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#ifndef SIMDUTF_UTF8_TO_UTF32_H
#define SIMDUTF_UTF8_TO_UTF32_H
namespace simdutf {
namespace scalar {
namespace {
namespace utf8_to_utf32 {
inline size_t convert(const char *buf, size_t len, char32_t *utf32_output) {
const uint8_t *data = reinterpret_cast<const uint8_t *>(buf);
size_t pos = 0;
char32_t *start{utf32_output};
while (pos < len) {
// try to convert the next block of 16 ASCII bytes
if (pos + 16 <=
len) { // if it is safe to read 16 more bytes, check that they are ascii
uint64_t v1;
::memcpy(&v1, data + pos, sizeof(uint64_t));
uint64_t v2;
::memcpy(&v2, data + pos + sizeof(uint64_t), sizeof(uint64_t));
uint64_t v{v1 | v2};
if ((v & 0x8080808080808080) == 0) {
size_t final_pos = pos + 16;
while (pos < final_pos) {
*utf32_output++ = char32_t(buf[pos]);
pos++;
}
continue;
}
}
uint8_t leading_byte = data[pos]; // leading byte
if (leading_byte < 0b10000000) {
// converting one ASCII byte !!!
*utf32_output++ = char32_t(leading_byte);
pos++;
} else if ((leading_byte & 0b11100000) == 0b11000000) {
// We have a two-byte UTF-8
if (pos + 1 >= len) {
return 0;
} // minimal bound checking
if ((data[pos + 1] & 0b11000000) != 0b10000000) {
return 0;
}
// range check
uint32_t code_point =
(leading_byte & 0b00011111) << 6 | (data[pos + 1] & 0b00111111);
if (code_point < 0x80 || 0x7ff < code_point) {
return 0;
}
*utf32_output++ = char32_t(code_point);
pos += 2;
} else if ((leading_byte & 0b11110000) == 0b11100000) {
// We have a three-byte UTF-8
if (pos + 2 >= len) {
return 0;
} // minimal bound checking
if ((data[pos + 1] & 0b11000000) != 0b10000000) {
return 0;
}
if ((data[pos + 2] & 0b11000000) != 0b10000000) {
return 0;
}
// range check
uint32_t code_point = (leading_byte & 0b00001111) << 12 |
(data[pos + 1] & 0b00111111) << 6 |
(data[pos + 2] & 0b00111111);
if (code_point < 0x800 || 0xffff < code_point ||
(0xd7ff < code_point && code_point < 0xe000)) {
return 0;
}
*utf32_output++ = char32_t(code_point);
pos += 3;
} else if ((leading_byte & 0b11111000) == 0b11110000) { // 0b11110000
// we have a 4-byte UTF-8 word.
if (pos + 3 >= len) {
return 0;
} // minimal bound checking
if ((data[pos + 1] & 0b11000000) != 0b10000000) {
return 0;
}
if ((data[pos + 2] & 0b11000000) != 0b10000000) {
return 0;
}
if ((data[pos + 3] & 0b11000000) != 0b10000000) {
return 0;
}
// range check
uint32_t code_point = (leading_byte & 0b00000111) << 18 |
(data[pos + 1] & 0b00111111) << 12 |
(data[pos + 2] & 0b00111111) << 6 |
(data[pos + 3] & 0b00111111);
if (code_point <= 0xffff || 0x10ffff < code_point) {
return 0;
}
*utf32_output++ = char32_t(code_point);
pos += 4;
} else {
return 0;
}
}
return utf32_output - start;
}
inline result convert_with_errors(const char *buf, size_t len,
char32_t *utf32_output) {
const uint8_t *data = reinterpret_cast<const uint8_t *>(buf);
size_t pos = 0;
char32_t *start{utf32_output};
while (pos < len) {
// try to convert the next block of 16 ASCII bytes
if (pos + 16 <=
len) { // if it is safe to read 16 more bytes, check that they are ascii
uint64_t v1;
::memcpy(&v1, data + pos, sizeof(uint64_t));
uint64_t v2;
::memcpy(&v2, data + pos + sizeof(uint64_t), sizeof(uint64_t));
uint64_t v{v1 | v2};
if ((v & 0x8080808080808080) == 0) {
size_t final_pos = pos + 16;
while (pos < final_pos) {
*utf32_output++ = char32_t(buf[pos]);
pos++;
}
continue;
}
}
uint8_t leading_byte = data[pos]; // leading byte
if (leading_byte < 0b10000000) {
// converting one ASCII byte !!!
