common/src/main/java/org/apache/abdera2/common/io/PeekAheadInputStream.java

package org.apache.abdera2.common.io;

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  The ASF licenses this file to You
 * 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.  For additional information regarding
 * copyright in this work, please see the NOTICE file in the top level
 * directory of this distribution.
 */

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

/**
 * A version of RewindableInputStream that provides methods for peeking ahead in the stream (equivalent to read()
 * followed by an appropriate unread()
 */
public class PeekAheadInputStream extends RewindableInputStream {

    public PeekAheadInputStream(InputStream in) {
        super(in);
    }

    public PeekAheadInputStream(InputStream in, int initialSize) {
        super(in, initialSize);
    }

    /**
     * Peek the next byte in the stream
     */
    public int peek() throws IOException {
        int m = read();
        unread(m);
        return m;
    }

    /**
     * Peek the next bytes in the stream. Returns the number of bytes peeked. Will return -1 if the end of the stream is
     * reached
     */
    public int peek(byte[] buf) throws IOException {
        return peek(buf, 0, buf.length);
    }

    /**
     * Peek the next bytes in the stream. Returns the number of bytes peeked. Will return -1 if the end of the stream is
     * reached
     */
    public int peek(byte[] buf, int off, int len) throws IOException {
        int r = read(buf, off, len);
        if (r > -1) unread(buf, off, r);
        return r;
    }

}