2.1/dev/core/src/com/google/gwt/core/ext/linker/impl/SelectionScriptLinker.java - gwt - Git at Google

 /*
  * Copyright 2008 Google Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not
  * use this file except in compliance with the License. You may obtain a copy of
  * the License at
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  * License for the specific language governing permissions and limitations under
  * the License.
  */
 package com.google.gwt.core.ext.linker.impl;

 import com.google.gwt.core.ext.LinkerContext;
 import com.google.gwt.core.ext.TreeLogger;
 import com.google.gwt.core.ext.UnableToCompleteException;
 import com.google.gwt.core.ext.linker.AbstractLinker;
 import com.google.gwt.core.ext.linker.Artifact;
 import com.google.gwt.core.ext.linker.ArtifactSet;
 import com.google.gwt.core.ext.linker.CompilationResult;
 import com.google.gwt.core.ext.linker.EmittedArtifact;
 import com.google.gwt.core.ext.linker.ScriptReference;
 import com.google.gwt.core.ext.linker.SelectionProperty;
 import com.google.gwt.core.ext.linker.SoftPermutation;
 import com.google.gwt.core.ext.linker.StylesheetReference;
 import com.google.gwt.dev.util.StringKey;
 import com.google.gwt.dev.util.Util;
 import com.google.gwt.dev.util.collect.HashSet;
 import com.google.gwt.dev.util.collect.Lists;
 import com.google.gwt.util.tools.Utility;

 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.net.URLConnection;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.SortedMap;
 import java.util.TreeMap;

 /**
  * A base class for Linkers that use an external script to boostrap the GWT
  * module. This implementation injects JavaScript Snippets into a JS program
  * defined in an external file.
  */
 public abstract class SelectionScriptLinker extends AbstractLinker {
   /**
    * TODO(bobv): Move this class into c.g.g.core.linker when HostedModeLinker
    * goes away?
    */

   /**
    * This represents the combination of a unique content hash (i.e. the MD5 of
    * the bytes to be written into the cache.html file) and a soft permutation
    * id.
    */
   protected static class PermutationId extends StringKey {
     private final int softPermutationId;
     private final String strongName;

     public PermutationId(String strongName, int softPermutationId) {
       super(strongName + ":" + softPermutationId);
       this.strongName = strongName;
       this.softPermutationId = softPermutationId;
     }

     public int getSoftPermutationId() {
       return softPermutationId;
     }

     public String getStrongName() {
       return strongName;
     }
   }

   /**
    * File name for computeScriptBase.js.
    */
   protected static final String COMPUTE_SCRIPT_BASE_JS = "com/google/gwt/core/ext/linker/impl/computeScriptBase.js";

   /**
    * The extension added to demand-loaded fragment files.
    */
   protected static final String FRAGMENT_EXTENSION = ".cache.js";

   /**
    * A subdirectory to hold all the generated fragments.
    */
   protected static final String FRAGMENT_SUBDIR = "deferredjs";

   /**
    * File name for permutations.js.
    */
   protected static final String PERMUTATIONS_JS = "com/google/gwt/core/ext/linker/impl/permutations.js";

   /**
    * File name for processMetas.js.
    */
   protected static final String PROCESS_METAS_JS = "com/google/gwt/core/ext/linker/impl/processMetas.js";

   /**
    * Determines whether or not the URL is relative.
    *
    * @param src the test url
    * @return <code>true</code> if the URL is relative, <code>false</code> if not
    */
   protected static boolean isRelativeURL(String src) {
     // A straight absolute url for the same domain, server, and protocol.
     if (src.startsWith("/")) {
       return false;
     }

     // If it can be parsed as a URL, then it's probably absolute.
     try {
       // Just check to see if it can be parsed, no need to store the result.
       new URL(src);

       // Let's guess that it is absolute (thus, not relative).
       return false;
     } catch (MalformedURLException e) {
       // Do nothing, since it was a speculative parse.
     }

     // Since none of the above matched, let's guess that it's relative.
     return true;
   }

   protected static void replaceAll(StringBuffer buf, String search,
       String replace) {
     int len = search.length();
     for (int pos = buf.indexOf(search); pos >= 0; pos = buf.indexOf(search,
         pos + 1)) {
       buf.replace(pos, pos + len, replace);
     }
   }

   /**
    * This maps each unique permutation to the property settings for that
    * compilation. A single compilation can have multiple property settings if
    * the compiles for those settings yielded the exact same compiled output.
    */
   private final SortedMap<PermutationId, List<Map<String, String>>> propMapsByPermutation = new TreeMap<PermutationId, List<Map<String, String>>>();

   /**
    * This method is left in place for existing subclasses of
    * SelectionScriptLinker that have not been upgraded for the sharding API.
    */
   @Override
   public ArtifactSet link(TreeLogger logger, LinkerContext context,
       ArtifactSet artifacts) throws UnableToCompleteException {
     ArtifactSet toReturn = link(logger, context, artifacts, true);
     toReturn = link(logger, context, toReturn, false);
     return toReturn;
   }

   @Override
   public ArtifactSet link(TreeLogger logger, LinkerContext context,
       ArtifactSet artifacts, boolean onePermutation)
       throws UnableToCompleteException {
     if (onePermutation) {
       ArtifactSet toReturn = new ArtifactSet(artifacts);

       /*
        * Support having multiple compilation results because this method is also
        * called from the legacy link method.
        */
       for (CompilationResult compilation : toReturn.find(CompilationResult.class)) {
         toReturn.addAll(doEmitCompilation(logger, context, compilation));
       }
       return toReturn;
     } else {
       processSelectionInformation(artifacts);

