IOUtil.java

package org.codehaus.plexus.util;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.codehaus.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache Turbine" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact codehaus@codehaus.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache Turbine", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
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 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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 * information on the Apache Software Foundation, please see
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import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.Writer;
import java.nio.channels.Channel;

/**
 * General IO Stream manipulation.
 * <p>
 * This class provides static utility methods for input/output operations, particularly buffered copying between sources
 * (<code>InputStream</code>, <code>Reader</code>, <code>String</code> and <code>byte[]</code>) and destinations
 * (<code>OutputStream</code>, <code>Writer</code>, <code>String</code> and <code>byte[]</code>).
 * </p>
 * <p>
 * Unless otherwise noted, these <code>copy</code> methods do <em>not</em> flush or close the streams. Often, doing so
 * would require making non-portable assumptions about the streams' origin and further use. This means that both
 * streams' <code>close()</code> methods must be called after copying. if one omits this step, then the stream resources
 * (sockets, file descriptors) are released when the associated Stream is garbage-collected. It is not a good idea to
 * rely on this mechanism. For a good overview of the distinction between "memory management" and "resource management",
 * see <a href="http://www.unixreview.com/articles/1998/9804/9804ja/ja.htm">this UnixReview article</a>
 * </p>
 * <p>
 * For each <code>copy</code> method, a variant is provided that allows the caller to specify the buffer size (the
 * default is 4k). As the buffer size can have a fairly large impact on speed, this may be worth tweaking. Often "large
 * buffer -&gt; faster" does not hold, even for large data transfers.
 * </p>
 * <p>
 * For byte-to-char methods, a <code>copy</code> variant allows the encoding to be selected (otherwise the platform
 * default is used).
 * </p>
 * <p>
 * The <code>copy</code> methods use an internal buffer when copying. It is therefore advisable <em>not</em> to
 * deliberately wrap the stream arguments to the <code>copy</code> methods in <code>Buffered*</code> streams. For
 * example, don't do the following:
 * </p>
 * <code>copy( new BufferedInputStream( in ), new BufferedOutputStream( out ) );</code>
 * <p>
 * The rationale is as follows:
 * </p>
 * <p>
 * Imagine that an InputStream's read() is a very expensive operation, which would usually suggest wrapping in a
 * BufferedInputStream. The BufferedInputStream works by issuing infrequent
 * {@link java.io.InputStream#read(byte[] b, int off, int len)} requests on the underlying InputStream, to fill an
 * internal buffer, from which further <code>read</code> requests can inexpensively get their data (until the buffer
 * runs out).
 * </p>
 * <p>
 * However, the <code>copy</code> methods do the same thing, keeping an internal buffer, populated by
 * {@link InputStream#read(byte[] b, int off, int len)} requests. Having two buffers (or three if the destination stream
 * is also buffered) is pointless, and the unnecessary buffer management hurts performance slightly (about 3%, according
 * to some simple experiments).
 * </p>
 *
 * @author <a href="mailto:peter@codehaus.org">Peter Donald</a>
 * @author <a href="mailto:jefft@codehaus.org">Jeff Turner</a>
 *
 * @since 4.0
 */

/*
 * Behold, intrepid explorers; a map of this class: Method Input Output Dependency ------ ----- ------ ------- 1 copy
 * InputStream OutputStream (primitive) 2 copy Reader Writer (primitive) 3 copy InputStream Writer 2 4 toString
 * InputStream String 3 5 toByteArray InputStream byte[] 1 6 copy Reader OutputStream 2 7 toString Reader String 2 8
 * toByteArray Reader byte[] 6 9 copy String OutputStream 2 10 copy String Writer (trivial) 11 toByteArray String byte[]
 * 9 12 copy byte[] Writer 3 13 toString byte[] String 12 14 copy byte[] OutputStream (trivial) Note that only the first
 * two methods shuffle bytes; the rest use these two, or (if possible) copy using native Java copy methods. As there are
 * method variants to specify buffer size and encoding, each row may correspond to up to 4 methods.
 */

public final class IOUtil
{
    private static final int DEFAULT_BUFFER_SIZE = 1024 * 16;

