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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 import java.lang.reflect.Field;
     20 import java.util.LinkedHashMap;
     21 import java.util.List;
     22 import java.util.Map;
     23 import java.util.Map.Entry;
     24 
     25 /**
     26  * Base class for all options classes. Extend this class, adding public instance fields annotated
     27  * with {@link Option}. Then you can create instances 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 {@code OptionsBase} <i>must</i> be constructed reflectively, i.e. using not
     44  * {@code new MyOptions()}, but one of the above methods instead. (Direct construction creates an
     45  * empty instance, not containing default values. This leads to surprising behavior and often {@code
     46  * NullPointerExceptions}, etc.)
     47  */
     48 public abstract class OptionsBase {
     49 
     50   private static final Escaper ESCAPER = new CharEscaperBuilder()
     51       .addEscape('\\', "\\\\").addEscape('"', "\\\"").toEscaper();
     52 
     53   /**
     54    * Subclasses must provide a default (no argument) constructor.
     55    */
     56   protected OptionsBase() {
     57     // There used to be a sanity check here that checks the stack trace of this constructor
     58     // invocation; unfortunately, that makes the options construction about 10x slower. So be
     59     // careful with how you construct options classes.
     60   }
     61 
     62   /**
     63    * Returns a mapping from option names to values, for each option on this object, including
     64    * inherited ones. The mapping is a copy, so subsequent mutations to it or to this object are
     65    * independent. Entries are sorted alphabetically.
     66    */
     67   public final <O extends OptionsBase> Map<String, Object> asMap() {
     68     // Generic O is needed to tell the type system that the toMap() call is safe.
     69     // The casts are safe because "this" is an instance of "getClass()"
     70     // which subclasses OptionsBase.
     71     @SuppressWarnings("unchecked")
     72     O castThis = (O) this;
     73     @SuppressWarnings("unchecked")
     74     Class<O> castClass = (Class<O>) getClass();
     75 
     76     Map<String, Object> map = new LinkedHashMap<>();
     77     for (Map.Entry<Field, Object> entry : OptionsParser.toMap(castClass, castThis).entrySet()) {
     78       OptionDefinition optionDefinition = OptionDefinition.extractOptionDefinition(entry.getKey());
     79       map.put(optionDefinition.getOptionName(), entry.getValue());
     80     }
     81     return map;
     82   }
     83 
     84   @Override
     85   public final String toString() {
     86     return getClass().getName() + asMap();
     87   }
     88 
     89   /**
     90    * Returns a string that uniquely identifies the options. This value is
     91    * intended for analysis caching.
     92    */
     93   public final String cacheKey() {
     94     StringBuilder result = new StringBuilder(getClass().getName()).append("{");
     95 
     96     for (Entry<String, Object> entry : asMap().entrySet()) {
     97       result.append(entry.getKey()).append("=");
     98 
     99       Object value = entry.getValue();
    100       // This special case is needed because List.toString() prints the same
    101       // ("[]") for an empty list and for a list with a single empty string.
    102       if (value instanceof List<?> && ((List<?>) value).isEmpty()) {
    103         result.append("EMPTY");
    104       } else if (value == null) {
    105         result.append("NULL");
    106       } else {
    107         result
    108             .append('"')
    109             .append(ESCAPER.escape(value.toString()))
    110             .append('"');
    111       }
    112       result.append(", ");
    113     }
    114 
    115     return result.append("}").toString();
    116   }
    117 
    118   @Override
    119   public final boolean equals(Object that) {
    120     return that != null &&
    121         this.getClass() == that.getClass() &&
    122         this.asMap().equals(((OptionsBase) that).asMap());
    123   }
    124 
    125   @Override
    126   public final int hashCode() {
    127     return this.getClass().hashCode() + asMap().hashCode();
    128   }
    129 }
    130