Each header contains a mspg array (tuple) encoded object:

xlHeaderVersion version == 1:

```
//msgp:tuple xlMetaV2VersionHeader
type xlMetaV2VersionHeader struct {
 VersionID [16]byte  // Version UUID, raw.
 ModTime   int64     // Unix nanoseconds.
 Signature [4]byte   // Signature of metadata.
 Type      uint8     // Type if the version
 Flags     uint8
}
```

The following flags are defined:

```
const (

	return io.CopyBuffer(writerOnly{dst}, src, buf)
}

// SameFile returns if the files are same.
func SameFile(fi1, fi2 os.FileInfo) bool {
	if !os.SameFile(fi1, fi2) {
		return false
	}
	if !fi1.ModTime().Equal(fi2.ModTime()) {
		return false
	}
	if fi1.Mode() != fi2.Mode() {
		return false
	}
	return fi1.Size() == fi2.Size()
}

// DirectioAlignSize - DirectIO alignment needs to be 4K. Defined here as

//	Size              | uint33 | unlimited |    uint89
//	Mode              | uint21 |    uint21 |    uint57
//	Uid/Gid           | uint21 | unlimited |    uint57
//	Uname/Gname       |    32B | unlimited |       32B
//	ModTime           | uint33 | unlimited |     int89
//	AccessTime        |    n/a | unlimited |     int89
//	ChangeTime        |    n/a | unlimited |     int89
//	Devmajor/Devminor | uint21 |    uint21 |    uint57

		}
	}
}

// Tests - CheckPreconditions()
func TestCheckPreconditions(t *testing.T) {
	objModTime := time.Date(2024, time.August, 26, 0o2, 0o1, 0o1, 0, time.UTC)
	objInfo := ObjectInfo{ETag: "aa", ModTime: objModTime}
	testCases := []struct {
		name              string
		ifMatch           string
		ifNoneMatch       string
		ifModifiedSince   string
		ifUnmodifiedSince string
		objInfo           ObjectInfo

			}
			fieldBuf.uint32()              // AcTime (ignored)
			ts := int64(fieldBuf.uint32()) // ModTime since Unix epoch
			modified = time.Unix(ts, 0)
		case extTimeExtraID:
			if len(fieldBuf) < 5 || fieldBuf.uint8()&1 == 0 {
				continue parseExtras
			}
			ts := int64(fieldBuf.uint32()) // ModTime since Unix epoch
			modified = time.Unix(ts, 0)
		}
	}

	distribution := fi.Erasure.Distribution

	init := fi.ModTime.IsZero()
	// Shuffle slice xl metadata for expected distribution.
	for index := range partsMetadata {
		if disks[index] == nil {
			continue
		}
		if !init && !partsMetadata[index].IsValid() {
			// Check for parts metadata validity for only
			// fi.ModTime is not empty - ModTime is always set,
			// if object was ever written previously.
			continue

	tmp := struct {
		VersionID string
		ModTime   time.Time
		Signature string
		Type      uint8
		Flags     uint8
		EcM, EcN  uint8 // Note that these will be 0/0 for non-v2 objects and older xl.meta
	}{
		VersionID: hex.EncodeToString(z.VersionID[:]),
		ModTime:   time.Unix(0, z.ModTime),
		Signature: hex.EncodeToString(z.Signature[:]),
		Type:      z.Type,

		Bucket:      bucket,
		Name:        object,
		Size:        r.Size(),
		IsLatest:    true,
		ContentType: string(mimeXML),
		NumVersions: 1,
		ETag:        etag,
		ModTime:     UTCNow(),
	}, opts)

			},
		}
		// default timestamps to ModTime unless present in metadata
		lkMap := caseInsensitiveMap(objInfo.UserDefined)
		if _, ok := lkMap.Lookup(xhttp.AmzObjectLockLegalHold); ok {
			dstOpts.Internal.LegalholdTimestamp = objInfo.ModTime
		}
		if _, ok := lkMap.Lookup(xhttp.AmzObjectLockRetainUntilDate); ok {
			dstOpts.Internal.RetentionTimestamp = objInfo.ModTime
		}
		if objInfo.UserTags != "" {

			errs, bucket, object, versionID), err
	}

	result.ParityBlocks = result.DiskCount - readQuorum
	result.DataBlocks = readQuorum

	// List of disks having latest version of the object xl.meta
	// (by modtime).
	onlineDisks, quorumModTime, quorumETag := listOnlineDisks(storageDisks, partsMetadata, errs, readQuorum)

	// Latest FileInfo for reference. If a valid metadata is not
	// present, it is as good as object not found.