       ArtifactSet toReturn = new ArtifactSet(artifacts);
       toReturn.add(emitSelectionScript(logger, context, artifacts));
       maybeAddHostedModeFile(logger, toReturn);
       return toReturn;
     }
   }

   @Override
   public boolean supportsDevMode() {
     return (getHostedFilename() != "");
   }

   protected Collection<Artifact<?>> doEmitCompilation(TreeLogger logger,
       LinkerContext context, CompilationResult result)
       throws UnableToCompleteException {
     String[] js = result.getJavaScript();
     byte[][] bytes = new byte[js.length][];
     bytes[0] = generatePrimaryFragment(logger, context, result, js);
     for (int i = 1; i < js.length; i++) {
       bytes[i] = Util.getBytes(generateDeferredFragment(logger, context, i,
           js[i]));
     }

     Collection<Artifact<?>> toReturn = new ArrayList<Artifact<?>>();
     toReturn.add(emitBytes(logger, bytes[0], result.getStrongName()
         + getCompilationExtension(logger, context)));
     for (int i = 1; i < js.length; i++) {
       toReturn.add(emitBytes(logger, bytes[i], FRAGMENT_SUBDIR + File.separator
           + result.getStrongName() + File.separator + i + FRAGMENT_EXTENSION));
     }

     toReturn.addAll(emitSelectionInformation(result.getStrongName(), result));

     return toReturn;
   }

   protected EmittedArtifact emitSelectionScript(TreeLogger logger,
       LinkerContext context, ArtifactSet artifacts)
       throws UnableToCompleteException {
     String selectionScript = generateSelectionScript(logger, context, artifacts);
     selectionScript = context.optimizeJavaScript(logger, selectionScript);

     /*
      * Last modified is important to keep hosted mode refreses from clobbering
      * web mode compiles. We set the timestamp on the hosted mode selection
      * script to the same mod time as the module (to allow updates). For web
      * mode, we just set it to now.
      */
     long lastModified;
     if (propMapsByPermutation.isEmpty()) {
       lastModified = context.getModuleLastModified();
     } else {
       lastModified = System.currentTimeMillis();
     }

     return emitString(logger, selectionScript, context.getModuleName()
         + ".nocache.js", lastModified);
   }

   /**
    * @param logger a TreeLogger
    * @param context a LinkerContext
    * @param fragment the fragment number
    */
   protected String generateDeferredFragment(TreeLogger logger,
       LinkerContext context, int fragment, String js) {
     return js;
   }

   /**
    * Generate the primary fragment. The default implementation is based on
    * {@link #getModulePrefix(TreeLogger, LinkerContext, String, int)} and
    * {@link #getModuleSuffix(TreeLogger, LinkerContext)}.
    */
   protected byte[] generatePrimaryFragment(TreeLogger logger,
       LinkerContext context, CompilationResult result, String[] js)
       throws UnableToCompleteException {
     StringBuffer b = new StringBuffer();
     b.append(getModulePrefix(logger, context, result.getStrongName(), js.length));
     b.append(js[0]);
     b.append(getModuleSuffix(logger, context));
     return Util.getBytes(b.toString());
   }

   protected String generatePropertyProvider(SelectionProperty prop) {
     StringBuffer toReturn = new StringBuffer();

     if (prop.tryGetValue() == null && !prop.isDerived()) {
       toReturn.append("providers['" + prop.getName() + "'] = function()");
       toReturn.append(prop.getPropertyProvider());
       toReturn.append(";");

       toReturn.append("values['" + prop.getName() + "'] = {");
       boolean needsComma = false;
       int counter = 0;
       for (String value : prop.getPossibleValues()) {
         if (needsComma) {
           toReturn.append(",");
         } else {
           needsComma = true;
         }
         toReturn.append("'" + value + "':");
         toReturn.append(counter++);
       }
       toReturn.append("};");
     }

     return toReturn.toString();
   }

   protected String generateScriptInjector(String scriptUrl) {
     if (isRelativeURL(scriptUrl)) {
       return "  if (!__gwt_scriptsLoaded['"
           + scriptUrl
           + "']) {\n"
           + "    __gwt_scriptsLoaded['"
           + scriptUrl
           + "'] = true;\n"
           + "    document.write('<script language=\\\"javascript\\\" src=\\\"'+base+'"
           + scriptUrl + "\\\"></script>');\n" + "  }\n";
     } else {
       return "  if (!__gwt_scriptsLoaded['" + scriptUrl + "']) {\n"
           + "    __gwt_scriptsLoaded['" + scriptUrl + "'] = true;\n"
           + "    document.write('<script language=\\\"javascript\\\" src=\\\""
           + scriptUrl + "\\\"></script>');\n" + "  }\n";
     }
   }

   /**
    * Generate a selection script. The selection information should previously
    * have been scanned using {@link #processSelectionInformation(ArtifactSet)}.
    */
   protected String generateSelectionScript(TreeLogger logger,
       LinkerContext context, ArtifactSet artifacts) throws UnableToCompleteException {
     StringBuffer selectionScript = getSelectionScriptStringBuffer(logger, context);

     String computeScriptBase;
     String processMetas;
     try {
       computeScriptBase = Utility.getFileFromClassPath(COMPUTE_SCRIPT_BASE_JS);
       processMetas = Utility.getFileFromClassPath(PROCESS_METAS_JS);
     } catch (IOException e) {
       logger.log(TreeLogger.ERROR, "Unable to read selection script template",
           e);
       throw new UnableToCompleteException();
     }
     replaceAll(selectionScript, "__COMPUTE_SCRIPT_BASE__", computeScriptBase);
     replaceAll(selectionScript, "__PROCESS_METAS__", processMetas);

