modules/bytecode/src/main/java/com/facebook/presto/bytecode/Scope.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.facebook.presto.bytecode;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.TreeMap;
import com.facebook.presto.bytecode.expression.BytecodeExpression;
import org.objectweb.asm.Type;

import static com.facebook.presto.bytecode.BytecodeUtils.checkArgument;
import static com.facebook.presto.bytecode.BytecodeUtils.checkState;
import static com.facebook.presto.bytecode.ParameterizedType.type;
import static java.util.Objects.requireNonNull;

public class Scope {
    private final Map<String, Variable> variables = new TreeMap<>();
    private final List<Variable> allVariables = new ArrayList<>();

    private final Variable thisVariable;

    private int nextTempVariableId;

    // This can only be constructed by a method definition
    Scope(Optional<ParameterizedType> thisType, Iterable<Parameter> parameters) {
        if (thisType.isPresent()) {
            thisVariable = new Variable("this", thisType.get());
            variables.put("this", thisVariable);
            allVariables.add(thisVariable);
        }
        else {
            thisVariable = null;
        }

        for (Parameter parameter : parameters) {
            variables.put(parameter.getName(), parameter);
            allVariables.add(parameter);
        }
    }

    public List<Variable> getVariables() {
        return List.copyOf(allVariables);
    }

    public Variable createTempVariable(Class<?> type) {
        // reserve a slot for this variable
        Variable variable = new Variable("temp_" + nextTempVariableId, type(type));
        nextTempVariableId += Type.getType(type(type).getType()).getSize();

        allVariables.add(variable);

        return variable;
    }

    public Variable getThis() {
        checkState(thisVariable != null, "Static methods do not have a 'this' variable");
        return thisVariable;
    }

    public Variable getVariable(String name) {
        Variable variable = variables.get(name);
        checkArgument(variable != null, "Variable %s not defined", name);
        return variable;
    }

    public Variable declareVariable(Class<?> type, String variableName) {
        return declareVariable(type(type), variableName);
    }

    public Variable declareVariable(ParameterizedType type, String variableName) {
        requireNonNull(type, "type is null");
        requireNonNull(variableName, "variableName is null");
        checkArgument(!variables.containsKey(variableName), "There is already a variable named %s", variableName);
        checkArgument(!"this".equals(variableName), "The 'this' variable can not be declared");

        Variable variable = new Variable(variableName, type);

        variables.put(variableName, variable);
        allVariables.add(variable);

        return variable;
    }

    public Variable declareVariable(String variableName, BytecodeBlock block, BytecodeExpression initialValue) {
        Variable variable = declareVariable(initialValue.getType(), variableName);
        block.append(variable.set(initialValue));
        return variable;
    }
}