Java Code Examples for java.nio.channels.ByteChannel#read()

/**
 * ByteChannelからdouble配列を読み込む
 * @param channel
 * @return
 * @throws IOException
 */
public static double[] readDoubleArray(@NonNull final ByteChannel channel)
	throws IOException {
	
	final int n = readInt(channel);
	final ByteBuffer buf = ByteBuffer.allocate(n * 8).order(ByteOrder.BIG_ENDIAN);
	final int readBytes = channel.read(buf);
	if (readBytes != n * 8) throw new IOException();
	buf.clear();
	final DoubleBuffer result = buf.asDoubleBuffer();
	if (result.hasArray()) {
		return result.array();
	}  else {
		final double[] b = new double[n];
		result.get(b);
		return b;
	}
}
 

/**
 * ByteChannelからfloat配列を読み込む
 * @param channel
 * @return
 * @throws IOException
 */
public static float[] readFloatArray(@NonNull final ByteChannel channel)
	throws IOException {
	
	final int n = readInt(channel);
	final ByteBuffer buf = ByteBuffer.allocate(n * 4).order(ByteOrder.BIG_ENDIAN);
	final int readBytes = channel.read(buf);
	if (readBytes != n * 4) throw new IOException();
	buf.clear();
	final FloatBuffer result = buf.asFloatBuffer();
	if (result.hasArray()) {
		return result.array();
	}  else {
		final float[] b = new float[n];
		result.get(b);
		return b;
	}
}
 

/**
 * ByteChannelからint配列を読み込む
 * @param channel
 * @return
 * @throws IOException
 */
public static int[] readIntArray(@NonNull final ByteChannel channel)
	throws IOException {
	
	final int n = readInt(channel);
	final ByteBuffer buf = ByteBuffer.allocate(n * 4).order(ByteOrder.BIG_ENDIAN);
	final int readBytes = channel.read(buf);
	if (readBytes != n * 4) throw new IOException();
	buf.clear();
	final IntBuffer result = buf.asIntBuffer();
	if (result.hasArray()) {
		return result.array();
	}  else {
		final int[] b = new int[n];
		result.get(b);
		return b;
	}
}
 

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
  String indexHtmlPath = getServletContext().getRealPath("index.html");
  File indexHtml = new File(indexHtmlPath);

  RandomAccessFile raf = new RandomAccessFile(indexHtml, "r");
  ByteChannel channel = raf.getChannel();

  ByteBuffer buffer = ByteBuffer.allocate(8192);
  while (channel.read(buffer) != -1) {
    buffer.flip();
    int len = buffer.remaining();
    byte[] bytes = new byte[len];
    buffer.get(bytes);
    buffer.flip();
    response.getOutputStream().write(bytes, 0, len);
  }

  channel.close();
}
 

/**
 * ByteChannelからStringを読み込む
 * @param channel
 * @return
 * @throws IOException
 */
public static String readString(@NonNull final ByteChannel channel)
	throws IOException {
	
	final int bytes = readInt(channel);
	final byte[] buf = new byte[bytes];
	final ByteBuffer b = ByteBuffer.wrap(buf);
	final int readBytes = channel.read(b);
	if (readBytes != bytes) throw new IOException();
	return new String(buf, CharsetsUtils.UTF8);
}
 

/**
 * ByteChannelからByteBufferを読み込む
 * @param channel
 * @param readBuf
 * @param canReAllocate trueなら　指定したreadBufのremainingが読み込むサイズよりも小さい場合は
 * 						IOExceptionを投げる、falseなら必要な分を確保し直す
 * @return 読み込めた時はpositionは元のまま(読んだデータの先頭), limitをデータの最後に変更して返す
 * canReAllocate=falseなら元のreadBufとは異なるByteBufferを返すかもしれない
 * IOExceptionを投げた時は内容・position,limitは不定
 * @throws IOException
 */
public static ByteBuffer readByteBuffer(@NonNull final ByteChannel channel,
	@Nullable final ByteBuffer readBuf, final boolean canReAllocate)
		throws IOException {
	
	final int n = readInt(channel);
	final int pos = readBuf != null ? readBuf.position() : 0;
	ByteBuffer buf = readBuf;
	if ((buf == null) || (buf.remaining() < n)) {
		if (canReAllocate) {
			if (buf == null) {
				buf = ByteBuffer.allocateDirect(n);
			} else {
				final ByteBuffer temp = ByteBuffer.allocateDirect(
					readBuf.limit() + n);
				buf.flip();
				temp.put(buf);
				buf = temp;
			}
		} else {
			throw new IOException();
		}
	}
	buf.limit(pos + n);
	final int readBytes = channel.read(buf);
	if (readBytes != n) throw new IOException();
	buf.position(pos);
	buf.limit(pos + n);
	return buf;
}
 

@Override
protected int read(ByteChannel src, ByteBuf dst) throws IOException {
    if (src instanceof ScatteringByteChannel) {
        return dst.writeBytes((ScatteringByteChannel) src, dst.writableBytes());
    }

    final int readBytes = src.read(dst.nioBuffer(dst.writerIndex(), dst.writableBytes()));
    if (readBytes > 0) {
        dst.writerIndex(dst.writerIndex() + readBytes);
    }
    return readBytes;
}
 

