/*
 * Copyright (C) 2007 The Guava 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 com.google.common.io;

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;

import javax.annotation.Nullable;

import com.google.common.annotations.Beta;

/**
 * An {@link InputStream} that counts the number of bytes read.
 *
 * @author Chris Nokleberg
 * @since 1.0
 */
@Beta
public final class CountingInputStream extends FilterInputStream {

	private long count;
	private long mark = -1;

	/**
	 * Wraps another input stream, counting the number of bytes read.
	 *
	 * @param in the input stream to be wrapped
	 */
	public CountingInputStream(@Nullable InputStream in) {
		super(in);
	}

	/** Returns the number of bytes read. */
	public long getCount() {
		return count;
	}

	@Override
	public int read() throws IOException {
		int result = in.read();
		if (result != -1) {
			count++;
		}
		return result;
	}

	@Override
	public int read(byte[] b, int off, int len) throws IOException {
		int result = in.read(b, off, len);
		if (result != -1) {
			count += result;
		}
		return result;
	}

	@Override
	public long skip(long n) throws IOException {
		long result = in.skip(n);
		count += result;
		return result;
	}

	@Override
	public synchronized void mark(int readlimit) {
		in.mark(readlimit);
		mark = count;
		// it's okay to mark even if mark isn't supported, as reset won't work
	}

	@Override
	public synchronized void reset() throws IOException {
		if (!in.markSupported()) {
			throw new IOException("Mark not supported");
		}
		if (mark == -1) {
			throw new IOException("Mark not set");
		}

		in.reset();
		count = mark;
	}
}
