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Utility Java classes for I/O
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package com.cloudhopper.commons.io;

/*
 * #%L
 * ch-commons-io
 * %%
 * Copyright (C) 2012 - 2013 Cloudhopper by Twitter
 * %%
 * 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.
 * #L%
 */

import java.io.InputStream;
import java.io.OutputStream;
import java.nio.channels.FileChannel;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.WritableByteChannel;

/**
 * A simple interface for writing/reading files (or arbitrary byte arrays and streams)
 * to a underlying persistence mechanism.
 * @author garth
 */
public interface FileStore
{

    /**
     * Write an InputStream's bytes to the FileStore.
     * @param is The input stream (e.g. from a ServletInputStream)
     * @return The file's Id.
     * @throws FileStoreException if the underlying FileStore cannot write the file.
     */
    public Id write(InputStream is) throws FileStoreException;

    /**
     * Write a ReadableByteChannel's bytes to the FileStore. This will use zero-copy if available.
     * @param channel The channel to read from.
     * @return The file's Id.
     * @throws FileStoreException if the underlying FileStore cannot write the file.
     */
    public Id write(ReadableByteChannel channel) throws FileStoreException;

    /**
     * Read an file's bytes to an InputStream.
     * @return The Id of the file you want to read. 
     * @return The input stream
     * @throws FileStoreException if the underlying FileStore cannot read the file.
     */
    public InputStream readStream(Id id) throws FileStoreException;

    /**
     * Read an file's bytes to a ReadableByteChannel.
     * @return The Id of the file you want to read. 
     * @return The readable byte channel
     * @throws FileStoreException if the underlying FileStore cannot read the file.
     */
    public ReadableByteChannel readChannel(Id id) throws FileStoreException;

    /**
     * Transfer a file's contents to a given OutputStream.
     * @param os The OutputStream to write to.
     * @param id The Id of the file you want to read.
     * @throws FileStoreException if the underlying FileStore cannot read the file.
     */
    public void transferToOutputStream(OutputStream os, Id id) throws FileStoreException;

    /**
     * Transfer a file's contents to a given WritableByteChannel. This will use zero-copy if available.
     * @param os The WritableByteChannel to write to.
     * @param id The Id of the file you want to read.
     * @throws FileStoreException if the underlying FileStore cannot read the file.
     */
    public void transferToChannel(WritableByteChannel channel, Id id) throws FileStoreException;

    /**
     * Get the file's FileChannel. This is useful for doing zero-copy reads from a file.
     * @param id The Id of the file you want to read.
     * @throws FileStoreException if the underlying FileStore cannot read the file.
     */
    public FileChannel getFileChannel(Id id) throws FileStoreException;

    /**
     * Remove the file specified. This is a hint to the FileStore, and does not guarantee synchronous deletion.
     * @param id The Id of the file you want to delete.
     * @throws FileStoreException if the underlying FileStore cannot delete the file.
     */
    public void remove(Id id) throws FileStoreException;

}