com.github.fge.grappa.transform.process.VarFramingGenerator.java Source code

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Here is the source code for com.github.fge.grappa.transform.process.VarFramingGenerator.java

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/*
 * Copyright (C) 2009-2011 Mathias Doenitz
 *
 * 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.github.fge.grappa.transform.process;

import com.github.fge.grappa.matchers.wrap.VarFramingMatcher;
import com.github.fge.grappa.rules.Rule;
import com.github.fge.grappa.support.Var;
import com.github.fge.grappa.transform.CodeBlock;
import com.github.fge.grappa.transform.base.ParserClassNode;
import com.github.fge.grappa.transform.base.RuleMethod;
import me.qmx.jitescript.util.CodegenUtils;
import org.objectweb.asm.tree.AbstractInsnNode;
import org.objectweb.asm.tree.InsnList;
import org.objectweb.asm.tree.LocalVariableNode;

import javax.annotation.Nonnull;
import java.util.Objects;

import static org.objectweb.asm.Opcodes.ARETURN;

/**
 * Inserts code for wrapping the created rule into a VarFramingMatcher if the
 * method contains local variables assignable to {@link Var}.
 */
public final class VarFramingGenerator implements RuleMethodProcessor {
    @Override
    public boolean appliesTo(@Nonnull ParserClassNode classNode, @Nonnull RuleMethod method) {
        Objects.requireNonNull(classNode, "classNode");
        Objects.requireNonNull(method, "method");
        return !method.getLocalVarVariables().isEmpty();
    }

    @Override
    public void process(@Nonnull ParserClassNode classNode, @Nonnull RuleMethod method) throws Exception {
        Objects.requireNonNull(classNode, "classNode");
        Objects.requireNonNull(method, "method");
        InsnList instructions = method.instructions;

        AbstractInsnNode ret = instructions.getLast();
        while (ret.getOpcode() != ARETURN)
            ret = ret.getPrevious();

        CodeBlock block = CodeBlock.newCodeBlock();

        block.newobj(CodegenUtils.p(VarFramingMatcher.class)).dup_x1().swap();

        createVarFieldArray(block, method);

        block.invokespecial(CodegenUtils.p(VarFramingMatcher.class), "<init>",
                CodegenUtils.sig(void.class, Rule.class, Var[].class));

        instructions.insertBefore(ret, block.getInstructionList());

        method.setBodyRewritten();
    }

    private static void createVarFieldArray(CodeBlock block, RuleMethod method) {
        int count = method.getLocalVarVariables().size();

        block.bipush(count).anewarray(CodegenUtils.p(Var.class));

        LocalVariableNode var;
        String varName;

        for (int i = 0; i < count; i++) {
            var = method.getLocalVarVariables().get(i);
            varName = method.name + ':' + var.name;

            block.dup().bipush(i).aload(var.index).dup().ldc(varName)
                    .invokevirtual(CodegenUtils.p(Var.class), "setName", CodegenUtils.sig(void.class, String.class))
                    .aastore();
        }
    }
}