murmur.go 1.0 KB

1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950
  1. package murmur3
  2. type bmixer interface {
  3. bmix(p []byte) (tail []byte)
  4. Size() (n int)
  5. reset()
  6. }
  7. type digest struct {
  8. clen int // Digested input cumulative length.
  9. tail []byte // 0 to Size()-1 bytes view of `buf'.
  10. buf [16]byte // Expected (but not required) to be Size() large.
  11. seed uint32 // Seed for initializing the hash.
  12. bmixer
  13. }
  14. func (d *digest) BlockSize() int { return 1 }
  15. func (d *digest) Write(p []byte) (n int, err error) {
  16. n = len(p)
  17. d.clen += n
  18. if len(d.tail) > 0 {
  19. // Stick back pending bytes.
  20. nfree := d.Size() - len(d.tail) // nfree ∈ [1, d.Size()-1].
  21. if nfree < len(p) {
  22. // One full block can be formed.
  23. block := append(d.tail, p[:nfree]...)
  24. p = p[nfree:]
  25. _ = d.bmix(block) // No tail.
  26. } else {
  27. // Tail's buf is large enough to prevent reallocs.
  28. p = append(d.tail, p...)
  29. }
  30. }
  31. d.tail = d.bmix(p)
  32. // Keep own copy of the 0 to Size()-1 pending bytes.
  33. nn := copy(d.buf[:], d.tail)
  34. d.tail = d.buf[:nn]
  35. return n, nil
  36. }
  37. func (d *digest) Reset() {
  38. d.clen = 0
  39. d.tail = nil
  40. d.bmixer.reset()
  41. }