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ASP.NET Custom Control for High Performance Web Scripts

, 13 May 2009 CPOL 31.5K 461 78
Presents a custom control replacement for the script tag that optimizes JavaScript for web pages. Automatically merges, prevents duplicates, externalizes, orders, adds expires headers, caches, minifies, and places your scripts.
// Downloaded from http://www.crockford.com/javascript/jsmin.cs
// by Adrian Akison, on 2009-01-30.
// Modified the Minify function by overloading to write to a TextWriter instead
// of a file.  Also, change the StreamWriter sw to a TextWriter to support
// writing to streams as well as StringWriters.

using System;
using System.IO;

/* Originally written in 'C', this code has been converted to the C# language.
 * The author's copyright message is reproduced below.
 * All modifications from the original to C# are placed in the public domain.
 */

/* jsmin.c
   2007-05-22

Copyright (c) 2002 Douglas Crockford  (www.crockford.com)

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is furnished to do
so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

The Software shall be used for Good, not Evil.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

namespace JavaScriptSupport {
    class JavaScriptMinifier {
        const int EOF = -1;

        TextReader sr;
        TextWriter sw;
        int theA;
        int theB;
        int theLookahead = EOF;


        static void Main(string[] args) {
            if(args.Length != 2) {
                Console.WriteLine("invalid arguments, 2 required, 1 in, 1 out");
                return;
            }
            new JavaScriptMinifier().Minify(args[0], args[1]);
        }

        /// <summary>
        /// Reads a javascript file named 'src' and writes a minified javascript file to file named 'dst'.
        /// </summary>
        public void Minify(string src, string dst) {
            using(sr = new StreamReader(src)) {
                using(sw = new StreamWriter(dst)) {
                    jsmin();
                }
            }
        }

        /// <summary>
        /// Reads a javascript file named 'source' and writes the minified javascript to the stream destination.
        /// </summary>
        public void Minify(string source, TextWriter destination) {
            using(sr = new StreamReader(source)) {
                sw = destination;
                jsmin();
            }
        }

        /// <summary>
        /// Reads a javascript file named 'source' and writes the minified javascript to the stream destination.
        /// </summary>
        public void Minify(TextReader source, TextWriter destination) {
            sr = source;
            sw = destination;
            jsmin();
        }

