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#include "cru/common/StringUtil.hpp"
#include <codecvt>
namespace cru {
template <typename UInt, int number_of_bit>
inline std::enable_if_t<std::is_unsigned_v<UInt>, CodePoint> ExtractBits(
UInt n) {
return static_cast<CodePoint>(n & ((1u << number_of_bit) - 1));
}
CodePoint Utf16Iterator::Previous() {
if (position_ <= 0) return k_invalid_code_point;
const auto cu0 = static_cast<std::uint16_t>(string_[--position_]);
if (cu0 < 0xd800u || cu0 >= 0xe000u) { // 1-length code point
return static_cast<CodePoint>(cu0);
} else if (cu0 < 0xdc00u || cu0 > 0xdfffu) { // 2-length code point
if (position_ <= 0) {
throw TextEncodeException(
"Unexpected end when reading first code unit of surrogate pair "
"during backward.");
}
const auto cu1 = static_cast<std::uint16_t>(string_[--position_]);
#ifdef CRU_DEBUG
if (cu1 <= 0xdbffu) {
throw TextEncodeException(
"Unexpected bad-range first code unit of surrogate pair during "
"backward.");
}
#endif
const auto s0 = ExtractBits<std::uint16_t, 10>(cu1) << 10;
const auto s1 = ExtractBits<std::uint16_t, 10>(cu0);
return s0 + s1 + 0x10000;
} else {
throw TextEncodeException(
"Unexpected bad-range second code unit of surrogate pair during "
"backward.");
}
}
CodePoint Utf16Iterator::Next() {
if (position_ >= static_cast<Index>(string_.length()))
return k_invalid_code_point;
const auto cu0 = static_cast<std::uint16_t>(string_[position_++]);
if (cu0 < 0xd800u || cu0 >= 0xe000u) { // 1-length code point
return static_cast<CodePoint>(cu0);
} else if (cu0 <= 0xdbffu) { // 2-length code point
if (position_ >= static_cast<Index>(string_.length())) {
throw TextEncodeException(
"Unexpected end when reading second code unit of surrogate pair "
"during forward.");
}
const auto cu1 = static_cast<std::uint16_t>(string_[position_++]);
#ifdef CRU_DEBUG
if (cu1 < 0xdc00u || cu1 > 0xdfffu) {
throw TextEncodeException(
"Unexpected bad-format second code unit of surrogate pair during "
"forward.");
}
#endif
const auto s0 = ExtractBits<std::uint16_t, 10>(cu0) << 10;
const auto s1 = ExtractBits<std::uint16_t, 10>(cu1);
return s0 + s1 + 0x10000;
} else {
throw TextEncodeException(
"Unexpected bad-format first code unit of surrogate pair during "
"forward.");
}
}
Index PreviousIndex(std::u16string_view string, Index current) {
Utf16Iterator iterator{string, current};
iterator.Previous();
return iterator.CurrentPosition();
}
Index NextIndex(std::u16string_view string, Index current) {
Utf16Iterator iterator{string, current};
iterator.Next();
return iterator.CurrentPosition();
}
std::string ToUtf8(const std::u16string& s) {
// TODO: Implement this by myself.
return std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t>{}
.to_bytes(s);
}
// CodePoint Utf8Iterator::Next() {
// if (position_ == static_cast<Index>(string_.length()))
// return k_invalid_code_point;
// const auto cu0 = static_cast<std::uint8_t>(string_[position_++]);
// auto read_next_folowing_code = [this]() -> CodePoint {
// if (this->position_ == static_cast<Index>(string_.length()))
// throw TextEncodeException(
// "Unexpected end when read continuing byte of multi-byte code
// point.");
// #ifdef CRU_DEBUG
// const auto u = static_cast<std::uint8_t>(string_[position_]);
// if (!(u & (1u << 7)) || (u & (1u << 6))) {
// throw TextEncodeException(
// "Unexpected bad-format (not 0b10xxxxxx) continuing byte of "
// "multi-byte code point.");
// }
// #endif
// return ExtractBits<std::uint8_t, 6>(string_[position_++]);
// };
// if ((1u << 7) & cu0) {
// if ((1u << 6) & cu0) { // 2~4-length code point
// if ((1u << 5) & cu0) { // 3~4-length code point
// if ((1u << 4) & cu0) { // 4-length code point
// #ifdef CRU_DEBUG
// if (cu0 & (1u << 3)) {
// throw TextEncodeException(
// "Unexpected bad-format begin byte (not 0b10xxxxxx) of 4-byte
// " "code point.");
// }
// #endif
// const CodePoint s0 = ExtractBits<std::uint8_t, 3>(cu0) << (6 * 3);
// const CodePoint s1 = read_next_folowing_code() << (6 * 2);
// const CodePoint s2 = read_next_folowing_code() << 6;
// const CodePoint s3 = read_next_folowing_code();
// return s0 + s1 + s2 + s3;
// } else { // 3-length code point
// const CodePoint s0 = ExtractBits<std::uint8_t, 4>(cu0) << (6 * 2);
// const CodePoint s1 = read_next_folowing_code() << 6;
// const CodePoint s2 = read_next_folowing_code();
// return s0 + s1 + s2;
// }
// } else { // 2-length code point
// const CodePoint s0 = ExtractBits<std::uint8_t, 5>(cu0) << 6;
// const CodePoint s1 = read_next_folowing_code();
// return s0 + s1;
// }
// } else {
// throw TextEncodeException(
// "Unexpected bad-format (0b10xxxxxx) begin byte of a code point.");
// }
// } else {
// return static_cast<CodePoint>(cu0);
// }
// }
} // namespace cru
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