1 files changed, 174 insertions, 0 deletions
diff --git a/contrib/simdutf/src/haswell/avx2_convert_utf32_to_utf16.cpp b/contrib/simdutf/src/haswell/avx2_convert_utf32_to_utf16.cpp
new file mode 100644
index 000000000..ffd6f1e47
--- /dev/null
+++ b/contrib/simdutf/src/haswell/avx2_convert_utf32_to_utf16.cpp
@@ -0,0 +1,174 @@
+template <endianness big_endian>
+std::pair<const char32_t *, char16_t *>
+avx2_convert_utf32_to_utf16(const char32_t *buf, size_t len,
+                            char16_t *utf16_output) {
+  const char32_t *end = buf + len;
+
+  const size_t safety_margin =
+      12; // to avoid overruns, see issue
+          // https://github.com/simdutf/simdutf/issues/92
+  __m256i forbidden_bytemask = _mm256_setzero_si256();
+
+  while (end - buf >= std::ptrdiff_t(8 + safety_margin)) {
+    __m256i in = _mm256_loadu_si256((__m256i *)buf);
+
+    const __m256i v_00000000 = _mm256_setzero_si256();
+    const __m256i v_ffff0000 = _mm256_set1_epi32((int32_t)0xffff0000);
+
+    // no bits set above 16th bit <=> can pack to UTF16 without surrogate pairs
+    const __m256i saturation_bytemask =
+        _mm256_cmpeq_epi32(_mm256_and_si256(in, v_ffff0000), v_00000000);
+    const uint32_t saturation_bitmask =
+        static_cast<uint32_t>(_mm256_movemask_epi8(saturation_bytemask));
+
+    if (saturation_bitmask == 0xffffffff) {
+      const __m256i v_f800 = _mm256_set1_epi32((uint32_t)0xf800);
+      const __m256i v_d800 = _mm256_set1_epi32((uint32_t)0xd800);
+      forbidden_bytemask = _mm256_or_si256(
+          forbidden_bytemask,
+          _mm256_cmpeq_epi32(_mm256_and_si256(in, v_f800), v_d800));
+
+      __m128i utf16_packed = _mm_packus_epi32(_mm256_castsi256_si128(in),
+                                              _mm256_extractf128_si256(in, 1));
+      if (big_endian) {
+        const __m128i swap =
+            _mm_setr_epi8(1, 0, 3, 2, 5, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14);
+        utf16_packed = _mm_shuffle_epi8(utf16_packed, swap);
+      }
+      _mm_storeu_si128((__m128i *)utf16_output, utf16_packed);
+      utf16_output += 8;
+      buf += 8;
+    } else {
+      size_t forward = 7;
+      size_t k = 0;
+      if (size_t(end - buf) < forward + 1) {
+        forward = size_t(end - buf - 1);
+      }
+      for (; k < forward; k++) {
+        uint32_t word = buf[k];
+        if ((word & 0xFFFF0000) == 0) {
+          // will not generate a surrogate pair
+          if (word >= 0xD800 && word <= 0xDFFF) {
+            return std::make_pair(nullptr, utf16_output);
+          }
+          *utf16_output++ =
+              big_endian
+                  ? char16_t((uint16_t(word) >> 8) | (uint16_t(word) << 8))
+                  : char16_t(word);
+        } else {
+          // will generate a surrogate pair
+          if (word > 0x10FFFF) {
+            return std::make_pair(nullptr, utf16_output);
+          }
+          word -= 0x10000;
+          uint16_t high_surrogate = uint16_t(0xD800 + (word >> 10));
+          uint16_t low_surrogate = uint16_t(0xDC00 + (word & 0x3FF));
+          if (big_endian) {
+            high_surrogate =
+                uint16_t((high_surrogate >> 8) | (high_surrogate << 8));
+            low_surrogate =
+                uint16_t((low_surrogate >> 8) | (low_surrogate << 8));
+          }
+          *utf16_output++ = char16_t(high_surrogate);
+          *utf16_output++ = char16_t(low_surrogate);
+        }
+      }
+      buf += k;
+    }
+  }
+
+  // check for invalid input
+  if (static_cast<uint32_t>(_mm256_movemask_epi8(forbidden_bytemask)) != 0) {
