Does there exist a native Python implementation of the Jenkins hash algorithm(s)?
I need a hash algorithm that takes an arbitrary string and turns it into an 32-bit integer. For a given string, it must guarantee to return the same integer across platforms.
I have looked at the ELF hash algorithm, of which I have found a Python implementation. Could this be a suitable replacement given the above criteria? (http://www.partow.net/programming/hashfunctions/#ELFHashFunction)
This native python-code should give you the same hash as the original lookup3.c
# Need to constrain U32 to only 32 bits using the & 0xffffffff
# since Python has no native notion of integers limited to 32 bit
# http://docs.python.org/library/stdtypes.html#numeric-types-int-float-long-complex
'''Original copyright notice:
By Bob Jenkins, 1996. bob_jenkins@burtleburtle.net. You may use this
code any way you wish, private, educational, or commercial. Its free.
'''
def rot(x,k):
return (((x)<<(k)) | ((x)>>(32-(k))))
def mix(a, b, c):
a &= 0xffffffff; b &= 0xffffffff; c &= 0xffffffff
a -= c; a &= 0xffffffff; a ^= rot(c,4); a &= 0xffffffff; c += b; c &= 0xffffffff
b -= a; b &= 0xffffffff; b ^= rot(a,6); b &= 0xffffffff; a += c; a &= 0xffffffff
c -= b; c &= 0xffffffff; c ^= rot(b,8); c &= 0xffffffff; b += a; b &= 0xffffffff
a -= c; a &= 0xffffffff; a ^= rot(c,16); a &= 0xffffffff; c += b; c &= 0xffffffff
b -= a; b &= 0xffffffff; b ^= rot(a,19); b &= 0xffffffff; a += c; a &= 0xffffffff
c -= b; c &= 0xffffffff; c ^= rot(b,4); c &= 0xffffffff; b += a; b &= 0xffffffff
return a, b, c
def final(a, b, c):
a &= 0xffffffff; b &= 0xffffffff; c &= 0xffffffff
c ^= b; c &= 0xffffffff; c -= rot(b,14); c &= 0xffffffff
a ^= c; a &= 0xffffffff; a -= rot(c,11); a &= 0xffffffff
b ^= a; b &= 0xffffffff; b -= rot(a,25); b &= 0xffffffff
c ^= b; c &= 0xffffffff; c -= rot(b,16); c &= 0xffffffff
a ^= c; a &= 0xffffffff; a -= rot(c,4); a &= 0xffffffff
b ^= a; b &= 0xffffffff; b -= rot(a,14); b &= 0xffffffff
c ^= b; c &= 0xffffffff; c -= rot(b,24); c &= 0xffffffff
return a, b, c
def hashlittle2(data, initval = 0, initval2 = 0):
length = lenpos = len(data)
a = b = c = (0xdeadbeef + (length) + initval)
c += initval2; c &= 0xffffffff
p = 0 # string offset
while lenpos > 12:
a += (ord(data[p+0]) + (ord(data[p+1])<<8) + (ord(data[p+2])<<16) + (ord(data[p+3])<<24)); a &= 0xffffffff
b += (ord(data[p+4]) + (ord(data[p+5])<<8) + (ord(data[p+6])<<16) + (ord(data[p+7])<<24)); b &= 0xffffffff
c += (ord(data[p+8]) + (ord(data[p+9])<<8) + (ord(data[p+10])<<16) + (ord(data[p+11])<<24)); c &= 0xffffffff
a, b, c = mix(a, b, c)
p += 12
lenpos -= 12
if lenpos == 12: c += (ord(data[p+8]) + (ord(data[p+9])<<8) + (ord(data[p+10])<<16) + (ord(data[p+11])<<24)); b += (ord(data[p+4]) + (ord(data[p+5])<<8) + (ord(data[p+6])<<16) + (ord(data[p+7])<<24)); a += (ord(data[p+0]) + (ord(data[p+1])<<8) + (ord(data[p+2])<<16) + (ord(data[p+3])<<24));
if lenpos == 11: c += (ord(data[p+8]) + (ord(data[p+9])<<8) + (ord(data[p+10])<<16)); b += (ord(data[p+4]) + (ord(data[p+5])<<8) + (ord(data[p+6])<<16) + (ord(data[p+7])<<24)); a += (ord(data[p+0]) + (ord(data[p+1])<<8) + (ord(data[p+2])<<16) + (ord(data[p+3])<<24));
