code: private HeaderEntry getEntry(CharSequence name, CharSequence value) {
          if (length() == 0 || name == null || value == null) {
              return null;
          }
          int h = AsciiString.hashCode(name);
          int i = index(h);
          for (HeaderEntry e = headerFields[i]; e != null; e = e.next) {
              // To avoid short circuit behavior a bitwise operator is used instead of a boolean operator.
              if (e.hash == h && (equalsConstantTime(name, e.name) & equalsConstantTime(value, e.value)) != 0) {
                  return e;
              }
          }
          return null;
      }
docs: Returns the header entry with the lowest index value for the header field. Returns null if
  header field is not in the dynamic table.