org.neo4j.codegen.bytecode.ByteCodeClassWriter Maven / Gradle / Ivy

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Simple library for generating code.
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/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [https://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */
package org.neo4j.codegen.bytecode;

import static org.neo4j.codegen.ByteCodeUtils.byteCodeName;
import static org.neo4j.codegen.ByteCodeUtils.outerName;
import static org.neo4j.codegen.ByteCodeUtils.signature;
import static org.neo4j.codegen.ByteCodeUtils.typeName;
import static org.objectweb.asm.Opcodes.ACC_FINAL;
import static org.objectweb.asm.Opcodes.ACC_PUBLIC;
import static org.objectweb.asm.Opcodes.ACC_STATIC;
import static org.objectweb.asm.Opcodes.ACC_SUPER;
import static org.objectweb.asm.Opcodes.PUTSTATIC;
import static org.objectweb.asm.Opcodes.RETURN;
import static org.objectweb.asm.Opcodes.V1_8;

import java.lang.reflect.Modifier;
import java.nio.ByteBuffer;
import java.util.HashMap;
import java.util.Map;
import org.neo4j.codegen.ByteCodes;
import org.neo4j.codegen.ClassWriter;
import org.neo4j.codegen.Expression;
import org.neo4j.codegen.FieldReference;
import org.neo4j.codegen.MethodDeclaration;
import org.neo4j.codegen.MethodWriter;
import org.neo4j.codegen.TypeReference;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.FieldVisitor;
import org.objectweb.asm.MethodVisitor;

/**
 * Writes classes directly as java byte code.
 */
class ByteCodeClassWriter implements ClassWriter {
    private final org.objectweb.asm.ClassWriter classWriter;
    private final ClassVisitor classVisitor;
    private final TypeReference type;
    private final Map staticFields = new HashMap<>();
    private final TypeReference base;

    ByteCodeClassWriter(TypeReference type, TypeReference base, TypeReference[] interfaces) {
        this.classWriter = new org.objectweb.asm.ClassWriter(org.objectweb.asm.ClassWriter.COMPUTE_FRAMES);
        this.classVisitor = classWriter; // this separation is useful if we want to add intermediary visitors
        String[] iNames = new String[interfaces.length];
        for (int i = 0; i < interfaces.length; i++) {
            iNames[i] = byteCodeName(interfaces[i]);
        }
        classVisitor.visit(
                V1_8,
                ACC_PUBLIC + ACC_FINAL + ACC_SUPER,
                byteCodeName(type),
                signature(type),
                byteCodeName(base),
                iNames.length != 0 ? iNames : null);
        if (base.isInnerClass()) {
            classVisitor.visitInnerClass(
                    byteCodeName(base), outerName(base), base.simpleName(), ACC_PUBLIC + ACC_STATIC);
        }
        this.type = type;
        this.base = base;
    }

    @Override
    public MethodWriter method(MethodDeclaration signature) {
        return new ByteCodeMethodWriter(classVisitor, signature, base);
    }

    @Override
    public void field(FieldReference field, Expression value) {
        // keep track of all static field->value, and initiate in  in done
        if (Modifier.isStatic(field.modifiers()) && value != null) {
            staticFields.put(field, value);
        }
        FieldVisitor fieldVisitor = classVisitor.visitField(
                field.modifiers(), field.name(), typeName(field.type()), signature(field.type()), null);
        fieldVisitor.visitEnd();
    }

    @Override
    public void done() {
        if (!staticFields.isEmpty()) {
            MethodVisitor methodVisitor = classVisitor.visitMethod(ACC_STATIC, "", "()V", null, null);
            ByteCodeExpressionVisitor expressionVisitor = new ByteCodeExpressionVisitor(methodVisitor);
            methodVisitor.visitCode();
            for (Map.Entry entry : staticFields.entrySet()) {
                FieldReference field = entry.getKey();
                Expression value = entry.getValue();
                value.accept(expressionVisitor);
                methodVisitor.visitFieldInsn(
                        PUTSTATIC, byteCodeName(field.owner()), field.name(), typeName(field.type()));
            }
            methodVisitor.visitInsn(RETURN);
            methodVisitor.visitMaxs(0, 0);
            methodVisitor.visitEnd();
        }
        classVisitor.visitEnd();
    }

    ByteCodes toByteCodes() {
        byte[] bytecode = classWriter.toByteArray();
        return new ByteCodes() {
            @Override
            public String name() {
                return type.fullName();
            }

            @Override
            public ByteBuffer bytes() {
                return ByteBuffer.wrap(bytecode);
            }
        };
    }
}