import java.nio.charset.Charset;

/**
 * A destination to which bytes can be written, such as a file. Unlike an {@link OutputStream}, a
 * {@code ByteSink} is not an open, stateful stream that can be written to and closed. Instead, it
 * is an immutable <i>supplier</i> of {@code OutputStream} instances.
 *
 * <p>{@code ByteSink} provides two kinds of methods:
 *
 * <ul>

import java.nio.charset.Charset;

/**
 * A destination to which bytes can be written, such as a file. Unlike an {@link OutputStream}, a
 * {@code ByteSink} is not an open, stateful stream that can be written to and closed. Instead, it
 * is an immutable <i>supplier</i> of {@code OutputStream} instances.
 *
 * <p>{@code ByteSink} provides two kinds of methods:
 *
 * <ul>

          .build(),
      )

    val exception =
      assertFailsWith<IOException> {
        call2.execute()
      }
    assertThat(exception.message).isIn("Socket closed", "Socket is closed")
  }

   * most [BufferedSource] instances, but not of [Buffer].
   */
  private fun responseBody(content: String): ResponseBody {
    val data = Buffer().writeUtf8(content)
    val source: Source =
      object : Source {
        var closed = false

        override fun close() {
          closed = true
        }

        override fun read(

  MultiReader(Iterator<? extends CharSource> readers) throws IOException {
    this.it = readers;
    advance();
  }

  /** Closes the current reader and opens the next one, if any. */
  private void advance() throws IOException {
    close();
    if (it.hasNext()) {
      current = it.next().openStream();
    }
  }

  @Override

  }

  @Override
  public String toString() {
    return comparator
        + ":"
        + (lowerBoundType == CLOSED ? '[' : '(')
        + (hasLowerBound ? lowerEndpoint : "-\u221e")
        + ','
        + (hasUpperBound ? upperEndpoint : "\u221e")
        + (upperBoundType == CLOSED ? ']' : ')');
  }

  @Nullable T getLowerEndpoint() {
    return lowerEndpoint;
  }

  }

  public void testCopyToAppendable_doesNotCloseIfWriter() throws IOException {
    TestWriter writer = new TestWriter();
    assertFalse(writer.closed());
    source.copyTo(writer);
    assertFalse(writer.closed());
  }

  public void testClosesOnErrors_copyingToCharSinkThatThrows() {
    for (TestOption option : EnumSet.of(OPEN_THROWS, WRITE_THROWS, CLOSE_THROWS)) {

      )

    val part = parts.nextPart()!!
    parts.close()

    assertFailsWith<IllegalStateException> {
      part.body.request(10)
    }.also { expected ->
      assertThat(expected).hasMessage("closed")
    }
  }

  @Test fun `cannot call nextPart after calling close`() {
    val parts =
      MultipartReader(
        boundary = "simple boundary",

// the upstream reader after close has been called.
type disconnectReader struct {
	r  io.Reader
	mu sync.Mutex
}

func (d *disconnectReader) Read(p []byte) (n int, err error) {
	d.mu.Lock()
	defer d.mu.Unlock()
	if d.r != nil {
		return d.r.Read(p)
	}
	return 0, errors.New("reader closed")
}

func (d *disconnectReader) Close() error {
	d.mu.Lock()
	d.r = nil

      return multiset().subMultiset(fromElement, CLOSED, toElement, OPEN).elementSet();
    }

    @Override
    public SortedSet<E> headSet(@ParametricNullness E toElement) {
      return multiset().headMultiset(toElement, OPEN).elementSet();
    }

    @Override
    public SortedSet<E> tailSet(@ParametricNullness E fromElement) {
      return multiset().tailMultiset(fromElement, CLOSED).elementSet();
    }

    @Override