com.google.template.soy.jbcsrc.ControlFlow.java Source code

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Here is the source code for com.google.template.soy.jbcsrc.ControlFlow.java

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/*
 * Copyright 2015 Google Inc.
 *
 * 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.template.soy.jbcsrc;

import static com.google.common.base.Preconditions.checkArgument;

import com.google.auto.value.AutoValue;
import com.google.common.base.Optional;

import org.objectweb.asm.Label;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;

import java.util.List;

/**
 * Utilities for encoding control flow in terms of statements and expressions.
 */
final class ControlFlow {
    private ControlFlow() {
    }

    @AutoValue
    abstract static class IfBlock {
        static IfBlock create(Expression cond, Statement block) {
            cond.checkAssignableTo(Type.BOOLEAN_TYPE);
            return new AutoValue_ControlFlow_IfBlock(cond, block);
        }

        abstract Expression condition();

        abstract Statement block();
    }

    /**
     * Returns a statement that encodes the given sequence of {@link IfBlock if blocks} as an 
     * if-elseif-else chain.
     */
    static Statement ifElseChain(final List<IfBlock> ifs, final Optional<Statement> elseBlock) {
        checkArgument(!ifs.isEmpty());
        return new Statement() {
            @Override
            void doGen(CodeBuilder adapter) {
                Label end = new Label();
                Label next;
                for (int i = 0; i < ifs.size(); i++) {
                    IfBlock curr = ifs.get(i);
                    boolean isLastIfBlock = i == ifs.size() - 1;
                    if (isLastIfBlock && !elseBlock.isPresent()) {
                        next = end;
                    } else {
                        next = new Label();
                    }
                    curr.condition().gen(adapter);
                    adapter.ifZCmp(Opcodes.IFEQ, next);
                    curr.block().gen(adapter);
                    if (end != next) {
                        adapter.goTo(end);
                    }
                    adapter.mark(next);
                }
                if (elseBlock.isPresent()) {
                    elseBlock.get().gen(adapter);
                    adapter.mark(end);
                }
            }
        };
    }
}