function META () {
	return {
		name: "sha1Hash",
		description: "SHA-1 Hash"
	};
}

function str (x) {
	warn(x);
	if (x instanceof Object) {
		warn('-> Node');
		if (x.is_literal()) {
			warn('-> literal');
			warn(x.literal_value);
			return x.literal_value;
		} else if (x.is_resource()) {
			warn('-> resource');
			return x.uri_value;
		} else {
			warn('-> blank');
			return x.blank_identifier;
		}
	} else {
		warn('-> Non-Node');
		return x;
	}
}

function sha1Hash(msg)
{
	msg	= str(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]
	// note: most significant word would be ((len-1)*8 >>> 32, but since JS converts
	// bitwise-op args to 32 bits, we need to simulate this by arithmetic operators
	M[N-1][14] = ((msg.length-1)*8) / Math.pow(2, 32); M[N-1][14] = Math.floor(M[N-1][14])
	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;
}
