// If there's a "Expect: 100-continue" header on the request, wait for a "HTTP/1.1 100
        // Continue" response before transmitting the request body. If we don't get that, return
        // what we did get (such as a 4xx response) without ever transmitting the request body.
        if ("100-continue".equals(request.header("Expect"), ignoreCase = true)) {
          exchange.flushRequest()

      builder.header("", "Value")
    }
    assertFailsWith<IllegalArgumentException> {
      builder.addHeader("", "Value")
    }
  }

  @Test
  fun headerAllowsTabOnlyInValues() {
    val builder = Request.Builder()
    builder.header("key", "sample\tvalue")
    assertFailsWith<IllegalArgumentException> {
      builder.header("sample\tkey", "value")
    }
  }

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.

Some requests will have a cached response. When this cached response isn’t fresh, OkHttp can do a _conditional GET_ to download an updated response if it’s newer...

      ProtocolException::class.java,
      "Expected 'Sec-WebSocket-Accept' header value 'ujmZX4KXZqjwy6vi1aQFH5p4Ygk=' but was 'magic'",
    )
    webSocket.cancel()
  }

  @Test
  @Throws(IOException::class)
  fun clientIncludesForbiddenHeader() {
    newWebSocket(
      Request.Builder()
        .url(webServer.url("/"))
        .header("Sec-WebSocket-Extensions", "permessage-deflate")
        .build(),
    )

  return millis.toInt()
}

internal fun List<Header>.toHeaders(): Headers {
  val builder = Headers.Builder()
  for ((name, value) in this) {
    builder.addLenient(name.utf8(), value.utf8())
  }
  return builder.build()
}

internal fun Headers.toHeaderList(): List<Header> =
  (0 until size).map {
    Header(name(it), value(it))
  }

            .build()

        networkResponse.body.close()

        // Update the cache after combining headers but before stripping the
        // Content-Encoding header (as performed by initContentStream()).
        cache!!.trackConditionalCacheHit()
        cache.update(cacheResponse, response)
        return response.also {
          listener.cacheHit(call, it)
        }

import okhttp3.internal.commonNoStore
import okhttp3.internal.commonNoTransform
import okhttp3.internal.commonOnlyIfCached
import okhttp3.internal.commonParse
import okhttp3.internal.commonToString

/**
 * A Cache-Control header with cache directives from a server or client. These directives set policy
 * on what responses can be stored, and which requests can be satisfied by those stored responses.
 *

      frameHeader(
        streamId = 0,
        length = 0,
        type = TYPE_SETTINGS,
        flags = FLAG_ACK,
      )
      sink.flush()
    }
  }

  /**
   * HTTP/2 only. Send a push promise header block.
   *
   * A push promise contains all the headers that pertain to a server-initiated request, and a
   * `promisedStreamId` to which response frames will be delivered. Push promise frames are sent as

  require(name.isNotEmpty()) { "name is empty" }
  for (i in name.indices) {
    val c = name[i]
    require(c in '\u0021'..'\u007e') {
      "Unexpected char 0x${c.charCode()} at $i in header name: $name"
    }
  }
}

internal fun headersCheckValue(
  value: String,
  name: String,
) {
  for (i in value.indices) {
    val c = value[i]

    from major web browsers.
 *  New: Honor the `Retry-After` response header. HTTP 503 (Unavailable)
    responses are retried automatically if this header is present and its delay
    is 0 seconds. HTTP 408 (Client Timeout) responses are retried automatically
    if the header is absent or its delay is 0 seconds.
 *  New: Allow request bodies for all HTTP methods except GET and HEAD.