if lenpos == 10: c += (ord(data[p+8]) + (ord(data[p+9])<<8)); b += (ord(data[p+4]) + (ord(data[p+5])<<8) + (ord(data[p+6])<<16) + (ord(data[p+7])<<24)); a += (ord(data[p+0]) + (ord(data[p+1])<<8) + (ord(data[p+2])<<16) + (ord(data[p+3])<<24));
if lenpos == 9: c += (ord(data[p+8])); b += (ord(data[p+4]) + (ord(data[p+5])<<8) + (ord(data[p+6])<<16) + (ord(data[p+7])<<24)); a += (ord(data[p+0]) + (ord(data[p+1])<<8) + (ord(data[p+2])<<16) + (ord(data[p+3])<<24));
if lenpos == 8: b += (ord(data[p+4]) + (ord(data[p+5])<<8) + (ord(data[p+6])<<16) + (ord(data[p+7])<<24)); a += (ord(data[p+0]) + (ord(data[p+1])<<8) + (ord(data[p+2])<<16) + (ord(data[p+3])<<24));
if lenpos == 7: b += (ord(data[p+4]) + (ord(data[p+5])<<8) + (ord(data[p+6])<<16)); a += (ord(data[p+0]) + (ord(data[p+1])<<8) + (ord(data[p+2])<<16) + (ord(data[p+3])<<24));
if lenpos == 6: b += ((ord(data[p+5])<<8) + ord(data[p+4])); a += (ord(data[p+0]) + (ord(data[p+1])<<8) + (ord(data[p+2])<<16) + (ord(data[p+3])<<24))
if lenpos == 5: b += (ord(data[p+4])); a += (ord(data[p+0]) + (ord(data[p+1])<<8) + (ord(data[p+2])<<16) + (ord(data[p+3])<<24));
if lenpos == 4: a += (ord(data[p+0]) + (ord(data[p+1])<<8) + (ord(data[p+2])<<16) + (ord(data[p+3])<<24))
if lenpos == 3: a += (ord(data[p+0]) + (ord(data[p+1])<<8) + (ord(data[p+2])<<16))
if lenpos == 2: a += (ord(data[p+0]) + (ord(data[p+1])<<8))
if lenpos == 1: a += ord(data[p+0])
a &= 0xffffffff; b &= 0xffffffff; c &= 0xffffffff
if lenpos == 0: return c, b
a, b, c = final(a, b, c)
return c, b
def hashlittle(data, initval=0):
c, b = hashlittle2(data, initval, 0)
return c
if __name__ == "__main__":
import sys
hashstr = 'Four score and seven years ago'
hash, hash2 = hashlittle2(hashstr, 0xdeadbeef, 0xdeadbeef)
print '"%s": %x %x' % (hashstr, hash, hash2)
hash = hashlittle(hashstr, 0)
print '"%s": %x' % (hashstr, hash)
You can just use the first 32 bits of an md5sum
>>> from hashlib import md5
>>> from struct import unpack
>>> unpack("<IIII",md5("thestring").digest())[0]
1515985217
Ended up implementing it on my own. Released according to the original copyright notice (see below). Use at your own risk and have fun :-)
'''Implements a straight Jenkins lookup hash - http://burtleburtle.net/bob/hash/doobs.html
Usage:
from jhash import jhash
print jhash('My hovercraft is full of eels')
Returns: unsigned 32 bit integer value
Prereqs: None
Tested with Python 2.6.
Version 1.00 - der@dod.no - 23.08.2010
Partly based on the Perl module Digest::JHash
http://search.cpan.org/~shlomif/Digest-JHash-0.06/lib/Digest/JHash.pm
Original copyright notice:
By Bob Jenkins, 1996. bob_jenkins@burtleburtle.net. You may use this
code any way you wish, private, educational, or commercial. It's free.
See http://burtleburtle.net/bob/hash/evahash.html
Use for hash table lookup, or anything where one collision in 2^^32 is
acceptable. Do NOT use for cryptographic purposes.
'''
def mix(a, b, c):
'''mix() -- mix 3 32-bit values reversibly.
For every delta with one or two bits set, and the deltas of all three
high bits or all three low bits, whether the original value of a,b,c
is almost all zero or is uniformly distributed,
* If mix() is run forward or backward, at least 32 bits in a,b,c
have at least 1/4 probability of changing.
* If mix() is run forward, every bit of c will change between 1/3 and
2/3 of the time. (Well, 22/100 and 78/100 for some 2-bit deltas.)'''