    /**
     * Private constructor to prevent instantiation.
     */
    private IOUtil()
    {
    }

    ///////////////////////////////////////////////////////////////
    // Core copy methods
    ///////////////////////////////////////////////////////////////

    /**
     * Copy bytes from an <code>InputStream</code> to an <code>OutputStream</code>.
     */
    public static void copy( final InputStream input, final OutputStream output )
        throws IOException
    {
        copy( input, output, DEFAULT_BUFFER_SIZE );
    }

    /**
     * Copy bytes from an <code>InputStream</code> to an <code>OutputStream</code>.
     * 
     * @param bufferSize Size of internal buffer to use.
     */
    public static void copy( final InputStream input, final OutputStream output, final int bufferSize )
        throws IOException
    {
        final byte[] buffer = new byte[bufferSize];
        int n = 0;
        while ( 0 <= ( n = input.read( buffer ) ) )
        {
            output.write( buffer, 0, n );
        }
    }

    /**
     * Copy chars from a <code>Reader</code> to a <code>Writer</code>.
     */
    public static void copy( final Reader input, final Writer output )
        throws IOException
    {
        copy( input, output, DEFAULT_BUFFER_SIZE );
    }

    /**
     * Copy chars from a <code>Reader</code> to a <code>Writer</code>.
     * 
     * @param bufferSize Size of internal buffer to use.
     */
    public static void copy( final Reader input, final Writer output, final int bufferSize )
        throws IOException
    {
        final char[] buffer = new char[bufferSize];
        int n = 0;
        while ( 0 <= ( n = input.read( buffer ) ) )
        {
            output.write( buffer, 0, n );
        }
        output.flush();
    }

    ///////////////////////////////////////////////////////////////
    // Derived copy methods
    // InputStream -> *
    ///////////////////////////////////////////////////////////////

    ///////////////////////////////////////////////////////////////
    // InputStream -> Writer

    /**
     * Copy and convert bytes from an <code>InputStream</code> to chars on a <code>Writer</code>. The platform's default
     * encoding is used for the byte-to-char conversion.
     */
    public static void copy( final InputStream input, final Writer output )
        throws IOException
    {
        copy( input, output, DEFAULT_BUFFER_SIZE );
    }

    /**
     * Copy and convert bytes from an <code>InputStream</code> to chars on a <code>Writer</code>. The platform's default
     * encoding is used for the byte-to-char conversion.
     * 
     * @param bufferSize Size of internal buffer to use.
     */
    public static void copy( final InputStream input, final Writer output, final int bufferSize )
        throws IOException
    {
        final InputStreamReader in = new InputStreamReader( input );
        copy( in, output, bufferSize );
    }

    /**
     * Copy and convert bytes from an <code>InputStream</code> to chars on a <code>Writer</code>, using the specified
     * encoding.
     * 
     * @param encoding The name of a supported character encoding. See the
     *            <a href="http://www.iana.org/assignments/character-sets">IANA Charset Registry</a> for a list of valid
     *            encoding types.
     */
    public static void copy( final InputStream input, final Writer output, final String encoding )
        throws IOException
    {
        final InputStreamReader in = new InputStreamReader( input, encoding );
        copy( in, output );
    }

    /**
     * Copy and convert bytes from an <code>InputStream</code> to chars on a <code>Writer</code>, using the specified
     * encoding.
     * 
     * @param encoding The name of a supported character encoding. See the
     *            <a href="http://www.iana.org/assignments/character-sets">IANA Charset Registry</a> for a list of valid
     *            encoding types.
     * @param bufferSize Size of internal buffer to use.
     */
    public static void copy( final InputStream input, final Writer output, final String encoding, final int bufferSize )
        throws IOException
    {
        final InputStreamReader in = new InputStreamReader( input, encoding );
        copy( in, output, bufferSize );
    }

