2e.md

description	Reference for non-cryptographic hash functions in Hoon including MurmurHash3 and other fast hashing algorithms for data structures and scrambling.
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2e: Insecure Hashing

+mug {#mug}

Murmur3 scrambler.

Hashes a with the 31-bit murmur3 non-cryptographic hash algorithm, producing an atom.

Accepts

.a is a $noun.

Produces

An atom.

Source

++  mug
  ~/  %mug
  |=  a=*
  |^  ?@  a  (mum 0xcafe.babe 0x7fff a)
      =/  b  (cat 5 $(a -.a) $(a +.a))
      (mum 0xdead.beef 0xfffe b)
  ::
  ++  mum
    |=  [syd=@uxF fal=@F key=@]
    =/  wyd  (met 3 key)
    =|  i=@ud
    |-  ^-  @F
    ?:  =(8 i)  fal
    =/  haz=@F  (muk syd wyd key)
    =/  ham=@F  (mix (rsh [0 31] haz) (end [0 31] haz))
    ?.(=(0 ham) ham $(i +(i), syd +(syd)))
  --

Examples

> (mug 10.000)
795.713.195

> (mug 10.001)
420.521.697

> (mug 1)
1.901.865.568

> (mug (some 10))
750.200.080

> (mug [1 2 3 4 5 ~])
1.565.443.491

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+muk {#muk}

Standard MurmurHash3.

Implementation of the 32-bit MurmurHash3 non-cryptographic hash algorithm. Takes .syd as the seed, .len as the key length in blocks of size 3, and .key as the key, producing an atom.

Accepts

.syd is an atom.

.len is an atom.

.key is an atom.

Produces

An atom.

Source

++  muk
  ~/  %muk
  |=  [syd=@ len=@ key=@]
  ^-  @
  =+  ~(. fe 5)
  =.  syd      (end 5 syd)
  =/  nblocks  (div len 4)
  =/  h1  syd
  =+  [c1=0xcc9e.2d51 c2=0x1b87.3593]
  =/  i  nblocks
  =.  h1  =/  hi  h1  |-
    ?:  =(0 i)  hi
    =/  k1  (cut 5 [(sub nblocks i) 1] key)
    =.  k1  (sit (mul k1 c1))
    =.  k1  (rol 0 15 k1)
    =.  k1  (sit (mul k1 c2))
    =.  hi  (mix hi k1)
    =.  hi  (rol 0 13 hi)
    =.  hi  (sum (sit (mul hi 5)) 0xe654.6b64)
    $(i (dec i))
  =/  tail  (rsh [3 (mul 4 nblocks)] key)
  =/  k1    0
  =/  tlen  (dis len 3)
  =.  h1
    ?+  tlen  h1
      %3  =.  k1  (mix k1 (lsh [0 16] (cut 3 [2 1] tail)))
          =.  k1  (mix k1 (lsh [0 8] (cut 3 [1 1] tail)))
          =.  k1  (mix k1 (cut 3 [0 1] tail))
          =.  k1  (sit (mul k1 c1))
          =.  k1  (rol 0 15 k1)
          =.  k1  (sit (mul k1 c2))
          (mix h1 k1)
      %2  =.  k1  (mix k1 (lsh [0 8] (cut 3 [1 1] tail)))
          =.  k1  (mix k1 (cut 3 [0 1] tail))
          =.  k1  (sit (mul k1 c1))
          =.  k1  (rol 0 15 k1)
          =.  k1  (sit (mul k1 c2))
          (mix h1 k1)
      %1  =.  k1  (mix k1 (cut 3 [0 1] tail))
          =.  k1  (sit (mul k1 c1))
          =.  k1  (rol 0 15 k1)
          =.  k1  (sit (mul k1 c2))
          (mix h1 k1)
    ==
  =.  h1  (mix h1 (end 5 len))
  |^  (fmix32 h1)
  ++  fmix32
    |=  h=@
    =.  h  (mix h (rsh [0 16] h))
    =.  h  (sit (mul h 0x85eb.ca6b))
    =.  h  (mix h (rsh [0 13] h))
    =.  h  (sit (mul h 0xc2b2.ae35))
    =.  h  (mix h (rsh [0 16] h))
    h
  --

Examples

> (muk 6 1 3)
3.427.677.118

> (muk 6 2 'jerry')
! exit

> (muk 6 2 'je')
3.602.081.716

> (met 3 'jerry')
5

> (met 3 'je')
2

> (muk 6 5 'jerry')
1.276.447.489

> (muk 6 15 'jerry')
2.881.503.571

> =e (cut 3 [0 2] eny)
> e
44.228

> (muk e 11 10.000)
246.077.549

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