     // Add external dependencies
     int startPos = selectionScript.indexOf("// __MODULE_STYLES_END__");
     if (startPos != -1) {
       for (StylesheetReference resource : artifacts.find(StylesheetReference.class)) {
         String text = generateStylesheetInjector(resource.getSrc());
         selectionScript.insert(startPos, text);
         startPos += text.length();
       }
     }

     startPos = selectionScript.indexOf("// __MODULE_SCRIPTS_END__");
     if (startPos != -1) {
       for (ScriptReference resource : artifacts.find(ScriptReference.class)) {
         String text = generateScriptInjector(resource.getSrc());
         selectionScript.insert(startPos, text);
         startPos += text.length();
       }
     }

     // This method needs to be called after all of the .js files have been
     // swapped into the selectionScript since it will fill in __MODULE_NAME__
     // and many of the .js files contain that template variable
     selectionScript =
       processSelectionScriptCommon(selectionScript, logger, context);

     return selectionScript.toString();
   }

   /**
    * Generate a Snippet of JavaScript to inject an external stylesheet.
    *
    * <pre>
    * if (!__gwt_stylesLoaded['URL']) {
    *   var l = $doc.createElement('link');
    *   __gwt_styleLoaded['URL'] = l;
    *   l.setAttribute('rel', 'stylesheet');
    *   l.setAttribute('href', HREF_EXPR);
    *   $doc.getElementsByTagName('head')[0].appendChild(l);
    * }
    * </pre>
    */
   protected String generateStylesheetInjector(String stylesheetUrl) {
     String hrefExpr = "'" + stylesheetUrl + "'";
     if (isRelativeURL(stylesheetUrl)) {
       hrefExpr = "base + " + hrefExpr;
     }

     return "if (!__gwt_stylesLoaded['" + stylesheetUrl + "']) {\n           "
         + "  var l = $doc.createElement('link');\n                          "
         + "  __gwt_stylesLoaded['" + stylesheetUrl + "'] = l;\n             "
         + "  l.setAttribute('rel', 'stylesheet');\n                         "
         + "  l.setAttribute('href', " + hrefExpr + ");\n                    "
         + "  $doc.getElementsByTagName('head')[0].appendChild(l);\n         "
         + "}\n";
   }

   protected abstract String getCompilationExtension(TreeLogger logger,
       LinkerContext context) throws UnableToCompleteException;

   protected String getHostedFilename() {
     return "";
   }

   /**
    * Compute the beginning of a JavaScript file that will hold the main module
    * implementation.
    */
   protected abstract String getModulePrefix(TreeLogger logger,
       LinkerContext context, String strongName)
       throws UnableToCompleteException;

   /**
    * Compute the beginning of a JavaScript file that will hold the main module
    * implementation. By default, calls
    * {@link #getModulePrefix(TreeLogger, LinkerContext, String)}.
    *
    * @param strongName strong name of the module being emitted
    * @param numFragments the number of fragments for this module, including the
    *          main fragment (fragment 0)
    */
   protected String getModulePrefix(TreeLogger logger, LinkerContext context,
       String strongName, int numFragments) throws UnableToCompleteException {
     return getModulePrefix(logger, context, strongName);
   }

   protected abstract String getModuleSuffix(TreeLogger logger,
       LinkerContext context) throws UnableToCompleteException;

   protected StringBuffer getSelectionScriptStringBuffer(TreeLogger logger,
       LinkerContext context) throws UnableToCompleteException {
     StringBuffer selectionScript;
     try {
       selectionScript = new StringBuffer(
           Utility.getFileFromClassPath(getSelectionScriptTemplate(logger,
               context)));
     } catch (IOException e) {
       logger.log(TreeLogger.ERROR, "Unable to read selection script template",
           e);
       throw new UnableToCompleteException();
     }
     return selectionScript;
   }

   protected abstract String getSelectionScriptTemplate(TreeLogger logger,
       LinkerContext context) throws UnableToCompleteException;

   /**
    * Add the hosted file to the artifact set.
    */
   protected void maybeAddHostedModeFile(TreeLogger logger, ArtifactSet artifacts)
       throws UnableToCompleteException {
     String hostedFilename = getHostedFilename();
     if ("".equals(hostedFilename)) {
       return;
     }
     try {
       URL resource = SelectionScriptLinker.class.getResource(hostedFilename);
       if (resource == null) {
         logger.log(TreeLogger.ERROR,
             "Unable to find support resource: " + hostedFilename);
         throw new UnableToCompleteException();
       }

       final URLConnection connection = resource.openConnection();
       // TODO: extract URLArtifact class?
       EmittedArtifact hostedFile = new EmittedArtifact(
           SelectionScriptLinker.class, hostedFilename) {
         @Override
         public InputStream getContents(TreeLogger logger)
             throws UnableToCompleteException {
           try {
             return connection.getInputStream();
           } catch (IOException e) {
             logger.log(TreeLogger.ERROR, "Unable to copy support resource", e);
             throw new UnableToCompleteException();
           }
         }

         @Override
         public long getLastModified() {
           return connection.getLastModified();
         }
       };
       artifacts.add(hostedFile);
     } catch (IOException e) {
       logger.log(TreeLogger.ERROR, "Unable to copy support resource", e);
       throw new UnableToCompleteException();
     }
   }

