val result = Headers.Builder()
  result.namesAndValues += namesAndValues
  return result
}

internal fun Headers.commonEquals(other: Any?): Boolean = other is Headers && namesAndValues.contentEquals(other.namesAndValues)

internal fun Headers.commonHashCode(): Int = namesAndValues.contentHashCode()

internal fun Headers.commonToString(): String =
  buildString {
    for (i in 0 until size) {

    int chunk2 = dataSize - chunk1;

    // Write just enough to not trip the threshold
    if (chunk1 > 0) {
      write(out, data, 0, chunk1, singleByte);
      assertTrue(ByteSource.wrap(data).slice(0, chunk1).contentEquals(source));
    }
    File file = out.getFile();
    assertThat(file).isNull();

    // Write data to go over the threshold
    if (chunk2 > 0) {
      write(out, data, chunk1, chunk2, singleByte);

    iterable.forEach(t -> forEachBuilder.append(t.value));
    assertTrue(
        "Iterator content was " + builder + " but forEach content was " + forEachBuilder,
        builder.toString().contentEquals(forEachBuilder));
    return builder.toString();
  }

  public void testPreOrder() {
    assertThat(iterationOrder(ADAPTER.preOrderTraversal(h))).isEqualTo("hdabcegf");
  }

    int start = 0;
    for (Integer span : spans) {
      sources.add(newByteSource(start, span));
      start += span;
    }
    ByteSource joined = ByteSource.concat(sources);
    assertTrue(newByteSource(0, start).contentEquals(joined));
  }

  public void testReadSingleByte() throws Exception {
    ByteSource source = newByteSource(0, 10);
    ByteSource joined = ByteSource.concat(source, source);
    assertEquals(20, joined.size());

    int start = 0;
    for (Integer span : spans) {
      sources.add(newByteSource(start, span));
      start += span;
    }
    ByteSource joined = ByteSource.concat(sources);
    assertTrue(newByteSource(0, start).contentEquals(joined));
  }

  public void testReadSingleByte() throws Exception {
    ByteSource source = newByteSource(0, 10);
    ByteSource joined = ByteSource.concat(source, source);
    assertEquals(20, joined.size());

    int chunk2 = dataSize - chunk1;

    // Write just enough to not trip the threshold
    if (chunk1 > 0) {
      write(out, data, 0, chunk1, singleByte);
      assertTrue(ByteSource.wrap(data).slice(0, chunk1).contentEquals(source));
    }
    File file = out.getFile();
    assertThat(file).isNull();

    // Write data to go over the threshold
    if (chunk2 > 0) {
      write(out, data, chunk1, chunk2, singleByte);