1 /* Previous grapheme cluster function. 2 Copyright (C) 2010-2021 Free Software Foundation, Inc. 3 Written by Ben Pfaff <blp@cs.stanford.edu>, 2010. 4 5 This file is free software. 6 It is dual-licensed under "the GNU LGPLv3+ or the GNU GPLv2+". 7 You can redistribute it and/or modify it under either 8 - the terms of the GNU Lesser General Public License as published 9 by the Free Software Foundation; either version 3, or (at your 10 option) any later version, or 11 - the terms of the GNU General Public License as published by the 12 Free Software Foundation; either version 2, or (at your option) 13 any later version, or 14 - the same dual license "the GNU LGPLv3+ or the GNU GPLv2+". 15 16 This file is distributed in the hope that it will be useful, 17 but WITHOUT ANY WARRANTY; without even the implied warranty of 18 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 19 Lesser General Public License and the GNU General Public License 20 for more details. 21 22 You should have received a copy of the GNU Lesser General Public 23 License and of the GNU General Public License along with this 24 program. If not, see <https://www.gnu.org/licenses/>. */ 25 26 #include <config.h> 27 28 /* Specification. */ 29 #include "unigbrk.h" 30 31 #include "unistr.h" 32 33 const uint16_t * 34 u16_grapheme_prev (const uint16_t *s, const uint16_t *start) /* */ 35 { 36 ucs4_t next; 37 38 if (s == start) 39 return NULL; 40 41 s = u16_prev (&next, s, start); 42 while (s != start) 43 { 44 const uint16_t *prev_s; 45 ucs4_t prev; 46 47 prev_s = u16_prev (&prev, s, start); 48 if (prev_s == NULL) 49 { 50 /* Ill-formed UTF-16 encoding. */ 51 return start; 52 } 53 54 if (uc_is_grapheme_break (prev, next)) 55 break; 56 57 s = prev_s; 58 next = prev; 59 } 60 61 return s; 62 }