    ///////////////////////////////////////////////////////////////
    // InputStream -> String

    /**
     * Get the contents of an <code>InputStream</code> as a String. The platform's default encoding is used for the
     * byte-to-char conversion.
     */
    public static String toString( final InputStream input )
        throws IOException
    {
        return toString( input, DEFAULT_BUFFER_SIZE );
    }

    /**
     * Get the contents of an <code>InputStream</code> as a String. The platform's default encoding is used for the
     * byte-to-char conversion.
     * 
     * @param bufferSize Size of internal buffer to use.
     */
    public static String toString( final InputStream input, final int bufferSize )
        throws IOException
    {
        final StringWriter sw = new StringWriter();
        copy( input, sw, bufferSize );
        return sw.toString();
    }

    /**
     * Get the contents of an <code>InputStream</code> as a String.
     * 
     * @param encoding The name of a supported character encoding. See the
     *            <a href="http://www.iana.org/assignments/character-sets">IANA Charset Registry</a> for a list of valid
     *            encoding types.
     */
    public static String toString( final InputStream input, final String encoding )
        throws IOException
    {
        return toString( input, encoding, DEFAULT_BUFFER_SIZE );
    }

    /**
     * Get the contents of an <code>InputStream</code> as a String.
     * 
     * @param encoding The name of a supported character encoding. See the
     *            <a href="http://www.iana.org/assignments/character-sets">IANA Charset Registry</a> for a list of valid
     *            encoding types.
     * @param bufferSize Size of internal buffer to use.
     */
    public static String toString( final InputStream input, final String encoding, final int bufferSize )
        throws IOException
    {
        final StringWriter sw = new StringWriter();
        copy( input, sw, encoding, bufferSize );
        return sw.toString();
    }

    ///////////////////////////////////////////////////////////////
    // InputStream -> byte[]

    /**
     * Get the contents of an <code>InputStream</code> as a <code>byte[]</code>.
     */
    public static byte[] toByteArray( final InputStream input )
        throws IOException
    {
        return toByteArray( input, DEFAULT_BUFFER_SIZE );
    }

    /**
     * Get the contents of an <code>InputStream</code> as a <code>byte[]</code>.
     * 
     * @param bufferSize Size of internal buffer to use.
     */
    public static byte[] toByteArray( final InputStream input, final int bufferSize )
        throws IOException
    {
        final ByteArrayOutputStream output = new ByteArrayOutputStream();
        copy( input, output, bufferSize );
        return output.toByteArray();
    }

    ///////////////////////////////////////////////////////////////
    // Derived copy methods
    // Reader -> *
    ///////////////////////////////////////////////////////////////

    ///////////////////////////////////////////////////////////////
    // Reader -> OutputStream
    /**
     * Serialize chars from a <code>Reader</code> to bytes on an <code>OutputStream</code>, and flush the
     * <code>OutputStream</code>.
     */
    public static void copy( final Reader input, final OutputStream output )
        throws IOException
    {
        copy( input, output, DEFAULT_BUFFER_SIZE );
    }

    /**
     * Serialize chars from a <code>Reader</code> to bytes on an <code>OutputStream</code>, and flush the
     * <code>OutputStream</code>.
     * 
     * @param bufferSize Size of internal buffer to use.
     */
    public static void copy( final Reader input, final OutputStream output, final int bufferSize )
        throws IOException
    {
        final OutputStreamWriter out = new OutputStreamWriter( output );
        copy( input, out, bufferSize );
        // NOTE: Unless anyone is planning on rewriting OutputStreamWriter, we have to flush
        // here.
        out.flush();
    }

    ///////////////////////////////////////////////////////////////
    // Reader -> String
    /**
     * Get the contents of a <code>Reader</code> as a String.
     */
    public static String toString( final Reader input )
        throws IOException
    {
        return toString( input, DEFAULT_BUFFER_SIZE );
    }

