RepeatableFileInputStream.java

/*
 * Copyright 2010-2013 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Portions copyright 2006-2009 James Murty. Please see LICENSE.txt
 * for applicable license terms and NOTICE.txt for applicable notices.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file 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.amazonaws.services.s3.internal;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * A repeatable input stream for files. This input stream can be repeated an
 * unlimited number of times, without any limitation on when a repeat can occur.
 */
public class RepeatableFileInputStream extends InputStream {
    private static final Log log = LogFactory.getLog(RepeatableFileInputStream.class);

    private final File file;
    private FileInputStream fis = null;
    private long bytesReadPastMarkPoint = 0;
    private long markPoint = 0;

    /**
     * Creates a repeatable input stream based on a file.
     *
     * @param file
     *            The file from which this input stream reads data.
     *
     * @throws FileNotFoundException
     *             If the specified file doesn't exist, or can't be opened.
     */
    public RepeatableFileInputStream(File file) throws FileNotFoundException {
        if (file == null) {
            throw new IllegalArgumentException("File cannot be null");
        }
        this.fis = new FileInputStream(file);
        this.file = file;
    }

    /**
     * Returns the File this stream is reading data from.
     *
     * @return the File this stream is reading data from.
     */
    public File getFile() {
        return file;
    }

    /**
     * Resets the input stream to the last mark point, or the beginning of the
     * stream if there is no mark point, by creating a new FileInputStream based
     * on the underlying file.
     *
     * @throws IOException
     *             when the FileInputStream cannot be re-created.
     */
    public void reset() throws IOException {
        this.fis.close();
        this.fis = new FileInputStream(file);

        long skipped = 0;
        long toSkip = markPoint;
        while (toSkip > 0) {
            skipped = this.fis.skip(toSkip);
            toSkip -= skipped;
        }

        if (log.isDebugEnabled()) {
            log.debug("Reset to mark point " + markPoint
                    + " after returning " + bytesReadPastMarkPoint + " bytes");
        }
        this.bytesReadPastMarkPoint = 0;
    }

    /**
     * @see java.io.InputStream#markSupported()
     */
    public boolean markSupported() {
        return true;
    }

    /**
     * @see java.io.InputStream#mark(int)
     */
    public void mark(int readlimit) {
        this.markPoint += bytesReadPastMarkPoint;
        this.bytesReadPastMarkPoint = 0;
        if (log.isDebugEnabled()) {
            log.debug("Input stream marked at " + this.markPoint + " bytes");
        }
    }

    /**
     * @see java.io.InputStream#available()
     */
    public int available() throws IOException {
        return fis.available();
    }

    /**
     * @see java.io.InputStream#close()
     */
    public void close() throws IOException {
        fis.close();
    }

    /**
     * @see java.io.InputStream#read()
     */
    public int read() throws IOException {
        int byteRead = fis.read();
        if (byteRead != -1) {
            bytesReadPastMarkPoint++;
            return byteRead;
        } else {
            return -1;
        }
    }

    @Override
    public long skip(long n) throws IOException {
        long skipped = fis.skip(n);
        bytesReadPastMarkPoint += skipped;
        return skipped;
    }

    /**
     * @see java.io.InputStream#read(byte[], int, int)
     */
    public int read(byte[] arg0, int arg1, int arg2) throws IOException {
        int count = fis.read(arg0, arg1, arg2);
        bytesReadPastMarkPoint += count;
        return count;
    }

    public InputStream getWrappedInputStream() {
        return this.fis;
    }

}