org.cacheonix.impl.transformer.ByteInstruction.java Source code

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Here is the source code for org.cacheonix.impl.transformer.ByteInstruction.java

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/*
 * Cacheonix Systems licenses this file to You under the LGPL 2.1
 * (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.cacheonix.org/products/cacheonix/license-lgpl-2.1.htm
 *
 * 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 org.cacheonix.impl.transformer;

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

/**
 * Utility class to help get the Byte code instruction and the Stack Index for the local variables for a method
 */
public class ByteInstruction implements Opcodes {

    public int code;

    public int stackIndex;

    public int nextStackIndex;

    public static final int START_STACK_INDEX = 1;

    /**
     * Class constructor
     *
     * @param code       Byte code instruction to transfer value from local variables to the operand stack
     * @param stackIndex index of the local variable that must be read
     */
    public ByteInstruction(final int code, final int stackIndex) {

        this.code = code;
        this.stackIndex = stackIndex;
        this.nextStackIndex = stackIndex;
    }

    /**
     * Class Constructor
     */
    public ByteInstruction() {

        this.code = Opcodes.NOP;
        this.stackIndex = START_STACK_INDEX;
        this.nextStackIndex = START_STACK_INDEX;
    }

    /**
     * Computes the Opcode instruction for a given Type <code><code>org.objectweb.asm.Type</code>
     *
     * @param bi ByteInstruction class that contains the ByteCode and StackIndex
     * @param t  instruction for Type <code><code>org.objectweb.asm.Type</code>
     */
    public static void getInstruction(final ByteInstruction bi, final Type t) {

        bi.code = t.getOpcode(Opcodes.ILOAD);
        bi.stackIndex = bi.nextStackIndex;
        bi.nextStackIndex += t.getSize();
    }

    /**
     * Returns ByteInstruction object that is specific to a particular element type in the array
     *
     * @param argIndex Index of the element in the array
     * @param types    array of Types
     * @return ByteInstruction specific to the element in the array
     */
    public static ByteInstruction getByteInstructionAt(final int argIndex, final Type[] types) {

        final ByteInstruction bi = new ByteInstruction();
        for (int i = 0; i <= argIndex; ++i) {
            ByteInstruction.getInstruction(bi, types[i]);
        }
        return bi;
    }

    /**
     * Returns the Opcode for the specific return type
     *
     * @param desc method description
     * @return Opcode for the specific return type
     */
    public static int getReturnCode(final String desc) {

        final Type t = Type.getReturnType(desc);
        return t.getOpcode(Opcodes.IRETURN);
    }

}