ECMAScriptPacker.cs

using System;
using System.Text;
using System.Text.RegularExpressions;
using System.Collections;
using System.Collections.Specialized;
using System.Web;
using System.IO;

/*
	packer, version 2.0 (beta) (2005/02/01)
	Copyright 2004-2005, Dean Edwards
	Web: http://dean.edwards.name/

	This software is licensed under the CC-GNU LGPL
	Web: http://creativecommons.org/licenses/LGPL/2.1/
    
    Ported to C# by Jesse Hansen, twindagger2k@msn.com
    modified slightly by Andrew Arnott
*/

// http://dean.edwards.name/packer/

namespace Dean.Edwards
{
	/// <summary>
	/// Packs a javascript file into a smaller area, removing unnecessary characters from the output.
	/// </summary>
    internal class ECMAScriptPacker
    {
        /// <summary>
        /// The encoding level to use. See http://dean.edwards.name/packer/usage/ for more info.
        /// </summary>
        public enum PackerEncoding { None = 0, Numeric = 10, Mid = 36, Normal = 62, HighAscii = 95 };

        private PackerEncoding encoding = PackerEncoding.Normal;
        private bool fastDecode = true;
        private bool specialChars = false;
        private bool enabled = true;

        string IGNORE = "$1";

	    /// <summary>
	    /// The encoding level for this instance
	    /// </summary>
        public PackerEncoding Encoding
        {
            get { return encoding; }
            set { encoding = value; }
        }

        /// <summary>
        /// Adds a subroutine to the output to speed up decoding
        /// </summary>
        public bool FastDecode
        {
            get { return fastDecode; }
            set { fastDecode = value; }
        }

        /// <summary>
        /// Replaces special characters
        /// </summary>
        public bool SpecialChars
        {
            get { return specialChars; }
            set { specialChars = value; }
        }

        /// <summary>
        /// Packer enabled
        /// </summary>
        public bool Enabled
        {
            get { return enabled; }
            set { enabled = value; }
        }

        public ECMAScriptPacker()
        {
            Encoding = PackerEncoding.Normal;
            FastDecode = true;
            SpecialChars = false;
        }

        /// <summary>
        /// Constructor
        /// </summary>
        /// <param name="encoding">The encoding level for this instance</param>
        /// <param name="fastDecode">Adds a subroutine to the output to speed up decoding</param>
        /// <param name="specialChars">Replaces special characters</param>
        public ECMAScriptPacker(PackerEncoding encoding, bool fastDecode, bool specialChars)
        {
            Encoding = encoding;
            FastDecode = fastDecode;
            SpecialChars = specialChars;
        }

        /// <summary>
        /// Packs the script
        /// </summary>
        /// <param name="script">the script to pack</param>
        /// <returns>the packed script</returns>
        public string Pack(string script)
        {
            if (enabled)
            {
                script += "\n";
                script = basicCompression(script);
                if (SpecialChars)
                    script = encodeSpecialChars(script);
                if (Encoding != PackerEncoding.None)
                    script = encodeKeywords(script);
            }
            return script;
        }

        //zero encoding - just removal of whitespace and comments
        private string basicCompression(string script)
        {
            ParseMaster parser = new ParseMaster();
            // make safe
            parser.EscapeChar = '\\';
            // protect strings
            parser.Add("'[^'\\n\\r]*'", IGNORE);
            parser.Add("\"[^\"\\n\\r]*\"", IGNORE);
            // remove comments
            parser.Add("\\/\\/[^\\n\\r]*[\\n\\r]");
            parser.Add("\\/\\*[^*]*\\*+([^\\/][^*]*\\*+)*\\/");
            // protect regular expressions
            parser.Add("\\s+(\\/[^\\/\\n\\r\\*][^\\/\\n\\r]*\\/g?i?)", "$2");
            parser.Add("[^\\w\\$\\/'\"*)\\?:]\\/[^\\/\\n\\r\\*][^\\/\\n\\r]*\\/g?i?", IGNORE);
            // remove: ;;; doSomething();
            if (specialChars)
                parser.Add(";;[^\\n\\r]+[\\n\\r]");
            // remove redundant semi-colons
            parser.Add(";+\\s*([};])", "$2");
            // remove white-space
            parser.Add("(\\b|\\$)\\s+(\\b|\\$)", "$2 $3");
            parser.Add("([+\\-])\\s+([+\\-])", "$2 $3");
            parser.Add("\\s+");
            // done
            return parser.Exec(script);
        }

