const (
	AUNK   AlgKind = iota
	ANOEQ          // Types cannot be compared
	ANOALG         // implies ANOEQ, and in addition has a part that is marked Noalg
	AMEM           // Type can be compared/hashed as regular memory.
	AMEM0          // Specific subvariants of AMEM (TODO: move to ../reflectdata?)
	AMEM8
	AMEM16
	AMEM32
	AMEM64
	AMEM128
	ASTRING
	AINTER
	ANILINTER
	AFLOAT32
	AFLOAT64
	ACPLX64

	// Then iterate over that slice to fetch the values to be hashed.
	keys := []string{}
	for key := range cm.Data {
		keys = append(keys, key)
	}
	sort.Strings(keys)

	for _, key := range keys {
		hash.Write([]byte(cm.Data[key]))
	}

	// Do the same as above, but for binaryData this time.
	keys = []string{}
	for key := range cm.BinaryData {
		keys = append(keys, key)
	}
	sort.Strings(keys)

	"sort"
	"strings"
)

// DefaultHash is the default hash function used in new go.sum entries.
var DefaultHash Hash = Hash1

// A Hash is a directory hash function.
// It accepts a list of files along with a function that opens the content of each file.
// It opens, reads, hashes, and closes each file and returns the overall directory hash.
type Hash func(files []string, open func(string) (io.ReadCloser, error)) (string, error)

	// https://github.com/dchest/siphash#usage
	k0, k1 := binary.LittleEndian.Uint64(id[0:8]), binary.LittleEndian.Uint64(id[8:16])
	sum64 := siphash.Hash(k0, k1, []byte(key))
	return int(sum64 % uint64(cardinality))
}

// hashOrder - hashes input key to return consistent
// hashed integer slice. Returned integer order is salted
// with an input key. This results in consistent order.

/**
 * This is an implementation of the HMACT64 keyed hashing algorithm.
 * HMACT64 is defined by Luke Leighton as a modified HMAC-MD5 (RFC 2104)
 * in which the key is truncated at 64 bytes (rather than being hashed
 * via MD5).
 */ 
public class HMACT64 extends MessageDigest implements Cloneable {

    private static final int BLOCK_LENGTH = 64;

    private static final byte IPAD = (byte) 0x36;

/**
 * This is an implementation of the HMACT64 keyed hashing algorithm.
 * HMACT64 is defined by Luke Leighton as a modified HMAC-MD5 (RFC 2104)
 * in which the key is truncated at 64 bytes (rather than being hashed
 * via MD5).
 */
class HMACT64 extends MessageDigest implements Cloneable {

    private static final int BLOCK_LENGTH = 64;

    private static final byte IPAD = (byte) 0x36;

      new RegularImmutableSet<>(EMPTY_ARRAY, 0, EMPTY_ARRAY, 0);

  private final transient Object[] elements;
  private final transient int hashCode;
  // the same values as `elements` in hashed positions (plus nulls)
  @VisibleForTesting final transient @Nullable Object[] table;
  // 'and' with an int to get a valid table index.
  private final transient int mask;

  // The first `size` elements are non-null.
  @VisibleForTesting final transient @Nullable Object[] elements;
  private final transient int hashCode;
  // the same values as `elements` in hashed positions (plus nulls)
  @VisibleForTesting final transient @Nullable Object[] table;
  // 'and' with an int to get a valid table index.
  private final transient int mask;
  private final transient int size;

)

// xxhash64 is the state of a xxHash-64 checksum.
type xxhash64 struct {
	len uint64    // total length hashed
	v   [4]uint64 // accumulators
	buf [32]byte  // buffer
	cnt int       // number of bytes in buffer
}

// reset discards the current state and prepares to compute a new hash.
// We assume a seed of 0 since that is what zstd uses.
func (xh *xxhash64) reset() {
	xh.len = 0

 *
 * This strategy could be improved in several ways:
 *  - Don't use the timestamp for files that we've already hashed during this build.