    /**
     * Get the contents of a <code>Reader</code> as a String.
     * 
     * @param bufferSize Size of internal buffer to use.
     */
    public static String toString( final Reader input, final int bufferSize )
        throws IOException
    {
        final StringWriter sw = new StringWriter();
        copy( input, sw, bufferSize );
        return sw.toString();
    }

    ///////////////////////////////////////////////////////////////
    // Reader -> byte[]
    /**
     * Get the contents of a <code>Reader</code> as a <code>byte[]</code>.
     */
    public static byte[] toByteArray( final Reader input )
        throws IOException
    {
        return toByteArray( input, DEFAULT_BUFFER_SIZE );
    }

    /**
     * Get the contents of a <code>Reader</code> as a <code>byte[]</code>.
     * 
     * @param bufferSize Size of internal buffer to use.
     */
    public static byte[] toByteArray( final Reader input, final int bufferSize )
        throws IOException
    {
        ByteArrayOutputStream output = new ByteArrayOutputStream();
        copy( input, output, bufferSize );
        return output.toByteArray();
    }

    ///////////////////////////////////////////////////////////////
    // Derived copy methods
    // String -> *
    ///////////////////////////////////////////////////////////////

    ///////////////////////////////////////////////////////////////
    // String -> OutputStream

    /**
     * Serialize chars from a <code>String</code> to bytes on an <code>OutputStream</code>, and flush the
     * <code>OutputStream</code>.
     */
    public static void copy( final String input, final OutputStream output )
        throws IOException
    {
        copy( input, output, DEFAULT_BUFFER_SIZE );
    }

    /**
     * Serialize chars from a <code>String</code> to bytes on an <code>OutputStream</code>, and flush the
     * <code>OutputStream</code>.
     * 
     * @param bufferSize Size of internal buffer to use.
     */
    public static void copy( final String input, final OutputStream output, final int bufferSize )
        throws IOException
    {
        final StringReader in = new StringReader( input );
        final OutputStreamWriter out = new OutputStreamWriter( output );
        copy( in, out, bufferSize );
        // NOTE: Unless anyone is planning on rewriting OutputStreamWriter, we have to flush
        // here.
        out.flush();
    }

    ///////////////////////////////////////////////////////////////
    // String -> Writer

    /**
     * Copy chars from a <code>String</code> to a <code>Writer</code>.
     */
    public static void copy( final String input, final Writer output )
        throws IOException
    {
        output.write( input );
    }

    /**
     * Copy bytes from an <code>InputStream</code> to an <code>OutputStream</code>, with buffering. This is equivalent
     * to passing a {@link java.io.BufferedInputStream} and {@link java.io.BufferedOutputStream} to
     * {@link #copy(InputStream, OutputStream)}, and flushing the output stream afterwards. The streams are not closed
     * after the copy.
     * 
     * @deprecated Buffering streams is actively harmful! See the class description as to why. Use
     *             {@link #copy(InputStream, OutputStream)} instead.
     */
    @Deprecated
    public static void bufferedCopy( final InputStream input, final OutputStream output )
        throws IOException
    {
        final BufferedInputStream in = new BufferedInputStream( input );
        final BufferedOutputStream out = new BufferedOutputStream( output );
        copy( in, out );
        out.flush();
    }

    ///////////////////////////////////////////////////////////////
    // String -> byte[]
    /**
     * Get the contents of a <code>String</code> as a <code>byte[]</code>.
     */
    public static byte[] toByteArray( final String input )
        throws IOException
    {
        return toByteArray( input, DEFAULT_BUFFER_SIZE );
    }

