| // 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.compiler.ByteCodeUtils; |
| import com.google.devtools.build.lib.syntax.compiler.DebugInfo; |
| import com.google.devtools.build.lib.syntax.compiler.Jump; |
| import com.google.devtools.build.lib.syntax.compiler.Jump.PrimitiveComparison; |
| import com.google.devtools.build.lib.syntax.compiler.LabelAdder; |
| import com.google.devtools.build.lib.syntax.compiler.VariableScope; |
| |
| import net.bytebuddy.implementation.bytecode.ByteCodeAppender; |
| |
| import java.util.ArrayList; |
| import java.util.List; |
| |
| /** |
| * Syntax node for an if/else expression. |
| */ |
| public final class ConditionalExpression extends Expression { |
| |
| // Python conditional expressions: $thenCase if $condition else $elseCase |
| // https://docs.python.org/3.5/reference/expressions.html#conditional-expressions |
| private final Expression thenCase; |
| private final Expression condition; |
| private final Expression elseCase; |
| |
| public Expression getThenCase() { return thenCase; } |
| public Expression getCondition() { return condition; } |
| public Expression getElseCase() { return elseCase; } |
| |
| /** |
| * Constructor for a conditional expression |
| */ |
| public ConditionalExpression( |
| Expression thenCase, Expression condition, Expression elseCase) { |
| this.thenCase = thenCase; |
| this.condition = condition; |
| this.elseCase = elseCase; |
| } |
| |
| /** |
| * Constructs a string representation of the if expression |
| */ |
| @Override |
| public String toString() { |
| return thenCase + " if " + condition + " else " + elseCase; |
| } |
| |
| @Override |
| Object doEval(Environment env) throws EvalException, InterruptedException { |
| if (EvalUtils.toBoolean(condition.eval(env))) { |
| return thenCase.eval(env); |
| } else { |
| return elseCase.eval(env); |
| } |
| } |
| |
| @Override |
| public void accept(SyntaxTreeVisitor visitor) { |
| visitor.visit(this); |
| } |
| |
| @Override |
| void validate(ValidationEnvironment env) throws EvalException { |
| condition.validate(env); |
| thenCase.validate(env); |
| elseCase.validate(env); |
| } |
| |
| @Override |
| ByteCodeAppender compile(VariableScope scope, DebugInfo debugInfo) throws EvalException { |
| List<ByteCodeAppender> code = new ArrayList<>(); |
| LabelAdder afterLabel = new LabelAdder(); |
| LabelAdder elseLabel = new LabelAdder(); |
| // compile condition and convert to boolean |
| code.add(condition.compile(scope, debugInfo)); |
| append( |
| code, |
| EvalUtils.toBoolean, |
| // jump to else block if false |
| Jump.ifIntOperandToZero(PrimitiveComparison.EQUAL).to(elseLabel)); |
| // otherwise evaluate the expression for "then" and jump to end |
| code.add(thenCase.compile(scope, debugInfo)); |
| append( |
| code, |
| Jump.to(afterLabel), |
| // add label for "else" and evaluate the expression |
| elseLabel); |
| code.add(elseCase.compile(scope, debugInfo)); |
| append(code, afterLabel); |
| |
| return ByteCodeUtils.compoundAppender(code); |
| } |
| } |