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TwelveMonkeys Common I/O support classes.
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/*
 * Copyright (c) 2008, Harald Kuhr
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * * Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.
 *
 * * Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 *
 * * Neither the name of the copyright holder nor the names of its
 *   contributors may be used to endorse or promote products derived from
 *   this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package com.twelvemonkeys.io;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;

/**
 * A {@code SeekableInputStream} implementation that uses random access directly to a {@code File}.

 * @see FileCacheSeekableStream
 * @see MemoryCacheSeekableStream
 * @see RandomAccessFile
 *
 * @author Harald Kuhr
 * @version $Id: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-core/src/main/java/com/twelvemonkeys/io/FileSeekableStream.java#4 $
 */
public final class FileSeekableStream extends SeekableInputStream {

    // TODO: Figure out why this class is SLOWER than FileCacheSeekableStream in
    // my tests..?

    final RandomAccessFile mRandomAccess;

    /**
     * Creates a {@code FileSeekableStream} that reads from the given
     * {@code File}.
     *
     * @param pInput file to read from
     * @throws FileNotFoundException if {@code pInput} does not exist
     */
    public FileSeekableStream(final File pInput) throws FileNotFoundException {
        this(new RandomAccessFile(pInput, "r"));
    }

    /**
     * Creates a {@code FileSeekableStream} that reads from the given file.
     * The {@code RandomAccessFile} needs only to be open in read
     * ({@code "r"}) mode.
     *
     * @param pInput file to read from
     */
    public FileSeekableStream(final RandomAccessFile pInput) {
        mRandomAccess = pInput;
    }

    /// Seekable

    public boolean isCached() {
        return false;
    }

    public boolean isCachedFile() {
        return false;
    }

    public boolean isCachedMemory() {
        return false;
    }

    /// InputStream

    @Override
    public int available() throws IOException {
        long length = mRandomAccess.length() - position;
        return length > Integer.MAX_VALUE ? Integer.MAX_VALUE : (int) length;
    }

    public void closeImpl() throws IOException {
        mRandomAccess.close();
    }

    public int read() throws IOException {
        checkOpen();

        int read = mRandomAccess.read();
        if (read >= 0) {
            position++;
        }
        return read;
    }

    @Override
    public int read(byte pBytes[], int pOffset, int pLength) throws IOException {
        checkOpen();

        int read = mRandomAccess.read(pBytes, pOffset, pLength);
        if (read > 0) {
            position += read;
        }
        return read;
    }

    /**
     * Does nothing, as we don't really do any caching here.
     *
     * @param pPosition the position to flush to
     */
    protected void flushBeforeImpl(long pPosition) {
    }

    protected void seekImpl(long pPosition) throws IOException {
        mRandomAccess.seek(pPosition);
    }
}