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// Copyright 2014 The Bazel Authors. All rights reserved.
//
// 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.devtools.common.options;
import com.google.common.escape.CharEscaperBuilder;
import com.google.common.escape.Escaper;
import java.lang.reflect.Field;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
/**
* Base class for all options classes. Extend this class, adding public instance fields annotated
* with {@link Option}. Then you can create instances either programmatically:
*
* <pre>
* X x = Options.getDefaults(X.class);
* x.host = "localhost";
* x.port = 80;
* </pre>
*
* or from an array of command-line arguments:
*
* <pre>
* OptionsParser parser = OptionsParser.newOptionsParser(X.class);
* parser.parse("--host", "localhost", "--port", "80");
* X x = parser.getOptions(X.class);
* </pre>
*
* <p>Subclasses of {@code OptionsBase} <i>must</i> be constructed reflectively, i.e. using not
* {@code new MyOptions()}, but one of the above methods instead. (Direct construction creates an
* empty instance, not containing default values. This leads to surprising behavior and often {@code
* NullPointerExceptions}, etc.)
*/
public abstract class OptionsBase {
private static final Escaper ESCAPER = new CharEscaperBuilder()
.addEscape('\\', "\\\\").addEscape('"', "\\\"").toEscaper();
/**
* Subclasses must provide a default (no argument) constructor.
*/
protected OptionsBase() {
// There used to be a sanity check here that checks the stack trace of this constructor
// invocation; unfortunately, that makes the options construction about 10x slower. So be
// careful with how you construct options classes.
}
/**
* Returns a mapping from option names to values, for each option on this object, including
* inherited ones. The mapping is a copy, so subsequent mutations to it or to this object are
* independent. Entries are sorted alphabetically.
*/
public final <O extends OptionsBase> Map<String, Object> asMap() {
// Generic O is needed to tell the type system that the toMap() call is safe.
// The casts are safe because "this" is an instance of "getClass()"
// which subclasses OptionsBase.
@SuppressWarnings("unchecked")
O castThis = (O) this;
@SuppressWarnings("unchecked")
Class<O> castClass = (Class<O>) getClass();
Map<String, Object> map = new LinkedHashMap<>();
for (Map.Entry<Field, Object> entry : OptionsParser.toMap(castClass, castThis).entrySet()) {
OptionDefinition optionDefinition = OptionDefinition.extractOptionDefinition(entry.getKey());
map.put(optionDefinition.getOptionName(), entry.getValue());
}
return map;
}
@Override
public final String toString() {
return getClass().getName() + asMap();
}
/**
* Returns a string that uniquely identifies the options. This value is
* intended for analysis caching.
*/
public final String cacheKey() {
StringBuilder result = new StringBuilder(getClass().getName()).append("{");
for (Map.Entry<String, Object> entry : asMap().entrySet()) {
result.append(entry.getKey()).append("=");
Object value = entry.getValue();
// This special case is needed because List.toString() prints the same
// ("[]") for an empty list and for a list with a single empty string.
if (value instanceof List<?> && ((List<?>) value).isEmpty()) {
result.append("EMPTY");
} else if (value == null) {
result.append("NULL");
} else {
result
.append('"')
.append(ESCAPER.escape(value.toString()))
.append('"');
}
result.append(", ");
}
return result.append("}").toString();
}
@Override
public final boolean equals(Object that) {
return that != null &&
this.getClass() == that.getClass() &&
this.asMap().equals(((OptionsBase) that).asMap());
}
@Override
public final int hashCode() {
return this.getClass().hashCode() + asMap().hashCode();
}
}
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