mishmash/mishmash.go

package mishmash

var primes = [256]uint32{2781111551, 4115761697, 2188512439, 3902941499, 4078728127, 2919449173, 3950407729, 4081733563,
	4061783399, 2728829231, 3557004557, 3778858159, 2397085727, 3808921189, 3159484147, 4084759639,
	2938297727, 3839623429, 2441361773, 2471079053, 4270995293, 3336967261, 2717746523, 3306593077,
	2846319523, 2704420699, 2772002447, 2664263209, 3452941517, 3422898851, 2502691043, 3785866613,
	3164194337, 3348481009, 3448873073, 2340666883, 3742418039, 2298597811, 3061650257, 4286896921,
	2816281231, 3814879819, 3245870963, 2718113173, 3051925081, 2527351147, 2737897993, 3567396421,
	3422709179, 3542178331, 3740214493, 3720784621, 2821606727, 3764267237, 3923068349, 3880303043,
	3816527917, 3032326837, 4006470463, 4165427173, 2511539731, 2993685649, 2268550831, 2899250059,
	2432655553, 3959959639, 4142838449, 4100124029, 2962655827, 2648245423, 4117297801, 3331059481,
	2287716593, 4115533181, 2411037073, 3273978871, 2395052183, 2776949353, 3871801559, 2948305931,
	2257427881, 4288176181, 2624064151, 3144150523, 4282472071, 2206613407, 2960685401, 2761304627,
	3187632967, 2447380627, 2781789473, 3657272401, 3603710699, 4042745507, 4087095841, 2354409557,
	2239000559, 4164370321, 3636939347, 3622573529, 2202257819, 2792364713, 2803311809, 4006899277,
	2835975767, 2951997809, 3185753917, 2417651723, 2631379747, 2175388331, 4277708983, 3547799261,
	3093003779, 3653208029, 4084095199, 3161669417, 2698224923, 2746404013, 3209829191, 3024118079,
	3799471327, 3012753409, 2653321639, 2777700139, 3794895031, 3075822329, 2774150557, 3135465059,
	2294247001, 3557999149, 3189799397, 4080431539, 3397276529, 3931450153, 3518901437, 3135266501,
	3275906693, 4143264221, 3439131923, 2462856037, 2441331799, 2640219781, 3504419027, 3721296989,
	3434920081, 2852097271, 3199425679, 3785517557, 2984788193, 3678788947, 2308371491, 3354456173,
	4148931503, 3239885063, 3894052103, 3930187787, 3521437319, 3203332001, 2894779337, 4197047957,
	3080099353, 2304447583, 3731998477, 2733978179, 2235339121, 2490436339, 2147689987, 3276115639,
	3923204273, 3402325321, 3082785493, 3420863399, 3203562407, 2292225781, 3461192447, 2589852949,
	2772559931, 3667144931, 2163126419, 3412216831, 3699715037, 3619099453, 3875532569, 3047225267,
	3780456941, 2512094297, 3527794547, 3130190737, 3013107347, 3691645577, 3877430399, 4270767517,
	2797247227, 3976455169, 3541991143, 3737016677, 3801675821, 2233908737, 3210598117, 4200595549,
	2772203789, 2415614503, 2467043143, 2611954561, 2791210277, 2599276769, 4034287091, 3521719193,
	3060219497, 2799601709, 2178939557, 3800717749, 3426533269, 3519387097, 2861815447, 2884852603,
	2814915449, 3359572921, 3013763303, 3565679363, 3491538893, 2588490083, 3441048649, 2501343701,
	4191701149, 2251607773, 3543948791, 3511969763, 2966565907, 3640359409, 3640516129, 2586869203,
	2328651011, 4037640461, 3601356797, 4260950119, 3198526459, 3478546597, 3009442531, 3594323353,
	3205141207, 3592422991, 3357971081, 3217249313, 2903534827, 3716714951, 3388800011, 3045269987,
	2325616213, 2688355151, 3022034467, 4221197753, 2426944493, 3090262709, 3471570467, 2437347167,
}

func slct(n uint64) uint32 {
	return primes[n&0xff]
}

func Engine(buffer []byte, length int, accumulator uint64) uint64 {
	for i := 0; i < length; i++ {
		b := buffer[i]
		accumulator += uint64(slct(accumulator)) + uint64(b)
		accumulator *= uint64(slct(uint64(b)))
		accumulator += accumulator >> 32
	}
	return accumulator
}

func Mishmash(buffer []byte, nums ...uint64) uint32 {
	// nums is a seed/accumulator
	var accumulator uint64
	if 0 == len(nums) {
		// seeding with 0 by default - could be changed
		accumulator = Engine(buffer, len(buffer), 0)
	} else {
		accumulator = Engine(buffer, len(buffer), nums[0])
	}
	return uint32(accumulator & 0x00000000ffffffff)
}

func MishmashAccumulator(accumulator uint64) uint32 {
	// use when collecting accumulators for second hash
	return uint32(accumulator & 0x00000000ffffffff)
}

// example below shows calling Mishmash on "hello world"
// and then collecting the hash. Given
// a collision we simply call Mishmash again, giving it
// the first hash as a seed this time and get a second hash.
/*
func main() {
	buf := []byte("Hello world")
	// grab the accumulator if necessary
	accum := Engine(buf, len(buf), 0)
	// grab the hash - decode accumulator into hash
	hash := MishmashAccumulator(accum)
	fmt.Printf("%08x\n", hash)
	// now get second hash - seed with accumulator
	secondHash := Mishmash(buf, accum)
	fmt.Printf("%08x\n", secondHash)
	// you can also get a simple hash
	simpleMishmash := Mishmash(buf)
	fmt.Printf("%08x\n", simpleMishmash)
}
*/
// example below used to validate output against C++ mishmash
/*
func main() {
	buf := []byte("Hello world!")
	first := MishmashAccumulator(Engine(buf, len(buf), 0))
	second := MishmashAccumulator(Engine(buf, len(buf), 1))
	var combo uint64
	combo = uint64(first)<<32 | uint64(second)
	fmt.Println(first, second, combo)
}
*/