        WordList encodingLookup;
        private string encodeSpecialChars(string script)
        {
            ParseMaster parser = new ParseMaster();
            // replace: $name -> n, $$name -> na
            parser.Add("((\\$+)([a-zA-Z\\$_]+))(\\d*)", 
                new ParseMaster.MatchGroupEvaluator(encodeLocalVars));

            // replace: _name -> _0, double-underscore (__name) is ignored
            Regex regex = new Regex("\\b_[A-Za-z\\d]\\w*");
            
            // build the word list
            encodingLookup = analyze(script, regex, new EncodeMethod(encodePrivate));

            parser.Add("\\b_[A-Za-z\\d]\\w*", new ParseMaster.MatchGroupEvaluator(encodeWithLookup));
            
            script = parser.Exec(script);
            return script;
        }

        private string encodeKeywords(string script)
        {
		    // escape high-ascii values already in the script (i.e. in strings)
		    if (Encoding == PackerEncoding.HighAscii) script = escape95(script);
		    // create the parser
            ParseMaster parser = new ParseMaster();
            EncodeMethod encode = getEncoder(Encoding);

            // for high-ascii, don't encode single character low-ascii
            Regex regex = new Regex(
                    (Encoding == PackerEncoding.HighAscii) ? "\\w\\w+" : "\\w+"
                );
            // build the word list
            encodingLookup = analyze(script, regex, encode);

            // encode
            parser.Add((Encoding == PackerEncoding.HighAscii) ? "\\w\\w+" : "\\w+",
                new ParseMaster.MatchGroupEvaluator(encodeWithLookup));

            // if encoded, wrap the script in a decoding function
            return (script == string.Empty) ? "" : bootStrap(parser.Exec(script), encodingLookup);
        }

        private string bootStrap(string packed, WordList keywords)
        {
		    // packed: the packed script
		    packed = "'" + escape(packed) + "'";

		    // ascii: base for encoding
            int ascii = Math.Min(keywords.Sorted.Count, (int) Encoding);
            if (ascii == 0)
                ascii = 1;

		    // count: number of words contained in the script
		    int count = keywords.Sorted.Count;

		    // keywords: list of words contained in the script
            foreach (object key in keywords.Protected.Keys)
            {
                keywords.Sorted[(int) key] = "";
            }
		    // convert from a string to an array
            StringBuilder sbKeywords = new StringBuilder("'");
            foreach (string word in keywords.Sorted)
                sbKeywords.Append(word + "|");
            sbKeywords.Remove(sbKeywords.Length-1, 1);
            string keywordsout = sbKeywords.ToString() + "'.split('|')";

            string encode;
            string inline = "c";

            switch (Encoding)
            {
                case PackerEncoding.Mid:
                    encode = "function(c){return c.toString(36)}";
                    inline += ".toString(a)";
                    break;
                case PackerEncoding.Normal:
                    encode = "function(c){return(c<a?\"\":e(parseInt(c/a)))+" +
                        "((c=c%a)>35?String.fromCharCode(c+29):c.toString(36))}";
                    inline += ".toString(a)";
                    break;
                case PackerEncoding.HighAscii:
                    encode = "function(c){return(c<a?\"\":e(c/a))+" +
                        "String.fromCharCode(c%a+161)}";
                    inline += ".toString(a)";
                    break;
                default:
                    encode = "function(c){return c}";
                    break;
            }
            
