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Module containing support classes depending on Java SE 6, Guava 11 and Joda-Time 2.0

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/*
 * Copyright (C) the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License 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 net.derquinse.common.io;

import static com.google.common.base.Preconditions.checkNotNull;

import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;

import com.google.common.primitives.Ints;

/**
 * An input stream supplier backed by a byte buffer.
 * @author Andres Rodriguez
 */
final class ByteBufferInputStream extends InputStream {
	/** Backing buffer. */
	private final ByteBuffer buffer;

	/**
	 * Constructor.
	 * @param buffer Backing buffer. The buffer will not be modified by this object.
	 */
	ByteBufferInputStream(ByteBuffer buffer) {
		this.buffer = checkNotNull(buffer, "The backing buffer must be provided");
	}

	@Override
	public synchronized int available() throws IOException {
		return buffer.remaining();
	}

	@Override
	public synchronized int read() throws IOException {
		return buffer.remaining() > 0 ? (buffer.get() & 0xff) : -1;
	}

	@Override
	public synchronized int read(byte[] b, int off, int len) throws IOException {
		if (b == null) {
			throw new NullPointerException();
		} else if (off < 0 || len < 0 || len > b.length - off) {
			throw new IndexOutOfBoundsException();
		} else if (len == 0) {
			return 0;
		}
		final int r = buffer.remaining();
		if (r == 0) {
			return -1; // EOF
		}
		final int n = Math.min(len, r);
		buffer.get(b, off, n);
		return n;
	}

	@Override
	public synchronized long skip(long n) throws IOException {
		if (n <= 0) {
			return 0;
		}
		final int r = buffer.remaining();
		if (r == 0) {
			return 0; // EOF
		}
		final int skipped = Math.min(Ints.saturatedCast(n), r);
		buffer.position(buffer.position() + skipped);
		return skipped;
	}

}