internal const val CLOSE_NO_STATUS_CODE = 1005

  fun toggleMask(
    cursor: Buffer.UnsafeCursor,
    key: ByteArray,
  ) {
    var keyIndex = 0
    val keyLength = key.size
    do {
      val buffer = cursor.data
      var i = cursor.start
      val end = cursor.end
      if (buffer != null) {
        while (i < end) {

    deflaterSink.flush()

    if (deflatedBytes.endsWith(EMPTY_DEFLATE_BLOCK)) {
      val newSize = deflatedBytes.size - LAST_OCTETS_COUNT_TO_REMOVE_AFTER_DEFLATION
      deflatedBytes.readAndWriteUnsafe().use { cursor ->
        cursor.resizeBuffer(newSize)
      }
    } else {
      // Same as adding EMPTY_DEFLATE_BLOCK and then removing 4 bytes.
      deflatedBytes.writeByte(0x00)
    }

  var i = 0
  while (i < ranges.size) {
    val curr = ranges[i]
    if (curr is MappedRange.InlineDelta) {
      val j = i + 1
      mergeAdjacent@ while (j < ranges.size) {
        val next = ranges[j]
        if (next is MappedRange.InlineDelta &&
          curr.codepointDelta == next.codepointDelta
        ) {
          ranges.removeAt(j)
        } else {