General IO Stream manipulation
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import java.io.BufferedInputStream;
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;
/**
* 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 -> 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 Peter Donald
* @author <a href="mailto:jefft@apache.org">Jeff Turner</a>
* @version CVS $Revision: 494012 $ $Date: 2007-01-08 11:23:58 +0100 (Mo, 08 Jan 2007) $
* @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 * 4;
/**
* Private constructor to prevent instantiation.
*/
private IOUtil()
{
}
/**
* Unconditionally close an <code>Reader</code>.
* Equivalent to {@link Reader#close()}, except any exceptions will be ignored.
*
* @param input A (possibly null) Reader
*/
public static void shutdownReader( final Reader input )
{
if( null == input )
{
return;
}
try
{
input.close();
}
catch( final IOException ioe )
{
}
}
/**
* Unconditionally close an <code>Writer</code>.
* Equivalent to {@link Writer#close()}, except any exceptions will be ignored.
*
* @param output A (possibly null) Writer
*/
public static void shutdownWriter( final Writer output )
{
if( null == output )
{
return;
}
try
{
output.close();
}
catch( final IOException ioe )
{
}
}
/**
* Unconditionally close an <code>OutputStream</code>.
* Equivalent to {@link OutputStream#close()}, except any exceptions will be ignored.
* @param output A (possibly null) OutputStream
*/
public static void shutdownStream( final OutputStream output )
{
if( null == output )
{
return;
}
try
{
output.close();
}
catch( final IOException ioe )
{
}
}
/**
* Unconditionally close an <code>InputStream</code>.
* Equivalent to {@link InputStream#close()}, except any exceptions will be ignored.
* @param input A (possibly null) InputStream
*/
public static void shutdownStream( final InputStream input )
{
if( null == input )
{
return;
}
try
{
input.close();
}
catch( final IOException ioe )
{
}
}
///////////////////////////////////////////////////////////////
// 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( -1 != ( 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( -1 != ( n = input.read( buffer ) ) )
{
output.write( buffer, 0, n );
}
}
///////////////////////////////////////////////////////////////
// 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 );
}
///////////////////////////////////////////////////////////////
// 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( -1 != ch )
{
final int ch2 = bufferedInput2.read();
if( ch != ch2 )
{
return false;
}
ch = bufferedInput1.read();
}
final int ch2 = bufferedInput2.read();
if( -1 != ch2 )
{
return false;
}
else
{
return true;
}
}
}
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