1/* Iterate over previous character in UTF-16 string. 2 Copyright (C) 2002, 2006-2007, 2009-2010 Free Software Foundation, Inc. 3 Written by Bruno Haible <bruno@clisp.org>, 2002. 4 5 This program is free software: you can redistribute it and/or modify it 6 under the terms of the GNU Lesser General Public License as published 7 by the Free Software Foundation; either version 3 of the License, or 8 (at your option) any later version. 9 10 This program is distributed in the hope that it will be useful, 11 but WITHOUT ANY WARRANTY; without even the implied warranty of 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 13 Lesser General Public License for more details. 14 15 You should have received a copy of the GNU Lesser General Public License 16 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 17 18#include <config.h> 19 20/* Specification. */ 21#include "unistr.h" 22 23const uint16_t * 24u16_prev (ucs4_t *puc, const uint16_t *s, const uint16_t *start) 25{ 26 /* Keep in sync with unistr.h and utf16-ucs4.c. */ 27 if (s != start) 28 { 29 uint16_t c_1 = s[-1]; 30 31 if (c_1 < 0xd800 || c_1 >= 0xe000) 32 { 33 *puc = c_1; 34 return s - 1; 35 } 36#if CONFIG_UNICODE_SAFETY 37 if (c_1 >= 0xdc00) 38#endif 39 if (s - 1 != start) 40 { 41 uint16_t c_2 = s[-2]; 42 43#if CONFIG_UNICODE_SAFETY 44 if (c_2 >= 0xd800 && c_2 < 0xdc00) 45#endif 46 { 47 *puc = 0x10000 + ((c_2 - 0xd800) << 10) + (c_1 - 0xdc00); 48 return s - 2; 49 } 50 } 51 } 52 return NULL; 53} 54