How to generate a positive int64 from byte slice

[JohnGB]

I have a byte slice 32 bytes long, and I would like to use it to generate a positive int64.  Is there a standard way to do this, or do I need to write my own function (most likely using bit shifts)?

The backstory is that I need to generate unique (low collision likelihood) integer IDs from email addresses.  However it needs to be that every time a given email is used to generate an int64, that it generates the same int64.  I've settled on using a SHA3 hash with a salt to get a low collision byte slice, which I then need to generate a positive int64 from.

[Caleb Spare]

You'll probably want to use encoding/binary.

But which 8 of the 32 bytes are you going to use? (or really, which 63 bits?)

-Caleb

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[JohnGB]

The 32 bytes were just a product of the hash function that we were using, but I've simplified it by changing the hash function to one that only generates 8 bytes.

My current solution is:

func EmailToID(email, salt string) int64 {

d := sha3.NewShake256()

d.Write([]byte(email))

d.Write([]byte(salt))

h := make([]byte, 8)

d.Read(h)

var n int64

buff := bytes.NewBuffer(h)

binary.Read(buff, binary.LittleEndian, &n)

if n < 0 {

n *= -1

}

return n

}

So, I'm actually using all 64 bits, but taking the absolute value of the resulting int64, which in effect means that I'm only considering 63 bytes.