+    return std::make_pair(nullptr, utf16_output);
+  }
+
+  return std::make_pair(buf, utf16_output);
+}
+
+template <endianness big_endian>
+std::pair<result, char16_t *>
+avx2_convert_utf32_to_utf16_with_errors(const char32_t *buf, size_t len,
+                                        char16_t *utf16_output) {
+  const char32_t *start = buf;
+  const char32_t *end = buf + len;
+
+  const size_t safety_margin =
+      12; // to avoid overruns, see issue
+          // https://github.com/simdutf/simdutf/issues/92
+
+  while (end - buf >= std::ptrdiff_t(8 + safety_margin)) {
+    __m256i in = _mm256_loadu_si256((__m256i *)buf);
+
+    const __m256i v_00000000 = _mm256_setzero_si256();
+    const __m256i v_ffff0000 = _mm256_set1_epi32((int32_t)0xffff0000);
+
+    // no bits set above 16th bit <=> can pack to UTF16 without surrogate pairs
+    const __m256i saturation_bytemask =
+        _mm256_cmpeq_epi32(_mm256_and_si256(in, v_ffff0000), v_00000000);
+    const uint32_t saturation_bitmask =
+        static_cast<uint32_t>(_mm256_movemask_epi8(saturation_bytemask));
+
+    if (saturation_bitmask == 0xffffffff) {
+      const __m256i v_f800 = _mm256_set1_epi32((uint32_t)0xf800);
+      const __m256i v_d800 = _mm256_set1_epi32((uint32_t)0xd800);
+      const __m256i forbidden_bytemask =
+          _mm256_cmpeq_epi32(_mm256_and_si256(in, v_f800), v_d800);
+      if (static_cast<uint32_t>(_mm256_movemask_epi8(forbidden_bytemask)) !=
+          0x0) {
+        return std::make_pair(result(error_code::SURROGATE, buf - start),
+                              utf16_output);
+      }
+
+      __m128i utf16_packed = _mm_packus_epi32(_mm256_castsi256_si128(in),
+                                              _mm256_extractf128_si256(in, 1));
+      if (big_endian) {
+        const __m128i swap =
+            _mm_setr_epi8(1, 0, 3, 2, 5, 4, 7, 6, 9, 8, 11, 10, 13, 12, 15, 14);
+        utf16_packed = _mm_shuffle_epi8(utf16_packed, swap);
+      }
+      _mm_storeu_si128((__m128i *)utf16_output, utf16_packed);
+      utf16_output += 8;
+      buf += 8;
+    } else {
+      size_t forward = 7;
+      size_t k = 0;
+      if (size_t(end - buf) < forward + 1) {
+        forward = size_t(end - buf - 1);
+      }
+      for (; k < forward; k++) {
+        uint32_t word = buf[k];
+        if ((word & 0xFFFF0000) == 0) {
+          // will not generate a surrogate pair
+          if (word >= 0xD800 && word <= 0xDFFF) {
+            return std::make_pair(
+                result(error_code::SURROGATE, buf - start + k), utf16_output);
+          }
+          *utf16_output++ =
+              big_endian
+                  ? char16_t((uint16_t(word) >> 8) | (uint16_t(word) << 8))
+                  : char16_t(word);
+        } else {
+          // will generate a surrogate pair
+          if (word > 0x10FFFF) {
+            return std::make_pair(
+                result(error_code::TOO_LARGE, buf - start + k), utf16_output);
+          }
+          word -= 0x10000;
+          uint16_t high_surrogate = uint16_t(0xD800 + (word >> 10));
+          uint16_t low_surrogate = uint16_t(0xDC00 + (word & 0x3FF));
+          if (big_endian) {
+            high_surrogate =
+                uint16_t((high_surrogate >> 8) | (high_surrogate << 8));
+            low_surrogate =
+                uint16_t((low_surrogate >> 8) | (low_surrogate << 8));
+          }
+          *utf16_output++ = char16_t(high_surrogate);
+          *utf16_output++ = char16_t(low_surrogate);
+        }
+      }
+      buf += k;
+    }
+  }
+
+  return std::make_pair(result(error_code::SUCCESS, buf - start), utf16_output);
+}