   /**
    * Find all instances of {@link SelectionInformation} and add them to the
    * internal map of selection information.
    */
   protected void processSelectionInformation(ArtifactSet artifacts) {
     for (SelectionInformation selInfo : artifacts.find(SelectionInformation.class)) {
       processSelectionInformation(selInfo);
     }
   }

   protected StringBuffer processSelectionScriptCommon(StringBuffer selectionScript,
       TreeLogger logger, LinkerContext context)
       throws UnableToCompleteException {
     String permutations;
     try {
       permutations = Utility.getFileFromClassPath(PERMUTATIONS_JS);
     } catch (IOException e) {
       logger.log(TreeLogger.ERROR, "Unable to read selection script template",
           e);
       throw new UnableToCompleteException();
     }

     replaceAll(selectionScript, "__PERMUTATIONS__", permutations);
     replaceAll(selectionScript, "__MODULE_FUNC__",
         context.getModuleFunctionName());
     replaceAll(selectionScript, "__MODULE_NAME__", context.getModuleName());
     replaceAll(selectionScript, "__HOSTED_FILENAME__", getHostedFilename());

     int startPos;

     // Add property providers
     startPos = selectionScript.indexOf("// __PROPERTIES_END__");
     if (startPos != -1) {
       for (SelectionProperty p : context.getProperties()) {
         String text = generatePropertyProvider(p);
         selectionScript.insert(startPos, text);
         startPos += text.length();
       }
     }

     // Possibly add permutations
     startPos = selectionScript.indexOf("// __PERMUTATIONS_END__");
     if (startPos != -1) {
       StringBuffer text = new StringBuffer();
       if (propMapsByPermutation.size() == 0) {
         // Hosted mode link.
         text.append("alert(\"GWT module '" + context.getModuleName()
             + "' may need to be (re)compiled\");");
         text.append("return;");

       } else if (propMapsByPermutation.size() == 1) {
         // Just one distinct compilation; no need to evaluate properties
         text.append("strongName = '"
             + propMapsByPermutation.keySet().iterator().next().getStrongName()
             + "';");
       } else {
         Set<String> propertiesUsed = new HashSet<String>();
         for (PermutationId permutationId : propMapsByPermutation.keySet()) {
           for (Map<String, String> propertyMap : propMapsByPermutation.get(permutationId)) {
             // unflatten([v1, v2, v3], 'strongName' + ':softPermId');
             // The soft perm ID is concatenated to improve string interning
             text.append("unflattenKeylistIntoAnswers([");
             boolean needsComma = false;
             for (SelectionProperty p : context.getProperties()) {
               if (p.tryGetValue() != null) {
                 continue;
               } else if (p.isDerived()) {
                 continue;
               }

               if (needsComma) {
                 text.append(",");
               } else {
                 needsComma = true;
               }
               text.append("'" + propertyMap.get(p.getName()) + "'");
               propertiesUsed.add(p.getName());
             }

             text.append("], '").append(permutationId.getStrongName()).append(
                 "'");
             /*
              * For compatibility with older linkers, skip the soft permutation
              * if it's 0
              */
             if (permutationId.getSoftPermutationId() != 0) {
               text.append(" + ':").append(permutationId.getSoftPermutationId()).append(
                   "'");
             }
             text.append(");\n");
           }
         }

         // strongName = answers[compute('p1')][compute('p2')];
         text.append("strongName = answers[");
         boolean needsIndexMarkers = false;
         for (SelectionProperty p : context.getProperties()) {
           if (!propertiesUsed.contains(p.getName())) {
             continue;
           }
           if (needsIndexMarkers) {
             text.append("][");
           } else {
             needsIndexMarkers = true;
           }
           text.append("computePropValue('" + p.getName() + "')");
         }
         text.append("];");
       }
       selectionScript.insert(startPos, text);
     }

     return selectionScript;
   }

   private List<Artifact<?>> emitSelectionInformation(String strongName,
       CompilationResult result) {
     List<Artifact<?>> emitted = new ArrayList<Artifact<?>>();

     for (SortedMap<SelectionProperty, String> propertyMap : result.getPropertyMap()) {
       TreeMap<String, String> propMap = new TreeMap<String, String>();
       for (Map.Entry<SelectionProperty, String> entry : propertyMap.entrySet()) {
         propMap.put(entry.getKey().getName(), entry.getValue());
       }

       // The soft properties may not be a subset of the existing set
       for (SoftPermutation soft : result.getSoftPermutations()) {
         // Make a copy we can add add more properties to
         TreeMap<String, String> softMap = new TreeMap<String, String>(propMap);
         // Make sure this SelectionInformation contains the soft properties
         for (Map.Entry<SelectionProperty, String> entry : soft.getPropertyMap().entrySet()) {
           softMap.put(entry.getKey().getName(), entry.getValue());
         }
         emitted.add(new SelectionInformation(strongName, soft.getId(), softMap));
       }
     }

     return emitted;
   }

   private Map<String, String> processSelectionInformation(
       SelectionInformation selInfo) {
     TreeMap<String, String> entries = selInfo.getPropMap();
     PermutationId permutationId = new PermutationId(selInfo.getStrongName(),
         selInfo.getSoftPermutationId());
     if (!propMapsByPermutation.containsKey(permutationId)) {
       propMapsByPermutation.put(permutationId,
           Lists.<Map<String, String>> create(entries));
     } else {
       propMapsByPermutation.put(permutationId, Lists.add(
           propMapsByPermutation.get(permutationId), entries));
     }
     return entries;
   }
 }
	/*
	* Copyright 2008 Google Inc.
	*
	* Licensed under the Apache License, Version 2.0 (the "License"); you may not
	* use this file except in compliance with the License. You may obtain a copy of
	* the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
	* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
	* License for the specific language governing permissions and limitations under
	* the License.
	*/
	package com.google.gwt.core.ext.linker.impl;

