src/main/java/com/google/devtools/build/lib/syntax/NotExpression.java

// 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 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.VariableScope;

import net.bytebuddy.implementation.bytecode.ByteCodeAppender;

/**
 * As syntax node for the not boolean operation.
 */
public class NotExpression extends Expression {

  private final Expression expression;

  public NotExpression(Expression expression) {
    this.expression = expression;
  }

  Expression getExpression() {
    return expression;
  }

  @Override
  Object doEval(Environment env) throws EvalException, InterruptedException {
    return !EvalUtils.toBoolean(expression.eval(env));
  }

  @Override
  public String toString() {
    return "not " + expression;
  }

  @Override
  public void accept(SyntaxTreeVisitor visitor) {
    visitor.visit(this);
  }

  @Override
  void validate(ValidationEnvironment env) throws EvalException {
    expression.validate(env);
  }

  @Override
  ByteCodeAppender compile(VariableScope scope, DebugInfo debugInfo) throws EvalException {
    // since there is no byte code logical negation
    // compile expression and convert to boolean then negate and convert back to Boolean
    return new ByteCodeAppender.Compound(
        expression.compile(scope, debugInfo),
        new ByteCodeAppender.Simple(
            EvalUtils.toBoolean,
            ByteCodeUtils.intLogicalNegation(),
            ByteCodeMethodCalls.BCBoolean.valueOf));
  }
}