JWebAssembly/src/de/inetsoftware/jwebassembly/module/WasmLoadStoreInstruction.java

/*
   Copyright 2018 Volker Berlin (i-net software)

   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 de.inetsoftware.jwebassembly.module;

import java.io.IOException;

import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;

/**
 * WasmInstruction for load and store local variables.
 * 
 * @author Volker Berlin
 *
 */
class WasmLoadStoreInstruction extends WasmInstruction {

    private boolean               load;

    private int                   idx;

    private LocaleVariableManager localVariables;

    /**
     * Create an instance of a load/store instruction
     * 
     * @param load
     *            true: if load
     * @param idx
     *            the memory/slot idx of the variable
     * @param localVariables
     *            the manager for local variables
     * @param javaCodePos
     *            the code position/offset in the Java method
     */
    WasmLoadStoreInstruction( boolean load, @Nonnegative int idx, LocaleVariableManager localVariables, int javaCodePos ) {
        super( javaCodePos );
        this.load = load;
        this.idx = idx;
        this.localVariables = localVariables;
    }

    /**
     * {@inheritDoc}
     */
    public void writeTo( @Nonnull ModuleWriter writer ) throws IOException {
        int index = localVariables.get( idx ); // translate slot index to position index
        if( load ) {
            writer.writeLoad( index );
        } else {
            writer.writeStore( index );
        }
    }

    /**
     * {@inheritDoc}
     */
    ValueType getPushValueType() {
        return load ? localVariables.getValueType( idx ) : null;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    int getPopCount() {
        return load ? 0 : 1;
    }
}