	import com.google.gwt.core.ext.LinkerContext;
	import com.google.gwt.core.ext.TreeLogger;
	import com.google.gwt.core.ext.UnableToCompleteException;
	import com.google.gwt.core.ext.linker.AbstractLinker;
	import com.google.gwt.core.ext.linker.Artifact;
	import com.google.gwt.core.ext.linker.ArtifactSet;
	import com.google.gwt.core.ext.linker.CompilationResult;
	import com.google.gwt.core.ext.linker.EmittedArtifact;
	import com.google.gwt.core.ext.linker.ScriptReference;
	import com.google.gwt.core.ext.linker.SelectionProperty;
	import com.google.gwt.core.ext.linker.SoftPermutation;
	import com.google.gwt.core.ext.linker.StylesheetReference;
	import com.google.gwt.dev.util.StringKey;
	import com.google.gwt.dev.util.Util;
	import com.google.gwt.dev.util.collect.HashSet;
	import com.google.gwt.dev.util.collect.Lists;
	import com.google.gwt.util.tools.Utility;

	import java.io.File;
	import java.io.IOException;
	import java.io.InputStream;
	import java.net.MalformedURLException;
	import java.net.URL;
	import java.net.URLConnection;
	import java.util.ArrayList;
	import java.util.Collection;
	import java.util.List;
	import java.util.Map;
	import java.util.Set;
	import java.util.SortedMap;
	import java.util.TreeMap;

	/**
	* A base class for Linkers that use an external script to boostrap the GWT
	* module. This implementation injects JavaScript Snippets into a JS program
	* defined in an external file.
	*/
	public abstract class SelectionScriptLinker extends AbstractLinker {
	/**
	* TODO(bobv): Move this class into c.g.g.core.linker when HostedModeLinker
	* goes away?
	*/

	/**
	* This represents the combination of a unique content hash (i.e. the MD5 of
	* the bytes to be written into the cache.html file) and a soft permutation
	* id.
	*/
	protected static class PermutationId extends StringKey {
	private final int softPermutationId;
	private final String strongName;

	public PermutationId(String strongName, int softPermutationId) {
	super(strongName + ":" + softPermutationId);
	this.strongName = strongName;
	this.softPermutationId = softPermutationId;
	}

	public int getSoftPermutationId() {
	return softPermutationId;
	}

	public String getStrongName() {
	return strongName;
	}
	}

	/**
	* File name for computeScriptBase.js.
	*/
	protected static final String COMPUTE_SCRIPT_BASE_JS = "com/google/gwt/core/ext/linker/impl/computeScriptBase.js";

	/**
	* The extension added to demand-loaded fragment files.
	*/
	protected static final String FRAGMENT_EXTENSION = ".cache.js";

	/**
	* A subdirectory to hold all the generated fragments.
	*/
	protected static final String FRAGMENT_SUBDIR = "deferredjs";

	/**
	* File name for permutations.js.
	*/
	protected static final String PERMUTATIONS_JS = "com/google/gwt/core/ext/linker/impl/permutations.js";

	/**
	* File name for processMetas.js.
	*/
	protected static final String PROCESS_METAS_JS = "com/google/gwt/core/ext/linker/impl/processMetas.js";

	/**
	* Determines whether or not the URL is relative.
	*
	* @param src the test url
	* @return <code>true</code> if the URL is relative, <code>false</code> if not
	*/
	protected static boolean isRelativeURL(String src) {
	// A straight absolute url for the same domain, server, and protocol.
	if (src.startsWith("/")) {
	return false;
	}

	// If it can be parsed as a URL, then it's probably absolute.
	try {
	// Just check to see if it can be parsed, no need to store the result.
	new URL(src);

	// Let's guess that it is absolute (thus, not relative).
	return false;
	} catch (MalformedURLException e) {
	// Do nothing, since it was a speculative parse.
	}

	// Since none of the above matched, let's guess that it's relative.
	return true;
	}

	protected static void replaceAll(StringBuffer buf, String search,
	String replace) {
	int len = search.length();
	for (int pos = buf.indexOf(search); pos >= 0; pos = buf.indexOf(search,
	pos + 1)) {
	buf.replace(pos, pos + len, replace);
	}
	}

	/**
	* This maps each unique permutation to the property settings for that
	* compilation. A single compilation can have multiple property settings if
	* the compiles for those settings yielded the exact same compiled output.
	*/
	private final SortedMap<PermutationId, List<Map<String, String>>> propMapsByPermutation = new TreeMap<PermutationId, List<Map<String, String>>>();

	/**
	* This method is left in place for existing subclasses of
	* SelectionScriptLinker that have not been upgraded for the sharding API.
	*/
	@Override
	public ArtifactSet link(TreeLogger logger, LinkerContext context,
	ArtifactSet artifacts) throws UnableToCompleteException {
	ArtifactSet toReturn = link(logger, context, artifacts, true);
	toReturn = link(logger, context, toReturn, false);
	return toReturn;
	}

	@Override
	public ArtifactSet link(TreeLogger logger, LinkerContext context,
	ArtifactSet artifacts, boolean onePermutation)
	throws UnableToCompleteException {
	if (onePermutation) {
	ArtifactSet toReturn = new ArtifactSet(artifacts);

