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      1 // Copyright 2014 The Bazel Authors. All rights reserved.
      2 //
      3 // Licensed under the Apache License, Version 2.0 (the "License");
      4 // you may not use this file except in compliance with the License.
      5 // You may obtain a copy of the License at
      6 //
      7 //    http://www.apache.org/licenses/LICENSE-2.0
      8 //
      9 // Unless required by applicable law or agreed to in writing, software
     10 // distributed under the License is distributed on an "AS IS" BASIS,
     11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     12 // See the License for the specific language governing permissions and
     13 // limitations under the License.
     14 
     15 package com.google.devtools.common.options;
     16 
     17 import com.google.common.escape.CharEscaperBuilder;
     18 import com.google.common.escape.Escaper;
     19 
     20 import java.util.List;
     21 import java.util.Map;
     22 import java.util.Map.Entry;
     23 
     24 /**
     25  * Base class for all options classes.  Extend this class, adding public
     26  * instance fields annotated with @Option.  Then you can create instances
     27  * either programmatically:
     28  *
     29  * <pre>
     30  *   X x = Options.getDefaults(X.class);
     31  *   x.host = "localhost";
     32  *   x.port = 80;
     33  * </pre>
     34  *
     35  * or from an array of command-line arguments:
     36  *
     37  * <pre>
     38  *   OptionsParser parser = OptionsParser.newOptionsParser(X.class);
     39  *   parser.parse("--host", "localhost", "--port", "80");
     40  *   X x = parser.getOptions(X.class);
     41  * </pre>
     42  *
     43  * <p>Subclasses of OptionsBase <b>must</b> be constructed reflectively,
     44  * i.e. using not {@code new MyOptions}, but one of the two methods above
     45  * instead.  (Direct construction creates an empty instance, not containing
     46  * default values.  This leads to surprising behavior and often
     47  * NullPointerExceptions, etc.)
     48  */
     49 public abstract class OptionsBase {
     50 
     51   private static final Escaper ESCAPER = new CharEscaperBuilder()
     52       .addEscape('\\', "\\\\").addEscape('"', "\\\"").toEscaper();
     53 
     54   /**
     55    * Subclasses must provide a default (no argument) constructor.
     56    */
     57   protected OptionsBase() {
     58     // There used to be a sanity check here that checks the stack trace of this constructor
     59     // invocation; unfortunately, that makes the options construction about 10x slower. So be
     60     // careful with how you construct options classes.
     61   }
     62 
     63   /**
     64    * Returns this options object in the form of a (new) mapping from option
     65    * names, including inherited ones, to option values.  If the public fields
     66    * are mutated, this will be reflected in subsequent calls to {@code asMap}.
     67    * Mutation of this map by the caller does not affect this options object.
     68    */
     69   public final Map<String, Object> asMap() {
     70     return OptionsParserImpl.optionsAsMap(this);
     71   }
     72 
     73   @Override
     74   public final String toString() {
     75     return getClass().getName() + asMap();
     76   }
     77 
     78   /**
     79    * Returns a string that uniquely identifies the options. This value is
     80    * intended for analysis caching.
     81    */
     82   public final String cacheKey() {
     83     StringBuilder result = new StringBuilder(getClass().getName()).append("{");
     84 
     85     for (Entry<String, Object> entry : asMap().entrySet()) {
     86       result.append(entry.getKey()).append("=");
     87 
     88       Object value = entry.getValue();
     89       // This special case is needed because List.toString() prints the same
     90       // ("[]") for an empty list and for a list with a single empty string.
     91       if (value instanceof List<?> && ((List<?>) value).isEmpty()) {
     92         result.append("EMPTY");
     93       } else if (value == null) {
     94         result.append("NULL");
     95       } else {
     96         result
     97             .append('"')
     98             .append(ESCAPER.escape(value.toString()))
     99             .append('"');
    100       }
    101       result.append(", ");
    102     }
    103 
    104     return result.append("}").toString();
    105   }
    106 
    107   @Override
    108   public final boolean equals(Object that) {
    109     return that != null &&
    110         this.getClass() == that.getClass() &&
    111         this.asMap().equals(((OptionsBase) that).asMap());
    112   }
    113 
    114   @Override
    115   public final int hashCode() {
    116     return this.getClass().hashCode() + asMap().hashCode();
    117   }
    118 }
    119