uint64_t max_staleness = kDefaultMaxStaleness;

  // Apply the overrides for the block size (MB), max bytes (MB), and max
  // staleness (seconds) if provided.
  const char* block_size_env = std::getenv(kBlockSize);
  if (block_size_env && absl::SimpleAtoi(block_size_env, &value)) {
    block_size = value * 1024 * 1024;
  }
  const char* max_bytes_env = std::getenv(kMaxCacheSize);

	badDisks, badStaleDisks int

	blocksize, size int64
	algorithm       BitrotAlgorithm
	shouldFail      bool
}{
	{dataBlocks: 2, disks: 4, offDisks: 1, badDisks: 0, badStaleDisks: 0, blocksize: int64(blockSizeV2), size: oneMiByte, algorithm: SHA256, shouldFail: false},                   // 0

	{dataBlocks: 6, onDisks: 12, offDisks: 0, blocksize: int64(oneMiByte), data: oneMiByte, offset: oneMiByte, length: 0, algorithm: BLAKE2b512, shouldFail: false, shouldFailQuorum: false},
	// 4

	configLock.RLock()
	defer configLock.RUnlock()

	return c.Enable && c.BlockSize > 0 && size <= c.BlockSize
}

// Update updates new cache frequency
func (c *Config) Update(ncfg Config) {
	configLock.Lock()
	defer configLock.Unlock()

	c.Enable = ncfg.Enable
	c.Endpoint = ncfg.Endpoint
	c.BlockSize = ncfg.BlockSize
	c.clnt = ncfg.clnt
}

// cache related errors
var (

)

// blockPadding computes the number of bytes needed to pad offset up to the
// nearest block edge where 0 <= n < blockSize.
func blockPadding(offset int64) (n int64) {
	return -offset & (blockSize - 1)
}

var zeroBlock block

type block [blockSize]byte

// Convert block to any number of formats.
func (b *block) toV7() *headerV7       { return (*headerV7)(b) }

// refer https://github.com/golang/go/issues/24015
const blockSize = 8 << 10 // 8192

// By default at least 128 entries in single getdents call (1MiB buffer)
var (
	direntPool = sync.Pool{
		New: func() interface{} {
			buf := make([]byte, blockSize*128)
			return &buf
		},
	}

	direntNamePool = sync.Pool{
		New: func() interface{} {
			buf := make([]byte, blockSize)
			return &buf
		},
	}
)

					testReadFrom{fileOps{
						int64(1e10 - blockSize),
						strings.Repeat("\x00", blockSize-100) + strings.Repeat("0123456789", 10),
						int64(1e10 - blockSize),
						strings.Repeat("\x00", blockSize-100) + strings.Repeat("0123456789", 10),
						int64(1e10 - blockSize),
						strings.Repeat("\x00", blockSize-100) + strings.Repeat("0123456789", 10),
						int64(1e10 - blockSize),

	}
	flag &= ^(syscall.O_DIRECT)
	_, err = unix.FcntlInt(fd, unix.F_SETFL, flag)
	return err
}

// AlignedBlock - pass through to directio implementation.
func AlignedBlock(blockSize int) []byte {
	return directio.AlignedBlock(blockSize)

func (u UUIDHash) Reset() {
	return
}

// Size -  implement hash.Hash Size
func (u UUIDHash) Size() int {
	return len(u.uuid)
}

// BlockSize -  implement hash.Hash BlockSize
func (u UUIDHash) BlockSize() int {
	return md5.BlockSize
}

var _ hash.Hash = &UUIDHash{}

// NewUUIDHash - new UUIDHash
func NewUUIDHash(uuid []byte) *UUIDHash {
	return &UUIDHash{uuid: uuid}

	DataBlocks int `json:"data"`
	// ParityBlocks is the number of parity blocks for erasure-coding
	ParityBlocks int `json:"parity"`
	// BlockSize is the size of one erasure-coded block
	BlockSize int64 `json:"blockSize"`
	// Index is the index of the current disk
	Index int `json:"index"`
	// Distribution is the distribution of the data and parity blocks
	Distribution []int `json:"distribution"`