	/*
	* Support having multiple compilation results because this method is also
	* called from the legacy link method.
	*/
	for (CompilationResult compilation : toReturn.find(CompilationResult.class)) {
	toReturn.addAll(doEmitCompilation(logger, context, compilation));
	}
	return toReturn;
	} else {
	processSelectionInformation(artifacts);

	ArtifactSet toReturn = new ArtifactSet(artifacts);
	toReturn.add(emitSelectionScript(logger, context, artifacts));
	maybeAddHostedModeFile(logger, toReturn);
	return toReturn;
	}
	}

	@Override
	public boolean supportsDevMode() {
	return (getHostedFilename() != "");
	}

	protected Collection<Artifact<?>> doEmitCompilation(TreeLogger logger,
	LinkerContext context, CompilationResult result)
	throws UnableToCompleteException {
	String[] js = result.getJavaScript();
	byte[][] bytes = new byte[js.length][];
	bytes[0] = generatePrimaryFragment(logger, context, result, js);
	for (int i = 1; i < js.length; i++) {
	bytes[i] = Util.getBytes(generateDeferredFragment(logger, context, i,
	js[i]));
	}

	Collection<Artifact<?>> toReturn = new ArrayList<Artifact<?>>();
	toReturn.add(emitBytes(logger, bytes[0], result.getStrongName()
	+ getCompilationExtension(logger, context)));
	for (int i = 1; i < js.length; i++) {
	toReturn.add(emitBytes(logger, bytes[i], FRAGMENT_SUBDIR + File.separator
	+ result.getStrongName() + File.separator + i + FRAGMENT_EXTENSION));
	}

	toReturn.addAll(emitSelectionInformation(result.getStrongName(), result));

	return toReturn;
	}

	protected EmittedArtifact emitSelectionScript(TreeLogger logger,
	LinkerContext context, ArtifactSet artifacts)
	throws UnableToCompleteException {
	String selectionScript = generateSelectionScript(logger, context, artifacts);
	selectionScript = context.optimizeJavaScript(logger, selectionScript);

	/*
	* Last modified is important to keep hosted mode refreses from clobbering
	* web mode compiles. We set the timestamp on the hosted mode selection
	* script to the same mod time as the module (to allow updates). For web
	* mode, we just set it to now.
	*/
	long lastModified;
	if (propMapsByPermutation.isEmpty()) {
	lastModified = context.getModuleLastModified();
	} else {
	lastModified = System.currentTimeMillis();
	}

	return emitString(logger, selectionScript, context.getModuleName()
	+ ".nocache.js", lastModified);
	}

	/**
	* @param logger a TreeLogger
	* @param context a LinkerContext
	* @param fragment the fragment number
	*/
	protected String generateDeferredFragment(TreeLogger logger,
	LinkerContext context, int fragment, String js) {
	return js;
	}

	/**
	* Generate the primary fragment. The default implementation is based on
	* {@link #getModulePrefix(TreeLogger, LinkerContext, String, int)} and
	* {@link #getModuleSuffix(TreeLogger, LinkerContext)}.
	*/
	protected byte[] generatePrimaryFragment(TreeLogger logger,
	LinkerContext context, CompilationResult result, String[] js)
	throws UnableToCompleteException {
	StringBuffer b = new StringBuffer();
	b.append(getModulePrefix(logger, context, result.getStrongName(), js.length));
	b.append(js[0]);
	b.append(getModuleSuffix(logger, context));
	return Util.getBytes(b.toString());
	}

	protected String generatePropertyProvider(SelectionProperty prop) {
	StringBuffer toReturn = new StringBuffer();

	if (prop.tryGetValue() == null && !prop.isDerived()) {
	toReturn.append("providers['" + prop.getName() + "'] = function()");
	toReturn.append(prop.getPropertyProvider());
	toReturn.append(";");

	toReturn.append("values['" + prop.getName() + "'] = {");
	boolean needsComma = false;
	int counter = 0;
	for (String value : prop.getPossibleValues()) {
	if (needsComma) {
	toReturn.append(",");
	} else {
	needsComma = true;
	}
	toReturn.append("'" + value + "':");
	toReturn.append(counter++);
	}
	toReturn.append("};");
	}

	return toReturn.toString();
	}

	protected String generateScriptInjector(String scriptUrl) {
	if (isRelativeURL(scriptUrl)) {
	return " if (!__gwt_scriptsLoaded['"
	+ scriptUrl
	+ "']) {\n"
	+ " __gwt_scriptsLoaded['"
	+ scriptUrl
	+ "'] = true;\n"
	+ " document.write('<script language=\\\"javascript\\\" src=\\\"'+base+'"
	+ scriptUrl + "\\\"></script>');\n" + " }\n";
	} else {
	return " if (!__gwt_scriptsLoaded['" + scriptUrl + "']) {\n"
	+ " __gwt_scriptsLoaded['" + scriptUrl + "'] = true;\n"
	+ " document.write('<script language=\\\"javascript\\\" src=\\\""
	+ scriptUrl + "\\\"></script>');\n" + " }\n";
	}
	}

	/**
	* Generate a selection script. The selection information should previously
	* have been scanned using {@link #processSelectionInformation(ArtifactSet)}.
	*/
	protected String generateSelectionScript(TreeLogger logger,
	LinkerContext context, ArtifactSet artifacts) throws UnableToCompleteException {
	StringBuffer selectionScript = getSelectionScriptStringBuffer(logger, context);