            // decode: code snippet to speed up decoding
            string decode = "";
            if (fastDecode)
            {
                decode = "if(!''.replace(/^/,String)){while(c--)d[e(c)]=k[c]||e(c);k=[function(e){return d[e]}];e=function(){return'\\\\w+'};c=1;}";
                if (Encoding == PackerEncoding.HighAscii)
                    decode = decode.Replace("\\\\w", "[\\xa1-\\xff]");
                else if (Encoding == PackerEncoding.Numeric)
                    decode = decode.Replace("e(c)", inline);
                if (count == 0)
                    decode = decode.Replace("c=1", "c=0");
            }

            // boot function
            string unpack = "function(p,a,c,k,e,d){while(c--)if(k[c])p=p.replace(new RegExp('\\\\b'+e(c)+'\\\\b','g'),k[c]);return p;}";
            Regex r;
            if (fastDecode)
            {
                //insert the decoder
                r = new Regex("\\{");
                unpack = r.Replace(unpack, "{" + decode + ";", 1);
            }

            if (Encoding == PackerEncoding.HighAscii)
            {
                // get rid of the word-boundries for regexp matches
                r = new Regex("'\\\\\\\\b'\\s*\\+|\\+\\s*'\\\\\\\\b'");
                unpack = r.Replace(unpack, "");
            }
            if (Encoding == PackerEncoding.HighAscii || ascii > (int) PackerEncoding.Normal || fastDecode)
            {
                // insert the encode function
                r = new Regex("\\{");
                unpack = r.Replace(unpack, "{e=" + encode + ";", 1);
            }
            else
            {
                r = new Regex("e\\(c\\)");
                unpack = r.Replace(unpack, inline);
            }
            // no need to pack the boot function since i've already done it
            string _params = "" + packed + "," + ascii + "," + count + "," + keywordsout;
            if (fastDecode)
            {
                //insert placeholders for the decoder
                _params += ",0,{}";
            }
            // the whole thing
            return "eval(" + unpack + "(" + _params + "))\n";
        }

        private string escape(string input)
        {
            Regex r = new Regex("([\\\\'])");
            return r.Replace(input, "\\$1");
        }

        private EncodeMethod getEncoder(PackerEncoding encoding)
        {
            switch (encoding)
            {
                case PackerEncoding.Mid:
                    return new EncodeMethod(encode36);
                case PackerEncoding.Normal:
                    return new EncodeMethod(encode62);
                case PackerEncoding.HighAscii:
                    return new EncodeMethod(encode95);
                default:
                    return new EncodeMethod(encode10);
            }
        }

        private string encode10(int code)
        {
            return code.ToString();
        }

        //lookups seemed like the easiest way to do this since 
        // I don't know of an equivalent to .toString(36)
        private static string lookup36 = "0123456789abcdefghijklmnopqrstuvwxyz";

        private string encode36(int code)
        {
            string encoded = "";
            int i = 0;
            do
            {
                int digit = (code / (int) Math.Pow(36, i)) % 36;
                encoded = lookup36[digit] + encoded;
                code -= digit * (int) Math.Pow(36, i++);
            } while (code > 0);
            return encoded;
        }

        private static string lookup62 = lookup36 + "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

        private string encode62(int code)
        {
            string encoded = "";
            int i = 0;
            do
            {
                int digit = (code / (int) Math.Pow(62, i)) % 62;
                encoded = lookup62[digit] + encoded;
                code -= digit * (int) Math.Pow(62, i++);
            } while (code > 0);
            return encoded;
        }

        private static string lookup95 = "、�ウЖ��⑭�渦慨偽係杭纂従神疎団兎波品北洋椀冫嘖孛忤掣桀毳烙痰邃繙艾蜉謖邇關髓齡��巐鄕�";

        private string encode95(int code)
        {
            string encoded = "";
            int i = 0;
            do
            {
                int digit = (code / (int) Math.Pow(95, i)) % 95;
                encoded = lookup95[digit] + encoded;
                code -= digit * (int) Math.Pow(95, i++);
            } while (code > 0);
            return encoded;
        }

