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/*
Copyright (C) 2024 Selwin van Dijk
This file is part of signalbackup-tools.
signalbackup-tools 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.
signalbackup-tools 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 signalbackup-tools. If not, see <https://www.gnu.org/licenses/>.
*/
#include "signalbackup.ih"
#if __cpp_lib_unreachable >= 202202L
#include <utility>
#endif
// return:
// 0 = ok, finished
// -1 = error, stop!
// 1 = need more data to complete codepoint
int SignalBackup::utf16ToUnicodeCodepoint(uint16_t utf16, uint32_t *codepoint) const
{
/*
U = some unicode codepoint > 0x100000
U' = yyyyyyyyyyxxxxxxxxxx // U - 0x10000
W1 = 110110yyyyyyyyyy // 0xD800 + yyyyyyyyyy
W2 = 110111xxxxxxxxxx // 0xDC00 + xxxxxxxxxx
*/
// low surrogate
if (utf16 >= 0xDC00 && utf16 < 0xE000)
{
*codepoint += (utf16 & 0b0000'0011'1111'1111);
*codepoint += 0x10000;
return 0;
}
if (*codepoint != 0) [[unlikely]]
return -1;
// check if it is a high surrogate
if (utf16 >= 0xD800 && utf16 < 0xE000)
{
*codepoint = ((utf16 & 0b0000'0011'1111'1111) << 10);
return 1;
}
if (utf16 < 0xD800 || utf16 >= 0xE000) // single char codepoint
{
*codepoint = utf16;
return 0;
}
#if __cpp_lib_unreachable >= 202202L
std::unreachable();
#endif
return -1;
}
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