    /**
     * Get the contents of a <code>String</code> as a <code>byte[]</code>.
     * 
     * @param bufferSize Size of internal buffer to use.
     */
    public static byte[] toByteArray( final String input, final int bufferSize )
        throws IOException
    {
        ByteArrayOutputStream output = new ByteArrayOutputStream();
        copy( input, output, bufferSize );
        return output.toByteArray();
    }

    ///////////////////////////////////////////////////////////////
    // Derived copy methods
    // byte[] -> *
    ///////////////////////////////////////////////////////////////

    ///////////////////////////////////////////////////////////////
    // byte[] -> Writer

    /**
     * Copy and convert bytes from a <code>byte[]</code> to chars on a <code>Writer</code>. The platform's default
     * encoding is used for the byte-to-char conversion.
     */
    public static void copy( final byte[] input, final Writer output )
        throws IOException
    {
        copy( input, output, DEFAULT_BUFFER_SIZE );
    }

    /**
     * Copy and convert bytes from a <code>byte[]</code> to chars on a <code>Writer</code>. The platform's default
     * encoding is used for the byte-to-char conversion.
     * 
     * @param bufferSize Size of internal buffer to use.
     */
    public static void copy( final byte[] input, final Writer output, final int bufferSize )
        throws IOException
    {
        final ByteArrayInputStream in = new ByteArrayInputStream( input );
        copy( in, output, bufferSize );
    }

    /**
     * Copy and convert bytes from a <code>byte[]</code> to chars on a <code>Writer</code>, using the specified
     * encoding.
     * 
     * @param encoding The name of a supported character encoding. See the
     *            <a href="http://www.iana.org/assignments/character-sets">IANA Charset Registry</a> for a list of valid
     *            encoding types.
     */
    public static void copy( final byte[] input, final Writer output, final String encoding )
        throws IOException
    {
        final ByteArrayInputStream in = new ByteArrayInputStream( input );
        copy( in, output, encoding );
    }

    /**
     * Copy and convert bytes from a <code>byte[]</code> to chars on a <code>Writer</code>, using the specified
     * encoding.
     * 
     * @param encoding The name of a supported character encoding. See the
     *            <a href="http://www.iana.org/assignments/character-sets">IANA Charset Registry</a> for a list of valid
     *            encoding types.
     * @param bufferSize Size of internal buffer to use.
     */
    public static void copy( final byte[] input, final Writer output, final String encoding, final int bufferSize )
        throws IOException
    {
        final ByteArrayInputStream in = new ByteArrayInputStream( input );
        copy( in, output, encoding, bufferSize );
    }

    ///////////////////////////////////////////////////////////////
    // byte[] -> String

    /**
     * Get the contents of a <code>byte[]</code> as a String. The platform's default encoding is used for the
     * byte-to-char conversion.
     */
    public static String toString( final byte[] input )
        throws IOException
    {
        return toString( input, DEFAULT_BUFFER_SIZE );
    }

    /**
     * Get the contents of a <code>byte[]</code> as a String. The platform's default encoding is used for the
     * byte-to-char conversion.
     * 
     * @param bufferSize Size of internal buffer to use.
     */
    public static String toString( final byte[] input, final int bufferSize )
        throws IOException
    {
        final StringWriter sw = new StringWriter();
        copy( input, sw, bufferSize );
        return sw.toString();
    }

    /**
     * Get the contents of a <code>byte[]</code> as a String.
     * 
     * @param encoding The name of a supported character encoding. See the
     *            <a href="http://www.iana.org/assignments/character-sets">IANA Charset Registry</a> for a list of valid
     *            encoding types.
     */
    public static String toString( final byte[] input, final String encoding )
        throws IOException
    {
        return toString( input, encoding, DEFAULT_BUFFER_SIZE );
    }

    /**
     * Get the contents of a <code>byte[]</code> as a String.
     * 
     * @param encoding The name of a supported character encoding. See the
     *            <a href="http://www.iana.org/assignments/character-sets">IANA Charset Registry</a> for a list of valid
     *            encoding types.
     * @param bufferSize Size of internal buffer to use.
     */
    public static String toString( final byte[] input, final String encoding, final int bufferSize )
        throws IOException
    {
        final StringWriter sw = new StringWriter();
        copy( input, sw, encoding, bufferSize );
        return sw.toString();
    }

