net.derquinse.common.io.Chunks.java Source code

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Here is the source code for net.derquinse.common.io.Chunks.java

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/*
 * Copyright (C) the original author or authors.
 *
 * 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 net.derquinse.common.io;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static net.derquinse.common.io.InternalPreconditions.checkChunkSize;

import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.util.List;

import com.google.common.collect.ForwardingList;
import com.google.common.collect.ImmutableList;
import com.google.common.io.ByteSource;
import com.google.common.primitives.Ints;

/**
 * A collection of chunks.
 * @author Andres Rodriguez
 */
final class Chunks<T extends MemoryByteSource> extends ForwardingList<T> {
    /** Sources. */
    private final ImmutableList<T> sources;
    /** Backing supplier. */
    private final ByteSource supplier;
    /** Total size. */
    private final int totalSize;
    /** Chunk size. */
    private final int chunkSize;

    /**
     * Constructor.
     * @param sources Backing sources, there must be at least two.
     */
    Chunks(List<? extends T> sources) {
        checkNotNull(sources);
        checkArgument(sources.size() > 1, "There must be at least two chunks");
        this.sources = ImmutableList.copyOf(sources);
        int total = Ints.saturatedCast(this.sources.get(0).size());
        this.chunkSize = total;
        for (int i = 1; i < this.sources.size(); i++) {
            total += Ints.saturatedCast(this.sources.get(i).size());
        }
        this.totalSize = total;
        this.supplier = ByteSource.concat(this.sources);
    }

    protected List<T> delegate() {
        return sources;
    }

    /** Returns the chunk size. */
    int getChunkSize() {
        return chunkSize;
    }

    /** Opens a stream. */
    public InputStream openStream() throws IOException {
        return supplier.openStream();
    }

    /** Returns the total size. */
    int getTotalSize() {
        return totalSize;
    }

    /** Writes to a byte array, at a specified offset, returning the number of bytes written. */
    int writeTo(byte[] buffer, int offset) {
        int written = 0;
        for (T s : sources) {
            int n = s.writeTo(buffer, offset);
            written += n;
            offset += n;
        }
        return written;
    }

    /** Writes to a byte buffer, returning the number of bytes written. */
    int writeTo(ByteBuffer buffer) {
        int written = 0;
        for (T s : sources) {
            int n = s.writeTo(buffer);
            written += n;
        }
        return written;
    }

    /** Merges to a specified chunk size. */
    MemoryByteSource merge(MemoryByteSource container, int chunkSize) {
        checkChunkSize(chunkSize);
        if (chunkSize <= this.chunkSize) {
            return container;
        } else if (chunkSize >= totalSize) {
            return container.merge();
        }
        return MemoryByteSourceLoader.get().chunkSize(chunkSize).direct(container.isDirect()).copy(container);
    }

}