}
	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)

			Optional:    true,
		},
		config.HelpKV{
			Key:         BlockSize,
			Type:        "string",
			Description: "cache all objects below the specified block size" + defaultHelpPostfix(BlockSize),
			Optional:    true,
		},
	}

func (s *sum128) Size() int  { return 16 }
func (s *sum128a) Size() int { return 16 }

func (s *sum32) BlockSize() int   { return 1 }
func (s *sum32a) BlockSize() int  { return 1 }
func (s *sum64) BlockSize() int   { return 1 }
func (s *sum64a) BlockSize() int  { return 1 }
func (s *sum128) BlockSize() int  { return 1 }
func (s *sum128a) BlockSize() int { return 1 }

func (s *sum32) Sum(in []byte) []byte {
	v := uint32(*s)

)

// 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) }

}

// NewCTR returns a Stream which encrypts/decrypts using the AES block
// cipher in counter mode. The length of iv must be the same as [BlockSize].
func (c *aesCipherAsm) NewCTR(iv []byte) cipher.Stream {
	if len(iv) != BlockSize {
		panic("cipher.NewCTR: IV length must equal block size")
	}
	var ac aesctr
	ac.block = c
	ac.ctr[0] = byteorder.BeUint64(iv[0:]) // high bits

func stableOrdered[E cmp.Ordered](data []E, n int) {
	blockSize := 20 // must be > 0
	a, b := 0, blockSize
	for b <= n {
		insertionSortOrdered(data, a, b)
		a = b
		b += blockSize
	}
	insertionSortOrdered(data, a, n)

	for blockSize < n {
		a, b = 0, 2*blockSize
		for b <= n {
			symMergeOrdered(data, a, a+blockSize, b)
			a = b
			b += 2 * blockSize
		}
		if m := a + blockSize; m < n {

	Reset()

	// Size returns the number of bytes Sum will return.
	Size() int

	// BlockSize returns the hash's underlying block size.
	// The Write method must be able to accept any amount
	// of data, but it may operate more efficiently if all writes
	// are a multiple of the block size.
	BlockSize() int
}

// Hash32 is the common interface implemented by all 32-bit hash functions.
type Hash32 interface {

	blockSize := 20 // must be > 0
	a, b := 0, blockSize
	for b <= n {
		insertionSortCmpFunc(data, a, b, cmp)
		a = b
		b += blockSize
	}
	insertionSortCmpFunc(data, a, n, cmp)

	for blockSize < n {
		a, b = 0, 2*blockSize
		for b <= n {
			symMergeCmpFunc(data, a, a+blockSize, b, cmp)
			a = b
			b += 2 * blockSize
		}
		if m := a + blockSize; m < n {

// data in r.buffer. The blockSize argument is the compressed size.
// RFC 3.1.1.3.
func (r *Reader) compressedBlock(blockSize int) error {
	if len(r.compressedBuf) >= blockSize {
		r.compressedBuf = r.compressedBuf[:blockSize]
	} else {
		// We know that blockSize <= 128K,
		// so this won't allocate an enormous amount.
		need := blockSize - len(r.compressedBuf)

See the License for the specific language governing permissions and
limitations under the License.
*/

package tail

import (
	"io"
	"os"
)

const (
	// blockSize is the block size used in tail.
	blockSize = 1024
)

// ReadAtMost reads at most max bytes from the end of the file identified by path or
// returns an error. It returns true if the file was longer than max. It will