/*
* 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.operator.exchange;
import com.facebook.presto.spi.Page;
import com.facebook.presto.spi.block.Block;
import java.util.function.Function;
import java.util.stream.IntStream;
import static com.google.common.base.Preconditions.checkArgument;
import static java.util.Objects.requireNonNull;
public class PageChannelSelector
implements Function<Page, Page>
{
private final int[] channels;
public PageChannelSelector(int... channels)
{
checkArgument(IntStream.of(channels).allMatch(channel -> channel >= 0), "channels must be positive");
this.channels = requireNonNull(channels, "channels is null").clone();
}
@Override
public Page apply(Page page)
{
requireNonNull(page, "page is null");
Block[] blocks = new Block[channels.length];
for (int i = 0; i < channels.length; i++) {
int channel = channels[i];
blocks[i] = page.getBlock(channel);
}
return new Page(page.getPositionCount(), blocks);
}
}