	String computeScriptBase;
	String processMetas;
	try {
	computeScriptBase = Utility.getFileFromClassPath(COMPUTE_SCRIPT_BASE_JS);
	processMetas = Utility.getFileFromClassPath(PROCESS_METAS_JS);
	} catch (IOException e) {
	logger.log(TreeLogger.ERROR, "Unable to read selection script template",
	e);
	throw new UnableToCompleteException();
	}
	replaceAll(selectionScript, "__COMPUTE_SCRIPT_BASE__", computeScriptBase);
	replaceAll(selectionScript, "__PROCESS_METAS__", processMetas);

	// Add external dependencies
	int startPos = selectionScript.indexOf("// __MODULE_STYLES_END__");
	if (startPos != -1) {
	for (StylesheetReference resource : artifacts.find(StylesheetReference.class)) {
	String text = generateStylesheetInjector(resource.getSrc());
	selectionScript.insert(startPos, text);
	startPos += text.length();
	}
	}

	startPos = selectionScript.indexOf("// __MODULE_SCRIPTS_END__");
	if (startPos != -1) {
	for (ScriptReference resource : artifacts.find(ScriptReference.class)) {
	String text = generateScriptInjector(resource.getSrc());
	selectionScript.insert(startPos, text);
	startPos += text.length();
	}
	}

	// This method needs to be called after all of the .js files have been
	// swapped into the selectionScript since it will fill in __MODULE_NAME__
	// and many of the .js files contain that template variable
	selectionScript =
	processSelectionScriptCommon(selectionScript, logger, context);

	return selectionScript.toString();
	}

	/**
	* Generate a Snippet of JavaScript to inject an external stylesheet.
	*
	* <pre>
	* if (!__gwt_stylesLoaded['URL']) {
	* var l = $doc.createElement('link');
	* __gwt_styleLoaded['URL'] = l;
	* l.setAttribute('rel', 'stylesheet');
	* l.setAttribute('href', HREF_EXPR);
	* $doc.getElementsByTagName('head')[0].appendChild(l);
	* }
	* </pre>
	*/
	protected String generateStylesheetInjector(String stylesheetUrl) {
	String hrefExpr = "'" + stylesheetUrl + "'";
	if (isRelativeURL(stylesheetUrl)) {
	hrefExpr = "base + " + hrefExpr;
	}

	return "if (!__gwt_stylesLoaded['" + stylesheetUrl + "']) {\n "
	+ " var l = $doc.createElement('link');\n "
	+ " __gwt_stylesLoaded['" + stylesheetUrl + "'] = l;\n "
	+ " l.setAttribute('rel', 'stylesheet');\n "
	+ " l.setAttribute('href', " + hrefExpr + ");\n "
	+ " $doc.getElementsByTagName('head')[0].appendChild(l);\n "
	+ "}\n";
	}

	protected abstract String getCompilationExtension(TreeLogger logger,
	LinkerContext context) throws UnableToCompleteException;

	protected String getHostedFilename() {
	return "";
	}

	/**
	* Compute the beginning of a JavaScript file that will hold the main module
	* implementation.
	*/
	protected abstract String getModulePrefix(TreeLogger logger,
	LinkerContext context, String strongName)
	throws UnableToCompleteException;

	/**
	* Compute the beginning of a JavaScript file that will hold the main module
	* implementation. By default, calls
	* {@link #getModulePrefix(TreeLogger, LinkerContext, String)}.
	*
	* @param strongName strong name of the module being emitted
	* @param numFragments the number of fragments for this module, including the
	* main fragment (fragment 0)
	*/
	protected String getModulePrefix(TreeLogger logger, LinkerContext context,
	String strongName, int numFragments) throws UnableToCompleteException {
	return getModulePrefix(logger, context, strongName);
	}

	protected abstract String getModuleSuffix(TreeLogger logger,
	LinkerContext context) throws UnableToCompleteException;

	protected StringBuffer getSelectionScriptStringBuffer(TreeLogger logger,
	LinkerContext context) throws UnableToCompleteException {
	StringBuffer selectionScript;
	try {
	selectionScript = new StringBuffer(
	Utility.getFileFromClassPath(getSelectionScriptTemplate(logger,
	context)));
	} catch (IOException e) {
	logger.log(TreeLogger.ERROR, "Unable to read selection script template",
	e);
	throw new UnableToCompleteException();
	}
	return selectionScript;
	}

	protected abstract String getSelectionScriptTemplate(TreeLogger logger,
	LinkerContext context) throws UnableToCompleteException;

	/**
	* Add the hosted file to the artifact set.
	*/
	protected void maybeAddHostedModeFile(TreeLogger logger, ArtifactSet artifacts)
	throws UnableToCompleteException {
	String hostedFilename = getHostedFilename();
	if ("".equals(hostedFilename)) {
	return;
	}
	try {
	URL resource = SelectionScriptLinker.class.getResource(hostedFilename);
	if (resource == null) {
	logger.log(TreeLogger.ERROR,
	"Unable to find support resource: " + hostedFilename);
	throw new UnableToCompleteException();
	}

	final URLConnection connection = resource.openConnection();
	// TODO: extract URLArtifact class?
	EmittedArtifact hostedFile = new EmittedArtifact(
	SelectionScriptLinker.class, hostedFilename) {
	@Override
	public InputStream getContents(TreeLogger logger)
	throws UnableToCompleteException {
	try {
	return connection.getInputStream();
	} catch (IOException e) {
	logger.log(TreeLogger.ERROR, "Unable to copy support resource", e);
	throw new UnableToCompleteException();
	}
	}

	@Override
	public long getLastModified() {
	return connection.getLastModified();
	}
	};
	artifacts.add(hostedFile);
	} catch (IOException e) {
	logger.log(TreeLogger.ERROR, "Unable to copy support resource", e);
	throw new UnableToCompleteException();
	}
	}

