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std::pair<const char32_t *, char *>
avx2_convert_utf32_to_latin1(const char32_t *buf, size_t len,
char *latin1_output) {
const size_t rounded_len =
len & ~0x1F; // Round down to nearest multiple of 32
__m256i high_bytes_mask = _mm256_set1_epi32(0xFFFFFF00);
__m256i shufmask = _mm256_set_epi8(-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, 12, 8, 4, 0, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, 12, 8, 4, 0);
for (size_t i = 0; i < rounded_len; i += 16) {
__m256i in1 = _mm256_loadu_si256((__m256i *)buf);
__m256i in2 = _mm256_loadu_si256((__m256i *)(buf + 8));
__m256i check_combined = _mm256_or_si256(in1, in2);
if (!_mm256_testz_si256(check_combined, high_bytes_mask)) {
return std::make_pair(nullptr, latin1_output);
}
// Turn UTF32 bytes into latin 1 bytes
__m256i shuffled1 = _mm256_shuffle_epi8(in1, shufmask);
__m256i shuffled2 = _mm256_shuffle_epi8(in2, shufmask);
// move Latin1 bytes to their correct spot
__m256i idx1 = _mm256_set_epi32(-1, -1, -1, -1, -1, -1, 4, 0);
__m256i idx2 = _mm256_set_epi32(-1, -1, -1, -1, 4, 0, -1, -1);
__m256i reshuffled1 = _mm256_permutevar8x32_epi32(shuffled1, idx1);
__m256i reshuffled2 = _mm256_permutevar8x32_epi32(shuffled2, idx2);
__m256i result = _mm256_or_si256(reshuffled1, reshuffled2);
_mm_storeu_si128((__m128i *)latin1_output, _mm256_castsi256_si128(result));
latin1_output += 16;
buf += 16;
}
return std::make_pair(buf, latin1_output);
}
std::pair<result, char *>
avx2_convert_utf32_to_latin1_with_errors(const char32_t *buf, size_t len,
char *latin1_output) {
const size_t rounded_len =
len & ~0x1F; // Round down to nearest multiple of 32
__m256i high_bytes_mask = _mm256_set1_epi32(0xFFFFFF00);
__m256i shufmask = _mm256_set_epi8(-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, 12, 8, 4, 0, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, 12, 8, 4, 0);
const char32_t *start = buf;
for (size_t i = 0; i < rounded_len; i += 16) {
__m256i in1 = _mm256_loadu_si256((__m256i *)buf);
__m256i in2 = _mm256_loadu_si256((__m256i *)(buf + 8));
__m256i check_combined = _mm256_or_si256(in1, in2);
if (!_mm256_testz_si256(check_combined, high_bytes_mask)) {
// Fallback to scalar code for handling errors
for (int k = 0; k < 8; k++) {
char32_t codepoint = buf[k];
if (codepoint <= 0xFF) {
*latin1_output++ = static_cast<char>(codepoint);
} else {
return std::make_pair(result(error_code::TOO_LARGE, buf - start + k),
latin1_output);
}
}
buf += 8;
} else {
__m256i shuffled1 = _mm256_shuffle_epi8(in1, shufmask);
__m256i shuffled2 = _mm256_shuffle_epi8(in2, shufmask);
__m256i idx1 = _mm256_set_epi32(-1, -1, -1, -1, -1, -1, 4, 0);
__m256i idx2 = _mm256_set_epi32(-1, -1, -1, -1, 4, 0, -1, -1);
__m256i reshuffled1 = _mm256_permutevar8x32_epi32(shuffled1, idx1);
__m256i reshuffled2 = _mm256_permutevar8x32_epi32(shuffled2, idx2);
__m256i result = _mm256_or_si256(reshuffled1, reshuffled2);
_mm_storeu_si128((__m128i *)latin1_output,
_mm256_castsi256_si128(result));
latin1_output += 16;
buf += 16;
}
}
return std::make_pair(result(error_code::SUCCESS, buf - start),
latin1_output);
}
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