# Need to constrain U32 to only 32 bits using the & 0xffffffff
# since Python has no native notion of integers limited to 32 bit
# http://docs.python.org/library/stdtypes.html#numeric-types-int-float-long-complex
a &= 0xffffffff; b &= 0xffffffff; c &= 0xffffffff
a -= b; a -= c; a ^= (c>>13); a &= 0xffffffff
b -= c; b -= a; b ^= (a<<8); b &= 0xffffffff
c -= a; c -= b; c ^= (b>>13); c &= 0xffffffff
a -= b; a -= c; a ^= (c>>12); a &= 0xffffffff
b -= c; b -= a; b ^= (a<<16); b &= 0xffffffff
c -= a; c -= b; c ^= (b>>5); c &= 0xffffffff
a -= b; a -= c; a ^= (c>>3); a &= 0xffffffff
b -= c; b -= a; b ^= (a<<10); b &= 0xffffffff
c -= a; c -= b; c ^= (b>>15); c &= 0xffffffff
return a, b, c
def jhash(data, initval = 0):
'''hash() -- hash a variable-length key into a 32-bit value
data : the key (the unaligned variable-length array of bytes)
initval : can be any 4-byte value, defaults to 0
Returns a 32-bit value. Every bit of the key affects every bit of
the return value. Every 1-bit and 2-bit delta achieves avalanche.'''
length = lenpos = len(data)
# empty string returns 0
if length == 0:
return 0
# Set up the internal state
a = b = 0x9e3779b9 # the golden ratio; an arbitrary value
c = initval # the previous hash value
p = 0 # string offset
# ------------------------- handle most of the key in 12 byte chunks
while lenpos >= 12:
a += (ord(data[p+0]) + (ord(data[p+1])<<8) + (ord(data[p+2])<<16) + (ord(data[p+3])<<24))
b += (ord(data[p+4]) + (ord(data[p+5])<<8) + (ord(data[p+6])<<16) + (ord(data[p+7])<<24))
c += (ord(data[p+8]) + (ord(data[p+9])<<8) + (ord(data[p+10])<<16) + (ord(data[p+11])<<24))
a, b, c = mix(a, b, c)
p += 12
lenpos -= 12
# ------------------------- handle the last 11 bytes
c += length
if lenpos >= 11: c += ord(data[p+10])<<24
if lenpos >= 10: c += ord(data[p+9])<<16
if lenpos >= 9: c += ord(data[p+8])<<8
# the first byte of c is reserved for the length
if lenpos >= 8: b += ord(data[p+7])<<24
if lenpos >= 7: b += ord(data[p+6])<<16
if lenpos >= 6: b += ord(data[p+5])<<8
if lenpos >= 5: b += ord(data[p+4])
if lenpos >= 4: a += ord(data[p+3])<<24
if lenpos >= 3: a += ord(data[p+2])<<16
if lenpos >= 2: a += ord(data[p+1])<<8
if lenpos >= 1: a += ord(data[p+0])
a, b, c = mix(a, b, c)
# ------------------------- report the result
return c
if __name__ == "__main__":
hashstr = 'My hovercraft is full of eels'
myhash = jhash(hashstr)
print 'jhash("%s"): %d' % (hashstr, myhash)
There is already a "jenkins" package on PyPi. But it is not "native" as the core implementation is in C.
a simple implementation form the one_at_a_time hash given at wikipedia. Mind this algorithm has an avalanche behavior.
def getJenkinHash(ba : bytearray):
hash : int = 0
for i in range(len(ba)):
hash += ba[i]
hash &= 0xFFFFFFFF
hash += hash << 10
hash &= 0xFFFFFFFF
hash ^= hash >> 6
hash &= 0xFFFFFFFF
hash += hash << 3
hash &= 0xFFFFFFFF
hash ^= hash >> 11
hash &= 0xFFFFFFFF
hash += hash << 15
hash &= 0xFFFFFFFF
return hash
Here a minimal implementation:
def hash(x):
""" Jenkins Hash 32bits."""
x = (x + int('7ed55d16', 16)) + (x << 12)
x = (x ^ int('c761c23c', 16)) ^ (x >> 19)
x = (x + int('165667b1', 16)) + (x << 5)
x = (x + int('d3a2646c', 16)) ^ (x << 9)
x = (x + int('fd7046c5', 16)) + (x << 3)
x = (x ^ int('b55a4f09', 16)) ^ (x >> 16)
return x
