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// Copyright 2017 Elias Kosunen
//
// 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
//
// https://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.
//
// This file is a part of scnlib:
// https://github.com/eliaskosunen/scnlib
//
// The contents of this file are based on utfcpp:
// https://github.com/nemtrif/utfcpp
// Copyright (c) 2006 Nemanja Trifunovic
// Distributed under the Boost Software License, version 1.0
#ifndef SCN_UNICODE_UTF16_H
#define SCN_UNICODE_UTF16_H
#include "../detail/error.h"
#include "../util/expected.h"
#include "common.h"
namespace scn {
SCN_BEGIN_NAMESPACE
namespace detail {
namespace utf16 {
template <typename U16>
SCN_CONSTEXPR14 int get_sequence_length(U16 ch)
{
uint16_t lead = mask16(ch);
if (is_lead_surrogate(lead)) {
return 2;
}
if (SCN_UNLIKELY(is_trail_surrogate(lead))) {
return 0;
}
return 1;
}
template <typename I, typename S>
SCN_CONSTEXPR14 error validate_next(I& it, S end, code_point& cp)
{
SCN_EXPECT(it != end);
uint16_t lead = mask16(*it);
if (is_lead_surrogate(lead)) {
++it;
if (it == end) {
return {error::invalid_encoding,
"Lone utf16 lead surrogate"};
}
uint16_t trail = mask16(*it);
if (!is_trail_surrogate(trail)) {
return {error::invalid_encoding,
"Invalid utf16 trail surrogate"};
}
++it;
cp = static_cast<code_point>(
static_cast<uint32_t>(lead << 10u) + trail +
surrogate_offset);
return {};
}
if (is_trail_surrogate(lead)) {
return {error::invalid_encoding,
"Lone utf16 trail surrogate"};
}
cp = static_cast<code_point>(*it);
++it;
return {};
}
template <typename I, typename S>
SCN_CONSTEXPR14 expected<I> parse_code_point(I begin,
S end,
code_point& cp)
{
auto e = validate_next(begin, end, cp);
if (!e) {
return e;
}
return {begin};
}
template <typename I, typename S>
SCN_CONSTEXPR14 expected<I> encode_code_point(I begin,
S end,
code_point cp)
{
SCN_EXPECT(begin + 2 <= end);
if (!is_valid_code_point(cp)) {
return error(error::invalid_encoding,
"Invalid code point, cannot encode in UTF-16");
}
if (cp > 0xffffu) {
*begin++ = static_cast<uint16_t>(
(static_cast<uint32_t>(cp) >> 10u) + lead_offset);
*begin++ = static_cast<uint16_t>(
(static_cast<uint32_t>(cp) & 0x3ffu) +
trail_surrogate_min);
}
else {
*begin++ = static_cast<uint16_t>(cp);
}
return {begin};
}
template <typename I, typename S>
SCN_CONSTEXPR14 expected<std::ptrdiff_t> code_point_distance(
I begin,
S end)
{
std::ptrdiff_t dist{};
code_point cp{};
for (; begin < end; ++dist) {
auto e = validate_next(begin, end, cp);
if (!e) {
return e;
}
}
return {dist};
}
} // namespace utf16
} // namespace detail
SCN_END_NAMESPACE
} // namespace scn
#endif
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