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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 com.google.common.base.Optional;
import com.google.common.base.Preconditions;
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.LoopLabels;
import com.google.devtools.build.lib.syntax.compiler.VariableScope;
import net.bytebuddy.implementation.bytecode.ByteCodeAppender;
/**
* A class for flow statements (e.g. break and continue)
*/
public final class FlowStatement extends Statement {
public enum Kind {
BREAK("break"),
CONTINUE("continue");
private String name;
private Kind(String name) {
this.name = name;
}
}
private final Kind kind;
private final FlowException ex;
/**
*
* @param kind The label of the statement (either break or continue)
*/
public FlowStatement(Kind kind) {
this.kind = kind;
this.ex = new FlowException(kind);
}
Kind getKind() {
return kind;
}
@Override
void doExec(Environment env) throws EvalException {
throw ex;
}
@Override
void validate(ValidationEnvironment env) throws EvalException {
if (!env.isInsideLoop()) {
throw new EvalException(getLocation(), kind.name + " statement must be inside a for loop");
}
}
@Override
public String toString() {
return kind.name;
}
@Override
public void accept(SyntaxTreeVisitor visitor) {
visitor.visit(this);
}
@Override
ByteCodeAppender compile(
VariableScope scope, Optional<LoopLabels> loopLabels, DebugInfo debugInfo) {
Preconditions.checkArgument(loopLabels.isPresent(), "break/continue not within loop");
return new ByteCodeAppender.Simple(Jump.to(loopLabels.get().labelFor(kind)));
}
/**
* An exception that signals changes in the control flow (e.g. break or continue)
*/
class FlowException extends EvalException {
private final Kind kind;
public FlowException(Kind kind) {
super(FlowStatement.this.getLocation(), "FlowException with kind = " + kind.name);
this.kind = kind;
}
/**
* Returns whether the enclosing loop should be terminated completely (break)
*
* @return {@code True} for 'break', {@code false} for 'continue'
*/
public boolean mustTerminateLoop() {
return kind == Kind.BREAK;
}
@Override
public boolean canBeAddedToStackTrace() {
return false;
}
}
}
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