* 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!
 */

                int structStart = dstIndex;

                SMBUtil.writeInt4(0, dst, structStart); // Next
                if ( lastStart > 0 ) {
                    // set next pointer of previous CREATE_CONTEXT
                    SMBUtil.writeInt4(structStart - dstIndex, dst, lastStart);
                }

                dstIndex += 4;
                byte[] cnBytes = createContext.getName();

# Simple OAuth2 with Password and Bearer

Now let's build from the previous chapter and add the missing parts to have a complete security flow.

## Get the `username` and `password`

We are going to use **FastAPI** security utilities to get the `username` and `password`.

OAuth2 specifies that when using the "password flow" (that we are using) the client/user must send a `username` and `password` fields as form data.

   * element, to further specify that a successful call must always increment the count of the
   * element, and the overall size of the collection, by one.
   *
   * <p>To both add the element and obtain the previous count of that element, use {@link
   * #add(Object, int) add}{@code (element, 1)} instead.
   *
   * @param element the element to add one occurrence of; may be null only if explicitly allowed by
   *     the implementation

  - [Important Security Information](#important-security-information)
    - [CVE-2021-25735: Validating Admission Webhook does not observe some previous fields](#cve-2021-25735-validating-admission-webhook-does-not-observe-some-previous-fields)
  - [Changes by Kind](#changes-by-kind-2)
    - [API Change](#api-change-1)
    - [Feature](#feature)
    - [Bug or Regression](#bug-or-regression-2)

	bigFileThreshold = 128 * humanize.MiByte

	// XL metadata file carries per object metadata.
	xlStorageFormatFile = "xl.meta"

	// XL metadata file backup file carries previous per object metadata.
	xlStorageFormatFileBackup = "xl.meta.bkp"
)

var alignedBuf []byte

func init() {
	alignedBuf = disk.AlignedBlock(xioutil.DirectioAlignSize)
	_, _ = rand.Read(alignedBuf)
}

      // Group separator ":" delimiter.
      if (input.startsWith(":", startIndex = i)) {
        i++
      } else if (input.startsWith(".", startIndex = i)) {
        // If we see a '.', rewind to the beginning of the previous group and parse as IPv4.
        if (!decodeIpv4Suffix(input, groupOffset, limit, address, b - 2)) return null
        b += 2 // We rewound two bytes and then added four.
        break
      } else {

![put](https://raw.githubusercontent.com/minio/minio/master/docs/bucket/versioning/versioning_PUT_versionEnabled.png)

This protects against accidental overwrites or deletes of objects, allows previous versions to be retrieved.

When you DELETE an object, all versions remain in the bucket and MinIO adds a delete marker, as shown below:

(that is, if <i>W</i>(<i>r</i>) = <i>w</i>),
then <i>w</i> is synchronized before <i>r</i>.
Informally, the synchronized before relation is a subset of the implied total order
mentioned in the previous paragraph,
limited to the information that <i>W</i> directly observes.
</p>

<p>
The <i>happens before</i> relation is defined as the transitive closure of the

    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();