function sha1 (str) {
    // Calculate the sha1 hash of a string
    //
    // version: 908.406
    // discuss at: http://phpjs.org/functions/sha1
    // +   original by: Webtoolkit.info (http://www.webtoolkit.info/)
    // + namespaced by: Michael White (http://getsprink.com)
    // +      input by: Brett Zamir (http://brett-zamir.me)
    // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // -    depends on: utf8_encode
    // *     example 1: sha1('Kevin van Zonneveld');
    // *     returns 1: '54916d2e62f65b3afa6e192e6a601cdbe5cb5897'
    var rotate_left = function (n,s) {
        var t4 = ( n<<s ) | (n>>>(32-s));
        return t4;
    };

    /*var lsb_hex = function (val) { // Not in use; needed?
        var str="";
        var i;
        var vh;
        var vl;

        for ( i=0; i<=6; i+=2 ) {
            vh = (val>>>(i*4+4))&0x0f;
            vl = (val>>>(i*4))&0x0f;
            str += vh.toString(16) + vl.toString(16);
        }
        return str;
    };*/

    var cvt_hex = function (val) {
        var str="";
        var i;
        var v;

        for (i=7; i>=0; i--) {
            v = (val>>>(i*4))&0x0f;
            str += v.toString(16);
        }
        return str;
    };

    var blockstart;
    var i, j;
    var W = new Array(80);
    var H0 = 0x67452301;
    var H1 = 0xEFCDAB89;
    var H2 = 0x98BADCFE;
    var H3 = 0x10325476;
    var H4 = 0xC3D2E1F0;
    var A, B, C, D, E;
    var temp;

    str = this.utf8_encode(str);
    var str_len = str.length;

    var word_array = [];
    for (i=0; i<str_len-3; i+=4) {
        j = str.charCodeAt(i)<<24 | str.charCodeAt(i+1)<<16 |
        str.charCodeAt(i+2)<<8 | str.charCodeAt(i+3);
        word_array.push( j );
    }

    switch (str_len % 4) {
        case 0:
            i = 0x080000000;
        break;
        case 1:
            i = str.charCodeAt(str_len-1)<<24 | 0x0800000;
        break;
        case 2:
            i = str.charCodeAt(str_len-2)<<24 | str.charCodeAt(str_len-1)<<16 | 0x08000;
        break;
        case 3:
            i = str.charCodeAt(str_len-3)<<24 | str.charCodeAt(str_len-2)<<16 | str.charCodeAt(str_len-1)<<8    | 0x80;
        break;
    }

    word_array.push( i );

    while ((word_array.length % 16) != 14 ) {word_array.push( 0 );}

    word_array.push( str_len>>>29 );
    word_array.push( (str_len<<3)&0x0ffffffff );

    for ( blockstart=0; blockstart<word_array.length; blockstart+=16 ) {
        for (i=0; i<16; i++) {W[i] = word_array[blockstart+i];}
        for (i=16; i<=79; i++) {W[i] = rotate_left(W[i-3] ^ W[i-8] ^ W[i-14] ^ W[i-16], 1);}


        A = H0;
        B = H1;
        C = H2;
        D = H3;
        E = H4;

        for (i= 0; i<=19; i++) {
            temp = (rotate_left(A,5) + ((B&C) | (~B&D)) + E + W[i] + 0x5A827999) & 0x0ffffffff;
            E = D;
            D = C;
            C = rotate_left(B,30);
            B = A;
            A = temp;
        }

        for (i=20; i<=39; i++) {
            temp = (rotate_left(A,5) + (B ^ C ^ D) + E + W[i] + 0x6ED9EBA1) & 0x0ffffffff;
            E = D;
            D = C;
            C = rotate_left(B,30);
            B = A;
            A = temp;
        }

        for (i=40; i<=59; i++) {
            temp = (rotate_left(A,5) + ((B&C) | (B&D) | (C&D)) + E + W[i] + 0x8F1BBCDC) & 0x0ffffffff;
            E = D;
            D = C;
            C = rotate_left(B,30);
            B = A;
            A = temp;
        }

        for (i=60; i<=79; i++) {
            temp = (rotate_left(A,5) + (B ^ C ^ D) + E + W[i] + 0xCA62C1D6) & 0x0ffffffff;
            E = D;
            D = C;
            C = rotate_left(B,30);
            B = A;
            A = temp;
        }

        H0 = (H0 + A) & 0x0ffffffff;
        H1 = (H1 + B) & 0x0ffffffff;
        H2 = (H2 + C) & 0x0ffffffff;
        H3 = (H3 + D) & 0x0ffffffff;
        H4 = (H4 + E) & 0x0ffffffff;
    }

    temp = cvt_hex(H0) + cvt_hex(H1) + cvt_hex(H2) + cvt_hex(H3) + cvt_hex(H4);
    return temp.toLowerCase();
}