// that was previously preserved during PutObject() call
			// on a versioned bucket.
			s.moveToTrash(legacyDataPath, true, false)
		}
		if contextCanceled(ctx) {
			return res, ctx.Err()
		}
		if err = renameAll(srcDataPath, dstDataPath, skipParent); err != nil {
			if legacyPreserved {
				// Any failed rename calls un-roll previous transaction.

	return mac.Sum(make([]byte, 0, mac.Size())), nil
}

// parseCiphertext parses and converts a ciphertext into
// the format expected by a secretKey.
//
// Previous implementations of the secretKey produced a structured
// ciphertext. parseCiphertext converts all previously generated
// formats into the expected format.
func parseCiphertext(b []byte) ([]byte, kms.SecretKeyType) {
	if len(b) == 0 {
		return b, kms.AES256
	}

    AtomicBoolean setUpRan = new AtomicBoolean();
    Runnable setUp =
        new Runnable() {
          @Override
          public void run() {
            assertFalse("previous tearDown should have run before setUp", setUpRan.getAndSet(true));
          }
        };
    Runnable tearDown =
        new Runnable() {
          @Override
          public void run() {

# Extra Models { #extra-models }

Continuing with the previous example, it will be common to have more than one related model.

This is especially the case for user models, because:

* The **input model** needs to be able to have a password.
* The **output model** should not have a password.
* The **database model** would probably need to have a hashed password.

/// danger

This is the basic idea. But you will probably want to take care of some additional things, like:

* Security - HTTPS
* Running on startup
* Restarts
* Replication (the number of processes running)
* Memory
* Previous steps before starting

    setSucceeds(lastEntry, entryIndex);
    setSucceeds(entryIndex, ENDPOINT);
  }

  @Override
  void accessEntry(int index) {
    if (accessOrder) {
      // delete from previous position...
      setSucceeds(getPredecessor(index), getSuccessor(index));
      // ...and insert at the end.
      setSucceeds(lastEntry, index);
      setSucceeds(index, ENDPOINT);
      incrementModCount();

 * typically false on Windows.
 *
 * If this returns false we won't permit simultaneous reads and writes. When writes commit we need
 * to delete the previous snapshots, and that won't succeed if the file is open. (We do permit
 * multiple simultaneous reads.)
 *
 * @param file a file in the directory to check. This file shouldn't already exist!
 */

	}

	if cap(t.requestsPool) != apiRequestsMaxPerNode {
		// Only replace if needed.
		// Existing requests will use the previous limit,
		// but new requests will use the new limit.
		// There will be a short overlap window,
		// but this shouldn't last long.
		t.requestsPool = make(chan struct{}, apiRequestsMaxPerNode)
	}

	dst   chan [][]string // result of block decode
	err   error           // any error encountered will be set here
}

// Read - reads single record.
// Once Read is called the previous record should no longer be referenced.
func (r *Reader) Read(dst sql.Record) (sql.Record, error) {
	// If we have have any records left, return these before any error.
	for len(r.current) <= r.recordsRead {
		if r.err != nil {

`chain.proceed(request)` is a critical part of each interceptor’s implementation. This simple-looking method is where all the HTTP work happens, producing a response to satisfy the request. If `chain.proceed(request)` is being called more than once previous response bodies must be closed.

Interceptors can be chained. Suppose you have both a compressing interceptor and a checksumming interceptor: you'll need to decide whether data is compressed and then checksummed, or checksummed and then compressed....