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#include "utf8.hpp"
#include <format>
namespace
{
constexpr std::string_view UTF8PATT = "[%z\x01-\x7F\xC2-\xF4][\x80-\xBF]*"; // %z is deprecated in Lua5.2
// constexpr uint32_t MAXUTF = 0x7FFFFFFFu;
constexpr uint32_t MAXUNICODE = 0x10FFFFu;
inline bool isNilOrNone(const sol::stack_proxy arg)
{
return (arg.get_type() == sol::type::lua_nil || arg.get_type() == sol::type::none);
}
inline std::int64_t getInteger(const sol::stack_proxy arg, const size_t n, std::string_view name)
{
double integer;
if (!arg.is<double>())
throw std::runtime_error(std::format("bad argument #{} to '{}' (number expected, got {})", n, name,
sol::type_name(arg.lua_state(), arg.get_type())));
if (std::modf(arg, &integer) != 0)
throw std::runtime_error(
std::format("bad argument #{} to '{}' (number has no integer representation)", n, name));
return static_cast<std::int64_t>(integer);
}
// If the input 'pos' is negative, it is treated as counting from the end of the string,
// where -1 represents the last character position, -2 represents the second-to-last position,
// and so on. If 'pos' is non-negative, it is used as-is.
inline void relativePosition(int64_t& pos, const size_t len)
{
if (pos < 0)
pos = std::max<int64_t>(0, pos + len + 1);
}
inline void codepointToUTF8(char32_t codepoint, std::string& str)
{
if (codepoint <= 0x7Fu)
{
str.push_back(static_cast<char>(codepoint));
}
else if (codepoint <= 0x7FFu)
{
str.push_back(static_cast<char>(0xC0 | ((codepoint & 0x7C0) >> 6)));
str.push_back(static_cast<char>(0x80 | (codepoint & 0x3F)));
}
else if (codepoint <= 0xFFFFu)
{
str.push_back(static_cast<char>(0xE0 | ((codepoint & 0xF000) >> 12)));
str.push_back(static_cast<char>(0x80 | ((codepoint & 0xFC0) >> 6)));
str.push_back(static_cast<char>(0x80 | (codepoint & 0x3F)));
}
else if (codepoint <= MAXUNICODE)
{
str.push_back(static_cast<char>(0xF0 | ((codepoint & 0x1C0000) >> 18)));
str.push_back(static_cast<char>(0x80 | ((codepoint & 0x3F000) >> 12)));
str.push_back(static_cast<char>(0x80 | ((codepoint & 0xFC0) >> 6)));
str.push_back(static_cast<char>(0x80 | (codepoint & 0x3F)));
}
else
throw std::runtime_error("Invalid codepoint");
}
// returns: first - character pos in bytes, second - character codepoint
std::pair<int64_t, int64_t> decodeNextUTF8Character(std::string_view s, std::vector<int64_t>& posByte)
{
const int64_t pos = posByte.back() - 1;
const unsigned char ch = static_cast<unsigned char>(s[pos]);
int64_t codepoint = -1;
size_t byteSize = 0;
if ((ch & 0b10000000) == 0)
{
codepoint = ch;
byteSize = 1;
}
else if ((ch & 0b11100000) == 0b11000000)
{
codepoint = ch & 0b00011111;
byteSize = 2;
}
else if ((ch & 0b11110000) == 0b11100000)
{
codepoint = ch & 0b00001111;
byteSize = 3;
}
else if ((ch & 0b11111000) == 0b11110000)
{
codepoint = ch & 0b00000111;
byteSize = 4;
}
// construct codepoint for non-ascii
for (size_t i = 1; i < byteSize; ++i)
{
// if not a continuation byte
if ((pos + i) >= s.size() || (static_cast<unsigned char>(s[pos + i]) & 0b11000000) != 0b10000000)
{
return std::make_pair(0, -1);
}
codepoint = (codepoint << 6) | (static_cast<unsigned char>(s[pos + i]) & 0b00111111);
}
std::pair<size_t, int64_t> res = std::make_pair(posByte.back(), codepoint);
posByte.push_back(posByte.back() + byteSize); /* the next character (if exists) starts at this byte */
return res;
}
}
namespace LuaUtf8
{
sol::table initUtf8Package(sol::state_view& lua)
{
sol::table utf8(lua, sol::create);
utf8["charpattern"] = UTF8PATT;
utf8["char"] = [](const sol::variadic_args args) -> std::string {
std::string result{};
