apache-poi/src/java/org/apache/poi/util/IOUtils.java

/* ====================================================================
   Copyright 2002-2004   Apache Software Foundation

   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 org.apache.poi.util;

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

public class IOUtils
{
    private IOUtils()
    {
    }

    /**
     * Helper method, just calls <tt>readFully(in, b, 0, b.length)</tt>
     */
    public static int readFully(InputStream in, byte[] b)
    throws IOException
    {
        return readFully(in, b, 0, b.length);
    }

    /**
     * Same as the normal <tt>in.read(b, off, len)</tt>, but tries to ensure that
     * the entire len number of bytes is read.
     * <p>
     * If the end of file is reached before any bytes are read, returns -1.
     * Otherwise, returns the number of bytes read.
     */
    public static int readFully(InputStream in, byte[] b, int off, int len)
    throws IOException
    {
        int total = 0;
        for (;;) {
            int got = in.read(b, off + total, len - total);
            if (got < 0) {
                return (total == 0) ? -1 : total;
            } else {
                total += got;
                if (total == len)
                    return total;
            }
        }
    }
}