//   - Exactly 0 bytes are read and EOF is hit.
//   - Exactly 1 block of zeros is read and EOF is hit.
//   - At least 2 blocks of zeros are read.
func (tr *Reader) readHeader() (*Header, *block, error) {
	// Two blocks of zero bytes marks the end of the archive.
	if _, err := io.ReadFull(tr.r, tr.blk[:]); err != nil {
		return nil, nil, err // EOF is okay here; exactly 0 bytes read
	}

	processIORCharBytesMD             = NewCounterMD(processIORCharBytes, "Total bytes read by the process from the underlying storage system including cache, /proc/[pid]/io rchar")
	processIOReadBytesMD              = NewCounterMD(processIOReadBytes, "Total bytes read by the process from the underlying storage system, /proc/[pid]/io read_bytes")

	setupLogging()
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	fixture := connect(ctx)
	ztunClient := fixture.ztunClient
	uid := fixture.uid
	// read initial pod add
	readRequest(t, ztunClient)
	sendAck(ztunClient)
	// read snapshot sent
	m, fds := readRequest(t, ztunClient)
	assert.Equal(t, len(fds), 0)
	sent := m.Payload.(*zdsapi.WorkloadRequest_SnapshotSent).SnapshotSent
	if sent == nil {

	// check not at EOF
	b.WriteString("abcdefghijklmnopqrstuvwxyz")

	// after unsuccessful read
	if n, err := b.Read(nil); n != 0 || err != nil {
		t.Fatalf("Read(nil) = %d,%v; want 0,nil", n, err)
	}
	if err := b.UnreadByte(); err == nil {
		t.Fatal("UnreadByte after Read(nil): got no error")
	}

	// after successful read
	if _, err := b.ReadBytes('m'); err != nil {
		t.Fatalf("ReadBytes: %v", err)
	}

	isReadLock := false
	return dm.lockBlocking(ctx, cancel, id, source, isReadLock, opts)
}

// RLock holds a read lock on dm.
//
// If one or more read locks are already in use, it will grant another lock.
// Otherwise the calling go routine blocks until the mutex is available.
func (dm *DRWMutex) RLock(id, source string) {
	isReadLock := true

	bufCount := 0
	for _, b := range buf {
		if len(b) > 0 {
			bufCount++
		}
	}
	return bufCount >= p.dataBlocks
}

// Read reads from readers in parallel. Returns p.dataBlocks number of bufs.
func (p *parallelReader) Read(dst [][]byte) ([][]byte, error) {
	newBuf := dst
	if len(dst) != len(p.readers) {
		newBuf = make([][]byte, len(p.readers))
	} else {
		for i := range newBuf {

		internalByteBuffer.Put(&b)
		return
	}
}

// readAllInto reads from r and appends to b until an error or EOF and returns the data it read.
// A successful call returns err == nil, not err == EOF. Because readAllInto is
// defined to read from src until EOF, it does not treat an EOF from Read
// as an error to be reported.
func readAllInto(b []byte, r *wsutil.Reader) ([]byte, error) {
	for {
		if len(b) == cap(b) {

	}

	// Add a few concurrent read locks to the mix
	for i := 0; i < 50; i++ {
		resource := fmt.Sprintf("bucket/get-object-%d", i)
		lri := lockRequesterInfo{
			Name:   resource,
			UID:    mustGetUUID(),
			Owner:  owners[i%len(owners)],
			Quorum: 2,
		}
		lris = append(lris, lri)
		locksHeld[resource] = append(locksHeld[resource], lri)
		// concurrent read lock, same resource different uid

			err = fmt.Errorf("unlock attempted on a read locked entity: %s", resource)
			continue
		}
		if ok {
			reply = l.removeEntry(resource, args, &lri) || reply
		}
	}
	return
}

// removeEntry based on the uid of the lock message, removes a single entry from the
// lockRequesterInfo array or the whole array from the map (in case of a write lock
// or last read lock)

		"Reads per second on a drive",
		allDriveLabels...)
	driveReadsKBPerSecMD = NewGaugeMD(driveReadsKBPerSec,
		"Kilobytes read per second on a drive",
		allDriveLabels...)
	driveReadsAwaitMD = NewGaugeMD(driveReadsAwait,
		"Average time for read requests served on a drive",
		allDriveLabels...)
	driveWritesPerSecMD = NewGaugeMD(driveWritesPerSec,
		"Writes per second on a drive",
		allDriveLabels...)