for (size_t i = 0; i < args.size(); ++i)
{
int64_t codepoint = getInteger(args[i], (i + 1), "char");
if (codepoint < 0 || codepoint > MAXUNICODE)
throw std::runtime_error(std::format("bad argument #{} to 'char' (value out of range)", i + 1));
codepointToUTF8(static_cast<char32_t>(codepoint), result);
}
return result;
};
utf8["codes"] = [](std::string_view s) {
return sol::as_function(
[s, posByte = std::vector<int64_t>{ 1 }]() mutable -> sol::optional<std::pair<int64_t, int64_t>> {
if (posByte.back() <= static_cast<int64_t>(s.size()))
{
const auto pair = decodeNextUTF8Character(s, posByte);
if (pair.second == -1)
throw std::runtime_error(std::format("Invalid UTF-8 code at position {}", posByte.size()));
return pair;
}
return sol::nullopt;
});
};
utf8["len"] = [](std::string_view s,
const sol::variadic_args args) -> std::variant<size_t, std::pair<sol::object, int64_t>> {
const size_t len = s.size();
int64_t iv = isNilOrNone(args[0]) ? 1 : getInteger(args[0], 2, "len");
int64_t fv = isNilOrNone(args[1]) ? -1 : getInteger(args[1], 3, "len");
relativePosition(iv, len);
relativePosition(fv, len);
if (iv <= 0)
throw std::runtime_error("bad argument #2 to 'len' (initial position out of bounds)");
if (fv > static_cast<int64_t>(len))
throw std::runtime_error("bad argument #3 to 'len' (final position out of bounds)");
if (len == 0)
return len;
std::vector<int64_t> posByte = { iv };
while (posByte.back() <= fv)
{
if (decodeNextUTF8Character(s, posByte).second == -1)
return std::pair(sol::lua_nil, posByte.back());
}
return posByte.size() - 1;
};
utf8["codepoint"]
= [](std::string_view s, const sol::variadic_args args) -> sol::as_returns_t<std::vector<int64_t>> {
size_t len = s.size();
int64_t iv = isNilOrNone(args[0]) ? 1 : getInteger(args[0], 2, "codepoint");
int64_t fv = isNilOrNone(args[1]) ? iv : getInteger(args[1], 3, "codepoint");
relativePosition(iv, len);
relativePosition(fv, len);
if (iv <= 0)
throw std::runtime_error("bad argument #2 to 'codepoint' (initial position out of bounds)");
if (fv > static_cast<int64_t>(len))
throw std::runtime_error("bad argument #3 to 'codepoint' (final position out of bounds)");
if (iv > fv)
return sol::as_returns(std::vector<int64_t>{}); /* empty interval; return nothing */
std::vector<int64_t> posByte = { iv };
std::vector<int64_t> codepoints;
while (posByte.back() <= fv)
{
codepoints.push_back(decodeNextUTF8Character(s, posByte).second);
if (codepoints.back() == -1)
throw std::runtime_error(std::format("Invalid UTF-8 code at position {}", posByte.size()));
}
return sol::as_returns(std::move(codepoints));
};
utf8["offset"]
= [](std::string_view s, const int64_t n, const sol::variadic_args args) -> sol::optional<int64_t> {
size_t len = s.size();
int64_t iv;
if (isNilOrNone(args[0]))
{
if (n >= 0)
iv = 1;
else
iv = s.size() + 1;
}
else
iv = getInteger(args[0], 3, "offset");
std::vector<int64_t> posByte = { 1 };
relativePosition(iv, len);
if (iv > static_cast<int64_t>(len) + 1)
throw std::runtime_error("bad argument #3 to 'offset' (position out of bounds)");
while (posByte.back() <= static_cast<int64_t>(len))
decodeNextUTF8Character(s, posByte);
for (auto it = posByte.begin(); it != posByte.end(); ++it)
{
if (*it == iv)
{
if (n <= 0 && it + n >= posByte.begin())
return *(it + n);
if (n > 0 && it + n - 1 < posByte.end())
return *(it + n - 1);
break;
}
else if (*it > iv) /* a continuation byte */
{
if (n == 0)
return *(it - 1); /* special case */
else
throw std::runtime_error("initial position is a continuation byte");
}
}
return sol::nullopt;
};
return utf8;
}
}
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