You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: blake2b.go
    path of file: ./repos/sliver/vendor/golang.org/x/crypto/argon2
    
    the code of the file until where you have to start completion: // Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package argon2

import (
	"encoding/binary"
	"hash"

	"golang.org/x/crypto/blake2b"
)

// blake2bHash computes an arbitrary lo
    
func blake2bHash(out []byte, in []byte) {
	var b2 hash.Hash
	if n := len(out); n < blake2b.Size {
		b2, _ = blake2b.New(n, nil)
	} else {
		b2, _ = blake2b.New512(nil)
	}

	var buffer [blake2b.Size]byte
	binary.LittleEndian.PutUint32(buffer[:4], uint32(len(out)))
	b2.Write(buffer[:4])
	b2.Write(in)

	if len(out) <= blake2b.Size {
		b2.Sum(out[:0])
		return
	}

	outLen := len(out)
	b2.Sum(buffer[:0])
	b2.Reset()
	copy(out, buffer[:32])
	out = out[32:]
	for len(out) > blake2b.Size {
		b2.Write(buffer[:])
		b2.Sum(buffer[:0])
		copy(out, buffer[:32])
		out = out[32:]
		b2.Reset()
	}

	if outLen%blake2b.Size > 0 { // outLen > 64
		r := ((outLen + 31) / 32) - 2 // ⌈τ /32⌉-2
		b2, _ = blake2b.New(outLen-32*r, nil)
	}
	b2.Write(buffer[:])
	b2.Sum(out[:0])
}