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#ifndef U8_HH
#define U8_HH
#include "u.hh" // IWYU pragma: export
#include <cstdint> // IWYU pragma: export
#include <expected>
#include <iterator>
#include <type_traits>
#include <utility>
namespace u8 {
template <std::forward_iterator T>
requires std::is_same_v<std::iter_value_t<T>, uint8_t>
std::expected<uint32_t, u::ReadError> read(T& start, T const& end) {
if (start == end)
return std::unexpected(u::ReadError::End);
uint32_t u;
switch (*start >> 4) {
case 0xf:
// 11110uvv 10vvwwww 10xxxxyy 10yyzzzz
if (std::distance(start, end) < 4) {
return std::unexpected(u::ReadError::Incomplete);
}
u = (*start & 0x07) << 18;
std::advance(start, 1);
if ((*start & 0xc0) != 0x80) {
std::advance(start, 3);
return std::unexpected(u::ReadError::Invalid);
}
u |= (*start & 0x3f) << 12;
std::advance(start, 1);
if ((*start & 0xc0) != 0x80) {
std::advance(start, 2);
return std::unexpected(u::ReadError::Invalid);
}
u |= (*start & 0x3f) << 6;
std::advance(start, 1);
if ((*start & 0xc0) != 0x80) {
std::advance(start, 1);
return std::unexpected(u::ReadError::Invalid);
}
u |= *start & 0x3f;
if (u < 0x10000 || u > 0x10ffff) {
std::advance(start, 1);
return std::unexpected(u::ReadError::Invalid);
}
break;
case 0xe:
// 1110wwww 10xxxxyy 10yyzzzz
if (std::distance(start, end) < 3) {
return std::unexpected(u::ReadError::Incomplete);
}
u = (*start & 0x0f) << 12;
std::advance(start, 1);
if ((*start & 0xc0) != 0x80) {
std::advance(start, 2);
return std::unexpected(u::ReadError::Invalid);
}
u |= (*start & 0x3f) << 6;
std::advance(start, 1);
if ((*start & 0xc0) != 0x80) {
std::advance(start, 1);
return std::unexpected(u::ReadError::Invalid);
}
u |= *start & 0x3f;
if (u < 0x800 || (u >= 0xd800 && u <= 0xdfff)) {
std::advance(start, 1);
return std::unexpected(u::ReadError::Invalid);
}
break;
case 0xd:
case 0xc:
// 110xxxyy 10yyzzzz
if (std::distance(start, end) < 2) {
return std::unexpected(u::ReadError::Incomplete);
}
u = (*start & 0x1f) << 6;
std::advance(start, 1);
if ((*start & 0xc0) != 0x80) {
std::advance(start, 1);
return std::unexpected(u::ReadError::Invalid);
}
u |= *start & 0x3f;
if (u < 0x80) {
std::advance(start, 1);
return std::unexpected(u::ReadError::Invalid);
}
break;
case 0xb:
case 0xa:
case 0x9:
case 0x8:
std::advance(start, 1);
return std::unexpected(u::ReadError::Invalid);
default:
// 0yyyzzzz
u = *start;
break;
}
std::advance(start, 1);
return u;
}
template <std::forward_iterator T>
requires std::is_same_v<std::iter_value_t<T>, uint8_t>
std::expected<uint32_t, u::ReadErrorReplace> read_replace(T& start,
T const& end,
bool eof) {
auto const tmp = start;
auto ret = read(start, end);
if (ret.has_value())
return *ret;
switch (ret.error()) {
case u::ReadError::Incomplete:
if (eof)
break;
return std::unexpected(u::ReadErrorReplace::Incomplete);
case u::ReadError::End:
return std::unexpected(u::ReadErrorReplace::End);
case u::ReadError::Invalid:
break;
}
start = tmp + 1;
return 0xfffd;
}
template <std::forward_iterator T>
requires std::is_same_v<std::iter_value_t<T>, uint8_t>
bool write(T& start, T const& end, uint32_t code) {
if (code < 0x80) {
if (start == end)
return false;
*start = static_cast<uint8_t>(code);
} else if (code < 0x800) {
if (std::distance(start, end) < 2)
return false;
*start = 0xc0 | static_cast<uint8_t>(code >> 6);
std::advance(start, 1);
*start = 0x80 | static_cast<uint8_t>(code & 0x3f);
} else if (code < 0x10000) {
if (std::distance(start, end) < 3)
return false;
*start = 0xe0 | static_cast<uint8_t>(code >> 12);
std::advance(start, 1);
*start = 0x80 | static_cast<uint8_t>((code >> 6) & 0x3f);
std::advance(start, 1);
*start = 0x80 | static_cast<uint8_t>(code & 0x3f);
} else {
if (std::distance(start, end) < 4)
return false;
*start = 0xf0 | static_cast<uint8_t>(code >> 18);
std::advance(start, 1);
*start = 0x80 | static_cast<uint8_t>((code >> 12) & 0x3f);
std::advance(start, 1);
*start = 0x80 | static_cast<uint8_t>((code >> 6) & 0x3f);
std::advance(start, 1);
*start = 0x80 | static_cast<uint8_t>(code & 0x3f);
}
std::advance(start, 1);
return true;
}
template <std::forward_iterator T>
requires std::is_same_v<std::iter_value_t<T>, uint8_t>
bool skip(T& start, T const& end) {
if (start == end)
return false;
switch (*start >> 4) {
case 0xf:
if (std::distance(start, end) < 4)
return false;
std::advance(start, 4);
break;
case 0xe:
if (std::distance(start, end) < 3)
return false;
std::advance(start, 3);
break;
case 0xc:
case 0xd:
if (std::distance(start, end) < 2)
return false;
std::advance(start, 2);
break;
default:
std::advance(start, 1);
break;
}
return true;
}
} // namespace u8
#endif // U8_HH
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