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/*!A cross-platform build utility based on Lua
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Copyright (C) 2015-present, Xmake Open Source Community.
*
* @author ruki
* @file offset.c
*
*/
/* //////////////////////////////////////////////////////////////////////////////////////
* includes
*/
#include "utf8.h"
/* //////////////////////////////////////////////////////////////////////////////////////
* implementation
*/
/* offset(s, n, [i]) -> index where n-th character counting from
* position 'i' starts; 0 means character at 'i'.
*/
tb_int_t xm_utf8_offset(lua_State *lua) {
tb_assert_and_check_return_val(lua, 0);
size_t len;
tb_char_t const* s = luaL_checklstring(lua, 1, &len);
lua_Integer n = luaL_checkinteger(lua, 2);
lua_Integer posi = (n >= 0) ? 1 : len + 1;
posi = xm_utf8_posrelat((tb_long_t)luaL_optinteger(lua, 3, posi), len);
tb_long_t result = xm_utf8_offset_impl(s, len, (tb_long_t)n, (tb_long_t)posi);
if (result == -1) {
return luaL_argerror(lua, 3, "position out of bounds");
}
if (result == -2) {
return luaL_error(lua, "initial position is a continuation byte");
}
if (result == 0) {
lua_pushnil(lua);
return 1;
}
lua_pushinteger(lua, result);
return 1;
}
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