memory if web socket compression is negotiated but not used.


## Version 4.5.0-RC1

_2020-03-17_

**This release candidate turns on web socket compression.**

The [spec][rfc_7692] includes a sophisticated mechanism for client and server to negotiate
compression features. We strive to offer great performance in our default configuration and so we're

  var i = pos
  while (i < limit) {
    if (b == address.size) return null // Too many groups.

    // Read a delimiter.
    if (i + 2 <= limit && input.startsWith("::", startIndex = i)) {
      // Compression "::" delimiter, which is anywhere in the input, including its prefix.
      if (compress != -1) return null // Multiple "::" delimiters.
      i += 2
      b += 2
      compress = b
      if (i == limit) break

 *  * `com.twitter.hpack.HpackUtil`
 *
 * [twitter_hpack]: https://github.com/twitter/hpack
 */
object Huffman {
  // Appendix C: Huffman Codes
  // http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-12#appendix-B
  private val CODES =
    intArrayOf(
      0x1ff8, 0x7fffd8, 0xfffffe2, 0xfffffe3, 0xfffffe4, 0xfffffe5, 0xfffffe6,
      0xfffffe7, 0xfffffe8, 0xffffea, 0x3ffffffc, 0xfffffe9, 0xfffffea, 0x3ffffffd, 0xfffffeb,

OkHttp Brotli Implementation
============================

This module is an implementation of [Brotli][1] compression.
It enables Brotli support in addition to tranparent Gzip support,
provided Accept-Encoding is not set previously.  Modern web servers
must choose to return Brotli responses.  n.b. It is not used for
sending requests.

```java
OkHttpClient client = new OkHttpClient.Builder()
  .addInterceptor(BrotliInterceptor.INSTANCE)
  .build();

OkHttp may add headers that are absent from the original request, including `Content-Length`, `Transfer-Encoding`, `User-Agent`, `Host`, `Connection`, and `Content-Type`. It will add an `Accept-Encoding` header for transparent response compression unless the header is already present. If you’ve got cookies, OkHttp will add a `Cookie` header with them.

   * Variable-length quantity special cases strings which are longer than 127 bytes.  Values such as
   * cookies can be 4KiB, and should be possible to send.
   *
   *  http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-12#section-5.2
   */
  @Test
  fun largeHeaderValue() {
    val value = CharArray(4096)
    Arrays.fill(value, '!')
    val headerBlock = headerEntries("cookie", String(value))

  PROTOCOL_ERROR(1),

  INTERNAL_ERROR(2),

  FLOW_CONTROL_ERROR(3),

  SETTINGS_TIMEOUT(4),

  STREAM_CLOSED(5),

  FRAME_SIZE_ERROR(6),

  REFUSED_STREAM(7),

  CANCEL(8),

  COMPRESSION_ERROR(9),

  CONNECT_ERROR(0xa),

  ENHANCE_YOUR_CALM(0xb),

  INADEQUATE_SECURITY(0xc),

  HTTP_1_1_REQUIRED(0xd),
  ;

  companion object {

Content-Type: text/plain
Content-Length: 1759
Connection: keep-alive
```

The network requests also contain more data, such as the `Accept-Encoding: gzip` header added by OkHttp to advertise support for response compression. The network interceptor's `Chain` has a non-null `Connection` that can be used to interrogate the IP address and TLS configuration that were used to connect to the webserver.

class MessageDeflater(
  private val noContextTakeover: Boolean,
) : Closeable {
  private val deflatedBytes = Buffer()

  private val deflater =
    Deflater(
      Deflater.DEFAULT_COMPRESSION,
      // nowrap (omits zlib header):
      true,
    )

  private val deflaterSink = DeflaterSink(deflatedBytes, deflater)

  /** Deflates [buffer] in place as described in RFC 7692 section 7.2.1. */

  private fun skipName(source: Buffer) {
    // 0 - 63 bytes
    var length = source.readByte().toInt()

    if (length < 0) {
      // compressed name pointer, first two bits are 1
      // drop second byte of compression offset
      source.skip(1)
    } else {
      while (length > 0) {
        // skip each part of the domain name
        source.skip(length.toLong())
        length = source.readByte().toInt()
      }