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: md4block.go
    path of file: ./repos/scan4all/vendor/golang.org/x/crypto/md4
    
    the code of the file until where you have to start completion: // Copyright 2009 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.

// MD4 block step.
// In its own file so that a faster assembly or C version
// can be substituted easily.

package md4

import "math/bits"

var shift1 = []int{3, 7, 11, 19}
var shift2 = []int{3, 5, 9, 13}
var shift3 = []int{3, 9, 11, 15}

var xIndex2 = []uint{0, 4, 8, 12, 1, 5, 9, 13, 2, 6, 10, 14, 3, 7, 11, 15}
var xIndex3 = []uint{0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5, 13, 3, 11, 7, 15}

func _Block(dig *digest, p []byte) int {
	a := dig.s[0]
	b := dig.s[1]
	c := dig.s[2]
	d := dig.s[3]
	n := 0
	var X [16]uint32
	for len(p) >= _Chunk {
		aa, bb, cc, dd := a, b, c, d

		j := 0
		for i := 0; i < 16; i++ {
			X[i] = uint32(p[j]) | uint32(p[j+1])<<8 | uint32(p[j+2])<<16 | uint32(p[j+3])<<24
			j += 4
		}

		// If this needs to be made faster in the future,
		// the usual trick is to unroll each of these
		// loops by a factor of 4; that lets you replace
		// the shift[] lookups with constants and,
		// with suitable variable renaming in each
		// unrolled body, delete the a, b, c, d = d, a, b, c
		// (or you can let the opt
    
func _Block(dig *digest, p []byte) int {
	a := dig.s[0]
	b := dig.s[1]
	c := dig.s[2]
	d := dig.s[3]
	n := 0
	var X [16]uint32
	for len(p) >= _Chunk {
		aa, bb, cc, dd := a, b, c, d

		j := 0
		for i := 0; i < 16; i++ {
			X[i] = uint32(p[j]) | uint32(p[j+1])<<8 | uint32(p[j+2])<<16 | uint32(p[j+3])<<24
			j += 4
		}

		// If this needs to be made faster in the future,
		// the usual trick is to unroll each of these
		// loops by a factor of 4; that lets you replace
		// the shift[] lookups with constants and,
		// with suitable variable renaming in each
		// unrolled body, delete the a, b, c, d = d, a, b, c
		// (or you can let the optimizer do the renaming).
		//
		// The index variables are uint so that % by a power
		// of two can be optimized easily by a compiler.

		// Round 1.
		for i := uint(0); i < 16; i++ {
			x := i
			s := shift1[i%4]
			f := ((c ^ d) & b) ^ d
			a += f + X[x]
			a = bits.RotateLeft32(a, s)
			a, b, c, d = d, a, b, c
		}

		// Round 2.
		for i := uint(0); i < 16; i++ {
			x := xIndex2[i]
			s := shift2[i%4]
			g := (b & c) | (b & d) | (c & d)
			a += g + X[x] + 0x5a827999
			a = bits.RotateLeft32(a, s)
			a, b, c, d = d, a, b, c
		}

		// Round 3.
		for i := uint(0); i < 16; i++ {
			x := xIndex3[i]
			s := shift3[i%4]
			h := b ^ c ^ d
			a += h + X[x] + 0x6ed9eba1
			a = bits.RotateLeft32(a, s)
			a, b, c, d = d, a, b, c
		}

		a += aa
		b += bb
		c += cc
		d += dd

		p = p[_Chunk:]
		n += _Chunk
	}

	dig.s[0] = a
	dig.s[1] = b
	dig.s[2] = c
	dig.s[3] = d
	return n
}