        private string escape95(string input)
        {
            Regex r = new Regex("[\xa1-\xff]");
            return r.Replace(input, new MatchEvaluator(escape95Eval));
        }

        private string escape95Eval(Match match)
        {
            return "\\x" + ((int) match.Value[0]).ToString("x"); //return hexadecimal value
        }

        private string encodeLocalVars(Match match, int offset)
        {
            int length = match.Groups[offset + 2].Length;
            int start = length - Math.Max(length - match.Groups[offset + 3].Length, 0);
            return match.Groups[offset + 1].Value.Substring(start, length) + 
                match.Groups[offset + 4].Value;
        }

        private string encodeWithLookup(Match match, int offset)
        {
            return (string) encodingLookup.Encoded[match.Groups[offset].Value];
        }

        private delegate string EncodeMethod(int code);

        private string encodePrivate(int code)
        {
            return "_" + code;
        }

        private WordList analyze(string input, Regex regex, EncodeMethod encodeMethod)
        {
            // analyse
            // retreive all words in the script
            MatchCollection all = regex.Matches(input);
            WordList rtrn;
            rtrn.Sorted = new StringCollection(); // list of words sorted by frequency
            rtrn.Protected = new HybridDictionary(); // dictionary of word->encoding
            rtrn.Encoded = new HybridDictionary(); // instances of "protected" words
            if (all.Count > 0)
            {
                StringCollection unsorted = new StringCollection(); // same list, not sorted
                HybridDictionary Protected = new HybridDictionary(); // "protected" words (dictionary of word->"word")
                HybridDictionary values = new HybridDictionary(); // dictionary of charCode->encoding (eg. 256->ff)
                HybridDictionary count = new HybridDictionary(); // word->count
                int i = all.Count, j = 0;
                string word;
                // count the occurrences - used for sorting later
                do
                {
                    word = "$" + all[--i].Value;
                    if (count[word] == null)
                    {
                        count[word] = 0;
                        unsorted.Add(word);
                        // make a dictionary of all of the protected words in this script
                        //  these are words that might be mistaken for encoding
                        Protected["$" + (values[j] = encodeMethod(j))] = j++;
                    }
                    // increment the word counter
                    count[word] = (int) count[word] + 1;
                } while (i > 0);
                /* prepare to sort the word list, first we must protect
                    words that are also used as codes. we assign them a code
                    equivalent to the word itself.
                   e.g. if "do" falls within our encoding range
                        then we store keywords["do"] = "do";
                   this avoids problems when decoding */
                i = unsorted.Count;
                string[] sortedarr = new string[unsorted.Count];
                do
                {
                    word = unsorted[--i];
                    if (Protected[word] != null)
                    {
                        sortedarr[(int) Protected[word]] = word.Substring(1);
                        rtrn.Protected[(int) Protected[word]] = true;
                        count[word] = 0;
                    }
                } while (i > 0);
                string[] unsortedarr = new string[unsorted.Count];
                unsorted.CopyTo(unsortedarr, 0);
                // sort the words by frequency
                Array.Sort(unsortedarr, (IComparer) new CountComparer(count));
                j = 0;
                /*because there are "protected" words in the list
                  we must add the sorted words around them */
                do 
                {
				    if (sortedarr[i] == null) 
                        sortedarr[i] = unsortedarr[j++].Substring(1);
				    rtrn.Encoded[sortedarr[i]] = values[i];
			    } while (++i < unsortedarr.Length);
                rtrn.Sorted.AddRange(sortedarr);
            }
            return rtrn;
        }

        private struct WordList
        {
            public StringCollection Sorted;
            public HybridDictionary Encoded;
            public HybridDictionary Protected;
        }

        private class CountComparer : IComparer
        {
            HybridDictionary count;

            public CountComparer(HybridDictionary count)
            {
                this.count = count;
            }

            #region IComparer Members

            public int Compare(object x, object y)
            {
                return (int) count[y] - (int) count[x];
            }

            #endregion
        }
    }
}