*utf32_output++ = char32_t(leading_byte);
pos++;
} else if ((leading_byte & 0b11100000) == 0b11000000) {
// We have a two-byte UTF-8
if (pos + 1 >= len) {
return result(error_code::TOO_SHORT, pos);
} // minimal bound checking
if ((data[pos + 1] & 0b11000000) != 0b10000000) {
return result(error_code::TOO_SHORT, pos);
}
// range check
uint32_t code_point =
(leading_byte & 0b00011111) << 6 | (data[pos + 1] & 0b00111111);
if (code_point < 0x80 || 0x7ff < code_point) {
return result(error_code::OVERLONG, pos);
}
*utf32_output++ = char32_t(code_point);
pos += 2;
} else if ((leading_byte & 0b11110000) == 0b11100000) {
// We have a three-byte UTF-8
if (pos + 2 >= len) {
return result(error_code::TOO_SHORT, pos);
} // minimal bound checking
if ((data[pos + 1] & 0b11000000) != 0b10000000) {
return result(error_code::TOO_SHORT, pos);
}
if ((data[pos + 2] & 0b11000000) != 0b10000000) {
return result(error_code::TOO_SHORT, pos);
}
// range check
uint32_t code_point = (leading_byte & 0b00001111) << 12 |
(data[pos + 1] & 0b00111111) << 6 |
(data[pos + 2] & 0b00111111);
if (code_point < 0x800 || 0xffff < code_point) {
return result(error_code::OVERLONG, pos);
}
if (0xd7ff < code_point && code_point < 0xe000) {
return result(error_code::SURROGATE, pos);
}
*utf32_output++ = char32_t(code_point);
pos += 3;
} else if ((leading_byte & 0b11111000) == 0b11110000) { // 0b11110000
// we have a 4-byte UTF-8 word.
if (pos + 3 >= len) {
return result(error_code::TOO_SHORT, pos);
} // minimal bound checking
if ((data[pos + 1] & 0b11000000) != 0b10000000) {
return result(error_code::TOO_SHORT, pos);
}
if ((data[pos + 2] & 0b11000000) != 0b10000000) {
return result(error_code::TOO_SHORT, pos);
}
if ((data[pos + 3] & 0b11000000) != 0b10000000) {
return result(error_code::TOO_SHORT, pos);
}
// range check
uint32_t code_point = (leading_byte & 0b00000111) << 18 |
(data[pos + 1] & 0b00111111) << 12 |
(data[pos + 2] & 0b00111111) << 6 |
(data[pos + 3] & 0b00111111);
if (code_point <= 0xffff) {
return result(error_code::OVERLONG, pos);
}
if (0x10ffff < code_point) {
return result(error_code::TOO_LARGE, pos);
}
*utf32_output++ = char32_t(code_point);
pos += 4;
} else {
// we either have too many continuation bytes or an invalid leading byte
if ((leading_byte & 0b11000000) == 0b10000000) {
return result(error_code::TOO_LONG, pos);
} else {
return result(error_code::HEADER_BITS, pos);
}
}
}
return result(error_code::SUCCESS, utf32_output - start);
}
/**
* When rewind_and_convert_with_errors is called, we are pointing at 'buf' and
* we have up to len input bytes left, and we encountered some error. It is
* possible that the error is at 'buf' exactly, but it could also be in the
* previous bytes location (up to 3 bytes back).
*
* prior_bytes indicates how many bytes, prior to 'buf' may belong to the
* current memory section and can be safely accessed. We prior_bytes to access
* safely up to three bytes before 'buf'.
*
* The caller is responsible to ensure that len > 0.
*
* If the error is believed to have occurred prior to 'buf', the count value
* contain in the result will be SIZE_T - 1, SIZE_T - 2, or SIZE_T - 3.
*/
inline result rewind_and_convert_with_errors(size_t prior_bytes,
const char *buf, size_t len,
char32_t *utf32_output) {
size_t extra_len{0};
// We potentially need to go back in time and find a leading byte.
size_t how_far_back = 3; // 3 bytes in the past + current position
if (how_far_back > prior_bytes) {
how_far_back = prior_bytes;
}
bool found_leading_bytes{false};
// important: it is i <= how_far_back and not 'i < how_far_back'.
for (size_t i = 0; i <= how_far_back; i++) {
unsigned char byte = buf[-static_cast<std::ptrdiff_t>(i)];
found_leading_bytes = ((byte & 0b11000000) != 0b10000000);
if (found_leading_bytes) {
if (i > 0 && byte < 128) {
// If we had to go back and the leading byte is ascii
// then we can stop right away.
return result(error_code::TOO_LONG, 0 - i + 1);
}
buf -= i;
extra_len = i;
break;
}
}
//
// It is possible for this function to return a negative count in its result.
// C++ Standard Section 18.1 defines size_t is in <cstddef> which is described
// in C Standard as <stddef.h>. C Standard Section 4.1.5 defines size_t as an
// unsigned integral type of the result of the sizeof operator
//
// An unsigned type will simply wrap round arithmetically (well defined).
//
if (!found_leading_bytes) {
// If how_far_back == 3, we may have four consecutive continuation bytes!!!
// [....] [continuation] [continuation] [continuation] | [buf is
// continuation] Or we possibly have a stream that does not start with a
// leading byte.
return result(error_code::TOO_LONG, 0 - how_far_back);
}
result res = convert_with_errors(buf, len + extra_len, utf32_output);
if (res.error) {
res.count -= extra_len;
}
return res;
}
} // namespace utf8_to_utf32
} // unnamed namespace
} // namespace scalar
} // namespace simdutf
#endif
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