assertThat(source2.readUtf8(5)).isEqualTo("abcde")
    assertThat(source2.readUtf8(5)).isEqualTo("fghij")
    assertThat(source1.readUtf8(5)).isEqualTo("fghij")
    assertThat(source1.exhausted()).isTrue()
    assertThat(source2.exhausted()).isTrue()
    source1.close()
    source2.close()
    assertThat(relay.isClosed).isTrue()
    assertFile(Relay.PREFIX_CLEAN, 10L, metadata.size, "abcdefghij", metadata)
  }

  @Test

    apply {
      actions += { stream ->
        if (!stream.requestBody.exhausted()) throw AssertionError("expected exhausted")
      }
    }

  fun cancelStream() =
    apply {
      actions += { stream -> stream.cancel() }
    }

  fun requestIOException() =
    apply {
      actions += { stream ->
        try {
          stream.requestBody.exhausted()
          throw AssertionError("expected IOException")

}

private fun BufferedSource.skipWhitespace() {
  while (!exhausted()) {
    if (buffer[0] != ' '.code.toByte()) return
    skip(1L)
  }
}

private fun BufferedSource.skipRestOfLine() {
  when (val newline = indexOf('\n'.code.toByte())) {
    -1L -> skip(buffer.size) // Exhaust this source.
    else -> skip(newline + 1)
  }
}

class MappingListCodePointMapping(

   */
  operator fun invoke(input: String): String? = invoke(Buffer().writeUtf8(input))

  internal operator fun invoke(input: BufferedSource): String? {
    // 1. Map.
    val mapResult = Buffer()
    while (!input.exhausted()) {
      val codePoint = input.readUtf8CodePoint()
      when (val mappedCodePoint = mapping[codePoint]) {
        null -> mapResult.writeUtf8CodePoint(codePoint)
        else -> mapResult.writeUtf8(mappedCodePoint)

      UnmodifiableIterator<T> iterator) {
    return checkNotNull(iterator);
  }

  /**
   * Returns the number of elements remaining in {@code iterator}. The iterator will be left
   * exhausted: its {@code hasNext()} method will return {@code false}.
   */
  public static int size(Iterator<?> iterator) {
    long count = 0L;
    while (iterator.hasNext()) {
      iterator.next();
      count++;
    }

    if (peek == null) {
      if (!exhausted()) return // Expected a token; got something else.
      result.add(Challenge(schemeName, emptyMap()))
      return
    }

    var eqCount = skipAll('='.code.toByte())
    val commaSuffixed = skipCommasAndWhitespace()

    // It's a token68 because there isn't a value after it.
    if (!commaPrefixed && (commaSuffixed || exhausted())) {
      result.add(
        Challenge(

    val v1 = utf8.readDecimalLong()
    require(utf8.readByte() == '.'.code.toByte())
    val v2 = utf8.readDecimalLong()
    writeVariableLengthLong(v1 * 40 + v2)

    while (!utf8.exhausted()) {
      require(utf8.readByte() == '.'.code.toByte())
      val vN = utf8.readDecimalLong()
      writeVariableLengthLong(vN)
    }
  }

  fun writeRelativeObjectIdentifier(s: String) {

 * signatures.
 */
fun Buffer.isProbablyUtf8(): Boolean {
  try {
    val prefix = Buffer()
    val byteCount = size.coerceAtMost(64)
    copyTo(prefix, 0, byteCount)
    for (i in 0 until 16) {
      if (prefix.exhausted()) {
        break
      }
      val codePoint = prefix.readUtf8CodePoint()
      if (Character.isISOControl(codePoint) && !Character.isWhitespace(codePoint)) {
        return false
      }
    }
    return true

    get() = if (limit == -1L) -1L else (limit - byteCount)

  fun hasNext(): Boolean = peekHeader() != null

  /**
   * Returns the next header to process unless this scope is exhausted.
   *
   * This returns null if:
   *
   *  * The stream is exhausted.
   *  * We've read all of the bytes of an object whose length is known.
   *  * We've reached the [DerHeader.TAG_END_OF_CONTENTS] of an object whose length is unknown.
   */

    while (hasNextProxy()) {
      // Postponed routes are always tried last. For example, if we have 2 proxies and all the
      // routes for proxy1 should be postponed, we'll move to proxy2. Only after we've exhausted
      // all the good routes will we attempt the postponed routes.
      val proxy = nextProxy()
      for (inetSocketAddress in inetSocketAddresses) {
        val route = Route(address, proxy, inetSocketAddress)