Python implementation of Jenkins Hash?

Question

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)

Answer 1

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.  [email protected].  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)