Request
          .Builder()
          .url(server.url("/"))
          .post(
            object : RequestBody() {
              override fun contentType() = null

              override fun writeTo(sink: BufferedSink) {
                for (i in 0..9) {
                  sink.writeByte(0)
                  sink.flush()
                  sleep(100)
                }

        return queryBuilder.toXContent(builder, params);
    }

    @Override
    public void writeTo(final StreamOutput out) throws IOException {
        queryBuilder.writeTo(out);
    }

    @Override
    public int hashCode() {
        return queryBuilder.hashCode();
    }

    @Override

    var result = contentLength
    if (result == -1L) {
      result = writeOrCountBytes(null, true)
      contentLength = result
    }
    return result
  }

  @Throws(IOException::class)
  override fun writeTo(sink: BufferedSink) {
    writeOrCountBytes(sink, false)
  }

  /**
   * Either writes this request to [sink] or measures its content length. We have one method do

      override fun contentLength(): Long = original!!.contentLength()

      override fun writeTo(sink: BufferedSink) {
        val uppercase = uppercase(sink)
        val bufferedSink = uppercase.buffer()
        original!!.writeTo(bufferedSink)
        bufferedSink.emit()
      }
    }

  private fun uppercase(original: BufferedSink): Sink =

    object : RequestBody() {
      override fun contentType(): MediaType? = "text/plain".toMediaTypeOrNull()

      @Throws(IOException::class)
      override fun writeTo(sink: BufferedSink) {
        try {
          sink.writeUtf8("abc")
          sink.flush()
          Thread.sleep(sleepMillis.toLong())
          sink.writeUtf8("def")
        } catch (e: InterruptedException) {

      @Override public long contentLength() {
        return -1; // We don't know the compressed length in advance!
      }

      @Override public void writeTo(BufferedSink sink) throws IOException {
        BufferedSink gzipSink = Okio.buffer(new GzipSink(sink));
        body.writeTo(gzipSink);
        gzipSink.close();
      }
    };
  }
}
```

### Rewriting Responses

    setLevel(Level.HEADERS)
    server.enqueue(MockResponse())
    val body: RequestBody =
      object : RequestBody() {
        override fun contentType() = PLAIN

        override fun writeTo(sink: BufferedSink) {
          sink.writeUtf8("Hi!")
        }
      }
    val response = client.newCall(request().post(body).build()).execute()
    response.body.close()
    applicationLogs

	i := copy(b2, b)
	return b2[:i]
}

// WriteTo writes data to w until the buffer is drained or an error occurs.
// The return value n is the number of bytes written; it always fits into an
// int, but it is int64 to match the [io.WriterTo] interface. Any error
// encountered during the write is also returned.
func (b *Buffer) WriteTo(w io.Writer) (n int64, err error) {
	b.lastRead = opInvalid

pkg runtime/trace, method (*FlightRecorder) Enabled() bool #63185
pkg runtime/trace, method (*FlightRecorder) Start() error #63185
pkg runtime/trace, method (*FlightRecorder) Stop() #63185
pkg runtime/trace, method (*FlightRecorder) WriteTo(io.Writer) (int64, error) #63185
pkg runtime/trace, type FlightRecorder struct #63185
pkg runtime/trace, type FlightRecorderConfig struct #63185
pkg runtime/trace, type FlightRecorderConfig struct, MaxBytes uint64 #63185

    override fun contentType() = delegate.contentType()

    override fun isDuplex() = true

    override fun writeTo(sink: BufferedSink) {
      executorService.schedule({
        try {
          delegate.writeTo(sink)
          sink.close()
        } catch (e: IOException) {
          throw RuntimeException(e)
        }
      }, delayMillis, TimeUnit.MILLISECONDS)