com.khubla.jvmbasic.jvmbasicc.function.impl.rule.variableassignmentRule.java Source code

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Here is the source code for com.khubla.jvmbasic.jvmbasicc.function.impl.rule.variableassignmentRule.java

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package com.khubla.jvmbasic.jvmbasicc.function.impl.rule;

/*
 * jvmBasic Copyright 2012, khubla.com
 *
 *   This program 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 <http://www.gnu.org/licenses/>.
 */
import org.objectweb.asm.Opcodes;

import com.khubla.jvmbasic.jvmbasicc.antlr.jvmBasicParser.ExprlistContext;
import com.khubla.jvmbasic.jvmbasicc.antlr.jvmBasicParser.VardeclContext;
import com.khubla.jvmbasic.jvmbasicc.compiler.Dispatcher;
import com.khubla.jvmbasic.jvmbasicc.compiler.GenerationContext;
import com.khubla.jvmbasic.jvmbasicc.compiler.RTLHelper;
import com.khubla.jvmbasic.jvmbasicc.function.BaseFunction;
import com.khubla.jvmbasic.jvmbasicc.util.VariableNameUtil;

/**
 * @author tome
 *         <p>
 *         EQ sets the variable value in the execution context
 *         </p>
 *         <p>
 *         The assignment code looks like
 *         </p>
 *         <p>
 *         <code>
 *          Value x = executionContext.pop();
 *          this.executionContext.setVariable("name", x);
 *         </code>
 *         </p>
 */
public class variableassignmentRule extends BaseFunction {
    @Override
    public boolean execute(GenerationContext generationContext) throws Exception {
        try {
            /*
             * the tree should have 3 sub nodes like this "variableassignment : vardecl EQ exprlist"
             */
            String variableName = null;
            if (generationContext.getParseTree().getChildCount() == 3) {
                /*
                 * get the variable name
                 */
                variableName = VariableNameUtil
                        .getVariableName((VardeclContext) generationContext.getParseTree().getChild(0));
                /*
                 * get the tree for the value. this should push the value onto the ExecutionContextStack
                 */
                final ExprlistContext exprlistContext = (ExprlistContext) generationContext.getParseTree()
                        .getChild(2);
                final GenerationContext subGenerationContext = new GenerationContext(generationContext,
                        exprlistContext);
                Dispatcher.dispatch(subGenerationContext);
            } else {
                throw new Exception(
                        "Invalid number of arguments '" + generationContext.getParseTree().getChildCount() + "'");
            }
            /*
             * store the top of the stack into slot 1
             */
            generationContext.getMethodVisitor().visitVarInsn(Opcodes.ALOAD, 0);
            generationContext.getMethodVisitor().visitFieldInsn(Opcodes.GETFIELD, generationContext.getClassName(),
                    RTLHelper.EXECUTIONCONTEXT_NAME, RTLHelper.JASIC_RUNTIME_EXECUTIONCONTEXT_TYPE);
            generationContext.getMethodVisitor().visitMethodInsn(Opcodes.INVOKEVIRTUAL,
                    RTLHelper.JASIC_RUNTIME_EXECUTIONCONTEXT, "pop", "()Lcom/khubla/jvmbasic/jvmbasicrt/Value;");
            generationContext.getMethodVisitor().visitVarInsn(Opcodes.ASTORE, 1);
            /*
             * put the value in slot 1 into the variable in the execution context
             */
            generationContext.getMethodVisitor().visitVarInsn(Opcodes.ALOAD, 0);
            generationContext.getMethodVisitor().visitFieldInsn(Opcodes.GETFIELD, generationContext.getClassName(),
                    RTLHelper.EXECUTIONCONTEXT_NAME, RTLHelper.JASIC_RUNTIME_EXECUTIONCONTEXT_TYPE);
            generationContext.getMethodVisitor().visitLdcInsn(variableName);
            generationContext.getMethodVisitor().visitVarInsn(Opcodes.ALOAD, 1);
            generationContext.getMethodVisitor().visitMethodInsn(Opcodes.INVOKEVIRTUAL,
                    RTLHelper.JASIC_RUNTIME_EXECUTIONCONTEXT, "setVariable",
                    "(Ljava/lang/String;Lcom/khubla/jvmbasic/jvmbasicrt/Value;)V");
            return true;
        } catch (final Exception e) {
            throw new Exception("Exception in execute", e);
        }
    }
}