        /* jsmin -- Copy the input to the output, deleting the characters which are
                insignificant to JavaScript. Comments will be removed. Tabs will be
                replaced with spaces. Carriage returns will be replaced with linefeeds.
                Most spaces and linefeeds will be removed.
        */
        void jsmin() {
            theA = '\n';
            action(3);
            while(theA != EOF) {
                switch(theA) {
                    case ' ': {
                            if(isAlphanum(theB)) {
                                action(1);
                            }
                            else {
                                action(2);
                            }
                            break;
                        }
                    case '\n': {
                            switch(theB) {
                                case '{':
                                case '[':
                                case '(':
                                case '+':
                                case '-': {
                                        action(1);
                                        break;
                                    }
                                case ' ': {
                                        action(3);
                                        break;
                                    }
                                default: {
                                        if(isAlphanum(theB)) {
                                            action(1);
                                        }
                                        else {
                                            action(2);
                                        }
                                        break;
                                    }
                            }
                            break;
                        }
                    default: {
                            switch(theB) {
                                case ' ': {
                                        if(isAlphanum(theA)) {
                                            action(1);
                                            break;
                                        }
                                        action(3);
                                        break;
                                    }
                                case '\n': {
                                        switch(theA) {
                                            case '}':
                                            case ']':
                                            case ')':
                                            case '+':
                                            case '-':
                                            case '"':
                                            case '\'': {
                                                    action(1);
                                                    break;
                                                }
                                            default: {
                                                    if(isAlphanum(theA)) {
                                                        action(1);
                                                    }
                                                    else {
                                                        action(3);
                                                    }
                                                    break;
                                                }
                                        }
                                        break;
                                    }
                                default: {
                                        action(1);
                                        break;
                                    }
                            }
                            break;
                        }
                }
            }
        }
        /* action -- do something! What you do is determined by the argument:
                1   Output A. Copy B to A. Get the next B.
                2   Copy B to A. Get the next B. (Delete A).
                3   Get the next B. (Delete B).
           action treats a string as a single character. Wow!
           action recognizes a regular expression if it is preceded by ( or , or =.
        */
        void action(int d) {
            if(d <= 1) {
                put(theA);
            }
            if(d <= 2) {
                theA = theB;
                if(theA == '\'' || theA == '"') {
                    for(; ; ) {
                        put(theA);
                        theA = get();
                        if(theA == theB) {
                            break;
                        }
                        if(theA <= '\n') {
                            throw new Exception(string.Format("Error: JSMIN unterminated string literal: {0}\n", theA));
                        }
                        if(theA == '\\') {
                            put(theA);
                            theA = get();
                        }
                    }
                }
            }
            if(d <= 3) {
                theB = next();
                if(theB == '/' && (theA == '(' || theA == ',' || theA == '=' ||
                                    theA == '[' || theA == '!' || theA == ':' ||
                                    theA == '&' || theA == '|' || theA == '?' ||
                                    theA == '{' || theA == '}' || theA == ';' ||
                                    theA == '\n')) {
                    put(theA);
                    put(theB);
                    for(; ; ) {
                        theA = get();
                        if(theA == '/') {
                            break;
                        }
                        else if(theA == '\\') {
                            put(theA);
                            theA = get();
                        }
                        else if(theA <= '\n') {
                            throw new Exception(string.Format("Error: JSMIN unterminated Regular Expression literal : {0}.\n", theA));
                        }
                        put(theA);
                    }
                    theB = next();
                }
            }
        }
        /* next -- get the next character, excluding comments. peek() is used to see
                if a '/' is followed by a '/' or '*'.
        */
        int next() {
            int c = get();
            if(c == '/') {
                switch(peek()) {
                    case '/': {
                            for(; ; ) {
                                c = get();
                                if(c <= '\n') {
                                    return c;
                                }
                            }
                        }
                    case '*': {
                            get();
                            for(; ; ) {
                                switch(get()) {
                                    case '*': {
                                            if(peek() == '/') {
                                                get();
                                                return ' ';
                                            }
                                            break;
                                        }
                                    case EOF: {
                                            throw new Exception("Error: JSMIN Unterminated comment.\n");
                                        }
                                }
                            }
                        }
                    default: {
                            return c;
                        }
                }
            }
            return c;
        }
        /* peek -- get the next character without getting it.
        */
        int peek() {
            theLookahead = get();
            return theLookahead;
        }
        /* get -- return the next character from stdin. Watch out for lookahead. If
                the character is a control character, translate it to a space or
                linefeed.
        */
        int get() {
            int c = theLookahead;
            theLookahead = EOF;
            if(c == EOF) {
                c = sr.Read();
            }
            if(c >= ' ' || c == '\n' || c == EOF) {
                return c;
            }
            if(c == '\r') {
                return '\n';
            }
            return ' ';
        }
        void put(int c) {
            sw.Write((char)c);
        }
        /* isAlphanum -- return true if the character is a letter, digit, underscore,
                dollar sign, or non-ASCII character.
        */
        bool isAlphanum(int c) {
            return ((c >= 'a' && c <= 'z') || (c >= '0' && c <= '9') ||
                (c >= 'A' && c <= 'Z') || c == '_' || c == '$' || c == '\\' ||
                c > 126);
        }
    }
}

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About the Author

Adrian Akison
Program Manager SMS Management & Technology
Australia Australia
I have been a professional software developer for twenty years, starting with C++ and migrated to C#. While I have transitioned into full time management, writing code is still my passion. As I don't write code for work very often, I have had the opportunity to apply my programming skills as a hobby where I have recently authored two Windows 8 store apps. First, an Asteroids tribute game, 'Roid Rage and most recently Shared Whiteboard (which does what it says).

I make a habit of contributing production code to every project I run. Most notably, I have recently run teams to build The Navigator for The Advertiser newspaper and Street Lights Out for SA Power Networks.

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