package hash

import (
	"math/bits"
)

const (
	c1 uint32 = 0xcc9e2d51
	c2 uint32 = 0x1b873593
)

// Sum32WithSeed is a port of MurmurHash3_x86_32 function.
func Sum32WithSeed(data []byte, seed uint32) uint32 {
	h1 := seed
	dlen := len(data)

	for len(data) >= 4 {
		k1 := uint32(data[0]) | uint32(data[1])<<8 | uint32(data[2])<<16 | uint32(data[3])<<24
		data = data[4:]

		k1 *= c1
		k1 = bits.RotateLeft32(k1, 15)
		k1 *= c2

		h1 ^= k1
		h1 = bits.RotateLeft32(h1, 13)
		h1 = h1*5 + 0xe6546b64
	}

	var k1 uint32
	switch len(data) {
	case 3:
		k1 ^= uint32(data[2]) << 16
		fallthrough
	case 2:
		k1 ^= uint32(data[1]) << 8
		fallthrough
	case 1:
		k1 ^= uint32(data[0])
		k1 *= c1
		k1 = bits.RotateLeft32(k1, 15)
		k1 *= c2
		h1 ^= k1
	}

	h1 ^= uint32(dlen)

	h1 ^= h1 >> 16
	h1 *= 0x85ebca6b
	h1 ^= h1 >> 13
	h1 *= 0xc2b2ae35
	h1 ^= h1 >> 16

	return h1
}