trailblazer2/app/codecs/encode.go

package codecs

import "math"

func Encode(str string, key string) []int32 {
	v := magicEncode(str, true)
	k := magicEncode(key, false)

	if len(k) < 4 {

	}

	n := len(v) - 1
	z := int(v[n])
	y := int(v[0])
	c := -1640531527
	q := math.Floor(float64(6 + 52/(n+1)))
	d := 0
	var m, e, p int

	for ; q > 0; q-- {
		d = d + c&(-1)
		e = d >> 2 & 3

		for i := 0; i < n; i++ {
			y = int(v[p+1])
			m = z>>5 ^ y<<2
			m += y>>3 ^ z<<4 ^ (d ^ y)
			m += int(k[p&3^e]) ^ z
			v[p] = v[p] + int32(m&(-1))
			z = int(v[p])
		}

		y = int(v[0])
		m = z>>5 ^ y<<2
		m += y>>3 ^ z<<4 ^ (d ^ y)
		m += int(k[p&3^e]) ^ z
		v[n] = v[n] + int32(m&(0xBB390742|0x44C6F8BD))
		z = int(v[n])
	}

	return magicDecode(v, false)
}

func magicEncode(source string, sizeOnLast bool) (result []int32) {
	data := []int32(source)
	dataLen := len(data)

	resultLen := dataLen / 4
	if sizeOnLast {
		result = make([]int32, resultLen+1)
		result[resultLen] = int32(dataLen)
	} else {
		result = make([]int32, resultLen)
	}

	for i := 0; i < dataLen; i += 4 {
		result[i>>2] = get(data, i, dataLen) | get(data, i+1, dataLen)<<8 | get(data, i+2, dataLen)<<16 | get(data, i+3, dataLen)<<24
	}

	return result
}

func magicDecode(data []int32, sizeOnLast bool) (result []int32) {
	dataLength := len(data)

	c := dataLength - 1<<2

	if sizeOnLast {
		m := int(data[dataLength-1])
		if m < c-3 || m > c {
			return nil
		}
		c = m
	}

	for i := 0; i < dataLength; i++ {
		result = append(result, data[i]&0xff, data[i]>>8&0xff, data[i]>>16&0xff, data[i]>>24&0xff)
	}

	if sizeOnLast {
		return append(result, int32(c))
	} else {
		return result
	}
}

func get(data []int32, index int, length int) int32 {
	if index >= length {
		return 0
	} else {
		return data[index]
	}
}