    ///////////////////////////////////////////////////////////////
    // byte[] -> OutputStream

    /**
     * Copy bytes from a <code>byte[]</code> to an <code>OutputStream</code>.
     */
    public static void copy( final byte[] input, final OutputStream output )
        throws IOException
    {
        copy( input, output, DEFAULT_BUFFER_SIZE );
    }

    /**
     * Copy bytes from a <code>byte[]</code> to an <code>OutputStream</code>.
     * 
     * @param bufferSize Size of internal buffer to use.
     */
    public static void copy( final byte[] input, final OutputStream output, final int bufferSize )
        throws IOException
    {
        output.write( input );
    }

    /**
     * Compare the contents of two Streams to determine if they are equal or not.
     *
     * @param input1 the first stream
     * @param input2 the second stream
     * @return true if the content of the streams are equal or they both don't exist, false otherwise
     */
    public static boolean contentEquals( final InputStream input1, final InputStream input2 )
        throws IOException
    {
        final InputStream bufferedInput1 = new BufferedInputStream( input1 );
        final InputStream bufferedInput2 = new BufferedInputStream( input2 );

        int ch = bufferedInput1.read();
        while ( 0 <= ch )
        {
            final int ch2 = bufferedInput2.read();
            if ( ch != ch2 )
            {
                return false;
            }
            ch = bufferedInput1.read();
        }

        final int ch2 = bufferedInput2.read();
        if ( 0 <= ch2 )
        {
            return false;
        }
        else
        {
            return true;
        }
    }

    // ----------------------------------------------------------------------
    // closeXXX()
    // ----------------------------------------------------------------------

    /**
     * Closes the input stream. The input stream can be null and any IOException's will be swallowed.
     * 
     * @param inputStream The stream to close.
     * @deprecated use try-with-resources instead
     */
    @Deprecated
    public static void close( InputStream inputStream )
    {
        if ( inputStream == null )
        {
            return;
        }

        try
        {
            inputStream.close();
        }
        catch ( IOException ex )
        {
            // ignore
        }
    }

    /**
     * Closes a channel. Channel can be null and any IOException's will be swallowed.
     *
     * @param channel The stream to close.
     * @deprecated use try-with-resources instead
     */
    @Deprecated
    public static void close( Channel channel )
    {
        if ( channel == null )
        {
            return;
        }

        try
        {
            channel.close();
        }
        catch ( IOException ex )
        {
            // ignore
        }
    }

    /**
     * Closes the output stream. The output stream can be null and any IOException's will be swallowed.
     * 
     * @param outputStream The stream to close.
     * @deprecated use try-with-resources instead
     */
    @Deprecated
    public static void close( OutputStream outputStream )
    {
        if ( outputStream == null )
        {
            return;
        }

        try
        {
            outputStream.close();
        }
        catch ( IOException ex )
        {
            // ignore
        }
    }

    /**
     * Closes the reader. The reader can be null and any IOException's will be swallowed.
     * 
     * @param reader The reader to close.
     * @deprecated use try-with-resources instead
     */
    @Deprecated
    public static void close( Reader reader )
    {
        if ( reader == null )
        {
            return;
        }

        try
        {
            reader.close();
        }
        catch ( IOException ex )
        {
            // ignore
        }
    }

    /**
     * Closes the writer. The writer can be null and any IOException's will be swallowed.
     * 
     * @param writer The writer to close.
     * @deprecated use try-with-resources instead
     */
    @Deprecated
    public static void close( Writer writer )
    {
        if ( writer == null )
        {
            return;
        }

        try
        {
            writer.close();
        }
        catch ( IOException ex )
        {
            // ignore
        }
    }
}