ByteBufferReader.java

package org.araqne.log.api;

import java.io.ByteArrayOutputStream;
import java.io.Closeable;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.ByteChannel;

public class ByteBufferReader implements Closeable {
	private ByteChannel channel;

	public ByteBufferReader(ByteChannel channel) {
		this.channel = channel;
		buf = ByteBuffer.allocate(32768);
		buf.position(buf.limit());
	}

	boolean skipLF;
	int nextChar;
	private ByteBuffer buf = ByteBuffer.allocate(32768);
	private Object closeLock = new Object();

	public ByteBuffer readLine() throws IOException {
		return readLine(true);
	}

	public ByteBuffer readLine(boolean ignoreLF) throws IOException {
		ensureOpen();
		boolean omitLF = ignoreLF || skipLF;
		ByteArrayOutputStream b = null;

		for (;;) { // bufferloop
			if (!buf.hasRemaining())// if (nextChar >= nChars)
				fill();
			if (!buf.hasRemaining()) { /* EOF */
				if (b != null && b.size() > 0)
					return ByteBuffer.wrap(b.toByteArray()).asReadOnlyBuffer();
				else
					return null;
			}
			boolean eol = false;
			byte c = 0;

			/* Skip a leftover '\n', if necessary */
			if (omitLF && (buf.get(buf.position()) == '\n'))
				buf.get();
			skipLF = false;
			omitLF = false;

			// charloop
			int oldPos = buf.position();
			while (buf.hasRemaining()) {
				c = buf.get();
				if ((c == '\n') || (c == '\r')) {
					eol = true;
					break;
				}
			}

			if (eol) {
				ByteBuffer ret = null;
				if (b == null) {
					ret = buf.duplicate();
					ret.limit(buf.position() - 1);
					ret.position(oldPos);
					ret = ret.asReadOnlyBuffer();
				} else {
					b.write(buf.array(), oldPos, buf.position() - 1 - oldPos);
					ret = ByteBuffer.wrap(b.toByteArray()).asReadOnlyBuffer();
				}
				// nextChar++;
				if (c == '\r') {
					skipLF = true;
				}
				return ret;
			}

			if (b == null)
				b = new ByteArrayOutputStream(1024);
			b.write(buf.array(), oldPos, buf.position() - oldPos);
		}

	}

	private void fill() throws IOException {
		// buf has no remaining
		buf.limit(buf.capacity());
		buf.position(0);
		int read = channel.read(buf);
		buf.flip();
	}

	private void ensureOpen() throws IOException {
		synchronized (closeLock) {
			if (channel == null)
				throw new IOException("Stream closed");
		}
	}

	@Override
	public void close() throws IOException {
		synchronized (closeLock) {
			channel.close();
			channel = null;
		}
	}
}