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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.build.lib.syntax;
import static com.google.devtools.build.lib.syntax.compiler.ByteCodeUtils.append;
import com.google.devtools.build.lib.syntax.SkylarkList.MutableList;
import com.google.devtools.build.lib.syntax.compiler.ByteCodeMethodCalls;
import com.google.devtools.build.lib.syntax.compiler.ByteCodeUtils;
import com.google.devtools.build.lib.syntax.compiler.DebugInfo;
import com.google.devtools.build.lib.syntax.compiler.DebugInfo.AstAccessors;
import com.google.devtools.build.lib.syntax.compiler.NewObject;
import com.google.devtools.build.lib.syntax.compiler.Variable.InternalVariable;
import com.google.devtools.build.lib.syntax.compiler.VariableScope;
import net.bytebuddy.implementation.bytecode.ByteCodeAppender;
import net.bytebuddy.implementation.bytecode.Removal;
import java.util.ArrayList;
import java.util.List;
/**
* Syntax node for lists comprehension expressions.
*
*/
public final class ListComprehension extends AbstractComprehension {
private final Expression outputExpression;
public ListComprehension(Expression outputExpression) {
super('[', ']', outputExpression);
this.outputExpression = outputExpression;
}
@Override
String printExpressions() {
return outputExpression.toString();
}
@Override
OutputCollector createCollector() {
return new ListOutputCollector();
}
@Override
InternalVariable compileInitialization(VariableScope scope, List<ByteCodeAppender> code) {
InternalVariable list = scope.freshVariable(ArrayList.class);
append(code, NewObject.fromConstructor(ArrayList.class).arguments());
code.add(list.store());
return list;
}
@Override
ByteCodeAppender compileCollector(
VariableScope scope,
InternalVariable collection,
DebugInfo debugInfo,
AstAccessors debugAccessors)
throws EvalException {
List<ByteCodeAppender> code = new ArrayList<>();
append(code, collection.load());
code.add(outputExpression.compile(scope, debugInfo));
append(code, ByteCodeMethodCalls.BCList.add, Removal.SINGLE);
return ByteCodeUtils.compoundAppender(code);
}
@Override
ByteCodeAppender compileBuilding(VariableScope scope, InternalVariable collection) {
return new ByteCodeAppender.Simple(
NewObject.fromConstructor(MutableList.class, Iterable.class, Environment.class)
.arguments(collection.load(), scope.loadEnvironment()));
}
/**
* Helper class that collects the intermediate results of the {@code ListComprehension} and
* provides access to the resulting {@code List}.
*/
private final class ListOutputCollector implements OutputCollector {
private final List<Object> result;
ListOutputCollector() {
result = new ArrayList<>();
}
@Override
public void evaluateAndCollect(Environment env) throws EvalException, InterruptedException {
result.add(outputExpression.eval(env));
}
@Override
public Object getResult(Environment env) throws EvalException {
return new MutableList(result, env);
}
}
}
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