/*
* 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 com.facebook.presto.raptor;
import com.facebook.presto.spi.ConnectorPageSource;
import com.facebook.presto.spi.Page;
import com.facebook.presto.spi.block.Block;
import com.google.common.collect.ImmutableList;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import static com.google.common.base.Preconditions.checkState;
public class RaptorPageSource
implements ConnectorPageSource
{
private final List<Iterator<Block>> iterators;
private final List<BlockPosition> blockPositions;
private boolean finished;
private long sizeInBytes;
public RaptorPageSource(Iterable<Iterable<Block>> channels)
{
ImmutableList.Builder<Iterator<Block>> iterators = ImmutableList.builder();
for (Iterable<Block> channel : channels) {
iterators.add(channel.iterator());
}
this.iterators = iterators.build();
blockPositions = new ArrayList<>(this.iterators.size());
if (this.iterators.get(0).hasNext()) {
for (Iterator<Block> iterator : this.iterators) {
blockPositions.add(new BlockPosition(iterator.next()));
}
}
else {
// no data
for (Iterator<Block> iterator : this.iterators) {
checkState(!iterator.hasNext());
}
finished = true;
}
}
@Override
public long getTotalBytes()
{
return sizeInBytes;
}
@Override
public long getCompletedBytes()
{
return sizeInBytes;
}
@Override
public long getReadTimeNanos()
{
return 0;
}
@Override
public void close()
{
finished = true;
}
@Override
public boolean isFinished()
{
return finished;
}
@Override
public Page getNextPage()
{
if (finished) {
return null;
}
// all iterators should end together
if (blockPositions.get(0).getRemainingPositions() <= 0 && !iterators.get(0).hasNext()) {
for (Iterator<Block> iterator : iterators) {
checkState(!iterator.hasNext());
}
finished = true;
return null;
}
// determine maximum shared length
int length = Integer.MAX_VALUE;
for (int i = 0; i < iterators.size(); i++) {
Iterator<? extends Block> iterator = iterators.get(i);
BlockPosition blockPosition = blockPositions.get(i);
if (blockPosition.getRemainingPositions() <= 0) {
// load next block
blockPosition = new BlockPosition(iterator.next());
blockPositions.set(i, blockPosition);
}
length = Math.min(length, blockPosition.getRemainingPositions());
}
// build page
Block[] blocks = new Block[iterators.size()];
for (int i = 0; i < blockPositions.size(); i++) {
blocks[i] = blockPositions.get(i).getRegionAndAdvance(length);
}
Page page = new Page(blocks);
sizeInBytes += page.getSizeInBytes();
return page;
}
private final class BlockPosition
{
private final Block block;
private int position;
private BlockPosition(Block block)
{
this.block = block;
}
public Block getRegionAndAdvance(int length)
{
Block region = block.getRegion(position, length);
position += length;
return region;
}
public int getRemainingPositions()
{
return block.getPositionCount() - position;
}
}
}