length;
ending_char = uc;
spaces = 0;
break;
default:
break;
}
str += length;
continue;
}
if (state == 1)
{
switch (uc)
{
case ']': case '"': case '\'': case ')': case '}': case 0x201d:
state = 2;
break;
case '\0': case '\n':
/* State 3. */
*ending_charp = ending_char;
return match_start;
case ' ': case 0x00a0:
if (++spaces == sentence_end_required_spaces)
{
/* State 7. */
*ending_charp = ending_char;
return match_start;
}
state = 4;
break;
case '\t':
/* State 5. */
*ending_charp = ending_char;
return match_start;
default:
str = match_next;
state = 0;
continue;
}
str += length;
continue;
}
if (state == 2)
{
switch (uc)
{
case ']': case '"': case '\'': case ')': case '}': case 0x201d:
break;
case '\0': case '\n':
/* State 3. */
*ending_charp = ending_char;
return match_start;
case ' ': case 0x00a0:
if (++spaces == sentence_end_required_spaces)
{
/* State 7. */
*ending_charp = ending_char;
return match_start;
}
state = 4;
break;
case '\t':
/* State 5. */
*ending_charp = ending_char;
return match_start;
default:
state = 0;
str = match_next;
continue;
}
str += length;
continue;
}
if (state == 4)
{
switch (uc)
{
case '\0': case '\n':
/* State 6. */
*ending_charp = ending_char;
return match_start;
case ' ': case 0x00a0:
if (++spaces == sentence_end_required_spaces)
{
/* State 7. */
*ending_charp = ending_char;
return match_start;
}
break;
default:
state = 0;
str = match_next;
continue;
}
str += length;
continue;
}
}
*ending_charp = 0xfffd;
return str_limit;
}
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