	/**
	* Find all instances of {@link SelectionInformation} and add them to the
	* internal map of selection information.
	*/
	protected void processSelectionInformation(ArtifactSet artifacts) {
	for (SelectionInformation selInfo : artifacts.find(SelectionInformation.class)) {
	processSelectionInformation(selInfo);
	}
	}

	protected StringBuffer processSelectionScriptCommon(StringBuffer selectionScript,
	TreeLogger logger, LinkerContext context)
	throws UnableToCompleteException {
	String permutations;
	try {
	permutations = Utility.getFileFromClassPath(PERMUTATIONS_JS);
	} catch (IOException e) {
	logger.log(TreeLogger.ERROR, "Unable to read selection script template",
	e);
	throw new UnableToCompleteException();
	}

	replaceAll(selectionScript, "__PERMUTATIONS__", permutations);
	replaceAll(selectionScript, "__MODULE_FUNC__",
	context.getModuleFunctionName());
	replaceAll(selectionScript, "__MODULE_NAME__", context.getModuleName());
	replaceAll(selectionScript, "__HOSTED_FILENAME__", getHostedFilename());

	int startPos;

	// Add property providers
	startPos = selectionScript.indexOf("// __PROPERTIES_END__");
	if (startPos != -1) {
	for (SelectionProperty p : context.getProperties()) {
	String text = generatePropertyProvider(p);
	selectionScript.insert(startPos, text);
	startPos += text.length();
	}
	}

	// Possibly add permutations
	startPos = selectionScript.indexOf("// __PERMUTATIONS_END__");
	if (startPos != -1) {
	StringBuffer text = new StringBuffer();
	if (propMapsByPermutation.size() == 0) {
	// Hosted mode link.
	text.append("alert(\"GWT module '" + context.getModuleName()
	+ "' may need to be (re)compiled\");");
	text.append("return;");

	} else if (propMapsByPermutation.size() == 1) {
	// Just one distinct compilation; no need to evaluate properties
	text.append("strongName = '"
	+ propMapsByPermutation.keySet().iterator().next().getStrongName()
	+ "';");
	} else {
	Set<String> propertiesUsed = new HashSet<String>();
	for (PermutationId permutationId : propMapsByPermutation.keySet()) {
	for (Map<String, String> propertyMap : propMapsByPermutation.get(permutationId)) {
	// unflatten([v1, v2, v3], 'strongName' + ':softPermId');
	// The soft perm ID is concatenated to improve string interning
	text.append("unflattenKeylistIntoAnswers([");
	boolean needsComma = false;
	for (SelectionProperty p : context.getProperties()) {
	if (p.tryGetValue() != null) {
	continue;
	} else if (p.isDerived()) {
	continue;
	}

	if (needsComma) {
	text.append(",");
	} else {
	needsComma = true;
	}
	text.append("'" + propertyMap.get(p.getName()) + "'");
	propertiesUsed.add(p.getName());
	}

	text.append("], '").append(permutationId.getStrongName()).append(
	"'");
	/*
	* For compatibility with older linkers, skip the soft permutation
	* if it's 0
	*/
	if (permutationId.getSoftPermutationId() != 0) {
	text.append(" + ':").append(permutationId.getSoftPermutationId()).append(
	"'");
	}
	text.append(");\n");
	}
	}

	// strongName = answers[compute('p1')][compute('p2')];
	text.append("strongName = answers[");
	boolean needsIndexMarkers = false;
	for (SelectionProperty p : context.getProperties()) {
	if (!propertiesUsed.contains(p.getName())) {
	continue;
	}
	if (needsIndexMarkers) {
	text.append("][");
	} else {
	needsIndexMarkers = true;
	}
	text.append("computePropValue('" + p.getName() + "')");
	}
	text.append("];");
	}
	selectionScript.insert(startPos, text);
	}

	return selectionScript;
	}

	private List<Artifact<?>> emitSelectionInformation(String strongName,
	CompilationResult result) {
	List<Artifact<?>> emitted = new ArrayList<Artifact<?>>();

	for (SortedMap<SelectionProperty, String> propertyMap : result.getPropertyMap()) {
	TreeMap<String, String> propMap = new TreeMap<String, String>();
	for (Map.Entry<SelectionProperty, String> entry : propertyMap.entrySet()) {
	propMap.put(entry.getKey().getName(), entry.getValue());
	}

	// The soft properties may not be a subset of the existing set
	for (SoftPermutation soft : result.getSoftPermutations()) {
	// Make a copy we can add add more properties to
	TreeMap<String, String> softMap = new TreeMap<String, String>(propMap);
	// Make sure this SelectionInformation contains the soft properties
	for (Map.Entry<SelectionProperty, String> entry : soft.getPropertyMap().entrySet()) {
	softMap.put(entry.getKey().getName(), entry.getValue());
	}
	emitted.add(new SelectionInformation(strongName, soft.getId(), softMap));
	}
	}

	return emitted;
	}

	private Map<String, String> processSelectionInformation(
	SelectionInformation selInfo) {
	TreeMap<String, String> entries = selInfo.getPropMap();
	PermutationId permutationId = new PermutationId(selInfo.getStrongName(),
	selInfo.getSoftPermutationId());
	if (!propMapsByPermutation.containsKey(permutationId)) {
	propMapsByPermutation.put(permutationId,
	Lists.<Map<String, String>> create(entries));
	} else {
	propMapsByPermutation.put(permutationId, Lists.add(
	propMapsByPermutation.get(permutationId), entries));
	}
	return entries;
	}
	}