How to use the assert-plus.buffer function in assert-plus

function read(buf, options, forceType) {
	var input = buf;
	if (typeof (buf) !== 'string') {
		assert.buffer(buf, 'buf');
		buf = buf.toString('ascii');
	}

	var lines = buf.trim().split('\n');

	var m = lines[0].match(/*JSSTYLED*/
	    /[-]+[ ]*BEGIN ([A-Z0-9][A-Za-z0-9]+ )?(PUBLIC|PRIVATE) KEY[ ]*[-]+/);
	assert.ok(m, 'invalid PEM header');

	var m2 = lines[lines.length - 1].match(/*JSSTYLED*/
	    /[-]+[ ]*END ([A-Z0-9][A-Za-z0-9]+ )?(PUBLIC|PRIVATE) KEY[ ]*[-]+/);
	assert.ok(m2, 'invalid PEM footer');

	/* Begin and end banners must match key type */
	assert.equal(m[2], m2[2]);
	var type = m[2].toLowerCase();

function bufferSplit(buf, chr) {
	assert.buffer(buf);
	assert.string(chr);

	var parts = [];
	var lastPart = 0;
	var matches = 0;
	for (var i = 0; i < buf.length; ++i) {
		if (buf[i] === chr.charCodeAt(matches))
			++matches;
		else if (buf[i] === chr.charCodeAt(0))
			matches = 1;
		else
			matches = 0;

		if (matches >= chr.length) {
			var newPart = i + 1;
			parts.push(buf.slice(lastPart, newPart - matches));

function calculateX25519Public(k) {
	assert.buffer(k);

	if (nacl === undefined)
		nacl = require('tweetnacl');

	var kp = nacl.box.keyPair.fromSeed(new Uint8Array(k));
	return (new Buffer(kp.publicKey));
}

function Certificate(opts) {
	assert.object(opts, 'options');
	assert.arrayOfObject(opts.subjects, 'options.subjects');
	utils.assertCompatible(opts.subjects[0], Identity, [1, 0],
	    'options.subjects');
	utils.assertCompatible(opts.subjectKey, Key, [1, 0],
	    'options.subjectKey');
	utils.assertCompatible(opts.issuer, Identity, [1, 0], 'options.issuer');
	if (opts.issuerKey !== undefined) {
		utils.assertCompatible(opts.issuerKey, Key, [1, 0],
		    'options.issuerKey');
	}
	assert.object(opts.signatures, 'options.signatures');
	assert.buffer(opts.serial, 'options.serial');
	assert.date(opts.validFrom, 'options.validFrom');
	assert.date(opts.validUntil, 'optons.validUntil');

	this._hashCache = {};

	this.subjects = opts.subjects;
	this.issuer = opts.issuer;
	this.subjectKey = opts.subjectKey;
	this.issuerKey = opts.issuerKey;
	this.signatures = opts.signatures;
	this.serial = opts.serial;
	this.validFrom = opts.validFrom;
	this.validUntil = opts.validUntil;
}

function read(buf, options) {
	if (typeof (buf) === 'string') {
		if (buf.trim().match(/^[-]+[ ]*BEGIN/))
			return (pem.read(buf, options));
		if (buf.match(/^\s*ssh-[a-z]/))
			return (ssh.read(buf, options));
		if (buf.match(/^\s*ecdsa-/))
			return (ssh.read(buf, options));
		buf = new Buffer(buf, 'binary');
	} else {
		assert.buffer(buf);
		if (findPEMHeader(buf))
			return (pem.read(buf, options));
		if (findSSHHeader(buf))
			return (ssh.read(buf, options));
	}
	if (buf.readUInt32BE(0) < buf.length)
		return (rfc4253.read(buf, options));
	throw (new Error('Failed to auto-detect format of key'));
}

function calculateDSAPublic(g, p, x) {
	assert.buffer(g);
	assert.buffer(p);
	assert.buffer(x);
	try {
		var bigInt = require('jsbn').BigInteger;
	} catch (e) {
		throw (new Error('To load a PKCS#8 format DSA private key, ' +
		    'the node jsbn library is required.'));
	}
	g = new bigInt(g);
	p = new bigInt(p);
	x = new bigInt(x);
	var y = g.modPow(x, p);
	var ybuf = bigintToMpBuf(y);
	return (ybuf);
}

function zeroPadToLength(buf, len) {
	assert.buffer(buf);
	assert.number(len);
	while (buf.length > len) {
		assert.equal(buf[0], 0x00);
		buf = buf.slice(1);
	}
	while (buf.length < len) {
		var b = Buffer.alloc(buf.length + 1);
		b[0] = 0x00;
		buf.copy(b, 1);
		buf = b;
	}
	return (buf);
}

function SSHBuffer(opts) {
	assert.object(opts, 'options');
	if (opts.buffer !== undefined)
		assert.buffer(opts.buffer, 'options.buffer');

	this._size = opts.buffer ? opts.buffer.length : 1024;
	this._buffer = opts.buffer || (new Buffer(this._size));
	this._offset = 0;
}

function opensslKeyDeriv(cipher, salt, passphrase, count) {
	assert.buffer(salt, 'salt');
	assert.buffer(passphrase, 'passphrase');
	assert.number(count, 'iteration count');

	var clen = CIPHER_LEN[cipher];
	assert.object(clen, 'supported cipher');

	salt = salt.slice(0, PKCS5_SALT_LEN);

	var D, D_prev, bufs;
	var material = new Buffer(0);
	while (material.length < clen.key + clen.iv) {
		bufs = [];
		if (D_prev)
			bufs.push(D_prev);
		bufs.push(passphrase);
		bufs.push(salt);
		D = Buffer.concat(bufs);

function SSHBuffer(opts) {
	assert.object(opts, 'options');
	if (opts.buffer !== undefined)
		assert.buffer(opts.buffer, 'options.buffer');

	this._size = opts.buffer ? opts.buffer.length : 1024;
	this._buffer = opts.buffer || (new Buffer(this._size));
	this._offset = 0;
}