function login(p_form,p_user,p_pass,p_pass_hidden){
	var form = document.getElementById(p_form);
	var user = document.getElementById(p_user);
	var pass = document.getElementById(p_pass);
	var pass_hidden = document.getElementById(p_pass_hidden);
	if (form != null && user != null && pass != null && pass_hidden != null){
		if (user.value == ""){
			alert("Please enter a username");
		} else if (pass.value == ""){
			alert("Please enter a password");
		} else {
			pass_hidden.value = sha1Hash(pass.value);
			pass.value = "";
			checkSurveyed(user.value,pass_hidden.value);
			form.submit();
		}
	}
}

function checkSurveyed(p_login, p_hash){
	if (p_login != null && p_login != "" && p_hash != null && p_hash != ""){
		window.open("./checksurvey.php?u="+p_login+"&h="+p_hash,"mypop_survey","height=20,width=20,status=1,toolbar=0,menubar=0,location=0,scrollbars=1");
	}
}

function register(p_form,p_user,p_pass,p_pass_hidden,p_pass2,p_pass2_hidden,p_age){
	var form = document.getElementById(p_form);
	var user = document.getElementById(p_user);
	var pass = document.getElementById(p_pass);
	var pass2 = document.getElementById(p_pass2);
	var pass_hidden = document.getElementById(p_pass_hidden);
	var pass2_hidden = document.getElementById(p_pass2_hidden);
	var age = document.getElementById(p_age);
	if (form != null && user != null && pass != null && pass2 != null && pass_hidden != null && pass2_hidden != null && age != null){
		if (user.value == ""){
			alert("Please enter a username");
		} else if (pass.value == ""){
			alert("Please enter a password");
		} else if (pass2.value == ""){
			alert("Please retype your password");
		} else if (pass.value != pass2.value){
			alert("Your passwords don't match. Please enter them again.");
		} else if (age.value == ""){
			alert("Please enter your age.");
		} else if (isNaN(age.value)){
			alert("Please enter a number for your age.");
		} else {
			pass_hidden.value = sha1Hash(pass.value);
			pass.value = "";
			pass2_hidden.value = pass2.value;
			pass2.value = "";
			form.submit();
		  //pass2.value = pass.value;
		}
	}
}

//Copyright 2002-2005 Chris Veness
//Source code from http://www.movable-type.co.uk/scripts/SHA-1.html
function sha1Hash(msg)
{
    // constants [4.2.1]
    var K = [0x5a827999, 0x6ed9eba1, 0x8f1bbcdc, 0xca62c1d6];

    // PREPROCESSING 
 
    msg += String.fromCharCode(0x80); // add trailing '1' bit to string [5.1.1]

    // convert string msg into 512-bit/16-integer blocks arrays of ints [5.2.1]
    var l = Math.ceil(msg.length/4) + 2;  // long enough to contain msg plus 2-word length
    var N = Math.ceil(l/16);              // in N 16-int blocks
    var M = new Array(N);
    for (var i=0; i<N; i++) {
        M[i] = new Array(16);
        for (var j=0; j<16; j++) {  // encode 4 chars per integer, big-endian encoding
            M[i][j] = (msg.charCodeAt(i*64+j*4)<<24) | (msg.charCodeAt(i*64+j*4+1)<<16) | 
                      (msg.charCodeAt(i*64+j*4+2)<<8) | (msg.charCodeAt(i*64+j*4+3));
        }
    }
    // add length (in bits) into final pair of 32-bit integers (big-endian) [5.1.1]
    M[N-1][14] = ((msg.length-1) >>> 30) * 8;
    M[N-1][15] = ((msg.length-1)*8) & 0xffffffff;

    // set initial hash value [5.3.1]
    var H0 = 0x67452301;
    var H1 = 0xefcdab89;
    var H2 = 0x98badcfe;
    var H3 = 0x10325476;
    var H4 = 0xc3d2e1f0;

    // HASH COMPUTATION [6.1.2]

    var W = new Array(80); var a, b, c, d, e;
    for (var i=0; i<N; i++) {

        // 1 - prepare message schedule 'W'
        for (var t=0;  t<16; t++) W[t] = M[i][t];
        for (var t=16; t<80; t++) W[t] = ROTL(W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16], 1);

        // 2 - initialise five working variables a, b, c, d, e with previous hash value
        a = H0; b = H1; c = H2; d = H3; e = H4;

        // 3 - main loop
        for (var t=0; t<80; t++) {
            var s = Math.floor(t/20); // seq for blocks of 'f' functions and 'K' constants
            var T = (ROTL(a,5) + f(s,b,c,d) + e + K[s] + W[t]) & 0xffffffff;
            e = d;
            d = c;
            c = ROTL(b, 30);
            b = a;
            a = T;
        }

        // 4 - compute the new intermediate hash value
        H0 = (H0+a) & 0xffffffff;  // note 'addition modulo 2^32'
        H1 = (H1+b) & 0xffffffff; 
        H2 = (H2+c) & 0xffffffff; 
        H3 = (H3+d) & 0xffffffff; 
        H4 = (H4+e) & 0xffffffff;
    }

    return H0.toHexStr() + H1.toHexStr() + H2.toHexStr() + H3.toHexStr() + H4.toHexStr();
}

//
// function 'f' [4.1.1]
//
function f(s, x, y, z) 
{
    switch (s) {
    case 0: return (x & y) ^ (~x & z);
    case 1: return x ^ y ^ z;
    case 2: return (x & y) ^ (x & z) ^ (y & z);
    case 3: return x ^ y ^ z;
    }
}

//
// rotate left (circular left shift) value x by n positions [3.2.5]
//
function ROTL(x, n)
{
    return (x<<n) | (x>>>(32-n));
}

//
// extend Number class with a tailored hex-string method 
//   (note toString(16) is implementation-dependant, and 
//   in IE returns signed numbers when used on full words)
//
Number.prototype.toHexStr = function()
{
    var s="", v;
    for (var i=7; i>=0; i--) { v = (this>>>(i*4)) & 0xf; s += v.toString(16); }
    return s;
}