Method DoUtf8TrimString

be/src/exprs/string-functions-ir.cc:825–852

template <StringFunctions::TrimPosition D>
StringVal StringFunctions::DoUtf8TrimString(const StringVal& str,
    const TrimContext& trim_ctx) {
  if (UNLIKELY(str.len == 0)) return str;

  const uint8_t* begin = str.ptr;
  const uint8_t* end = begin + str.len;
  // Find new starting position.
  if constexpr (D == LEADING || D == BOTH) {
    while (begin < end) {
      size_t char_size = BitUtil::NumBytesInUtf8Encoding(*begin);
      if (UNLIKELY(begin + char_size > end)) char_size = end - begin;
      if (!trim_ctx.Contains(begin, char_size)) break;
      begin += char_size;
    }
  }
  // Find new ending position.
  if constexpr (D == TRAILING || D == BOTH) {
    while (begin < end) {
      int char_index = FindUtf8PosBackward(begin, end - begin, 0);
      DCHECK_NE(char_index, -1);
      const uint8_t* char_begin = begin + char_index;
      if (!trim_ctx.Contains(char_begin, end - char_begin)) break;
      end = char_begin;
    }
  }

  return StringVal(const_cast<uint8_t*>(begin), end - begin);
}

StringVal StringFunctions::Trim(FunctionContext* context, const StringVal& str) {
  return DoTrimString<BOTH, true>(context, str, StringVal(" "));