SquirrelJME/SquirrelJME

// -*- Mode: Java; indent-tabs-mode: t; tab-width: 4 -*-
// ---------------------------------------------------------------------------
// SquirrelJME
//     Copyright (C) Stephanie Gawroriski <xer@multiphasicapps.net>
// ---------------------------------------------------------------------------
// SquirrelJME is under the Mozilla Public License Version 2.0.
// See license.mkd for licensing and copyright information.
// ---------------------------------------------------------------------------

package net.multiphasicapps.zip.blockreader;

import java.io.EOFException;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;

/**
 * This wraps a file channel and provides block level access to it.
 *
 * @since 2016/12/27
 */
@SuppressWarnings("DuplicateThrows")
public class FileChannelBlockAccessor
    implements BlockAccessor
{
    /** The file channel to wrap. */
    protected final FileChannel channel;
    
    /**
     * Initializes the block accessor for the given path.
     *
     * @param __p The path to open.
     * @throws IOException On read errors.
     * @throws NullPointerException On null arguments.
     * @since 2017/11/29
     */
    public FileChannelBlockAccessor(Path __p)
        throws IOException, NullPointerException
    {
        this(FileChannel.open(__p, StandardOpenOption.READ));
    }
    
    /**
     * Initializes the block accessor for the file channel.
     *
     * @param __fc The channel to access data from.
     * @throws IOException On read errors.
     * @throws NullPointerException On null arguments.
     * @since 2016/12/27
     */
    public FileChannelBlockAccessor(FileChannel __fc)
        throws IOException, NullPointerException
    {
        // Check
        if (__fc == null)
            throw new NullPointerException("NARG");
        
        // Set
        this.channel = __fc;
    }
    
    /**
     * {@inheritDoc}
     * @since 2016/12/27
     */
    @Override
    public void close()
        throws IOException
    {
        this.channel.close();
    }
    
    /**
     * {@inheritDoc}
     * @since 2016/12/29
     */
    @Override
    public byte read(long __addr)
        throws EOFException, IOException
    {
        /* {@squirreljme.error BF07 Cannot read from a negative offset.} */
        if (__addr < 0)
            throw new IOException("BF07");
        
        // Just forward to the array variant
        byte[] val = new byte[1];
        int rv = this.read(__addr, val, 0, 1);
        
        /* {@squirreljme.error BF08 Read past end of file.} */
        if (rv < 0)
            throw new EOFException("BF08");
        
        return val[0];
    }
    
    /**
     * {@inheritDoc}
     * @since 2016/12/27
     */
    @Override
    public int read(long __addr, byte[] __b, int __o, int __l)
        throws ArrayIndexOutOfBoundsException, IOException,
            NullPointerException
    {
        // Check
        if (__b == null)
            throw new NullPointerException("NARG");
        if (__o < 0 || __l < 0 || (__o + __l) < 0 || (__o + __l) > __b.length)
            throw new ArrayIndexOutOfBoundsException("AIOB");
        
        /* {@squirreljme.error BF09 Cannot read from a negative offset.} */
        if (__addr < 0)
            throw new IOException("BF09");
        
        // Read until every byte has been read so that partial reads are not
        // returned
        ByteBuffer buf = ByteBuffer.wrap(__b, __o, __l);
        FileChannel channel = this.channel;
        int n;
        while (buf.hasRemaining())
            if (channel.read(buf, __addr + buf.position()) < 0)
                if ((n = buf.position()) <= 0)
                    return -1;
                else
                    return n;
        
        // Use the read position
        return buf.position();
    }
    
    /**
     * {@inheritDoc}
     * @since 2016/12/27
     */
    @Override
    public long size()
        throws IOException
    {
        return this.channel.size();
    }
}