/**
 * May be invoked after {@link #initialize(String, int, int)} for replacing the seekable byte channel
 * by a non-seekable one. Used for testing different code paths in {@link ChannelDataOutput}.
 */
private void nonSeekableChannel() throws IOException {
    final ByteChannel channel = (ByteChannel) testedStream.channel;
    testedStream = new ChannelDataOutput(testedStream.filename, new ByteChannel() {
        @Override public boolean isOpen()                                 {return channel.isOpen();}
        @Override public int     read(ByteBuffer dst)  throws IOException {return channel.read(dst);}
        @Override public int     write(ByteBuffer src) throws IOException {return channel.write(src);}
        @Override public void    close()               throws IOException {channel.close();}
    }, testedStream.buffer);
}
 

public static InputStream newInputStream(final ByteChannel channel) {
	final ByteBuffer buf = ByteBuffer.allocate(2048);

	return new InputStream() {
        public synchronized int read() throws IOException {
            if (!buf.hasRemaining()) {
                channel.read(buf);
            }
            return buf.get();
        }

        public synchronized int read(byte[] bytes, int off, int len) throws IOException {
        	int rem = buf.remaining();

        	while (rem < len) {
        		if (rem > 0) {
	            	buf.get(bytes, off, rem);
	            	off += rem;
	            	len -= rem;
        		}
            	channel.read(buf);
            	rem = buf.remaining();
            }
            
            buf.get(bytes, off, len);
            
            return len;
        }
    };
}
 

/**
 * ByteChannelからbyte配列を読み込む
 * @param channel
 * @return
 * @throws IOException
 */
public static byte[] readByteArray(@NonNull final ByteChannel channel)
	throws IOException {
	
	final int n = readInt(channel);
	final byte[] result = new byte[n];
	final ByteBuffer buf = ByteBuffer.wrap(result);
	final int readBytes = channel.read(buf);
	if (readBytes != n) throw new IOException();
	return result;
}
 

/**
 * ByteChannelからboolean配列を読み込む
 * @param channel
 * @return
 * @throws IOException
 */
public static boolean[] readBooleanArray(@NonNull final ByteChannel channel)
	throws IOException {
	
	final int n = readInt(channel);
	final ByteBuffer buf = ByteBuffer.allocate(n);
	final int readBytes = channel.read(buf);
	if (readBytes != n) throw new IOException();
	buf.clear();
	final boolean[] result = new boolean[n];
	for (int i = 0; i < n; i++) {
		result[i] = buf.get() != 0;
	}
	return result;
}
 

/**
 * ByteChannelからdoubleを読み込む
 * @param channel
 * @return
 * @throws IOException
 */
public static double readDouble(@NonNull final ByteChannel channel,
	@Nullable final ByteBuffer work) throws IOException {

	final ByteBuffer buf = checkBuffer(work, 8);
	final int readBytes = channel.read(buf);
	if (readBytes != 8) throw new IOException();
	buf.clear();
	return buf.getDouble();
}
 

/**
 * ByteChannelからfloatを読み込む
 * @param channel
 * @return
 * @throws IOException
 */
public static float readFloat(@NonNull final ByteChannel channel,
	@Nullable final ByteBuffer work) throws IOException {
	
	final ByteBuffer buf = checkBuffer(work, 4);
	final int readBytes = channel.read(buf);
	if (readBytes != 4) throw new IOException();
	buf.clear();
	return buf.getFloat();
}
 

/**
 * ByteChannelからfloatを読み込む
 * @param channel
 * @return
 * @throws IOException
 */
public static float readFloat(@NonNull final ByteChannel channel)
	throws IOException {
	
	final ByteBuffer buf = ByteBuffer.allocate(4);
	final int readBytes = channel.read(buf);
	if (readBytes != 4) throw new IOException();
	buf.clear();
	return buf.getFloat();
}
 

/**
 * ByteChannelからintを読み込む
 * @param channel
 * @param work
 * @return
 * @throws IOException
 */
public static int readInt(@NonNull final ByteChannel channel,
	@Nullable final ByteBuffer work) throws IOException {
	
	final ByteBuffer buf = checkBuffer(work, 4);
	final int readBytes = channel.read(buf);
	if (readBytes != 4) throw new IOException();
	buf.clear();
	return buf.getInt();
}
 

/**
 * ByteChannelからshortを読み込む
 * @param channel
 * @param work
 * @return
 * @throws IOException
 */
public static short readShort(@NonNull final ByteChannel channel,
	@Nullable final ByteBuffer work) throws IOException {
	
	final ByteBuffer buf = checkBuffer(work, 2);
	final int readBytes = channel.read(buf);
	if (readBytes != 2) throw new IOException();
	buf.clear();
	return buf.getShort();
}
 

/**
 * ByteChannelからcharを読み込む
 * @param channel
 * @param work
 * @return
 * @throws IOException
 */
public static char readChar(@NonNull final ByteChannel channel,
	@Nullable final ByteBuffer work) throws IOException {
	
	final ByteBuffer buf = checkBuffer(work, 2);
	final int readBytes = channel.read(buf);
	if (readBytes != 2) throw new IOException();
	buf.clear();
	return buf.getChar();
}
 

/**
 * ByteChannelからbyeを読み込む
 * @param channel
 * @return
 * @throws IOException
 */
public static byte readByte(@NonNull final ByteChannel channel,
	@Nullable final ByteBuffer work) throws IOException {
	
	final ByteBuffer buf = checkBuffer(work, 1);
	final int readBytes = channel.read(buf);
	if (readBytes != 1) throw new IOException();
	buf.clear();
	return buf.get();
}
 

/**
 * ByteChannelからbooleanを読み込む
 * @param channel
 * @param work
 * @return
 * @throws IOException
 */
public static boolean readBoolean(
	@NonNull final ByteChannel channel,
	@Nullable final ByteBuffer work) throws IOException {
	
	final ByteBuffer buf = checkBuffer(work, 1);
	final int readBytes = channel.read(buf);
	if (readBytes != 1) throw new IOException();
	buf.clear();
	return buf.get() != 0;
}
 

@Override
protected int read(NioSession session, IoBuffer buf) throws Exception {
    ByteChannel channel = session.getChannel();

    return channel.read(buf.buf());
}