Tweaking.

src/fallback/dom_parser_implementation.cpp

@@ -243,6 +243,93 @@ WARN_UNUSED error_code implementation::minify(const uint8_t *buf, size_t len, ui
   // for fear of aliasing
   return SUCCESS;
 }
+WARN_UNUSED bool implementation::validate_utf8(const char *buf, size_t len) const noexcept { 
+  const uint8_t *data = (const uint8_t *)buf;
+  uint64_t pos = 0;
+  uint64_t next_pos = 0;
+  uint32_t code_point = 0;
+  while (pos < len) {
+
+    // check of the next 8 bytes are ascii.
+    next_pos = pos + 16;
+    if (next_pos <=
+        len) { // if it is safe to read 8 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) {
+        pos = next_pos;
+        continue;
+      }
+    }
+    unsigned char byte = data[pos];
+
+    if (byte < 0b10000000) {
+      pos++;
+      continue;
+    } else if ((byte & 0b11100000) == 0b11000000) {
+      next_pos = pos + 2;
+      if (next_pos > len) {
+        return false;
+      }
+      if ((data[pos + 1] & 0b11000000) != 0b10000000) {
+        return false;
+      }
+      // range check
+      code_point = (byte & 0b00011111) << 6 | (data[pos + 1] & 0b00111111);
+      if (code_point < 0x80 || 0x7ff < code_point) {
+        return false;
+      }
+    } else if ((byte & 0b11110000) == 0b11100000) {
+      next_pos = pos + 3;
+      if (next_pos > len) {
+        return false;
+      }
+      if ((data[pos + 1] & 0b11000000) != 0b10000000) {
+        return false;
+      }
+      if ((data[pos + 2] & 0b11000000) != 0b10000000) {
+        return false;
+      }
+      // range check
+      code_point = (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 false;
+      }
+    } else if ((byte & 0b11111000) == 0b11110000) { // 0b11110000
+      next_pos = pos + 4;
+      if (next_pos > len) {
+        return false;
+      }
+      if ((data[pos + 1] & 0b11000000) != 0b10000000) {
+        return false;
+      }
+      if ((data[pos + 2] & 0b11000000) != 0b10000000) {
+        return false;
+      }
+      if ((data[pos + 3] & 0b11000000) != 0b10000000) {
+        return false;
+      }
+      // range check
+      code_point =
+          (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 false;
+      }
+    } else {
+      // we may have a continuation
+      return false;
+    }
+    pos = next_pos;
+  }
+  return true;
+}
 
 } // namespace fallback
 } // namespace simdjson