/*
* 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 net.hydromatic.optiq.rules.java;
import net.hydromatic.linq4j.expressions.BlockBuilder;
import org.eigenbase.rex.RexNode;
import java.util.*;
/**
* Allows to build nested code blocks with tracking of current context and
* the nullability of particular {@link org.eigenbase.rex.RexNode} expressions.
* @see net.hydromatic.optiq.rules.java.StrictAggImplementor#implementAdd(AggContext, AggAddContext)
*/
public class NestedBlockBuilderImpl implements NestedBlockBuilder {
private final List<BlockBuilder> blocks = new ArrayList<BlockBuilder>();
private final List<Map<RexNode, Boolean>> nullables =
new ArrayList<Map<RexNode, Boolean>>();
/**
* Constructs nested block builders starting of a given code block.
* @param block root code block
*/
public NestedBlockBuilderImpl(BlockBuilder block) {
nestBlock(block);
}
/**
* Starts nested code block. The resulting block can optimize expressions
* and reuse already calculated values from the parent blocks.
* @return new code block that can optimize expressions and reuse already
* calculated values from the parent blocks.
*/
public final BlockBuilder nestBlock() {
BlockBuilder block = new BlockBuilder(true, currentBlock());
nestBlock(block, Collections.<RexNode, Boolean>emptyMap());
return block;
}
/**
* Uses given block as the new code context.
* The current block will be restored after {@link #exitBlock()} call.
* @param block new code block
* @see #exitBlock()
*/
public final void nestBlock(BlockBuilder block) {
nestBlock(block, Collections.<RexNode, Boolean>emptyMap());
}
/**
* Uses given block as the new code context and the map of nullability.
* The current block will be restored after {@link #exitBlock()} call.
* @param block new code block
* @param nullables map of expression to its nullability state
* @see #exitBlock()
*/
public final void nestBlock(BlockBuilder block,
Map<RexNode, Boolean> nullables) {
blocks.add(block);
Map<RexNode, Boolean> prev = this.nullables.isEmpty()
? Collections.<RexNode, Boolean>emptyMap()
: this.nullables.get(this.nullables.size() - 1);
Map<RexNode, Boolean> next;
if (nullables == null || nullables.isEmpty()) {
next = prev;
} else {
next = new HashMap<RexNode, Boolean>(nullables);
next.putAll(prev);
next = Collections.unmodifiableMap(next);
}
this.nullables.add(next);
}
/**
* Returns the current code block
* @return current code block
*/
public final BlockBuilder currentBlock() {
return blocks.get(blocks.size() - 1);
}
/**
* Returns the current nullability state of rex nodes.
* The resulting value is the summary of all the maps in the block hierarchy.
* @return current nullability state of rex nodes
*/
public final Map<RexNode, Boolean> currentNullables() {
return nullables.get(nullables.size() - 1);
}
/**
* Leaves the current code block.
* @see #nestBlock()
*/
public final void exitBlock() {
blocks.remove(blocks.size() - 1);
nullables.remove(nullables.size() - 1);
}
}
// End NestedBlockBuilder.java